The Appliance Of New Processing Aid In RPVC And The Study On HDPE Special Material For Plastic Pallet

In this paper, the effect of a new low-molecular-weight processing aid (M) with rigid molecular structure which was synthesized in the laboratory on the melt flowability and mechanical properties of rigid polyvinyl chloride (RPVC) were studied in detail. Furthermore, the mechanical properties and hydrostatic pressure testing of unplasticized PVC pipes for water supply with different dosage of M was also investigated. The results of mechanical properties testing showed that the tensile strength and anti-hydrostatic pressure capability were improved obviously. Compared with UPVC pipes without M, those with 5phr M could be filled with more 6phr CaCO₃ and remained eligible hydrostatic pressure testing, but the property of impact resistance decreases in some certain. Additionally, the analysis of rheological characteristics showed that with the increase of M, balancing torque of torque rheometer decreased obviously which meant the fluidity of PVC melt become well. Besides, the disappearance of some peaks in WAXD spectrum implied that there was strong interaction between PVC and M, and crystallization behavior of M was restrained by PVC; The results of DSC analysis showed that glass transition temperature (Tg) of PVC decreased gradually with the increase of M and the plasticizing degree of PVC was evidently improved; Thermogravimetric analysis found that heat-resistant property of PVC with M decreased slightly.Moreover, aimed at the problem that HDPE pallets were liable to warpage and deformation after injection molding, the effect of crystallinity and flowability of blends such as HDPE/LLDPE,HDPE/PP,HDPE/Inorganic Filler, etc., on the shrinkage of injection molding and mechanical properties were discussed. The results show that the shrinkage of HDPE/LLDPE blends didn't decrease actually with the drop of the crystallinity of the system, but was affected synchronously by the fluidity and the crystallinity of the system. The variation of the shrinkage comprised of three stages observably, increasing very fast at first, keeping nearly steady and then slowing down finally. However, mechanical properties decreased obviously with the increase of wt% LLDPE. To HDPE/LLDPE blends, there were better mechanical strengths and lower shrinkage, but there were the poor impact strength because of incompatibility between PP and PE. A small amount of inorganic filler (calcium carbonate or talcum powder) could not only result in the drop of the shrinkage but also made the bending strength and modulus improved obviously. Compared with CaCO₃, Talc had an obvious reinforcement on matrix. The tensile strength of the blends with Talc increased at first and then decreased whereas those with CaCO₃ decreased all through; the bending modulus of blend with 30phr Talc and that with 30phr CaCO₃ was respectively 1.2 times and 0.6 times that of the matrix. However, after the dosage of Talc exceeded 10phr, the elongation at break of blends reduced dramatically. To consider the shrinkage and mechanical properties together, we thought that the blend with about 10phr Talc could obtain optimal practical effect.