A Study On The Synthetic Technology Of Semiaromatic Polyamide PA12T

Due to the excellent mechanical properties, heat resistance and dimensional stability, semiaromatic polyamides are more and more widely used. Currently, there are mainly two kinds of industrialized semiaromatic polyamides, polyhexamethylene terephthalamide (PA6T) and polynonamethylene tereph thalamide (PA9T). But, PA6T cannot be processed by melting method because its melting point is higher than the thermal decomposition temperature, and PA9T has high costs, which, to some extent, limit their wide application. Therefore, it is of great significance to synthesize novel,(?)w-cost and environment-friendly semiaromatic polyamides with high strength and high heat resistant. Recently, a novel long chain semiaromatic polyamide, poly(dodecamethylene terephthalamide) (PA12T), has been successfully prepared in the laboratory. It is found that the comprehensive performance of PA12T is superior to these of PA6T and PA9T. And it is expected to replace PA9T in many fields in the future.However, the high melting point and viscosity of PA12T lead to discharge difficultily, which makes its industrialization process greatly affected. We have obtained PA12T powders successfully in aqueous solution and organic solvent respectively. Nevertheless, the molecular weight of PA12T obtained under this condition is too low to be processed.The preparation process of PA12T was studied in this thesis. The granular PA12T with high molecular weight was prepared, and its melting point was 310℃. The effect of the amount of solvent, solvent purity and antioxidants on the molecular weight of PA12T was also studied. It was found that, it was better to add 110 mL ethanol as solvent for the 2 L kettle, and changes in the concentration started to diminish the impact on the molecular weight of PA12T when the ethanol mass fraction was above 95%. The addition of antioxidant, phosphorous acid, helped to improve the molecular weight of PA12T. Then the structure and properties of obtained PA12T were characterized. The results showed that the PA12T synthesized under new process had good mechanical properties. The glass transition temperature of PA12T tested by DMTA was 144℃The corresponding activation energy of PA12T was calculated through Arrhenius formula. The isothermal crystallization process and its kinetics were also investigated using DSC method. The Avrami index n and activation energy of PA12T under isothermal crystallization were calculated, respectively.