The Preparation And Performance Research Of PVC/CPVC/Hydrotalcite Composites

In this paper,CPVC and modified hydrotalcite (LDHs) was selected to modify heat resistance of PVC. PVC/LDHs,PVC/CPVC and PVC/CPVC/LDHs composite material was prepared by melt blending extrusion.Effect of modified method and group distribution ratio of LDHs on the mechanical properties,heat resistance and processing rheological properties of various composite system of PVC was studied in detail. The structure of the material was characterized through X-ray diffraction (XRD),infrared spectrum (FTIR) and scanning electron microscope (SEM).By ion exchange method, sodium dodecyl benzene sulfonate (DBS) and sodium dodecyl sulfate (SDS) were inserted into the layer of LDHs respectively. The results indicated that the pillared hydrotalcite had a complete lamellar structure.The best conditions of anion intercalation was:reaction temperature was 70℃; reaction pH was 4; reaction time was 6 hours; the quality ratio of SDS and LDHs was 1.5 and the quality ratio of DBS and LDHs was 1.0,when the organic anion intercalated into the layer of LDHs to substitute the CO32- completely.The surface of LDHs was treated with sodium stearate (NaSt) and y-methacryloxy propyl trimethoxy silane (KH570). The results showed that the functional groups of LDHs changed and the layered structure of LDHs remained after modified with two kinds of surface modification agent.The composite modified KH570-SDS-LDHs was prepared by modifying the LDHs organically with intercalation modification agent (SDS) and surface modification agent (KH570). The results from the XRD and FTIR showed that SDS intercalated into the layers of LDHs perpendicularly with a spacing of 2.72 nm,KH570 only covered the surface of LDHs coupling with the hydroxyl groups on the hydrotalcite surface.The effect of the kinds and contents of LDHs on mechanical properties, rheological properties and heat resistance properties of PVC/LDHs composite system was investigated. The results show:the modified LDHs could significantly improve the toughness and strength of composite materials; with increasing content of various modified LDHs, the impact strength and vicat softening temperature of the composites materials increased, the tensile strength and flexural strength showed a trend of decrease after the first increase, the best value appeared in the adding amount of 5, the rheological properties of system were improved after adding the modified LDHs;the modification effect of composite modified KH570-SDS-LDHs was the best.The effects of CPVC content on the property of PVC/CPVC system was investigated. The results showed that with increasing content of CPVC, the heat resistance and strength increased, the toughness decreased slightly and the processing performance became poor.When the best content of CPVC was 35 wt%,the vicat softening temperature of material increased 19.64℃ than the pure PVC,while the impact strength of material decreased less.The study from PVC/CPVC/LDHs ternary complex system found that composite modified KH570-SDS-LDHs had the best dispersibility and interfacial adhesion in the substrate of PVC/CPVC. Adding quantity of KH570-SDS-LDHs was 7,the comprehensive properties of composite material was best.