共聚结构和分子量对热塑性聚酰亚胺树脂熔融与耐热性能的影响

基于具有刚性主链结构的4,4'-(六氟亚异丙基)双邻苯二甲酸酐/对苯二胺(6FDA/p-PDA)树脂体系, 通过共聚引入间苯二胺(m-PDA)、 4,4'-二氨基-2,2'-双三氟甲基联苯(TFDB)和9,9'-双(4-氨基苯基)芴(BAFL)等主链刚性且兼具大自由体积特性的芳香二胺, 以非反应性封端剂邻苯二甲酸酐(PA)对分子量进行调控, 设计制备了系列分子量可控的热塑性聚酰亚胺(TPI)树脂. 系统研究了共聚结构和分子量对TPI树脂熔融性能和耐热性能的影响, 构建了聚合物的聚集态结构与树脂熔融性能的对应关系, 并对树脂的室温和高温力学性能进行了评价. 研究结果表明, 大自由体积的芳香二胺共聚结构的引入可有效降低分子链堆砌密度, 增大聚合物的自由体积, 从而赋予树脂良好的熔融性能. 降低设计分子量可进一步改善树脂的熔融加工性. 这类具有刚性主链结构的TPI树脂兼具优异的耐热性能和力学性能, 树脂的玻璃化转变温度在308~338 ℃之间, 以TFDB和BAFL共聚制备的TPI-C-25K和TPI-D-25K树脂表现出高强高韧的特性, 拉伸和弯曲强度分别超过120 MPa和190 MPa, 断裂伸长率大于8.2%, 并且在250 ℃高温下表现出良好的耐热稳定性.

Effect of Copolymerization Structure and Molecular Weight on Melt Fluidity and Thermal Properties of Thermoplastic Polyimide Resins

A series of molecular-weight controlled thermoplastic polyimide（TPI） resins was synthesized based on 4，4'-（hexafluoroisopropylidene）diphthalic anhydride/p-phenylenediamine（6FDA/p-PDA） endcapped with phthalic anhydride（PA）， in which the aromatic diamides with rigid backbone and large free volume， i.e.，m-phenylenediamine（m-PDA）， 2，2'-bis（trifluoromethyl） benzidine（TFDB） and 9，9-bis（4-aminophenyl） fluorene（BAFL）， were incorporated respectively. The effects of copolymerization structure and molecular weight on the melt fluidity and thermal properties of TPI resins were investigated. The correlation between the aggregation structures of TPI resins and their melting performance was constructed. The mechanical properties of TPI resins were evaluated at ambient and elevated temperatures. The results indicated that incorporation of aromatic diamines with large free volume as copolymerization structure can effectively reduce the molecular chain stacking density and increase the free volume of polymer， as a result， providing the resin good melting performance. The melt processability of resins can be further improved by reducing their designed molecular weight. These TPI resins with rigid backbone have excellent thermal stability and mechanical properties. The glass transition temperatures of these resins were in the range of 308—338 ^oC. TPI-C-25k and TPI-D-25k resins with the copolymerization structure of TFDB and BAFL， respectively， revealed high strength and toughness. They gave the tensile strength and flexural strength exceeding 120 MPa and 190 MPa， respectively， and showed the elongation at break over 8.2%. These TPI resins also exhibited good thermal stability at 250^℃.