Studies On The Crystallization Behavior And Properties Of PET/GF Composites

In this paper,the effects of three kinds of molecular weight Polyethylene glycol(PEG) such as:PEG4000, PEG6000 and PEG8000 on the crystallization behaviors, crystallization morphology and crystallization structure of PET were systematically studied, and the effects of glass fiber on the mechanical properties and crystallization behavior of PET were studied too. The crystallization behaviors of PET/PEG composites and PET/GF composites were studied by Differential Scanning Calorimetry (DSC), and the kinetics of PET crystallization were analysed by Jeziorny theory; the crystallization morphology were investigated by Polarizing Optical Microscope (POM), and the crystallization structure were investigated by X Ray Diffraction (XRD).For PET/PEG composites, PEG with three kinds of molecular weight joining in PET melt, all made the glass transition temperature and cold crystallization temperature of PET reduced, the crystallization temperature and melting temperature of PET increased, at the same time, the apparent induction period, the half time of crystallization, the apparent total time of crystallization of PET/PEG blends were shorter than pure PET. Non-isothermal crystallization kinetics of PET/PEG blends were studied by Jeziorny theory, the results showed that Avrami constant n decreased and the crystallization Zc increased with PEG adding. That was to say the adding of PEG improved the moving of the link segments of PET molecule, because of the limitations of the compatibility of PET and PEG, PEG played the role of nucleation and shorten the crystallization cycle, speeding up the crystallization rate of PET. When PEG8000 were added for 10wt%, the effect was the best. The results of the study on crystallization morphology of PET/PEG composites by POM indicated that PEG increased the density of nucleating, lessened the size of crystals, and the crystals were distributed more evenly. Crystallization structure of PET/PEG composites were analysed by XRD, the results showed that crystal cells were not changed, but the average size of crystals which were perpendicular to the crystal surface [110] and [100] were lessened, and the average size of crystals which were perpendicular to the crystal surface [010] were not changed, while the total degree of crystallization was increased, which also indicated that it could lessened the size of crystal and promote the crystallization of PET by adding PEG.The mechanical properties and crystallization behaviors of PET/GF composites were studied at the same time, and the results show that the adding of GF which the surface was treated with KH550 improve the tensile strength and impact strength of PET, and when the additive quantity is 30wt%, the effect is the best. The results of DSC show that GF plays a role as nucleation, improved the heat crystallization ability, but it make the cold crystallization ability decreased because it hold up the moving of link segments of PET molecule. The XRD results show that when added GF in PET, the crystal cells of PET were not changed, but the average size of crystals which were perpendicular to the crystal surface [010], [110] and [100] were lessened, and the total degree of crystallization was increased.