Synthesis And Properties Of PVC/CLAY Nanocomposites

Nanocomposites are a new class of composites, that are particle-filled polymers for which at least one dimension of the dispersed particles is in the nanometer range. Due to the special effect of the nanometer-size particles, the nanocomposites often exhibit remarkably improved properties. Nowadays, among all the potential nanocomposites, polymer/layered silicate (PLS) nanocomposites have attracted intensive interest from academic and industrial researchers.In this thesis, PVC/Na+-montmorillonite(MMT) nanocomposites were synthesized by emulsion polymerization. The structure of the composites was characterized by X-ray diffraction(XRD) and transmission electric microscope(TEM). The experimental results revealed the formation of a mixture of intercalated and exfoliated nano-structure. The emulsion polymerization could realize the nanometer-size dispersion of MMT in the PVC matrix. The addition and amount of MMT could not apparently affect the mean particle diameters of PVC/ MMT nanocomposite latex. After the addition of MMT, the average molecular weights and PDI(Mw/Mn) of PVC matrix were lower than that of pure PVC. The proper amount of MMT could improve the mechanical and thermal properties of the nanocomposites. For systems containing clay in the range of 2.1wt% to 3.5wt%, the impact strength was almost two times as large as that of pure PVC.We have also prepared PVC/MMT nanocomposites by emulsion polymerization under different emulsifier content. The effect of the emulsifier content on the properties of composites has been studied. Then the native MMT was used to prepare PVC/clay nanocomposites by emulsion polymerization.Besides, PVC/organo-MMT (OMMT) nanocomposites were synthesized with two types of OMMT by suspension polymerization. The OMMT used in this study were prepared by replacing Na+ ions in layered silicates with alkylammonium or alkylphosphonium cations by ion exchange. The two kinds of OMMT can be represented by ammo-MMT and pho-MMT. The XRD and TEM results revealed that the silicate layers could be fully dispersed in the PVC matrix. The mechanical properties of the composites could be unproved under a proper amountof OMMT. The glass transition temperature (Tg) of nanocomposites was higher than that of pure PVC. The modification of OMMT has greatly affected the Thermogravimetric analyses (TGA) curves and Vicat softening point(VSP) temperature of the materials. The addition of ammo-MMT could improve the composites thermal stability and VSP temperature. However, the pho-MMT speeded up the HC1 loss of PVC chains, and lower the thermal stability of the composites during the second stage of PVC thermal degradation. It wasn't until the third and fourth stages of PVC thermal degradation that the pho-MMT began to improve the thermal stability of the composites. Further more, the addition of pho-MMT have not apparently effect on the VSP of the composites.Poly butyl acrylate (PBA)/MMT composites were prepared by emulsion polymerization. Then, PVC/(PBA-MMT) nanocomposites were prepared by suspension polymerization of Vinyl chloride in the presence of PBA/MMT composites. It could be found that MMT was partially exfoliated and partially intercalated in the matrix. A proper amount of MMT could improve the mechanical and thermal propertied of the PVC/(PB A-MMT) nanocomposites.