Startseite Robust biaxially stretchable polylactic acid films based on the highly oriented chain network and “nano-walls” containing zinc phenylphosphonate and calcium sulfate whisker: Superior mechanical, barrier, and optical properties
Artikel Open Access

Robust biaxially stretchable polylactic acid films based on the highly oriented chain network and “nano-walls” containing zinc phenylphosphonate and calcium sulfate whisker: Superior mechanical, barrier, and optical properties

  • Shi-Juan Ding , Ling-Na Cui EMAIL logo und Yue-Jun Liu EMAIL logo
Veröffentlicht/Copyright: 31. Mai 2024
Artikel downloaden (PDF)
Veröffentlichen auch Sie bei De Gruyter Brill
Manuskript einreichen Informationen für Autor*innen
e-Polymers
Aus der Zeitschrift e-Polymers Band 24 Heft 1

Abstract

It is urgent to acquire a feasible strategy for balancing the strength and ductility of polylactic acid (PLA) in the application of biodegradable packaging materials. In this study, a new strategy is provided to enhance mechanical, barrier, and optical properties by the synergetic effect of manipulating the amorphous chain entanglement network and constructing the “nano- walls” of highly aligned calcium sulfate whisker (CSW), zinc phenylphosphonate (PPZn), and well-defined crystals via biaxial stretching. PPZn is verified as a nucleator to accelerate the crystallization rate and induce α-form crystals. CSW is regarded as a supporting skeleton to strengthen the entanglement density of the chain network. The extensional stress, which is induced by biaxial stretching, regulates the amorphous chain entanglement network and facilitates the chain orientation. As a result, the synergetic structure displays an outstanding capacity for improving the mechanical, barrier, and optical properties of PLA. Compared to the PLA film, the biaxially stretched PLA/PPZn/CSW films exhibit high strength, excellent ductility, and superior crystallinity, which are significantly increased by up to 53.2%, 381.3%, and 748.9%, respectively. And their gas and water vapor barrier properties remarkably increased by 65.39% and 73.11%, respectively. The optical property with a haze value of 52.4% and good transmittance of 97.4% is also obtained via the synergetic effect. With the excellent comprehensive properties of PLA films, this new strategy explores a new field in environmentally friendly packaging materials and is relevant to future work.

Graphical Abstract

Keywords: polylactic acid; biaxial stretching; ductility; barrier properties; chain entanglement network

1 Introduction

Nowadays, many have focused on developing eco-friendly biodegradable polymers to cope with the serious environmental pollution caused by petroleum-based plastics (1,2). Polylactic acid (PLA), a biodegradable polyester derived from renewable resources, exhibits promising applicability due to its unique advantages of eminent transparency, easy processing, and level of strength (3,4,5). However, the PLA semi-rigid chains, involving the strong polarity of ester groups and the steric effect of side methyl groups, result in low mobility and slow crystallization (6). These inherent structures and characteristics fail to provide good comprehensive properties for PLA, such as barrier properties, ductility, and optical properties, and limit its application in multifunctional packaging film. Therefore, it is considered that tailoring crystalline lamellae and regulating amorphous chain are the fundamental and efficient ways to change the final macro-properties of PLA.

As for PLA, crystalline lamellae could as a key microstructure for functional film, which is closely governed by the factors involving polymorphism, crystallinity, crystal size, and crystal morphology (7). It is generally recognized that the incorporation of nucleators, such as montmorillonite, cellulose, and nanoparticles, is the most simple and effective strategy to tailor the crystalline lamellae (8,9,10). As heterogeneous nuclei, the nucleator augments the free energy for the formation of critical nuclei, which accelerates the crystal growth in a short time (11). In recent years, various nucleators have been developed and their effects in the matrix of PLA have been widely explored (12,13,14). For example, zinc phenylphosphonate (PPZn), a kind of synthetic inorganic/organic hybrid metal phosphonate with a layered structure, has attracted much attention for inducing dense fine PLA crystals in short half-crystallization time (15,16,17). As a heterogeneous nucleating agent, the layered PPZn can induce orderly α-form PLA lamellae based on the excellent epitaxial lattice matching along its [010] and [110] directions. The induced α-form crystal is more favored over the δ-form crystal due to its orderly and tight structural features, which are favorable for further enhancing the macro-properties (18). However, owing to its intrinsic self-lubricating property, PPZn is insufficient to enhance crystallinity and strength simultaneously for PLA (15). Many attempts have been devoted to developing the strength materials, in which the incorporation of filler is the mainstream to address the strength issue in an economical and simple way (19,20). Calcium sulfate whisker (CSW), as a supporting skeleton in the matrix, can strengthen the stress tolerance and heat resistance of PLA, although it has little positive effect on crystallization (21). The combination of PPZn and CSW plays to their own advantages and promotes the development of crystallinity and strength simultaneously for PLA. Meanwhile, the “nano-walls” can be constructed by the α-form crystal, PPZn, and CSW to enhance the barrier properties and strength of PLA. However, owing to the poor dispersion of PPZn and CSW in the PLA matrix, the construction of the “nano-walls” has difficulty in achieving PLA performance up to par and even makes it more brittle.

Recently, the discovery of biaxial stretching for glassy PLA provided a new idea for manipulating its amorphous chain network and dispersing the additional particles (22,23). It is well documented that agglomerated particles can be dispersed under isotropous extensional stress, which can effectively solve the problem of mechanical property deterioration caused by particles (24). Meanwhile, due to the conformational change of high-energy gauche–gauche conformers induced by the deformed chains, the critical onset stress for yielding is reduced, which prolongs the deformation length of PLA films and even triggers the transition from brittle to ductile (25,26). Chen et al. (27) reported that the dense network structure could be formed in the strain softening stage for PLA stretched near the glass transition temperature. Xu et al. (26) found that the critical molecular chain orientation of the amorphous phase is the necessary condition to induce ductile behavior in PLA films. Consequently, dense chain entanglement networks and high chain orientation are obtained by biaxial stretching under proper stretching parameters, which have the potential to endow PLA with superior ductility and other comprehensive performance (24,28).

To sum up the viewpoints expressed earlier, a flexible combination of constructing the strong “nano-walls” of the well-defined α-form crystals, highly dispersed PPZn and CSW, and regulating the amorphous chain entanglement network via biaxial stretching seems to be a positive strategy to endow PLA films with superior mechanical, barrier, and optical properties. On the one hand, the “nano-walls” tailored by α-form lamellae and supporting skeletons serve as strength and barrier units, compelling the stress to distribute uniformly and making the permeability pathway more tortuous. On the other hand, the dense chain entanglement network manipulated by biaxial stretching extends the elongation and reduces the free volume. In this study, PLA/PPZn/CSW films are prepared using a laboratory stretching machine (Brückner KARO V). The crystalline structure, amorphous structure, and macroscopic properties are investigated to reveal the structure–property relationship of the PLA/PPZn/CSW films.

2 Experimental section

2.1 Materials

PLA (Luminy® LX175) was obtained by TotalEnergies Corbion Co. Ltd, Thailand, with a molecular weight and dextrolactic acid content of 1.7 × 105 g·mol−1 and 4%, respectively. And the density and melt flow index were 1.24 g·cm−3 and 3 g per 10 min (190°C per 2.16 kg), respectively. PPZn was a heterogeneous nucleating agent obtained from Shanxi Provincial Institute of Chemical industry, whose melt temperature was beyond 300°C. CSWs were purchased from Hui-Yi chemical reagent factory, Dongguan, China. Stearic acid (SA) with 98% purity was purchased from Macklin lnc.

2.2 Preparation of biaxially stretched PLA/PPZn/CSW films

The schematic diagram of the preparation process of PLA/PPZn/CSW films via the extrusion casting–biaxial stretching procedure is illustrated in Figure 1. Before preparation, the CSW was modified using SA to reduce its aggregation in the PLA matrix. Then, after the raw materials were dried under vacuum, the PLA/PPZn/CSW sheets containing 0.6 wt% PPZn and 4 wt% CSW were prepared by the method of extrusion casting, and their thickness was approximately 300 μm. Then, the obtained PLA/PPZn/CSW sheets were simultaneously biaxially stretched into various times of their original size at a stretching rate and stretching temperature of 100%·s−1 and 85°C, respectively, using a biaxial stretcher (KARO V, Brückner, Germany). For convenience, PLA/PPZn/CSW films were denoted as PZnCS-X, where X represents the different stretching ratios, i.e., 1 × 1, 2 × 2, 3 × 3, and 4 × 4.

Figure 1 Schematic diagram of the preparation process of PZnCS films via extrusion casting–biaxial stretching procedure.
Figure 1

Schematic diagram of the preparation process of PZnCS films via extrusion casting–biaxial stretching procedure.

2.3 Characterization

2.3.1 Scanning electron microscopy (SEM)

Morphology of samples was observed on a scanning electron microscope (ZEISS Sigma 300, Germany) at an accelerating voltage of 5 kV. Before testing, the surface of sample was coated with a thin layer of gold.

2.3.2 Differential scanning calorimetry (DSC) measurement

DSC measurement was taken using DSC25 (TA instrument) under nitrogen atmosphere at a heating rate of 10°C·min−1 from 25°C to 210°C. Before testing, all the samples were weighed (5–10 mg) and sealed into aluminum pans. The crystallinity (X c) was calculated as follows:

(1) X c = Δ H m − Δ H c Δ H m 0 ( 1 − φ ) × 100 %

where Δ H m and Δ H c are the melting enthalpy and cooling crystallization enthalpy, respectively, φ is the mass fraction of the nucleating agent and filler, and Δ H m 0 is the enthalpy of PLA completely crystallized (93 J·g−1) (29).

Besides, the temperature-modulated DSC (TMDSC) was used to investigate the nonreversible and reversible heat flow change in the vicinity of the glass transition temperature (T g). All the samples were heated from 30°C to 100°C at a heating rate of 3°C·min−1 with a modulation amplitude of ±0.5°C and an oscillation period of 60 s. The contents of mobile amorphous fraction (X MAF) and rigid amorphous fraction (X RAF) were obtained from the reversible heat capacity (C P) around the glass transition regions. The corresponding calculation equations were as follows:

(2) X MAF = Δ C p Δ C p 0

(3) X RAF = 1 − X MAF − X c

where Δ C p 0 is the heat capacity for totally amorphous PLA (0.628 J·g−1·°C−1) (30).

2.3.3 Wide- and small-angle X-ray scattering (WAXS/SAXS)

Two-dimensional (2D) WAXS/SAXS measurement with the wavelength (λ) of 0.15418 nm was taken on XUESS 3.0 bench with a copper internal source (Genix 3D). To balance the strength and accuracy of signal, high resolution was set with a spot size of 0.8 mm × 0.5 mm. The sample-to-detector distances were 60 mm and 500 mm for WAXS and SAXS measurements, respectively. All the 2D patterns were integrated into one-dimensional (1D) intensity profiles as a function of scattering vector (q), which can be expressed as 4πsin θ/λ, and 2θ is the scattering angle. The orientation parameter was measured by the Herman’s orientation function calculated by the following equations:

(4) f h k l = 3 ( cos 2 φ h k l ) − 1 2

(5) cos 2 φ h k l = ∫ 0 π 2 I h k l ( φ ) cos 2 φ sin φ d φ ∫ 0 π 2 I h k l ( φ ) sin φ d φ

where φ is the azimuthal angle, and I hkl ( φ ) is the azimuthal intensity distribution along (hkl) reflection of PLA. The average size of crystal domain (L hkl ) was calculated by the Scherrer equation (31):

(6) L h k l = K λ β cos θ

where K is the Scherrer constant with a value of 0.89 and β is peak width at half-height of specific crystal plane (200/110) of PLA (31). In order to obtain the electron density correlation function K(z) intensity, the inverse Fourier transform was applied to 1D-SAXS intensity profile I(q) as follows (32):

(7) K ( z ) = ∫ 0 ∞ I ( q ) q 2 cos ( q z ) d q ∫ 0 ∞ I ( q ) q 2 d q

where z and I(q) are the location measured along a trajectory normal to the lamellar surface and intensity distribution, respectively. The long period (L p) and lamellar thickness (L c) were obtained by applying the correlation function K(z) (33). Owing to the crystallinity being lower than 50%, the smaller value was assigned as the average L c, and the amorphous layer thickness (L a) was calculated by L a = L p − L c (30).

2.3.4 Fourier transform infrared (FTIR) measurements

FTIR spectroscopic analysis was carried out using a Bruker TENSOR Ⅱ at room temperature. The scanned wavenumber range was 4,000–400 cm−1 with a resolution of 4 cm−1 and scan numbers at 16 for averaging. Polarized FTIR was also measured to collect the infrared (IR) spectrum of samples under different polarized angles. The S M, S T, and S MN were captured with the polarization parallel to 0°, 90°, and 45°, respectively. The S M and ST corresponded to the spectrum of the film along the machine direction (MD) and transverse direction (TD), respectively. And the S MN was obtained by tilting the films at 45° with regard to the IR beam about the TD. According to the S M and S MN, the spectrum of the film along the normal direction (S N) was calculated as follows (34):

(8) S N = 2 n 2 1 − 1 2 n 2 S MN − ( 2 n 2 − 1 ) S N

where n is the effective refractive index reported to be equal to 1.46 for PLA. The average spectrum S 0 was calculated from the following equation:

(9) S 0 = 1 3 ( S M + S T + S N )

Thus, the orientation function was calculated by the following equation:

(10) f i j = 1 2 A j A 0 − 1

where A j and A 0 are the band intensities in the S j and S 0 spectrum, respectively. The three orientation functions must obey the following equation:

(11) f i M + f i N + f i T = 0

2.3.5 Dynamic mechanical analysis (DMA)

DMA test was conducted on a NETZSCH 242E instrument in the tension mode to obtain T g. All the samples were heated from 30°C to 100°C at a heating rate, fixed frequency, and amplitude of 3°C·min−1, 1 Hz, and 20 μm, respectively.

2.3.6 Mechanical property testing

The mechanical properties of samples were determined on universal testing machine (ETM-1048, China). The testing was measured according to the GB/T 1040-2006 standard at a strain rate of 10 mm·min−1. Before testing, the samples were cut into a dumbbell-shaped specimen with a dimension of 5 mm × 75 mm. The average values were evaluated based on at least five samples.

2.3.7 Barrier property measurement

The oxygen permeability measurement was taken using a BTY-B1 oxygen permeability tester (Labthink instrument, Jinan, China) at room temperature with 50% relative humidity according to GB/T 1038-2000. The water vapor permeability was measured using a C303H water vapor permeability tester (Labthink instrument, Jinan, China) at 23°C and 90% relative humidity according to GB/T 26253-2010.

2.3.8 Optical property measurement

Optical property measurement was taken according to GB/T 2410-2008 standard. All samples were cut into square with dimensions of 50 mm × 50 mm. Transmittance and haze of all the films were determined on a WGT-S instrument (Shanghai, China). In order to eliminate the effect of thickness of film, the haze of unit thickness and absorbance coefficient of light were calculated by the following equations (35,36):

(12) 1 − H n = ( 1 − h ) n

(13) T = e − α d

where H n is the haze value of the films, h is the haze of unit thickness of the films, n is the number of layers that divided the film into unit thickness (1 μm), T is the transmittance value of the films, α is the absorbance coefficient of light, and d is the thickness of the films.

2.3.9 Atomic force microscopy (AFM) measurement

AFM measurement was taken using Dimension Icon (Bruker, Germany) tester in tapping mode. And BRUKER OTESPA-R3 cantilever tips possessing force constants of 26 N·m−1 and oscillated at frequencies of 300 kHz were used.

3 Results and discussion

3.1 Dispersion morphology of PPZn and CSW in PLA matrix

The dispersion morphology of PPZn and CSW in the PLA matrix plays a significant role in developing the microstructure of the PZnCS films in the process of biaxial stretching. Figure 2 shows the typical SEM images of the PZnCS film surface with various stretching ratios. It is visible that PPZn and CSW are homogeneously dispersed in the PLA matrix during biaxial stretching while conspicuously agglomerating in the unstretched film. Hence, PPZn and CSW in PZnCS film exhibit excellent dispersed morphology realized by biaxial stretching. The highly dispersed morphology of PPZn and CSW not only promotes the formation and development of crystals but also allows PZnCS films to hold great potential as multifunctional packaging materials, which will be mentioned in the following sections.

Figure 2 SEM image at the surface of (a) PZnCS-1 × 1, (b) PZnCS-2 × 2, (c) PZnCS-3 × 3, and (d) PZnCS-4 × 4; (a1)–(d1) are the enlarged images corresponding to (a)–(d).
Figure 2

SEM image at the surface of (a) PZnCS-1 × 1, (b) PZnCS-2 × 2, (c) PZnCS-3 × 3, and (d) PZnCS-4 × 4; (a1)–(d1) are the enlarged images corresponding to (a)–(d).

3.2 Crystalline structure of PLA/PPZn/CSW films

3.2.1 Thermal behavior of PLA/PPZn/CSW films

DSC is used to evaluate the thermal behavior of films, which reflects the formation and development of crystalline structure. Figure 3 shows the DSC curves of PLA and PZnCS films with various stretching ratios. At first sight, distinct cold crystallization peaks are observed in both PLA-1 × 1 and PZnCS-1 × 1, as shown in Figure 3(a) and (b), indicating that the formation of PLA crystals is restrained by the rapid quenching rate in casting. After biaxial stretching, the gradually weakening cold crystallization peaks can be seen in both PLA and PZnCS films as the stretching ratio increases, which suggests the acceleration of the crystallization rate upon stretching. For evaluating crystallization quantitatively, the cold crystallization temperature (T cc), melt temperature (T m), and crystallinity (X c) are listed in Table 1, respectively. Obviously, the value of T cc certainly drops as the stretching ratio increases in both PLA and PZnCS films, which is widely regarded as one of the signals of the improvement in crystallization properties. With regard to the X c value, for PLA films, the slightly increased X c value upon stretching implies the formation of strain-induced crystals with the support of biaxial stretching, which is another remarkable signal of improvement in crystallization properties. And the signal in PZnCS films is more pronounced. As the stretching ratio reaches 3 × 3, the PZnCS films possess a higher X c with a value of 24%, which is 8.49, 4.01, and 2.01 times higher than PLA-1 × 1, PZnCS-1 × 1, and PLA-3 × 3, respectively. The significant increment in crystallinity for PZnCS film is attributed to the incorporation of PPZn and the driven stress of biaxial orientation. As an efficient heterogeneous nucleator, PPZn distributed evenly in the PLA matrix may contribute to improved nucleating efficiency and density, and also promote the perfection of the crystals during biaxial stretching process. The T m value, related to the lamellae thickness, is the indirect evidence to verify the role of PPZn (37). It can be seen that the PZnCS films possess higher T m value than PLA films due to the incorporation of PPZn, indicating the excellent crystallization promotion of PPZn.

Figure 3 DSC curves of (a) PLA and (b) PZnCS films.
Figure 3

DSC curves of (a) PLA and (b) PZnCS films.

Table 1

Crystallization parameters of PLA and PZnCS films

Samples T cc (°C) T m (°C) X c (%)
PLA-1 × 1 107 148 3
PLA-2 × 2 89 151 14
PLA-3 × 3 78 151 12
PZnCS-1 × 1 99 154 6
PZnCS-2 × 2 93 154 8
PZnCS-3 × 3 83 153 24
PZnCS-4 × 4 81 152 26

3.2.2 Crystalline structure evolution of PLA/PPZn/CSW films

Figure 4 depicts the representative 2D-WAXS patterns of PLA and PZnCS films to further reveal their evolution of crystalline structure in the process of biaxial stretching. Compared with the diffuse signals for PLA-1 × 1, PZnCS-1 × 1 signals exhibit weak scattering ring, implying the superior potential in crystallization of PPZn. After biaxial stretching, the PZnCS films are expected to promote the formation of more perfect PLA crystals, exhibiting uniform multiple scattering rings. However, the non-uniform and weak rings can be observed in PLA films. For evaluating crystal structure and average size of crystal domain (L hkl ) quantitatively, the 1D-WAXS curves of PLA and PZnCS films integrated circularly from the corresponding 2D-WAXS patterns are shown in Figure 5. And the corresponding Herman’s orientation function and average size of crystal dominant are also plotted in Figure 6(a) and (b), respectively. It is clearly found that two strong scattering peaks after biaxial stretching appear at 16.4° and 18.7° in both PLA and PZnCS films, representing (200)/(110) and (203) reflection of the PLA δ-form crystals (28). PLA δ-form crystals mainly come from strain-induced crystallization by biaxial stretching as the stretching is applied near the glass transition temperature (T g). For PLA films shown in Figure 5(a), as the ratio further rises to 3 × 3, the peak assigned to the (200/110) reflection becomes broader, and the peak assigned to the (203) reflection almost disappears. Combining with the results of DSC and WAXS (Figures 3(a) and 6(a)), the splitting melt crystallization peak and the decreasing degree of lamellae orientation in PLA-3 × 3 occur at the same time, which further verifies that the highly biaxial stress possesses the potential to damage the crystal structure. As for PZnCS films, the intensity of the two peaks assigned to (200/110) and (203) reflection and the corresponding lamellae orientation increase with the stretching ratios. Although the stretching ratio is as high as 4 × 4, the intensity of PZnCS has not deteriorated, and more perfect PLA crystals are formed with a larger L khl value of 13.6 nm than PLA films. These results indicate that the degree of strain-induced crystallization and the perfection of crystal are effectively maintained in high stretching ratios. That is to say, the incorporation of PPZn and CSW relieves the crystalline structure deterioration resulting from biaxial stretching. And the synergistic effect of biaxial stretching, PPZn, and CSW effectively maintains the perfection of crystals and accelerate the crystallization rate of PLA crystals. Interestingly, two additional scattering peaks in PZnCS films are observed at 14.5° and 25.6°, empirically assigning to (010) and (206) reflections of PLA α-form crystals (17,38). The formation of PLA α-form crystals is attributed to PPZn, but the development of that is affected by biaxial stretching. With the increase in stretching ratio, the intensity of the scattering peak at 25.6° assigned to (206) gradually drops, while that at 14.5° assigned to (010) effectively augments. As reported in the literature, it is hard to induce PLA α-form crystals except the crystallization temperature exceeding 120°C (39,40). With the assistance of extensional stress, the well-dispersed PPZn in the matrix of PLA exerts its effectiveness by attracting PLA chains to epitaxially crystallize on its surface, thereby enhancing the diffraction intensity of (010) reflection (17). There is no exact reason to explain why the diffraction intensity of (206) reflection reduces with the stretching ratio increasing, and a speculative viewpoint is that steady (206) reflection transforms into metastable δ-form crystal reflection. More in-depth experiments will be conducted to verify this viewpoint in a future study.

Figure 4 Representative 2D-WAXS patterns of PLA and PZnCS films with various stretching ratios.
Figure 4

Representative 2D-WAXS patterns of PLA and PZnCS films with various stretching ratios.

Figure 5 Representative 1D-WAXS intensity profiles of (a) PLA and (b) PZnCS films with various stretching ratios.
Figure 5

Representative 1D-WAXS intensity profiles of (a) PLA and (b) PZnCS films with various stretching ratios.

Figure 6 (a) Herman’s orientation function and (b) average size of crystal associated with the PLA (200/110) reflection in both PLA and PZnCS films.
Figure 6

(a) Herman’s orientation function and (b) average size of crystal associated with the PLA (200/110) reflection in both PLA and PZnCS films.

Except for the α- and δ-form crystals, the incomplete mesophase is also found in DSC curves of PLA and PZnCS films after the glass transition. The mesophase is an intermediate phase between amorphous and crystal, which is considered as the relaxation of pre-order chains. A similar phenomenon has been found by Jariyasakoolroj et al. (28). For the sake of describing the transformation from mesophase to crystals clearly, the FTIR technique is used to characterize the developed regularization in PLA and PZnCS films. Similar to Chen et al. (27), the important characteristic IR peaks of α- and/or δ-form crystals, the amorphous phase, and the mesophase of PLA are identified at 921 cm−1, 918 cm−1, and 958 cm−1, respectively. Figure 7 shows the amorphous phase peak at 958 cm−1, which gradually decreases with the increase in stretching ratios. The band at 918 cm−1 is detected in PLA-1 × 1 and PZnCS-1 × 1, indicating that mesophase exists with little crystal. The band at 921 cm−1 appears in PZnCS-3 × 3 and PZnCS-4 × 4, dominating with crystal. The band in the range of 918–921 cm−1 is to be reflected in PLA-2 × 2, PLA-3 × 3, and PZnCS-2 × 2. Clearly, mesophase, the precursor crystal, is observed to exist at a low stretching ratio before transforming into crystal at relatively high stretching ratios. This fact can be used to explain the phenomenon that the temperature of the mesophase in the DSC experiment monotonically increases with the stretching ratios. The transformation from the mesophase to crystal mainly occurs in the stretching ratio from 2 × 2 to 3 × 3. The presence of the mesophase and the crystal manifest that the random PLA chains in the amorphous region are rearranged to the ordered structures. However, it is difficult to distinguish the mass fraction between mesophase and crystal because of the object peak merging with 918 cm−1 and 921 cm−1. This probably originates from strain-induced crystallization along with transformation between mesophase and crystal, and there is an undetectable electron density contrast between them by FTIR (26). Herein, for evaluating the microstructure quantitatively, the 1D-WAXS curves is separated into amorphous, mesophase, and crystal fractions using a multiple peak-fitting method (illustrated in Figure S1). According to the calculation of the peak area, the mass fractions, including amorphous, mesophase, and crystal, of PLA and PZnCS films are illustrated in Figure 8. The amorphous fraction drops and the crystal fraction rises significantly in both PLA and PZnCS films as the stretching ratio increases. The variation of X c value calculated by WAXS is consistent with that calculated by DSC, but the value is different. It can be explained by the fact that the crystal transformed by thermodynamically unstable mesophase is counted in the heating process of DSC measurement, leading to higher X c values calculated by DSC. As for mesophase, a sharp rise in PLA and PZnCS films is observed when the stretching ratio reaches 2 × 2. As the stretching ratio further increases to 3 × 3, the mesophase fraction in PZnCS films visibly decreases from 0.24 to 0.14; meanwhile, the crystal fraction obviously increases from 0.05 to 0.18. It can be attributed to the transition of the thermodynamically unstable mesophase into crystals associated with the enhancement of regularization at high stretching ratios. There is little increase in the mesophase and crystal fraction of PLA-3 × 3, probably related to the chain slipping and the crystal rupture. Consequently, the significant increment of mesophase and its successful transition with crystal reveal that the random chains in amorphous regions rearrange into orderly structure, and confirm the excellent strain-induced crystallization by the coupling of biaxial stretching, PPZn, and CSW.

Figure 7 FTIR spectra of (a) PLA and (b) PZnCS films with varied biaxial stretching ratios.
Figure 7

FTIR spectra of (a) PLA and (b) PZnCS films with varied biaxial stretching ratios.

Figure 8 Amorphous, mesophase, and crystal fractions of (a) PLA and (b) PZnCS films.
Figure 8

Amorphous, mesophase, and crystal fractions of (a) PLA and (b) PZnCS films.

Besides, SAXS is performed to acquire more information that is absent in WAXS and DSC analyses. Figure S2 depicts the representative 2D-SAXS patterns and corresponding 1D-SAXS curves of PLA and PZnCS films in the process of biaxial stretching. No obvious scattering signal is captured probably originating from the tiny crystal and an undetectable electron density contrast exists between the amorphous and crystalline phases. Figure 9 plots the long period (L p), amorphous layer thickness (L a), and lamellar thickness (L c) of PLA and PZnCS films through the electron density correlation function K(z) intensity. Compared with PLA films, PZnCS films exhibit a larger L p and L c value during the biaxial stretching process. A viewpoint that causes this phenomenon is that lattice densification of PLA crystal is restricted by PPZn. On the basis of the special mode of epitaxial crystallization, α-form crystal can be induced on the surface of PPZn that acts as a “sandwich” and expands the spacing between crystals (17). With the assistance of PPZn, obvious values of L p and L c exist in PZnCS films. The high L c value obtained in PZnCS film endows PLA with thick lamellar, leading to higher T m than PLA films, as mentioned in Section 3.2.1.

Figure 9 Electron density correlation function of (a) PLA and (b) PZnCS films.
Figure 9

Electron density correlation function of (a) PLA and (b) PZnCS films.

It is clearly evident from the aforementioned analyses that the oriented crystalline lamellae are successfully tailored under the coupling of biaxial stretching, PPZn, and CSW. The combination of epitaxial crystallization and strain-induced crystallization facilitates the polymorphic crystalline lamellae consisting of α-/δ-form crystals and mesophase, which can serve as “nano-walls” for further enhancing the properties.

3.3 Amorphous phase of PLA/PPZn/CSW films

Except for the structural evolution of the crystalline structure, it is also critical for the amorphous phase to assess the chain orientation and entanglement during the biaxial stretching process qualitatively. The orientation functions of the chain axis are calculated through the polarized FTIR spectrum (shown in Figure S3), and the corresponding f values for PLA and PZnCS films are summarized in Table 2. As expected, for both PLA and PZnCS films, the chain axis progressively orients along the MT plane with the increase of stretching ratios. Note that under the same stretching ratios, the orientation functions are slightly different between two films, and a particularly higher and more isotropic chain orientation is obtained for PZnCS films. It can provide a reasonable explanation for the anisotropic 2D-WAXS patterns of PLA films. The fast and isotropic orientation kinetic observed for PZnCS films could be ascribed to the coupling of biaxial stretching, PPZn, and CSW. Certainly, the fine α-/δ-form crystals and CSW can be considered as physical entanglement points that promote chain orientation by restricting the mobility of molecular chains.

Table 2

Orientation functions of amorphous chains obtained from the polarized FTIR spectra with band at 956 cm–1

PLA films PLA/PPZn/CSW films
λ f cM f cT f cN λ f cM f cT f cN
2 × 2 0.064 0.130 −0.194 2 × 2 0.032 0.084 −0.116
3 × 3 0.141 0.201 −0.342 3 × 3 0.175 0.181 −0.356
4 × 4 0.221 0.228 −0.449

In addition, the thermal behavior of the two films, shown in Figure 3, indicates that the T g seems to shift to the higher temperature region as the stretching ratio increases. In order to be more accurate, DMA is used to detect the T g signal of PLA and PZnCS films. As shown in Figure 10 and Table 3, the coupling of biaxial stretching, PPZn, and CSW has more significant effect on the glass transition for PLA. With regard to the PZnCS films, a remarkable increase to 78°C in T g signal is observed for PZnCS-2 × 2. With the film further stretched, PZnCS-3 × 3 and PZnCS-4 × 4 are highly sensitive to the biaxial stretching ratios, which display the T g signal of 83°C and 86°C, respectively. It is well known that glass transition extremely relies on the mobility of polymer chains (24). The more energy needs for chain mobility, the higher the T g becomes. The significant increment in T g value means the restriction of the molecular mobility, confirming the fast orientation kinetics of PZnCS films (41). Indeed, more crystals induced by biaxial stretching could endow both PLA and PZnCS films with higher T g, yet the higher crystallinity and finer grains did not bring the hoped-for high T g in PLA-2 × 2. Instead, the PZnCS-2 × 2 with relative lower X c and larger L hkl shows higher T g. It can be inferred that the high T g may be due to the enhancement of chain entanglement brought by fine crystals and CSW. These results are indicative of denser amorphous PLA chain entanglement network constructed by coupling of biaxial stretching, PPZn, and CSW. Need to add that, the PLA/PPZn films exhibit a relatively low T g signal, as shown in Figure S4, indicating that CSW also plays a crucial role in the chain entanglement network of PZnCS films. The inorganic fillers CSW and the fine crystals playing crosslinking points in PLA effectively constrain the mobility of PLA chains to some extent and slow down the disentangle rate of chains in the process of biaxial stretching. Besides, the robust chain entanglement network in PZnCS films plays critical roles in maintaining the perfection of crystals as the high stretching ratio is applied because of the reinforcement of the coupling of the crystalline phase with the amorphous phase. Consequently, as both films are stretched at the same condition, the molecular chains of PZnCS films can be expected to possess robust chain entanglement network, which may explain the observed faster orientation kinetics and slower chain mobility.

Figure 10 Tan delta of (a) PLA and (b) PZnCS films.
Figure 10

Tan delta of (a) PLA and (b) PZnCS films.

Table 3

Structural parameter in amorphous region of PLA and PZnCS films, including T g-DMA, X MAF, and X RAF, summarized from DMA and TMDSC results

Samples T g-DMA (°C) X MAF (%) X RAF (%)
PLA-1 × 1 72 95 2
PLA-2 × 2 73 70 16
PLA-3 × 3 82 62 26
PZnCS-1 × 1 73 93 1
PZnCS-2 × 2 78 72 21
PZnCS-3 × 3 83 55 22
PZnCS-4 × 4 86 51 24

To clearly reveal the evolution of chain entanglement network, TMDSC is characterized to separate the reversible and non-reversible heat flows that overlap around the glass transition region in the standard DSC. The reversible heat capacity (C p) curves of PLA and PZnCS films are illustrated in Figure 11(a) and (b), respectively. It can be seen that PZnCS films exhibit higher T g and widener glass transition. The phenomenon is that relatively widening relaxation time distribution of chains probably originates from lessening in mobile molecular chain content and nonhomogeneous mobility of amorphous chains (18). Nonhomogeneous mobility of amorphous chains is restricted by the order chain entanglement network and ordered structure. For PZnCS stretched films, C p signal remains stable with no sharp drop after finishing the glass transition compared with PLA films. It is attributed to the fast crystallization rate and the perfection of crystal with the coupling of biaxial process, PPZn, and CSW. Besides, the non-reversible heat flow curves of PLA and PZnCS films are displayed in Figure 11(c) and (d), respectively. Endothermic peaks (chain relaxation peaks) and exothermic peaks (cold crystallization peak) are observed in the non-reversible heat flow of PLA and PZnCS films. The endothermic peaks shift to higher temperature as the stretching ratios increase, indicating that the chain entanglement network is reinforced during the biaxial stretching process. Based on the three-phase model, the molecular chain is divided into crystal phase, mobile amorphous phase (MAF), and rigid amorphous phase (RAF). The X MAF and X RAF of PLA and PZnCS films are summarized in Table 3. The X MAF values are determined as 93% of PZnCS-1 × 1 and 51% of PZnCS-4 × 4, 95% of PLA-1 × 1, and 62% of PLA-3 × 3. Most MAF chains are consumed and become constrained in the process of biaxial stretching. Correspondingly, X RAF values of PZnCS and PLA films gradually increase from 1% to 24% and from 2% to 26%, respectively. The increase of RAF fraction is favorable to construct robust amorphous chain entanglement network in the process of biaxial stretching. PPZn and CSW under the biaxial stretching possess huge potentials for accelerating the decrease of mobile molecular chains and strength in the degree of chain entanglement, exerting their effectiveness by inducing fine crystals and crosslinking.

Figure 11 TMDSC reversible heat capacity curves and non-reversible heat flow curves for (a, c) the PLA films and (b, d) PZnCS films, respectively.
Figure 11

TMDSC reversible heat capacity curves and non-reversible heat flow curves for (a, c) the PLA films and (b, d) PZnCS films, respectively.

A robust amorphous chain entanglement network is established by internal effects and extensional stress. Well-dispersed PPZn and CSW exert their “being entangled” advantage in the PLA matrix internal by their micro-nanostructure and crystal induced. Biaxial stretching makes full use of strong orientation extensional stress to form the strain-induced crystallization and enhance the entanglement between solid matter (PPZn, CSW, and crystal) and chains. A robust chain network realized in multiple dimensions effectively stimulates the formation and perfection of crystals without fracture in the process of biaxial stretching, making it possible for PLA to possess high mechanical and barrier properties.

3.4 Comprehensive performance of PLA/PPZn/CSW films

3.4.1 Mechanical property

It is crucial for packaging materials to be endowed with high strength and ductility. As discussed earlier, the crystalline and amorphous structures of PLA and PZnCS films with various stretching ratios are differential, which probably has an impact on the mechanical property. The detailed mechanical performances, including modulus, tensile strength, and elongation at break, are depicted in Figure 12. To be specific, Figure 12(a) and (b) displays the typical stress–strain curves for one of the five parallel samples, and Figure 12(c) and (d) displays the average mechanical properties results with five parallel tests of all samples.

Figure 12 Typical strain–stress curves of (a) PLA and (b) PZnCS films, (c) modulus, and (d) the average tensile strength and elongation at break for both PLA and PZnCS films.
Figure 12

Typical strain–stress curves of (a) PLA and (b) PZnCS films, (c) modulus, and (d) the average tensile strength and elongation at break for both PLA and PZnCS films.

As shown in Figure 12(a) and (b), PLA-1 × 1 and PZnCS-1 × 1 show a typical brittle facture behavior with elongation at break and strength less than 5% and 60 MPa, respectively. This phenomenon originates from the low crystallinity of the PLA matrix and the agglomeration particles of PPZn and CSW in unstretched film. Surprisingly, the brittle-to-ductile transition occurs in the process of biaxial stretching with a simultaneous enhancement in strength and ductility. PLA and PZnCS stretched films show great advantage in the viscoelastic stage at low strains and yield stages, exhibiting high-level modulus and strength. What is more, PLA-2 × 2, PZnCS-2 × 2, and PZnCS-3 × 3 all exhibit a rubbery material-like behavior, displaying a relative long plateau after yielding. The long plateau, induced by strain softening, reveals the superior ductility of materials via the biaxial stretching process. Specifically speaking, as shown in Figure 12(c) and (d), the average tensile strength rises from 55.8 MPa to 73.8 MPa and 66.6 MPa for PLA-2 × 2 and PLA-3 × 3, and from 59.2 to 55.3 MPa, 81.2 MPa, and 85.5 MPa for the PZnCS-2 × 2, PZnCS-3 × 3, and PZnCS-4 × 4. And the average modulus increases by 9.6% and 19.4% for PLA-2 × 2 and PLA-3 × 3, and by 5.2%, 75.9%, and 98.0% for PZnCS-2 × 2, PZnCS-3 × 3, and PZnCS-4 × 4, respectively. The oriented amorphous phase and more perfect crystallite in the process of biaxial stretching make conspicuous contributions to the increased strength and modulus. Even more interesting is that a simultaneous improvement in mechanical ductility is observed. The average elongation at break of PLA-2 × 2 and PZnCS-2 × 2 is as high as 12.29% and 22.48%, increased by 163.11% and 519.28% relative to PLA-1 × 1 and PZnCS-1 × 1, respectively. The superior ductility of films is mainly attributed to the amorphous chain entanglement network in amorphous regions. The strain-induced crystals formed by biaxial stretching and the additives (CSW and PPZn) can serve as physical crosslinking points to restrict the mobility of PLA chains and greatly maintain the robust network of amorphous chains formed during the biaxial stretching process (42,43,44). With the support of entangled chain network, when a highly entangled PLA is stretched during tensile tests, before a chain breaks, external stress transmits along the chain and to many other chains through entanglements. When the chain breaks at a single covalent bond, the PLA dissipates the elastic energy in many chains over long lengths, thus achieving high ductility. It is worth noting that the yield strength and ductility of PZnCS films are enhanced significantly compared to traditional cast PLA films. Therefore, the incorporation of PPZn and CSW with the support of biaxial stretching is considered as a prospective strategy for manipulating the crystalline and amorphous regularization of PLA, thus achieving the goal of strengthening and toughening simultaneously.

3.4.2 Barrier property

Figure 13 summarizes the oxygen permeability (OP) and water vapor permeability (WVP) of PLA and PZnCS films. A remarkable decrease of OP and WVP value of PZnCS films with the increase of stretching ratio was observed. Specifically, the OP value of PLA-1 × 1 and PZnCS-1 × 1 is only 11.75 × 10−15 and 10.98 × 10−15 cm3·cm·(cm−2·s−1·Pa−1), respectively. After biaxial stretching, PLA films exhibit non-monotone change value of OP, i.e., decrease then increase. However, a gradually decreased OP of PZnCS films is achieved with increasing stretching ratio. As the stretching ratio rises up to 4 × 4, PZnCS film shows the OP value of 3.16 × 10−15 cm3·cm·(cm−2·s−1·Pa−1), reduced by 73.11% and 71.22% relative to PLA-1 × 1 and PZnCS-1 × 1, respectively. The oxygen barrier properties of PZnCS films are prominent and comparable to those of PET films and are superior to those of PLA-based films (such as PLA/graphene oxide nanosheet films, PLA/PBAT/montmorillonite films) reported in the literature (24,45,46,47). Moreover, with the increase stretching ratio, the WVP value of PLA and PZnCS films is decreased gradually. Due to the hygroscopicity of CSW, the PZnCS films at lower stretching ratios possess higher WVP value than PLA films. As the higher stretching ratio is applied, PZnCS films exhibit excellent water barrier properties. Specifically, compared with PLA-1 × 1, the WVP value of PZnCS-3 × 3 and PZnCS-4 × 4 is 8.48 × 10−14 and 4.70 × 10−14 g·cm·(cm−2·s−1·Pa−1), reduced 37.56% and 65.39%, respectively. Under the coupling of biaxial stretching, PPZn, and CSW, the PZnCS films are prominent in their barrier properties. Considering the microstructural evolution of PZnCS films, two main reasons for the significant improvement of PZnCS films can be inferred. First, the oriented structure consisting of fine crystals and highly dispersed PPZn and CSW serves as “nano-walls” to compel diffusing molecules to permeate through the PZnCS films along the longer and more tortuous pathways. Second, the tighter molecular packing of PLA chain in the α-form modification and denser chain entanglement network diminishes the free volume and reinforces the coupling with the crystalline structure, may reduce molecular diffusion through PZnCS films (18).

Figure 13 (a) OP and (b) WVP of PLA and PZnCS films.
Figure 13

(a) OP and (b) WVP of PLA and PZnCS films.

3.4.3 Optical property

The optical properties, including haze and transmittance, are summarized in Figure S5. In order to eliminate the effect of thickness on optical properties, the haze of unit thickness (h) and absorbance coefficient of light (α) are calculated, and the variation is plotted in Figure 14. Obviously, as shown in Figure 14(a) and (b), the values of h and α increase as the stretching ratio increases, indicating that highly dispersed fine crystals induced by biaxial stretching result in the enhancement of haze and transmittance. Compared to PLA films, PZnCS possesses more noticeable h values and relatively lower α values due to its rough surface and “nano-walls” existing. As shown in Figure 14(c), PZnCS-3 × 3 exhibits a rough surface that disperses the crystals, PPZn, and CSW, which leads to diffuse reflection on the surface of the film and hinders light transmission (48). This phenomenon provides a reasonable explanation for the high h value and low α value of the films obtained by coupling of biaxial stretching, PPZn, and CSW.

Figure 14 (a) Haze of unit thickness, (b) absorbance coefficient of PLA and PZnCS films with various stretching ratios, and (c) the AFM images of PZnCS-3 × 3.
Figure 14

(a) Haze of unit thickness, (b) absorbance coefficient of PLA and PZnCS films with various stretching ratios, and (c) the AFM images of PZnCS-3 × 3.

3.5 Comprehensive analysis of PZnCS films

Currently, the plastic packaging materials, such as biaxial oriented poly(ethylene terephthalate) (BOPET) (46), biaxial oriented polypropylene (BOPP) (49), polyethylene (PE) (50), commonly used on the market, have some obvious shortcomings. For example, BOPP and PE possess excellent ductility and water vapor barrier properties but poor oxygen barrier properties. The ductility and water vapor barrier properties of BOPET are not satisfactory. Compared with that, the PZnCS films shows excellent comprehensive properties, such as superior gas barrier properties, balanced mechanical performance, and good transparency. A performance polygon is depicted to clarify the excellent properties of PZnCS films clearly, as seen in Figure 15. It is a quantitative index for polygon area to assess the macroscopic properties, such as tensile strength, ductility, gas barrier property, water vapor barrier property, and haze. It can be seen that PLA-1 × 1 has the lowest area with high brittleness, relative low strength, and poor barrier property. With the assistance of PPZn, CSW, and biaxial stretching, a remarkable enhancement in polygon area is obtained, followed by enhancements in tensile strength, ductility, barrier property, and haze in PZnCS films. These results demonstrate that the proposed methodology is simple and effective to significantly improve the properties of PLA, permitting it to serve as packaging materials for products, buildings, and so on.

Figure 15 Performance polygon to evaluate the comprehensive properties of PLA and PZnCS films in terms of tensile strength, modulus, ductility, haze, and transmittance.
Figure 15

Performance polygon to evaluate the comprehensive properties of PLA and PZnCS films in terms of tensile strength, modulus, ductility, haze, and transmittance.

The improved performance is derived from the changed microstructure. In general, the structure of PLA has not undergone positive evolution without the support of PPZn, CSW, and biaxial stretching. PPZn is an efficient epitaxial nucleator to induce ordered α-form crystals. CSW is the crosslinking unit that acts as supporting skeletons and makes molecular chains entangle. What is more important is that the essential factor is the extensional stress induced by the biaxial stretching technology for PPZn and CSW to be able to fulfill their roles. With the support of biaxial stretching, PPZn and CSW can be evenly dispersed in the PLA matrix. And the highly oriented amorphous chain and crystalline lamellae can be regulated in harmony with the dense chain network. Therefore, under the coupling of biaxial stretching, PPZn, and CSW, the “nano-walls” and robust chain entanglement network are successfully constructed in the PLA matrix. To be specific, the “nano-walls” consist of highly dispersed PPZn, CSW, and isotropous crystalline lamellae. The isotropous crystalline lamellae, including strain-induced δ-form lamellae and epitaxial-induced α-form lamellae, are highly parallel along the stretching direction and maintain stability and perfection even at high stretching ratios. On the other hand, the chain orientation and dense chain entanglement network are reinforced since the “nano-walls” serving as physical entanglement points restrict molecular mobility. The highly oriented chain network enhances the coupling with crystalline lamellae and exerts their effectiveness to restrict the deformation of amorphous chains and preserve the perfection of crystals during the process of biaxial stretching. Consequently, with the coupling effect, the microstructure of PLA has evolved toward ordering, which plays a pivotal role in the improvement of properties. The uniform distribution of stress and strain, tortuous permeability pathway, and intensified light diffuse reflection effectively improve the mechanical, barrier, and optical properties of PLA films. This coupling provides a different perspective for developing high-performance biodegradable packaging materials and enlarging the applicable area.

4 Conclusions

A new strategy to make PLA with superior mechanical, barrier, and optical properties is proposed by constructing “nano-walls” and regulating the highly oriented chain entanglement network with coupling of biaxial stretching, PPZn, and CSW. Upon biaxial stretching, the “nano-walls,” which are composed of PPZn, CSW, and well-defined α-/δ-form crystals with crystallinity of 26%, are constructed to reinforce the tensile strength and modulus with an increase of 53.2% and 91.3%, respectively, compared to pure PLA. The dense chain entanglement network with fast orientation kinetics is also induced by biaxial stretching with the aid of crosslinking by the “nano-walls,” imparting a significant strain softening for PLA. An impressive elongation at break of 22.48% is achieved, which is around 4.8 times higher than that of the pure PLA. Besides, the combination of “nano-walls” and chain entanglement network allows for excellent barrier and optical properties. The gas permeability and water vapor permeability of PZnCS films reach 3.16 × 10−15 cm3·cm·(cm−2·s−1·Pa−1) and 4.70 × g·cm·(cm−2·s−1·Pa−1), respectively, which are 65.39% and 73.11% lower than pure PLA. And PZnCS films also possess superior haze and good transmittance. Therefore, this work exhibits a remarkable coupling effect of biaxial stretching, PPZn, and CSW, providing a new strategy to approach high-performance PZnCS films with a wider potential application range.

  1. Funding information: This work was financially supported by the National Nature Science Foundation of China (Grant No. 12372245), Education Department of Hunan Province (Grant No. 22B0595).

  2. Author contributions: Shi-Juan Ding: conceptualization, methodology, investigation, writing-original draft. Ling-Na Cui: formal analysis, validation, writing-reviewing and editing. Yue-Jun Liu: writing-reviewing and editing, funding acquisition, supervision, project administration.

  3. Conflict of interest: The authors state no conflict of interest. The authors declare no competing financial interest.

  4. Data availability statement: The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.

  5. Supplementary data: Supplementary data to this article can be found in the file of Supporting information.

References

(1) Li W, Liu Q, Zhang Y, Li C, He Z, Choy WCH, et al. Biodegradable materials and green processing for green electronics. Adv Mater. 2020;32(33):2001591.10.1002/adma.202001591Suche in Google Scholar PubMed

(2) Zambrano-Monserrate MA, Alejandra Ruano M. Do you need a bag? Analyzing the consumption behavior of plastic bags of households in Ecuador. Resour Conserv Recycling. 2020;152:104489.10.1016/j.resconrec.2019.104489Suche in Google Scholar

(3) Hamad K, Kaseem M, Ayyoob M, Joo J, Deri F. Polylactic acid blends: The future of green, light and tough. Prog Polym Sci. 2018;85:83–127.10.1016/j.progpolymsci.2018.07.001Suche in Google Scholar

(4) Ali W, Ali H, Gillani S, Zinck P, Souissi S. Polylactic acid synthesis, biodegradability, conversion to microplastics and toxicity: A review. Environ Chem Lett. 2023;21(3):1761–86.10.1007/s10311-023-01564-8Suche in Google Scholar

(5) Sun C, Wei S, Tan H, Huang Y, Zhang Y. Progress in upcycling polylactic acid waste as an alternative carbon source: A review. Chem Eng J. 2022;446:136881.10.1016/j.cej.2022.136881Suche in Google Scholar

(6) Li Z, Ye L, Zhao X, Coates P, Caton-Rose F, Martyn M. Structure and biocompatibility of highly oriented poly(lactic acid) film produced by biaxial solid hot stretching. J Ind Eng Chem. 2017;52:338–48.10.1016/j.jiec.2017.04.008Suche in Google Scholar

(7) Zhao X, Liu J, Li J, Liang X, Zhou W, Peng S. Strategies and techniques for improving heat resistance and mechanical performances of poly(lactic acid) (PLA) biodegradable materials. Int J Biol Macromolecules. 2022;218:115–34.10.1016/j.ijbiomac.2022.07.091Suche in Google Scholar PubMed

(8) Sarul DS, Arslan D, Vatansever E, Kahraman Y, Durmus A, Salehiyan R, et al. Preparation and characterization of PLA/PBAT/CNC blend nanocomposites. Colloid Polym Sci. 2021;299(6):987–98.10.1007/s00396-021-04822-9Suche in Google Scholar

(9) Niu D, Shen T, Xu P, Yu M, Liu T, Yang W, et al. Enhanced crystallization, heat resistance and transparency of poly(lactic acid) with self-assembling bis-amide nucleator. Int J Biol Macromol. 2023;234:123584.10.1016/j.ijbiomac.2023.123584Suche in Google Scholar PubMed

(10) Xia X, Shi X, Liu W, Zhao H, Li H, Zhang Y. Effect of flax fiber content on polylactic acid (PLA) crystallization in PLA/flax fiber composites. Iran Polym J. 2017;26(9):693–702.10.1007/s13726-017-0554-9Suche in Google Scholar

(11) Banpean A, Hararak B, Winotapun C, Wijaranakul P, Kitchaicharoenporn S, Naimlang S. Lignin nanoparticles as sustainable biobased nucleating agents of poly(L-lactic acid): Crystallization behavior and effect of particle sizes. J Mater Sci. 2023;58(15):6823–38.10.1007/s10853-023-08418-2Suche in Google Scholar

(12) Qin C, Chen K, Xu R, Wang Y. Nucleating effect of boron nitride nanotubes on poly(lactic acid) crystallization. Colloid Polym Sci. 2022;300(7):775–84.10.1007/s00396-022-04986-ySuche in Google Scholar

(13) Li C, Jiang T, Wang J, Peng S, Wu H, Shen J, et al. Enhancing the oxygen-barrier properties of polylactide by tailoring the arrangement of crystalline lamellae. ACS Sustain Chem Eng. 2018;6(5):6247–55.10.1021/acssuschemeng.8b00026Suche in Google Scholar

(14) Chen Q, Auras R, Corredig M, Kirkensgaard J, Mamakhel A, Uysal-Unalan I. New opportunities for sustainable bioplastic development: Tailorable polymorphic and three-phase crystallization of stereocomplex polylactide by layered double hydroxide. Int J Biol Macromol. 2022;222:1101–9.10.1016/j.ijbiomac.2022.09.205Suche in Google Scholar PubMed

(15) Yang T-C, Hung K-C, Wu T-L, Wu TM, Wu JH. A comparison of annealing process and nucleating agent (zinc phenylphosphonate) on the crystallization, viscoelasticity, and creep behavior of compression-molded poly(lactic acid) blends. Polym Degrad Stab. 2015;121:230–7.10.1016/j.polymdegradstab.2015.09.012Suche in Google Scholar

(16) Wu N, Wang H. Effect of zinc phenylphosphonate on the crystallization behavior of poly(l-lactide). J Appl Polym Sci. 2013;130(4):2744–52.10.1002/app.39471Suche in Google Scholar

(17) Pan P, Liang Z, Cao A, Inoue Y. Layered metal phosphonate reinforced poly(l-lactide) composites with a highly enhanced crystallization rate. ACS Appl Mater Interfaces. 2009;1(2):402–11.10.1021/am800106fSuche in Google Scholar PubMed

(18) Delpouve N, Stoclet G, Saiter A, Dargent E, Marais S. Water barrier properties in biaxially drawn poly(lactic acid) films. J Phys Chem B. 2012;116(15):4615–25.10.1021/jp211670gSuche in Google Scholar PubMed

(19) Wu F, Lan X, Ji D, Liu Z, Yang W, Yang M. Grafting polymerization of polylactic acid on the surface of nano-SiO2 and properties of PLA/PLA-grafted-SiO2 nanocomposites. J Appl Polym. 2013;129(5):3019–27.10.1002/app.38585Suche in Google Scholar

(20) Lovinčić Milovanović V, Hajdinjak I, Lovriša I, Vrsaljko D. The influence of the dispersed phase on the morphology, mechanical and thermal properties of PLA/PE-LD and PLA/PE-HD polymer blends and their nanocomposites with TiO2 and CaCO3. Polym Eng Sci. 2019;59(7):1395–408.10.1002/pen.25124Suche in Google Scholar

(21) Yang J-N, Nie S-B, Zhu J-B. Fabrication and characterization of poly(lactic acid) biocomposites reinforced by calcium sulfate whisker. J Polym Environ. 2018;26(8):3458–69.10.1007/s10924-018-1230-7Suche in Google Scholar

(22) Bai T, Zhu B, Liu H, Wang Y, Song G, Liu C, et al. Biodegradable poly(lactic acid) nanocomposites reinforced and toughened by carbon nanotubes/clay hybrids. Int J Biol Macromol. 2020;151:628–34.10.1016/j.ijbiomac.2020.02.209Suche in Google Scholar PubMed

(23) Zhang W, Chen J, Yan Q, Zhang Q, Zhao J, Wu T, et al. The formation of crystal cross-linked network in sequential biaxial stretching of poly(ethylene terephthalate): The essential role of MD pre-stretch. Polym Test. 2021;96:107143.10.1016/j.polymertesting.2021.107143Suche in Google Scholar

(24) Xu PP, Yang S, Gao XR, Chen SP, Xu L, Zhong GJ, et al. Constructing robust chain entanglement network, well-defined nanosized crystals and highly aligned graphene oxide nanosheets: Towards strong, ductile and high barrier Poly(lactic acid) nanocomposite films for green packaging. Compos Part B: Eng. 2021;222:109048.10.1016/j.compositesb.2021.109048Suche in Google Scholar

(25) Huang T, Miura M, Nobukawa S, Yamaguchi M. Chain packing and its anomalous effect on mechanical toughness for poly(lactic acid). Biomacromolecules. 2015;16(5):1660–6.10.1021/acs.biomac.5b00293Suche in Google Scholar PubMed

(26) Xu S, Tahon JF, De-Waele I, Stoclet G, Gaucher V. Brittle-to-ductile transition of PLA induced by macromolecular orientation. eXPRESS Polym Lett. 2020;14(11):1037–47.10.3144/expresspolymlett.2020.84Suche in Google Scholar

(27) Chen Y, Han L, Ju D, Liu T, Dong L. Disentanglement induced by uniaxial pre-stretching as a key factor for toughening poly(l-lactic acid) sheets. Polymer. 2018;140:47–55.10.1016/j.polymer.2018.02.032Suche in Google Scholar

(28) Jariyasakoolroj P, Tashiro K, Wang H, Yamamoto H, Chinsirikul W, Kerddonfag N, et al. Isotropically small crystalline lamellae induced by high biaxial-stretching rate as a key microstructure for super-tough polylactide film. Polymer. 2015;68:234–45.10.1016/j.polymer.2015.05.006Suche in Google Scholar

(29) Tsuji H, Ikada Y. Properties and morphologies of poly(l-lactide): 1. Annealing condition effects on properties and morphologies of poly(l-lactide). Polymer. 1995;36(14):2709–16.10.1016/0032-3861(95)93647-5Suche in Google Scholar

(30) Zuza E, Ugartemendia JM, Lopez A, Meaurio E, Lejardi A, Sarasua JR. Glass transition behavior and dynamic fragility in polylactides containing mobile and rigid amorphous fractions. Polymer. 2008;49(20):4427–32.10.1016/j.polymer.2008.08.012Suche in Google Scholar

(31) Zhou S-Y, Huang H-D, Ji X, Yan DX, Zhong GJ, Hsiao BS, et al. Super-robust polylactide barrier films by building densely oriented lamellae incorporated with ductile in situ nanofibrils of poly(butylene adipate-co-terephthalate). ACS Appl Mater Interfaces. 2016;8(12):8096–109.10.1021/acsami.6b00451Suche in Google Scholar PubMed

(32) Huang H, Zhou S, Zhou D, Ren P, Xu J, Ji X, et al. Highly efficient “Composite Barrier Wall” consisting of concentrated graphene oxide nanosheets and impermeable crystalline structure for poly(lactic acid) nanocomposite films. Ind Eng Chem Res. 2016;55(35):9544–54.10.1021/acs.iecr.6b02168Suche in Google Scholar

(33) Yang S, Luo C, Lin H, Xu PP, Xu L, Lei J, et al. Robust propylene-ethylene copolymer/polypropylene films: Extensional stress-induced orientation realized at low temperature processing. Polymer. 2020;206:122848.10.1016/j.polymer.2020.122848Suche in Google Scholar

(34) Cole KC, Depecker C, Jutigny M, Lefebvre JM, Krawczak P. Biaxial deformation of polyamide‐6: Assessment of orientation by means of infrared trichroism. Polym Eng Sci. 2004;44(2):231–40.10.1002/pen.20022Suche in Google Scholar

(35) Zheng C, Yao X, Tang Y, Ren M, Shi H, Zhang T. A new method to calculate the surface haze. J Polym Eng. 2020;40(4):300–6.10.1515/polyeng-2019-0348Suche in Google Scholar

(36) Tüzemen EŞ, Eker S, Kavak H, Esen R. Dependence of film thickness on the structural and optical properties of ZnO thin films. Appl Surf Sci. 2009;255(12):6195–200.10.1016/j.apsusc.2009.01.078Suche in Google Scholar

(37) Zhou H, Wilkes GL. Comparison of lamellar thickness and its distribution determined from d.s.c., SAXS, TEM and AFM for high-density polyethylene films having a stacked lamellar morphology. Polymer. 1997;38(23):5735–47.10.1016/S0032-3861(97)00145-6Suche in Google Scholar

(38) Ou X, Cakmak M. Comparative study on development of structural hierarchy in constrained annealed simultaneous and sequential biaxially stretched polylactic acid films. Polymer. 2010;51(3):783–92.10.1016/j.polymer.2009.11.058Suche in Google Scholar

(39) Tsuji H, Tezuka Y, Saha SK, Suzuki M, Itsuno S. Spherulite growth of l-lactide copolymers: Effects of tacticity and comonomers. Polymer. 2005;46(13):4917–27.10.1016/j.polymer.2005.03.069Suche in Google Scholar

(40) Brás AR, Viciosa MT, Wang Y, Dionísio M, Mano JF. Crystallization of poly(l-lactic acid) probed with dielectric relaxation spectroscopy. Macromolecules. 2006;39(19):6513–20.10.1021/ma061148rSuche in Google Scholar

(41) Delpouve N, Delbreilh L, Stoclet G, Saiter A, Dargent E. Structural dependence of the molecular mobility in the amorphous fractions of polylactide. Macromolecules. 2014;47(15):5186–97.10.1021/ma500839pSuche in Google Scholar

(42) Kim J, Zhang G, Shi M, Suo Z. Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links. Science (New York, NY). 2021;374(6564):212–6.10.1126/science.abg6320Suche in Google Scholar PubMed

(43) Jia D-Z, Ma G-Q, Liu Q, Zhang J, Li JQ, Lin H, et al. Extensional stress-induced ductility of poly(l-lactide) films: Role of the entangled network in amorphous regions. Biomacromolecules. 2023;24(7):3127–37.10.1021/acs.biomac.3c00188Suche in Google Scholar PubMed

(44) Zhang J, Jia D-Z, Ma G-Q, Lin H, Huang HD, Zhong GJ, et al. Mechanically rejuvenated glassy polylactide with spatial heterogeneity and packing efficiency: Time dependence of deformation behavior. Polymer. 2024;298:126876.10.1016/j.polymer.2024.126876Suche in Google Scholar

(45) Gao H, Cao W, He J, Bai Y. Highly transparent biaxially oriented poly (ester amide) film with improved gas barrier properties and good mechanical strength. Eur Polym J. 2021;156:110620.10.1016/j.eurpolymj.2021.110620Suche in Google Scholar

(46) Zekriardehani S, Joshi AS, Jabarin SA, Gidley DW, Coleman MR. Effect of dimethyl terephthalate and dimethyl isophthalate on the free volume and barrier properties of poly (ethylene terephthalate)(PET): amorphous PET. Macromolecules. 2018;51(2):456–67.10.1021/acs.macromol.7b02230Suche in Google Scholar

(47) Ludwiczak J, Frąckowiak S, Leluk K. Study of thermal, mechanical and barrier properties of biodegradable PLA/PBAT films with highly oriented MMT. Materials. 2021;14(23):7189.10.3390/ma14237189Suche in Google Scholar PubMed PubMed Central

(48) Wang L, Kamal MR, Rey AD. Light transmission and haze of polyethylene blown thin films. Polym Eng Sci. 2001;41(2):358–72.10.1002/pen.10734Suche in Google Scholar

(49) Zhang M, Li D, Xu W, Chang H, Liu Q, Fu Y, et al. Crystalline structure and morphology of biaxially oriented polypropylene film under the coexistence of organic silica particles and its influence on the adsorption diffusion of polar solvent molecules. Packag Technol Sci. 2019;32(2):75–84.10.1002/pts.2417Suche in Google Scholar

(50) Bumbudsanpharoke N, Wongphan P, Promhuad K, Leelaphiwat P, Harnkarnsujarit N. Morphology and permeability of bio-based poly(butylene adipate-co-terephthalate) (PBAT), poly(butylene succinate) (PBS) and linear low-density polyethylene (LLDPE) blend films control shelf-life of packaged bread. Food Control. 2022;132:108541.10.1016/j.foodcont.2021.108541Suche in Google Scholar
Received: 2024-03-10
Revised: 2024-04-08
Accepted: 2024-04-10
Published Online: 2024-05-31

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Artikel in diesem Heft

  1. Research Articles
  2. Flame-retardant thermoelectric responsive coating based on poly(3,4-ethylenedioxythiphene) modified metal–organic frameworks
  3. Highly stretchable, durable, and reversibly thermochromic wrapped yarns induced by Joule heating: With an emphasis on parametric study of elastane drafts
  4. Molecular dynamics simulation and experimental study on the mechanical properties of PET nanocomposites filled with CaCO3, SiO2, and POE-g-GMA
  5. Multifunctional hydrogel based on silk fibroin/thermosensitive polymers supporting implant biomaterials in osteomyelitis
  6. Marine antifouling coating based on fluorescent-modified poly(ethylene-co-tetrafluoroethylene) resin
  7. Preparation and application of profiled luminescent polyester fiber with reversible photochromism materials
  8. Determination of pesticide residue in soil samples by molecularly imprinted solid-phase extraction method
  9. The die swell eliminating mechanism of hot air assisted 3D printing of GF/PP and its influence on the product performance
  10. Rheological behavior of particle-filled polymer suspensions and its influence on surface structure of the coated electrodes
  11. The effects of property variation on the dripping behaviour of polymers during UL94 test simulated by particle finite element method
  12. Experimental evaluation on compression-after-impact behavior of perforated sandwich panel comprised of foam core and glass fiber reinforced epoxy hybrid facesheets
  13. Synthesis, characterization and evaluation of a pH-responsive molecular imprinted polymer for Matrine as an intelligent drug delivery system
  14. Twist-related parametric optimization of Joule heating-triggered highly stretchable thermochromic wrapped yarns using technique for order preference by similarity to ideal solution
  15. Comparative analysis of flow factors and crystallinity in conventional extrusion and gas-assisted extrusion
  16. Simulation approach to study kinetic heterogeneity of gadolinium catalytic system in the 1,4-cis-polyisoprene production
  17. Properties of kenaf fiber-reinforced polyamide 6 composites
  18. Cellulose acetate filter rods tuned by surface engineering modification for typical smoke components adsorption
  19. A blue fluorescent waterborne polyurethane-based Zn(ii) complex with antibacterial activity
  20. Experimental investigation on damage mechanism of GFRP laminates embedded with/without steel wire mesh under low-velocity-impact and post-impact tensile loading
  21. Preparation and application research of composites with low vacuum outgassing and excellent electromagnetic sealing performance
  22. Assessing the recycling potential of thermosetting polymer waste in high-density polyethylene composites for safety helmet applications
  23. Mesoscale mechanics investigation of multi-component solid propellant systems
  24. Preparation of HTV silicone rubber with hydrophobic–uvioresistant composite coating and the aging research
  25. Experimental investigation on tensile behavior of CFRP bolted joints subjected to hydrothermal aging
  26. Structure and transition behavior of crosslinked poly(2-(2-methoxyethoxy) ethylmethacrylate-co-(ethyleneglycol) methacrylate) gel film on cellulosic-based flat substrate
  27. Mechanical properties and thermal stability of high-temperature (cooking temperature)-resistant PP/HDPE/POE composites
  28. Preparation of itaconic acid-modified epoxy resins and comparative study on the properties of it and epoxy acrylates
  29. Synthesis and properties of novel degradable polyglycolide-based polyurethanes
  30. Fatigue life prediction method of carbon fiber-reinforced composites
  31. Thermal, morphological, and structural characterization of starch-based bio-polymers for melt spinnability
  32. Robust biaxially stretchable polylactic acid films based on the highly oriented chain network and “nano-walls” containing zinc phenylphosphonate and calcium sulfate whisker: Superior mechanical, barrier, and optical properties
  33. ARGET ATRP of styrene with low catalyst usage in bio-based solvent γ-valerolactone
  34. New PMMA-InP/ZnS nanohybrid coatings for improving the performance of c-Si photovoltaic cells
  35. Impacts of the calcinated clay on structure and gamma-ray shielding capacity of epoxy-based composites
  36. Preparation of cardanol-based curing agent for underwater drainage pipeline repairs
  37. Preparation of lightweight PBS foams with high ductility and impact toughness by foam injection molding
  38. Gamma-ray shielding investigation of nano- and microstructures of SnO on polyester resin composites: Experimental and theoretical study
  39. Experimental study on impact and flexural behaviors of CFRP/aluminum-honeycomb sandwich panel
  40. Normal-hexane treatment on PET-based waste fiber depolymerization process
  41. Effect of tannic acid chelating treatment on thermo-oxidative aging property of natural rubber
  42. Design, synthesis, and characterization of novel copolymer gel particles for water-plugging applications
  43. Influence of 1,1′-Azobis(cyclohexanezonitrile) on the thermo-oxidative aging performance of diolefin elastomers
  44. Characteristics of cellulose nanofibril films prepared by liquid- and gas-phase esterification processes
  45. Investigation on the biaxial stretching deformation mechanism of PA6 film based on finite element method
  46. Simultaneous effects of temperature and backbone length on static and dynamic properties of high-density polyethylene-1-butene copolymer melt: Equilibrium molecular dynamics approach
  47. Research on microscopic structure–activity relationship of AP particle–matrix interface in HTPB propellant
  48. Three-layered films enable efficient passive radiation cooling of buildings
  49. Electrospun nanofibers membranes of La(OH)3/PAN as a versatile adsorbent for fluoride remediation: Performance and mechanisms
  50. Preparation and characterization of biodegradable polyester fibers enhanced with antibacterial and antiviral organic composites
  51. Preparation of hydrophobic silicone rubber composite insulators and the research of anti-aging performance
  52. Surface modification of sepiolite and its application in one-component silicone potting adhesive
  53. Study on hydrophobicity and aging characteristics of epoxy resin modified with nano-MgO
  54. Optimization of baffle’s height in an asymmetric twin-screw extruder using the response surface model
  55. Effect of surface treatment of nickel-coated graphite on conductive rubber
  56. Experimental investigation on low-velocity impact and compression after impact behaviors of GFRP laminates with steel mesh reinforced
  57. Development and characterization of acetylated and acetylated surface-modified tapioca starches as a carrier material for linalool
  58. Investigation of the compaction density of electromagnetic moulding of poly(ether-ketone-ketone) polymer powder
  59. Experimental investigation on low-velocity-impact and post-impact-tension behaviors of GFRP T-joints after hydrothermal aging
  60. The repeated low-velocity impact response and damage accumulation of shape memory alloy hybrid composite laminates
  61. Exploring a new method for high-performance TPSiV preparation through innovative Si–H/Pt curing system in VSR/TPU blends
  62. Large-scale production of highly responsive, stretchable, and conductive wrapped yarns for wearable strain sensors
  63. Preparation of natural raw rubber and silica/NR composites with low generation heat through aqueous silane flocculation
  64. Molecular dynamics simulation of the interaction between polybutylene terephthalate and A3 during thermal-oxidative aging
  65. Crashworthiness of GFRP/aluminum hybrid square tubes under quasi-static compression and single/repeated impact
  66. Review Articles
  67. Recent advancements in multinuclear early transition metal catalysts for olefin polymerization through cooperative effects
  68. Impact of ionic liquids on the thermal properties of polymer composites
  69. Recent progress in properties and application of antibacterial food packaging materials based on polyvinyl alcohol
  70. Additive manufacturing (3D printing) technologies for fiber-reinforced polymer composite materials: A review on fabrication methods and process parameters
  71. Rapid Communication
  72. Design, synthesis, characterization, and adsorption capacities of novel superabsorbent polymers derived from poly (potato starch xanthate-graft-acrylamide)
  73. Special Issue: Biodegradable and bio-based polymers: Green approaches (Guest Editors: Kumaran Subramanian, A. Wilson Santhosh Kumar, and Venkatajothi Ramarao)
  74. Development of smart core–shell nanoparticles-based sensors for diagnostics of salivary alpha-amylase in biomedical and forensics
  75. Thermoplastic-polymer matrix composite of banana/betel nut husk fiber reinforcement: Physico-mechanical properties evaluation
  76. Special Issue: Electrospun Functional Materials
  77. Electrospun polyacrylonitrile/regenerated cellulose/citral nanofibers as active food packagings
https://doi.org/10.1515/epoly-2024-0032
Schlagwörter für diesen Artikel
polylactic acid; biaxial stretching; ductility; barrier properties; chain entanglement network
Creative Commons
BY 4.0

Artikel in diesem Heft

  1. Research Articles
  2. Flame-retardant thermoelectric responsive coating based on poly(3,4-ethylenedioxythiphene) modified metal–organic frameworks
  3. Highly stretchable, durable, and reversibly thermochromic wrapped yarns induced by Joule heating: With an emphasis on parametric study of elastane drafts
  4. Molecular dynamics simulation and experimental study on the mechanical properties of PET nanocomposites filled with CaCO3, SiO2, and POE-g-GMA
  5. Multifunctional hydrogel based on silk fibroin/thermosensitive polymers supporting implant biomaterials in osteomyelitis
  6. Marine antifouling coating based on fluorescent-modified poly(ethylene-co-tetrafluoroethylene) resin
  7. Preparation and application of profiled luminescent polyester fiber with reversible photochromism materials
  8. Determination of pesticide residue in soil samples by molecularly imprinted solid-phase extraction method
  9. The die swell eliminating mechanism of hot air assisted 3D printing of GF/PP and its influence on the product performance
  10. Rheological behavior of particle-filled polymer suspensions and its influence on surface structure of the coated electrodes
  11. The effects of property variation on the dripping behaviour of polymers during UL94 test simulated by particle finite element method
  12. Experimental evaluation on compression-after-impact behavior of perforated sandwich panel comprised of foam core and glass fiber reinforced epoxy hybrid facesheets
  13. Synthesis, characterization and evaluation of a pH-responsive molecular imprinted polymer for Matrine as an intelligent drug delivery system
  14. Twist-related parametric optimization of Joule heating-triggered highly stretchable thermochromic wrapped yarns using technique for order preference by similarity to ideal solution
  15. Comparative analysis of flow factors and crystallinity in conventional extrusion and gas-assisted extrusion
  16. Simulation approach to study kinetic heterogeneity of gadolinium catalytic system in the 1,4-cis-polyisoprene production
  17. Properties of kenaf fiber-reinforced polyamide 6 composites
  18. Cellulose acetate filter rods tuned by surface engineering modification for typical smoke components adsorption
  19. A blue fluorescent waterborne polyurethane-based Zn(ii) complex with antibacterial activity
  20. Experimental investigation on damage mechanism of GFRP laminates embedded with/without steel wire mesh under low-velocity-impact and post-impact tensile loading
  21. Preparation and application research of composites with low vacuum outgassing and excellent electromagnetic sealing performance
  22. Assessing the recycling potential of thermosetting polymer waste in high-density polyethylene composites for safety helmet applications
  23. Mesoscale mechanics investigation of multi-component solid propellant systems
  24. Preparation of HTV silicone rubber with hydrophobic–uvioresistant composite coating and the aging research
  25. Experimental investigation on tensile behavior of CFRP bolted joints subjected to hydrothermal aging
  26. Structure and transition behavior of crosslinked poly(2-(2-methoxyethoxy) ethylmethacrylate-co-(ethyleneglycol) methacrylate) gel film on cellulosic-based flat substrate
  27. Mechanical properties and thermal stability of high-temperature (cooking temperature)-resistant PP/HDPE/POE composites
  28. Preparation of itaconic acid-modified epoxy resins and comparative study on the properties of it and epoxy acrylates
  29. Synthesis and properties of novel degradable polyglycolide-based polyurethanes
  30. Fatigue life prediction method of carbon fiber-reinforced composites
  31. Thermal, morphological, and structural characterization of starch-based bio-polymers for melt spinnability
  32. Robust biaxially stretchable polylactic acid films based on the highly oriented chain network and “nano-walls” containing zinc phenylphosphonate and calcium sulfate whisker: Superior mechanical, barrier, and optical properties
  33. ARGET ATRP of styrene with low catalyst usage in bio-based solvent γ-valerolactone
  34. New PMMA-InP/ZnS nanohybrid coatings for improving the performance of c-Si photovoltaic cells
  35. Impacts of the calcinated clay on structure and gamma-ray shielding capacity of epoxy-based composites
  36. Preparation of cardanol-based curing agent for underwater drainage pipeline repairs
  37. Preparation of lightweight PBS foams with high ductility and impact toughness by foam injection molding
  38. Gamma-ray shielding investigation of nano- and microstructures of SnO on polyester resin composites: Experimental and theoretical study
  39. Experimental study on impact and flexural behaviors of CFRP/aluminum-honeycomb sandwich panel
  40. Normal-hexane treatment on PET-based waste fiber depolymerization process
  41. Effect of tannic acid chelating treatment on thermo-oxidative aging property of natural rubber
  42. Design, synthesis, and characterization of novel copolymer gel particles for water-plugging applications
  43. Influence of 1,1′-Azobis(cyclohexanezonitrile) on the thermo-oxidative aging performance of diolefin elastomers
  44. Characteristics of cellulose nanofibril films prepared by liquid- and gas-phase esterification processes
  45. Investigation on the biaxial stretching deformation mechanism of PA6 film based on finite element method
  46. Simultaneous effects of temperature and backbone length on static and dynamic properties of high-density polyethylene-1-butene copolymer melt: Equilibrium molecular dynamics approach
  47. Research on microscopic structure–activity relationship of AP particle–matrix interface in HTPB propellant
  48. Three-layered films enable efficient passive radiation cooling of buildings
  49. Electrospun nanofibers membranes of La(OH)3/PAN as a versatile adsorbent for fluoride remediation: Performance and mechanisms
  50. Preparation and characterization of biodegradable polyester fibers enhanced with antibacterial and antiviral organic composites
  51. Preparation of hydrophobic silicone rubber composite insulators and the research of anti-aging performance
  52. Surface modification of sepiolite and its application in one-component silicone potting adhesive
  53. Study on hydrophobicity and aging characteristics of epoxy resin modified with nano-MgO
  54. Optimization of baffle’s height in an asymmetric twin-screw extruder using the response surface model
  55. Effect of surface treatment of nickel-coated graphite on conductive rubber
  56. Experimental investigation on low-velocity impact and compression after impact behaviors of GFRP laminates with steel mesh reinforced
  57. Development and characterization of acetylated and acetylated surface-modified tapioca starches as a carrier material for linalool
  58. Investigation of the compaction density of electromagnetic moulding of poly(ether-ketone-ketone) polymer powder
  59. Experimental investigation on low-velocity-impact and post-impact-tension behaviors of GFRP T-joints after hydrothermal aging
  60. The repeated low-velocity impact response and damage accumulation of shape memory alloy hybrid composite laminates
  61. Exploring a new method for high-performance TPSiV preparation through innovative Si–H/Pt curing system in VSR/TPU blends
  62. Large-scale production of highly responsive, stretchable, and conductive wrapped yarns for wearable strain sensors
  63. Preparation of natural raw rubber and silica/NR composites with low generation heat through aqueous silane flocculation
  64. Molecular dynamics simulation of the interaction between polybutylene terephthalate and A3 during thermal-oxidative aging
  65. Crashworthiness of GFRP/aluminum hybrid square tubes under quasi-static compression and single/repeated impact
  66. Review Articles
  67. Recent advancements in multinuclear early transition metal catalysts for olefin polymerization through cooperative effects
  68. Impact of ionic liquids on the thermal properties of polymer composites
  69. Recent progress in properties and application of antibacterial food packaging materials based on polyvinyl alcohol
  70. Additive manufacturing (3D printing) technologies for fiber-reinforced polymer composite materials: A review on fabrication methods and process parameters
  71. Rapid Communication
  72. Design, synthesis, characterization, and adsorption capacities of novel superabsorbent polymers derived from poly (potato starch xanthate-graft-acrylamide)
  73. Special Issue: Biodegradable and bio-based polymers: Green approaches (Guest Editors: Kumaran Subramanian, A. Wilson Santhosh Kumar, and Venkatajothi Ramarao)
  74. Development of smart core–shell nanoparticles-based sensors for diagnostics of salivary alpha-amylase in biomedical and forensics
  75. Thermoplastic-polymer matrix composite of banana/betel nut husk fiber reinforcement: Physico-mechanical properties evaluation
  76. Special Issue: Electrospun Functional Materials
  77. Electrospun polyacrylonitrile/regenerated cellulose/citral nanofibers as active food packagings
Jetzt anmelden und 20% sparen
Institutioneller Zugang
Wie funktioniert Authentifizierung?
Haben Sie eine Idee, wie wir unsere Website verbessern können?
Bitte schreiben Sie uns.
© 2025 De Gruyter Brill
Heruntergeladen am 10.9.2025 von https://www.degruyterbrill.com/document/doi/10.1515/epoly-2024-0032/html
Button zum nach oben scrollen