Synthesis Of A New Polyamide-Imide And The Evaluation Of Its Application Performance

Polyamide acid was synthesized by polycondensation reaction with anhydride and the diamines with specific structure in N,N-dimethylacetamide(DMAc) by organic amine as a acid-catcher. The solid content in reaction is maintained at 20%, and the monomer ratio is 1:1. The polyamide acid obtained is converted into polyamide-imide by treating with anhydride. The structure of the polymer, solvent resistance, crystallization behavior and thermal properties are investigated by FT-IR, DSC, XRD, TG and DMA. The result shows that the polymer has the characteristic structure of PAI:amide linkages and imide linkages, the good solvent resistance and good thermal stability. The initial decomposing temperature is 430℃, and 30.6% weight loss in the range of 430℃-800℃in nitrogen atmosphere. The glass transition temperature is 298℃, and the polymer is hard to crystallize because of its structure.The solid content and monomer molar ratio are kept unchanged, the effect of monomer purity, environment humidity, acid-catcher and reaction time on the condensation polymerization are studied. The result shows that high monomer purity and low water content in monomer and in solvent are the key factors in the condensation polymerization. Greater ynamic viscosity could be obtained under lower temperature in the earlier stage and higher temperature in the later stage. The polymerization degree decreases with humidity increasing. The specific dynamic viscosity could be controlled by adjusting the amount of organic amine and reaction time. Under higher solid content, the longer the reaction time, the higher dynamic viscosity of the polymer solution is.Transparent film and fiber can be prepared with the PAI solution. The dynamic viscosity of the polymer is in proportion to the mechanical strength of the film and fiber. The PAI fiber has better thermal stability and higher tensile strength. Compared to the same type of domestic products in the market, our PAI fiber has excellent mechanical property and heat resisting property.