zhi He

Characteristics Study of Polymer Melt Conveying Capacity in Vane Plasticization Extruder

A vane extruder is novel equipment for polymer processing. The materials were conveyed and plasticized by a group of vane plasticization units and the materials suffered normal stress during processing. An analytic model was developed to analyze the conveying capacity of melt in the vane plasticization unit of which the melt can be conveyed positively. The analysis of conveying capacity of melt in the vane plasticization unit shows that the conveying capacity increased with the rotate speed, eccentricity distance, vane width, inner-diameter of stator. And the leakage flow model was developed to show that the leakage flow is increased with the width of leakage gaps but decreased with the apparent viscosity of melt. The experiment results show a linear variation of production with rotating speed, and small dependence effect of production with die pressure variation.

Properties of heat-treated sisal fiber/polylactide composites

Sisal fibers (SFs) were pretreated by heat treatment (HT). The SFs were mixed with a biodegradable material, polylactide (PLA), and the composites were prepared by hot press molding. The effects of the HT temperature and time on the mechanical properties of the composites were investigated, and the HT mechanism was studied by scanning electron microscopy and infrared, x-ray photoelectron, and nuclear magnetic resonance spectroscopies. The results show that an appropriate HT can remove strongly hydrophilic materials such as hemicelluloses from the fibers, and thus decrease their hydrophilicity, thereby improving the retting between the fibers and the matrix. This improves fiber–matrix interfacial adhesion, which can improve the mechanical properties of the composites. The HT also influences the fiber strength to some extent and affects the mechanical properties of composites.

Synthesis of a bioadsorbent from jute cellulose, and application for aqueous Cd (II) removal

A low-cost, high-adsorption-capacity, eco-friendly bioadsorbent for removing Cd2+ from aqueous solution is reported. J-g-P(AM-co-AANa) was prepared by hydrolysis of the grafted copolymer, which was synthesized by free radical polymerization of acrylamide (AM) with jute fibers (JSE) pretreated by continuous screw-extrusion steam explosion. Fourier transform infrared and solid-state 13C nuclear magnetic resonance spectroscopies, confirmed that amino and carboxylate groups were introduced into J-g-P(AM-co-AANa). X-ray diffraction showed that the crystallinity of J-g-P(AM-co-AANa) was significantly lower than that of JSE. The surface morphology of bioadsorbent was investigated by scanning electron microscopy (SEM). The adsorption capacity of Cd2+ on J-g-P(AM-co-AANa) was evaluated for different solution pH values, contact times, and initial Cd2+ concentrations. The adsorption kinetics followed the pseudo-second-order kinetic model, and the rate controlling step was chemisorption. The adsorption isotherm was well fitted by the Freundlich model, and the adsorption process was multilayer adsorption. The maximum adsorption capacity was 344.8 mg/g, which indicated that the bioadsorbent was effective for removing Cd2+ from aqueous solution.

Research on electromagnetic interference shielding effectiveness of sisal fiber/carbon black/HDPE composites by tri-screw extrusion molding

Polymer composites filled with fillers such as carbon black(CB) can become an electrical conductor, which is gaining popularity for electromagnetic shielding applications. In this paper, the method of tri-screw compounding was adopted to prepare SF/CB/HDPE composites, and the influence of different content of CB and SF on the properties such as shielding effectiveness(SE) and conductivity were studied. It was found that the composites with higher content of CB showed higher electromagnetic SE. Added 8% SF to CB/HDPE system, the performance of composites was significantly improved. Finally, values of theoretical and experimental SE of SF/CB/HDPE composites were compared and the results were in good correlation, which proved out the significance of theoretical guidance of Schelkunoff formula.

Research on properties of carbon black/polypropylene composites by dynamic injection molding

Polymer composites filled with conductive carbon black (CB) are gaining popularity for electromagnetic shielding applications. Dynamic injection molding method was adopted to study the influences of vibration force field on electrical properties of polypropylene/CB composites. The results showed that the percolation phenomenon of conductivity of composites occurred at 15wt% and the calculated SE was positive correlated with the variation trend of conductivity. The calculated SE of composite was more than 30dB at a CB concentration of 30wt%, which could obtain good shielding effects. The result could offer optimum vibration parameters for producing electromagnetic shielding composites by respectively changing the amplitudes and frequencies of the vibration force field.