Crystallization And Melting Behaviors Of Poly (Ethylene Terephthalate) Modified By Styrene-Sodium Methacrylate Ionomer

In this paper, Styrene-Sodium Methacrylate(SMA-Na) was synthesized by solution technique firstly. The solution polymerization of styrene and methacrylate acid was primarily studied. The structure,thermal stability,aggregation behaviors and glass transition temperature(Tg) of ionomers were investigated by IR, TG, XRD and DSC. It was found that SMA were more stable than polystrene. The Tg of ionomers increased as the content of sodium methacrylate in ionomer rised.PET/SMA-Na composites were prepared by melt compounding.The effect of different structuresof ionomers on the crystallization of PET were investigated. The results showed that the Tmc of PET increased and the Tcc decreased with the ionomers addition, the improvement of crystallization of PET modified by styrene-sodium methacrylate was extremely affected by the sodium methacrylate groups in ionomers. Styrene-sodium methacrylate ionomers can survive reaction with PET melt, and the ion-dipole interactions between ionomers and PET induce the formation of PET nuclei around the ionic aggregates of ionomer. The nucleation efficiency of styrene-sodium methacrylate was determined by the ion-dipole interactions directly.The morphology, isothermal and nonisothermal crystallization kinetics and melting behaviors of PET by styrene-sodium methacrylate (SMA-Na) and ethylene-sodium acrylate (Surlyn), have been studied by DSC, POM and SEM. The Avrami and Jeziorny equation were used to describe the isothermal and nonisothermal crystallization kinetics. With increasing the content of ionomer,the crystallization rate of PET/ionomer enhanced gradually.Kinetic analysis showed that for the isothermal melt-crystallization, the Avrami exponent n increased with the addition of ionomer, while the n did not change for the isothermal cold-crystallization. The Avrami exponent n of PET obtained from the nonisothermal crystallization kinetics was increased as SMA-Na and Surlyn added. After isothermal melt-crystallization, multiple melting endotherms were obtained for all the PET samples in the subsequent DSC heating scan. The second melting peaks of PET/ionomers were higher than that of neat PET. It was found that two kinds of ionomers were compatible with PET.