Band 42, Heft 10

Controlling temperature and pressure during the supercritical carbon dioxide (scCO 2 ) process can change the mount of CO 2 entered in polypropylene (PP) phase, thereby changing the mechanical properties of materials. The effect of scCO 2 treatment on the crystallization behavior is different in the semi-molten and molten states. This study investigates the PP treated with scCO 2 near the melting point and at various pressures, and explores the effects of temperature and pressure on the crystal structure, lamellar structure, and thermodynamic properties of PP. The results show that at a melting temperature of 165 °C, scCO 2 can enhances the ability of PP molecules to makes the PP crystal region more regular, and forms larger microcrystals and lamellae. Additionally, increasing the pressure can make more CO 2 enter the PP crystal region and further improve the regularity of the crystal. At a semi-melting temperature of 155 °C, scCO 2 is primarily in the amorphous region because it is difficult to enter the PP crystal region. Even if increasing the pressure, it has little effect on the crystal size and lamellar thickness of PP. The research has significant implications for developing and utilizing scCO 2 to remove ash from materials.

The potential effect of nano TiO 2 in poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) based polymer electrolyte and their application in a dye sensitized solar cell have been investigated. The solution casting process was used for fabrication of nano TiO 2 loaded in Mg 2+ ion based PVDF-HFP solid polymer electrolyte (SPE), and characterized using conductivity, scanning electron microscopy (SEM), X-ray diffraction (XRD) and photovoltaic studies. XRD investigations reveal the broadening of specific peaks, which shows the occurrence of α , β and γ polymorphous phase transitions that commence the amorphous character and ion mobility. The SEM pictures revealed an interconnecting network of micro-porous nature, and an average diameter of the pores of ∼0.38 µm was obtained by using Gaussian curve fitting. Ion transport is facilitated by the high concentration of pores, which is responsible for the efficient absorption of a significant amount of electrolyte. The photovoltaic characteristics of dye sensitized solar cell (DSSC) estimated efficiency ( η ) is 9.9999%, and the fill factor is 0.84. Furthermore, the stability performance of the nanocomposite polymer electrolyte was improved and sufficient for use over an extended length of time, suggesting potential applications as a separator in solid state ionic conductors.

In this research work, a two-dimensional model to predict the electrical percolation threshold (EPT) of the polymer/graphene-based nanocomposites in different concentrations of the randomly dispersed inclusions in various polymer matrices is introduced using the finite element method (FEM). The predicted EPT values were validated by other experimental results for different nanocomposites. Results showed that the electrical conductivity of different nanocomposites is significantly related to the percentage weight of the reinforcing phase in the polymer matrix. Furthermore, the addition of graphene-based nano-fillers in the polymer matrix caused a decrease in the tunneling distance in nanocomposites.

Four interfacial models, including the PBT-Al&P (Plane), PBT-Al&V (V-slot), PBT-ATD-Al&P (Plane), and PBT-ATD-Al&V (V-slot), were constructed. The molecular dynamics (MD) method was launched to study the interfacial interactions and bonding behaviors between heterogeneous interfaces in nano-injection molding. The influence mechanism of the 2-amino-1,3,5-triazine-4,6-dithiol (ATD) coating on adhesion properties of the PBT–Al interface was mainly explored. Results indicated that the nano-V-slot interface system exhibited a double-wall-slipping phenomenon, unlike the non-nano-interface (macroscale molding) one. In nano-V-slot interfacial models, although the ATD coating reduced the double-wall-slipping velocity, it also increased the polar bonding, thus strengthened a better anchoring connection in the PBT–ATD–Al interface. The addition of the ATD layer did not cause chemical bonding of the original PBT materials; the interlocking effect behavior occurred between them and only coexisted in the form of physical anchors. Whatever model it was, the ATD layer interface had significantly higher interface energy than the other one, which was formed solely by PBT and Al substrate. In nano-injection molding, when the ATD intermediate layer was added, the bonding behavior of the PBT–Al interface also changed from simple nonbonded rigid anchoring to the entanglement anchor between the PBT–ATD macrochains and the nonbonding connections between ATD-Al interfaces.

This study aimed to prepare cellulose nanofibrils (CNF) with tunable morphology and properties from wheat straw using enzyme-assisted ultrasonic treatment. The effects of different enzymatic hydrolysis duration on the morphology and the properties of the CNF were studied. The effects of different enzymatic hydrolysis duration on the morphology and the properties of the CNF were studied. AFM analysis showed that average height distribution for CNF-0 (without enzymatic pretreatment) decreased from 11.86 to 8.18 nm for CNF-4 (with the enzymatic hydrolysis duration of 4 h), while the crystallinity and water reserve value (WRV) for CNF-0 increased from 36 and 485% to 47 and 789% for CNF-4, respectively. The transmittance, wettability properties, and mechanical performances of CNF-based films were systematically studied. The results show that the film properties are highly dependent on the morphology of their corresponding CNF and can be effectively modulated by controlling the structural characteristics of CNF. The discoveries of this study provide an environment-friendly approach for the production of CNF with tunable morphology and fibril size, which can promote the production of cellulose-based nanomaterial as well as their related applications.

Nanofibers are materials used in a wide range of applications due to their unique physicochemical properties. As an alternative to the most common method of its manufacturing (electrospinning) blow spinning has been used since it has greater production efficiency and simplicity. A wide variety of polymers is used for its preparation and can be modified to improve the interaction and selectivity toward specific analytes. Thereby nanofibers have been used for the extraction or removal of organic compounds such as drugs but there are still few reports of drug extractions like losartan. In this work polysulfone-Aliquat 336 nanofibers were prepared using the blow spinning method to extract and preconcentrate losartan. The studies showed that Aliquat 336 incorporation significantly improve the extraction of losartan with polysulfone fibers. Adsorption process was thermodynamically favorable with an adsorption capacity of 15.45 mg·g −1 . Thus, it was possible to extract more than 92% of initial losartan using 10 mg of polysulfone-Aliquat 336 fibers (9 and 3.5% (w/v)), at pH 6 from deionized water and synthetic wastewater. Finally, losartan preconcentration was evaluated to facilitate its quantification using ultraviolet–visible spectrometry (UV-Vis), which allowed the determination of this drug at concentrations below the detection limit.

TiO 2 semiconductor photocatalysis is an effective technology for the treatment of wastewater containing organic dye pollutants, which has been received extensive focus. However, the problems in the recovery and reutilization process impede the large-scale applications of particulate photocatalytic materials. Herein, a macro sized hydrogel bead loaded with nano TiO 2 powder was successfully prepared by taking advantage of the cross-linking and gel property of alginate salt, which could form egg-box structure naturally when Na + ions in sodium alginate (SA) were replaced by divalent ions such as Cu 2+ , Co 2+ , and Sr 2+ ions. The photocatalytic degradation rate of methyl orange (MO) solution in the presence of the hydrogel beads reaches 99% within 60 min under the ultraviolet light irradiation, which is competitive with that of TiO 2 nano powder. Furthermore, the hydrogel beads prepared by this strategy maintain over 95% photocatalytic degradation rate after 10 cycles of degradation process. The results indicate that the network structure of alginate could immobilize and disperse TiO 2 particle effectively, and it is readily for the spherical beads to contact and harvest the light, making the alginate beads have excellent photocatalytic functions. Also, the alginate based beads integrate good performance with high stability and excellent recyclability perfectly.

In this paper, a three-dimensional viscoelastic flow model of double-layer micro coextrusion with circular cross-section was established. The simulations were carried out by the finite element method and the influence of wall slip coefficient on micro coextrusion was studied. The results show that gas-assisted technology is suitable for polymer micro coextrusion forming. The differences between the gas-assisted and conventional micro coextrusion process were compared by analyzing the distribution of melts velocity, pressure, shear rate and first normal stress difference. The research results show that in the conventional micro coextrusion process there are pressure drop, shear rate, first normal stress difference and secondary flow. And there is a gradient distribution of melts velocity. The die swell and deformation vary with the forming process parameters, and it is difficult to control the product quality. But in the gas-assisted micro coextrusion process, there is no pressure drop, shear rate, first normal stress difference and secondary flow. The velocity of polymer melts is evenly distributed and the melts are extruded in a plunger shape. The melts do not swell and deform and it is independent of forming process parameters. It is easy to ensure the products quality and the inherent problems of polymer conventional micro coextrusion are well solved.

In this paper, the crystallinity ( X c ) of ultra-high molecular weight polyethylene (UHMWPE) parts was adjusted within a wide range from 40 to 60%, and the influence of X c on wear performance and its relevant mechanism were surveyed. The volume wear rate of UHMWPE parts continuously decreased with increasing X c . Structural characterization revealed that the closely packing crystalline structure composed of high X c and large-size lamellae improves resistance to plastic deformation, which is responsible for excellent anti-wear performance. The efficiency of improving the wear resistance by high X c is comparable with the traditional method of irradiation-induced crosslink. But the latter may severely harm the anti-oxidation capacity. So, increasing X c is a promising candidate to develop high-performance UHMWPE materials with superior wear resistance.

In this study, three-dimensional (3D) printed polylactic acid (PLA) samples are annealed at slightly above the glass transition temperature to enhance the mechanical properties. Tensile and Izod impact tests are conducted to investigate the mechanical properties of 3D printed PLA specimens. Influence of different infill patterns on tensile strength and impact resistance are also observed. Porous structure of 3D printed PLA specimens is examined and average void area densities are determined via scanning electron microscope (SEM) images. Influence of void area density on mechanical properties is investigated. Tensile behaviour of 3D printed PLA parts is simulated with proposed nonlinear autoregressive with exogenous and transfer function models. While stress data and determined void area densities are used as inputs, strain data obtained from tensile tests used as output for the model structures.