Study On The Relationship Between Structure And Thermal Stabilities Of PVC And Its Blend

Poly (vinyl chloride)(PVC) is cheap, wide sources, which has good physical and mechanical properties, and widely used in various fields of social life. Since it has been found, PVC has been studied widely, including the study of its structure and performance, and research on the modification of the material or blend it which other materials, etc. However, because the PVC is obtained by free radical polymerization of vinyl chloride (VCM), thus more structural forms are produced, so the relationship between the PVC thermal degradation and its structure is still not recognized so for, all schools of thoughts contend for attention.In this paper, first of all, the molecular weight and Congo red, oven test of more than ten kinds of PVC at home and abroad were tested and took out three differences samples (P-1,P-2, and P-5) by thermal properties to the following study. Simulation and optimization the isotactic structure (mm) and syndiotatic structure (mr) in five conjoined structure of PVC by using B3LYP/6-31; meanwhile, we also calculated and compared the bond order of C-Cl in different isomers, it is concluded that the isotactic structure is more stable than syndiotactic structure, therefore, according to the content of syndiotactic and isotatic structure of PVC molecular chain can preliminarily concluded the thermal stability of different PVC. In order to prove the above theory, the two aspects work was undergo.On the one hand, using carbon spectrum-nuclear magnetic resonance (13C-NMR) to analyzed the molecular chain structure of P-1, P-2and P-5; Though calculating the integral calculation of nuclear magnetic spectra of the three PVC samples, the isotatic structure content from high to low is in the order:P-1> P-2> P-5, and the content of syndiotactic structure is on the contrary, so by the structure analysis we concluded that the thermal stability of P-2resin is the best, and P-5has the worst thermal stability of the three resin. On the other hand, in order to verify the above reasoning, the oven, Congo red method and thermogravimetric thermal stability of static and torque rheological of dynamic is test for the three samples,and the result is consistent with the test results of the speculate of the structure.Chlorinated polyvinyl chloride (CPVC) has better heat resistant and flame retardant properties than PVC, but because too much content of chlorine in the CPVC, leading the processing and toughness is poor, therefore, this paper blend a kind of PVC, which has good processing and toughness, to modify the CPVC, and through the study, it can be found that the PVC can improve the processing and impact resistance of CPVC by the heat resistance and flame retardant properties drop not so big.