扩链法制备高相对分子质量PPTA沉析纤维的研究

Preparation of high-relative molecular mass PPTA precipitated fiber by chain extension reaction

以对苯二甲酰氯(TPC)和对苯二胺(PPDA)为单体,通过共聚反应分别制备羧基封端和氨基封端的聚对苯二甲酰对苯二胺(PPTA)溶液,将二者按等摩尔比混合均匀后通过直接沉析法制备同时带有端羧基和端氨基的PPTA沉析纤维,再通过高温热处理扩链反应制备高相对分子质量PPTA沉析纤维,研究了共聚反应、沉析及扩链反应条件。结果表明:共聚反应时较佳的单体摩尔比为0.985,羧基封端和氨基封端PPTA溶液的比浓对数黏度(η)分别为2.78 dL/g和2.54 dL/g,二者混合后溶液的η变化不大,为2.73 dL/g;沉析过程中沉析分散机搅拌转速控制在2000 r/min,成纤性好,PPTA沉析纤维呈长径比较大的膜状结构;扩链反应较佳条件为300℃下反应60 min,扩链反应后PPTA沉析纤维的η由2.73 dL/g提高到4.21 dL/g,相对分子质量大幅提高,且扩链反应后PPTA沉析纤维的热稳定性能也得到提高。

Using terephthalamide(TPC)and p-phenylenediamine(PPDA)as monomers,carboxyl terminated and amino terminated poly(p-phenylenediamine)(PPTA)solutions were prepared by copolymerization reaction.The two solutions were mixed evenly in equimolar ratio to produce PPTA precipitated fibers with both carboxyl and amino terminated groups by direct precipitation method.And high-relative molecular mass PPTA precipitated fibers were prepared by high-temperature heat treatment and chain extension reaction.The copolymerization,precipitation and chain extension reaction conditions were studied.The results showed that the optimal monomer molar ratio for copolymerization reaction was 0.985,and the inherent viscosity(η)of carboxyl terminated and amino terminated PPTA solutions were 2.78 dL/g and 2.54 dL/g,respectively,and theηof the solution did not change significantly and reached 2.73 dL/g after mixing the two solutions;the stirring speed of the precipitation disperser was controlled at 2000 r/min during the precipitation process,resulting in good fiber forming properties,and the PPTA precipitated fibers exhibited a membranous structure with a high aspect ratio;and theηof PPTA precipitated fibers increased from 2.73 dL/g to 4.21 dL/g,the relative molecular mass was significantly increased,and the thermal stability was also improved after the chain extension reaction at 300℃for 60 min.