Volume 43, Issue 10

Sustainable oxygen barrier thermoplastic starch (TPS)/polyvinyl alcohol (PVA) blown films were successfully prepared by blending proper PVA loads during NaOH-treating and supercritical carbon dioxide (scCO 2 ) assisted processing. The NaOH-treated TPS or scCO 2 TPS films showed smaller free-volume-cavity characteristics (FVCC) and oxygen transmission rate (OTR) than those of TPS (or scCO 2 TPS) prepared without proper alkali-treatment. Smaller OTR and FVCC values were detected for NaOH-treated scCO 2 TPS films than those of NaOH-treated TPS films prepared without scCO 2 -assistance. All OTR and FVCC values detected for proper alkali-treated scCO 2 TPS y PVA z films diminished distinctly to a smallest value, when their PVA loads came near a solubility limit value of 27.5 wt%. An essential result is that the OTR of the optimal NaOH-treated scCO 2 TPS y PVA z film is merely 3.1 cm 3 /m 2  day atm, which meets the requirement of high oxygen barrier plastics. Dynamic molecular relaxations and WAXD patterns detected for proper NaOH-treated scCO 2 TPS y PVA z films disclosed that PVA was compatible with TPS, as PVA loads were ≤ the solubility limit value. The distinctly reduced OTR and FVCC detected for optimal NaOH-treated scCO 2 TPS y PVA z films are partially attributed to the reinforced molecular interactions between hydroxyl groups of TPS and PVA, as they were blended with proper PVA loads during their alkali-treating and scCO 2 -aid processing.

Polyurethane (PU) blended with nano-bactericidal agents was one of the most ways to obtain PU with antimicrobial properties. However, the bactericidal agent nanoparticles cannot effectively enrich the PU surface to reduce their antimicrobial properties. In this study, nano-silica particles with a large number of polar quaternary ammonium salt ( N , N -dimethyl-3-aminopropyl-12-alkyl-ammonium bromide trimethylsilyl, denoted as QAC) can easily enrich the PU surface to endow PU with excellent antibacterial properties after they were blended with PU film. The QAC on the surface of silica with different diameters (denoted as SiO 2 -Q- X ) can endow silica with antimicrobial properties and improve the repulsion between silica and PU to enhance the enrichment on PU surface of silica. A series of SiO 2 -Q- X /PU blend films were prepared and applied to inhibit the growth of the bacterial colony. The SiO 2 -Q- X /PU films can inhibit the growth of Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis . The SiO 2 -Q- X with more polar QAC was easily enriched on the surface of PU and had a better bactericidal effect than those of SiO 2 -Q- X with a minor polar QAC. Moreover, the aging of the SiO 2 -Q- X /PU films did not affect their antibacterial effect.

The appearance of terminal blend rubberized bitumen (TB) has improved a series of defects of traditional rubber bitumen, such as high viscosity, poor storage stability. Therefore, its wide application prospect is self-evident. However, different degrees of thermal-oxidative aging problem still exist in the process from production to use of TB, which seriously affects the service life of pavement. To improve the anti-aging performance of TB, grafting activated crumb rubber (GACR) was obtained by using acrylamide, and then compounded with TB. Firstly, TB was prepared in the self-developed nitrogen protection device. Secondly, GACR modified bitumen (GACR-MB), TB/CR composite modified bitumen (TB/CR) and TB/GACR composite modified bitumen (TB/GACR) were developed in the atmospheric environment. Finally, the performance of four kinds of crumb rubber modified bitumens before and after aging was compared and analyzed by testing high and low temperature rheological properties. The results show that GACR slowed down the formation rate and aggregation degree of asphaltenes and other macromolecular substances, and TB/GACR showed excellent aging resistance.

Natural fiber reinforced polymeric composites perform poor in mechanical and thermal properties at elevated temperatures due to the cellulose and hemicellulose contents of natural fiber start degrading at elevated temperature. In this research work, flame retardancy and thermal stability of treated and untreated kenaf fiber reinforced epoxy composites have been experimentally investigated and reported. Two composite laminates, one with 6 % NaOH Alkali treated and another with untreated woven kenaf mats, were fabricated by hand lay-up technique followed by compression molding with 40 % fiber weight fractions. Flame retardancy test and various thermal characteristics studies such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT), and morphological analysis via scanning electron microscopy (SEM) tests were carried out. The results showed that alkali treated kenaf fiber composite achieved V 0 fire retardancy grade. The major weight losses, 86 % and 75.5 % for untreated and treated composites respectively were recorded between 300 °C and 450 °C. 13.6 % increase in HDT was noted for treated composite with 0.25 mm deflection at 0.45 MPa pressure condition. Thus the composite laminate with 6 % NaOH alkali-treated kenaf fiber achieved the best thermal stability with less degradation which is more suitable for automobile and aerospace applications.

Acrylonitrile-butadiene-styrene (ABS) resin is a widely used engineering plastic at present. Due to its excellent mechanical properties and high fluidity, it is utilized in fused deposition molding (FDM) technology. In this paper, boron nitride nanosheets (BNNS) were prepared by hydrothermal exfoliation and used as nano-fillers for ABS resin, and ABS/BNNS composite wires for FDM printing were prepared by melt blending method. The results showed that BNNS with fewer layers were obtained; the addition of BNNS to the ABS resin matrix could effectively enhance the thermal conductivity of the composites. When the addition amount of BNNS was 15 wt%, the thermal conductivity of the composite increased to 0.369 W/(m K), which was 120.06 % higher than that of pure ABS (0.174 W/(m K)). In addition, BNNS also improves the mechanical properties, thermal stability, and melt flow rate of the composites, thus making ABS composite wires more suitable for FDM printing.

In this work, an improved wet spinning method was proposed to prepare high-tensile-strength carrageenan fibers by pre-crosslinking process. Pre-crosslinking was achieved by adding a small amount of Al 3+ ions into the spinning solution. The properties of the carrageenan spinning solution were analyzed by polarizing microscope, dynamic light scattering, and viscosity, the results showed that the modified spinning solution pre-crosslinked with Al 3+ ions was orderly and high-viscosity, and the average particle size of the spinning solution was increased. The properties of the carrageenan fibers were characterized using scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, and tensile tests. The results showed that the new carrageenan fibers were formed by coordination and ionic bonds between Al 3+ , –OH and sulfate groups. The tensile strength was up to 1.77 cN/dtex of Al-3.0/CAF (the best of newly prepared carrageenan fiber in this work), which is the highest strength carrageenan fiber prepared at present. Compared with the traditional process, this method reduced the concentration of Al 3+ ions in coagulation bath and stretch bath, thus saving the production cost and protecting the environment.

The aim of the present work is the development and characterization of new formulation of emulsified films based on soluble starch/sodium alginate blend and microcrystalline wax. The developed films were studied in order to use them as new formulations to produce food packaging. The obtained films were generally homogeneous, thin, and slightly flexible. These films appeared more opaque compared to the non-emulsified film. Incorporation of microcrystalline wax was caused modifications of mechanical properties of films; these modifications were principally due to the formation of amylose–lipid complex. It was found that microcrystalline significantly reduced film water vapor permeability (WVP) of emulsified films. Atomic force microscope (AFM) was used to evaluate surface topography and roughness of the films. The surface topography was significantly affected, in the other word high roughness values were obtained. Microemultion formation in which the microcrystalline wax particles are distributed homogeneously within the polymer matrix was investigated by scanning electron microscopy (SEM). Moreover, the polysaccharides blend/microcrystalline wax emulsified films can be useful as a biodegradable packaging material to maintain the quality of food products.

In this study, a modified torque rheometer is used to investigate the volatilization behavior of monomer and oligomers in polyamide-6 (PA6) melt under dynamic film–forming conditions with negative pressure. The surface renewal model is employed to simulate the volatilization behavior. The effects of actual processing factors and simulation results on the volatilization behavior of monomer and oligomer are analyzed comparatively. It is found that the monomer and oligomers removal rate increase continuously with increasing temperature, residence time, and rotational speed. And, the cyclic dimer, which is extremely harmful to spinning, can be removed. It is found that the removal of monomer and oligomers continued to increase with increasing temperature, residence time, and spinning speed. Moreover, cyclic dimers, which are extremely harmful to spinning, are also removed. Additionally, it is discovered that the polycondensation reaction of PA6 results in an increase in the molecular weight and viscosity at lower temperatures (250 °C), while a higher temperature (270 °C) and shear rate (150 r/min) cause a reduction in viscosity and molecular weight.

A novel speed sinusoidal pulsating system is designed by applying differential drive, which is loaded on the plasticizing screw in an extruder or in an injection molding machine. With the CFD software ANSYS POLYFLOW 19.2, this paper builds simplified physical and mesh models for the double wave screw unit, carries out numerical simulation by using particle tracing manner, and finally analyses comparatively the mixing behavior of the wave screw mixing unit with and without sinusoidal pulsating field. It is found that the mixing screw unit with the superimposed excitation field takes on lower transportation efficiency and a descending melt pressure, while there are different reactions on the various pulsating amplitude and frequency for the max shear rate and mixing index. On the other hand, the introducing pulsating field can strengthen the shear field and gain a higher mixing efficiency. The results are of great importance and reference for improving the plasticizing performance and engineering application of the speed pulsating system.

During the gas-assisted extrusion process of plastic tubes embedded with antibacterial particles, the particles tend to agglomerate. The dispersion effect of these agglomerates using the nozzle-pressure-difference method is significantly influenced by the gas flow state. Therefore, this study establishes the nozzle dispersion model. The gas flow state near the nozzle is simulated and analyzed by using Ansys Fluent software. Gas-assisted extrusion experiments are conducted with different nozzle inlet pressures, and the size distribution of antibacterial particles is observed by using electron microscopy. The simulation results indicate that increasing the nozzle inlet pressure enhances the dispersion effect and expands the effective dispersion area. The experimental results demonstrate that using the nozzle disperses the agglomerates into particles with a diameter of approximately 100 nm. Furthermore, the nanoparticles diameter size decreases with the increase of the inlet pressure, validating the accuracy of the numerical analysis results.