The modified prepolymer was first synthesized by-NH_2 of gelatin condensating with anhydride of low molecular weight polyamic acid terminated with anhydride at higher temperature, and then the modified polyamic acid with gelatin was obtained by prepolymer chain-extending. The different reacting factors during prepolymer stage were studied by determining intrinsic viscosity of modified polyamic acid, as the structure and thermal property were determined by infrared spectroscopy and differential scanning calorimetry. The results showed that the most intrinsic viscosity of modified polyam-ic acid with gelatin can be obtained as the mass of gelatin was 35% at 40℃ for 25min. The structure of polyamic acid was changed through modified with gelatin, and the glass transition temperature of modified polyamic acid film with chemical imidization was reduced by 39℃, compared to that of polyamic acid film.%通过明胶链上的-NH_2与低分子酸酐封端的聚酰胺酸链端酸酐首先在较高温度下缩合反应生成改性预聚体,然后再对改性预聚体扩链,得到明胶改性聚酰胺酸.通过测定明胶改性聚酰胺酸的特性黏度,研究了改性预聚体反应阶段不同反应条件对聚合物特性黏度的影响,同时采用红外光谱和示差扫描量热测定了明胶改性聚酰胺酸的结构与热性能.结果表明,在改性预聚体合成阶段,当明胶用量为35%、反应温度为40℃和反应时间为25min时,明胶改性聚酰胺酸的特性黏度最大.经过明胶改性,改变了聚酰胺酸的结构,使其化学亚胺化薄膜的玻璃化温度比聚酰胺酸化学亚胺化薄膜的降低39℃.
展开▼
