Preparation And Characterization Of Poly (Ethylene Terephthalate) Nanocomposites

Poly (ethylene terephthalate) (PET) is widely used as packing and engineering materials due to its high performance. But PET has low permeability to oxygen, carbon dioxide and water. Its application as an engineering plastic for injection molding applications is rather limited by its lower crystallization rate. In this paper, in-situ polymerizations were applied to prepare PET/montorillonite (MMT), PET/layered double hydroxides (LDHs) and PET/ZnO nanocomposites. Influences of polymerization technology on dispersion or intercalation of inorganic particles, and addition of inorganic particles on the molecular weight and crystallization behavior of PET were investigated emphatically.PET/MMT nanocomposites were prepared by in-situ intercalation polymerizations, in which MMT was added in ethylene glycol or in bis-hydroxyethyl terethalate (BHET). The results showed that the molecular weights of PET were much lower than those of the pure PET. The glass transition temperature, cold crystallization temperature and the melt temperature decreased slowly as MMT content increased. It found that MMT dispersed uniformly in the PET composites. The solid-condensation polymerization could increase the molecular weights of PET, but had no obvious influence on the crystallization.PET/LDHs nanocomposites were prepared by in-situ intercalation polymerizations, in which MMT was added in ethylene glycol. It found LDHs dispersed as intercalated form more than exfoliated form in composites. The molecular weights of PET decreased as the LDHs content increased. The nonisothermal crystallization temperature became higher and the crystallization time became shorter.ZnO has a particular absorption of ultraviolet. PET/ZnO nanocomposites were prepared by in-situ polymerization. The results showed that ZnO aggregated in PET composites. The molecular weights of PET increased slightly as ZnO added. Theglass transition temperature decreased firstly with the content of ZnO and increased when the content of ZnO exceeded 1.0%. Treating with poly(ethyl glycol)(PEG) had no obvious influence on disaggregation of ZnO. The molecular weights of PET decreased, and the crystallization ability improved as PEG added.