Preparation And Performance Research Of Modified Semi-aromatic Nylon Copolymers

Semi aromatic nylon MXD6 become a striking new ultra materials in various fields with the rapid development of economy, the urgent demand for new materials, as well as the strong trend of the "plastic steel". Based on the solution polycondensation method in high temperature and high pressure, the monomer first salified then performed and final polymerized as MXD6. PA66 salt was used as the modified “monomer” for the block copolymerization of MXD6-PA66 block copolymers, and the spinnability of MXD6 will increased. For its application, MXD6-PA66 block copolymers laid the foundation of light-duty production with high strength and high modulus of tire material. In this paper, MXD6 and PA66 salt ware prepared and they ware used for the preparation of MXD6-PA66 copolymer. FT-infrared spectroscopy(FT-IR), nuclear magnetic resonance(NMR), thermo gravimetric analyzer(TG) and differential scanning calorimetry(DSC) ware used for characterization of MXD6-PA66 copolymers, and many kinds of physical testing ware also used for copolymers. In the study of purification of nylon salt, 50% and 82% ethanol solution was best for the purification of MXD6 and PA66 salt respectively, nonisothermal crystallization kinetics analysis was used for the study of nonisothermal crystallization process of copolymers, using Avrami equation, Jeziorny method, Ozawa equation and Mo method. Results show that with the addition of PA66 flexible chain segments, the crystallization rate increased, to some extent. when the PA66 content is low, they played an important role in inducing crystallization rate, but when PA66 content is high, PA66 segments which had faster crystallization rate than MXD6 formed crystal phase, which increased the difficulty of crystallization of MXD6 segments. There is a decreasing nucleation which is no longer constant through the transformation process. There may be polymorphic changes from need-like growth to disc-like or spherulitic growth during the transformation process, which implies that there may be simultaneous appearance of different growth mechanism during crystallization process. Also, a dense granular texture of crystals was formed in the presence of PA66 and the size of spherulite became smaller.Avrami equation was used for the study of isothermal crystallization kinetics in this paper. Avrami index and crystallization rate which ware related to the mechanism of nucleation, growth mode and crystallization rate and other information were obtained from our experiment. Differential scanning calorimetry and polarized optical microscope(POM) ware used in our study, results showed that isothermal crystallization process can well consistent with Avrami equation, the Avrami index n ware between 1.2 and 1.7, indicated that there may be complex crystallization contain fibril-like and disc-like growth during the transformation process.Thermo gravimetric analyzer and derivative thermogravimetric analysisused(DTG) ware used for heat decomposition of MXD6-PA66 copolymers. The activation energies and kinetic parameters of heat decomposition of MXD6-PA66 copolymers caculated by Kissinger equation and Ozawa equation respectively, and the reaction order was obtained from Grane method. Results indicated that the heat-decomposition reaction of MXD6-PA66 copolymers ware a complex reaction with the same reaction order which is approximate to 1. In this paper, the reasonable heat-decomposition mechanics had also been shown.