Preparation And Performance Characterization Of Copolyimide PA(56-co-66)

Bio-based polyamide 56(PA56)synthesized from pentamethylene diamine obtained by biological fermentation as a new polyamide(PA)material has many excellent properties,that is a promising polymer material.This article takes bio-based PA56 and PA66 and their copolyamides as the object,and explores the influence of component content on the thermal properties,mechanical properties,rheology,crystal structure and crystallinity of PA materials.The main contents are as follow:(1)By analyzing the thermal degradation process of PA66 salt and bio-based PA56 salt,it was determined that the prepolymerization temperature of copolyamide PA(56-co-66)was184 ?? 205 ?.A series of high molecular weight(relative viscosity greater than 2.8)PA(56-co-66)copolymers with different component contents were successfully prepared by solution polymerization at high temperature and high pressure.(2)The study on the structure and properties of copolyamide PA(56-co-66)by component content shows that copolymerization changes the crystal morphology of the polymer.At the same time,copolymerization reduces the melting point and crystallization temperature of the polymer.When the component content of PA56 is less than 50%,the melting point and crystallization temperature of copolyamide decrease with the increase of PA56 component content in copolyamide.When the component content of PA56 is greater than 50%,the melting point and crystallization temperature of copolyamide decrease with the increase of PA66 component content in copolyamide.However,the thermal stability of copolyamide PA(56-co-66)with different component contents did not decrease significantly.In terms of mechanical properties,with the increase of PA56 content,the tensile strength and tensile modulus of copolyamide PA(56-co-66)first decreased and then increased,while the elongation at break was just the opposite.When the content of PA56 component was 50%,the elongation at break of copolyamide reached the maximum value of 229.34%,increased by 809.7% compared with PA56 and 473.5% compared with PA66.At the same time,the water absorption of copolyamide PA(56-co-66)increases with the increase of PA56 content.(3)The study on the crystallization kinetics of copolyamide PA(56-co-66)shows that the Avrami index n of all copolyamide PA(56-co-66)is between 2 and 3 during isothermal crystallization.The grain growth of all samples during isothermal crystallization is threedimensional spherulite growth.The copolymerization of PA56 and PA66 does not significantly change the crystallization mode of the material.The study of non isothermal crystallization process shows that jeziorny's modified Avrami equation can not well describe the non isothermal crystallization process of copolyamide,and Mo method can well describe the non isothermal crystallization process of copolyamide.(4)The rheological properties of copolyamide PA(56-co-66)show that all copolyamide PA(56-co-66)are pseudoplastic fluids.After copolymerization,the regularity of PA molecular chain is destroyed,the number of hydrogen bond binding atoms is reduced,and the density of entanglement nodes in the molecular chain is increased,which makes the molecular chain of copolyamide melt highly entangled to form a closer pseudo network structure,and the viscosity of polymer melt is increased,At the same time,the phenomenon of "shear stress thinning" becomes more and more obvious at low shear rate.