Synthesis And Properties Of PVC/nano-SiO₂ Composites

Research and development of general plastics with super properties and high additional values have been an important trend. But little attention has been paid on the relationships between the structure and mechanical properties of Polyvinyl chloride (PVC) nanocomposite. In this paper, with the different surface modified nano-SiO2, PVC /nano-SiO2 composites were prepared by in situ polymerization and melt-blending methods. The effects of different surface modified nano-SiO2 on the polymerization process, grains properties of PVC resins and the structure and properties of composites were investigated. The main results are summarized as follows:1. The effects of different surface modified nano-SiO2 on the polymerization process, grains properties of PVC resinsThe effects of the dispersible and the reactable nano-SiO2 on the polymerization process, grains properties of PVC resins were researched in the process of polymerization.The results showed that RNS-A, RNS-SR, DNS-2 were disadvantageous to the polymerization process, the agglomeration of PVC grains were found in polymerization process. But RNS-D and DNS-3 didn't affect the polymerization when the content of nano-SiO2 was under 3%.Afterwards, the effects of RNS-D on the polymerization time and PVC grains properties were established mainly. It was found that external morphology of PVC nano-resin grains was more symmetrical, inner structure was looser than the pure PVC. Viscidity number of PVC and absorption amount of DOP is increased obviously, apparent density was decreased in a way because of the introduction of RNS-D. The effect of RNS-D on the PVC grain size was unconspicuous.2. The analysis of interface structure of PVC/nano-SiO2 compositesIn order to investigate the reason of effect of nano-SiO2 on the properties of PVC, RNS-D and DNS-3 extracted from PVC nano-resins were analyzed by TGA, FT-IR and XPS technology. The results indicated that there were some PVC chains on the surface of the extracted RNS-D, but there was nothing on the surface of the extracted DNS-3, it was proved that nanosilica reacted with VC and was linked with PVC by covalent bond.3. The mechanical performance of PVC/nano-SiO2 compositesThe mechanical performance of different PVC/nano-SiO2 composites, which prepared by in situ polymerization and melt-blending methods, were established, especially the tensile and impact properties. It was found that tensile strength, elongation at break, Young's modulus of PVC/RNS-D nanocomposites prepared by in situ polymerization method were improved obviously, but the notched impact strength was decreased heavy. The impact strength of PVC/DNS-2 nanocomposites prepared by melt-blending method increased by 141% when the content of DNS-2 was 6%, and the tensile strength dropped a little only. The impact strength of PVC/RNS-D nanocomposites prepared by melt-blending method increased by 70% when the content of RNS-D was 6%, and the tensile strength increased a little.4. The thermal stabilization and rheology properties of PVC/nano-SiO2 compositesThe heat-properties of PVC/nano-SiO2 composites were also investigated. It was indicated that the Vicat soften point of PVC/RNS-D nanocomposites prepared by in situ polymerization method was increased obviously, and the degradation speed of PVC nano-resin was slower than the pure PVC. The heat-stabilization of PVC nanocomposites prepared by the melt-blending method also was improved compared with the pure PVC.The effect on PVC fusion properties of different surface-modified nano-SiO2 was investigated by HAKKE RHEOLOGY INSTRUMENT. It was found that the rheology properties of PVC/RNS-D nanocomposites prepared by the in situ polymerization method dropped a little and the fusion time was prolonged. But the rheology properties of PVC/nano-SiO2 composites prepared by the melt-blending method improved evidently. The fusion time of PVC/nano-SiO2 composites is decreased as the amount of nano-SiO2 increased, on the contrary, the torque (Tmax, Tmin, Teq) was dropped.