4-苯乙炔苯酐封端聚酰亚胺树脂的合成与性能研究

使用3,3′,4,4′-二苯醚四酸二酐(ODPA)、3,3′,4,4′-联苯四酸二酐(BPDA)、1,3-双(4-氨基苯氧基)苯(1,3,4-APB)、3,4′-二氨基二苯醚(3,4′-ODA)和反应性封端剂4-苯乙炔苯酐(4-PEPA)合成了设计分子量为5000的系列苯乙炔基封端的聚酰亚胺低聚物,并使用XRD、DSC、TGA、FT-IR、DMA和流变仪等对低聚物的化学结构、热性能和熔体性能,固化后树脂的热性能和力学性能进行了测试.研究结果表明基于ODPA的低聚物具有低的熔体粘度和良好的熔体粘度稳定性,固化后的树脂具有很高的热失重温度,较高的玻璃化转变温度以及良好的力学性能尤其是高的断裂伸长率(>10%);基于BPDA的低聚物具有一定的结晶性,其结晶熔融温度与苯乙炔基固化交联温度相近,影响了材料的成型工艺性能.

Synthesis and Characterization of 4-Phenylethynylphthalic Anhydride Terminated Oligoimides and Polyimides

Thermosetting phenylethynyl terminated polyimides are well known for their super thermo-oxidative stability and excellent toughness,and have been widely used in aerospace area.PETI-5 (PhenylEthynyl Terminated Imide-5) developed by NASA is the-state-of-art of this type polyimides,while it is a semi-crystalline polyimide with melting temperature of 353℃ near the crosslinking temperature of phenylethynyl groups,which made it difficult for PETI-5 to fabricate complex shape parts.In the pursuit of novel phenylethynyl terminated polyimides with high melt processability,researchers have developed several polyimides by introduction of fluorine groups and twisty structures.In this paper,a series of oligoimides (PIO) with calculated molecular weight of 5000 were prepared using flexible dianhydride of 4,4′-oxydiphthalic anhydride (ODPA),and mixtures of two diamines of 1,3-bis(4-aminophenoxy)benzene (1,3,4-APB) and 3,4′-oxydianiline (3,4′-ODA) in the presence of 4-phenylethynylphthalic anhydride (4-PEPA) as endcapping agent in order to enhance the processability.In addition,oligoimides (PIB) using 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) were also prepared for comparison.Effects of the kind of dianhydride and diamine on their properties and melt processabilities were systematically investigated.Experimental results indicated that PIO was amorphous in nature,and exhibited low melt viscosity and high melt viscosity stability at elevated temperatures,and with the increase of the content of 1,3,4-APB the melt viscosity decreased correspondingly.The PIB is semi-crystalline in nature and exhibited high melt viscosity at elevated temperatures,meanwhile,the melt temperature of PI-B was close to the cure temperature of phenylethynyl groups,which reduced the processability.The molecular weight-controlled oligoimides could be thermally cured at 371℃ to yield thermosetting polyimides by polymer chain extension and crosslinking of phenylethynyl groups.All cured resins showed good thermal stability with 5% weight loss temperature of>500℃,and high glass transition temperatures of>243℃.In addition,with the increase of the content of 1,3,4-APB,the glass transition temperatures of PIO cured resin decreased from 281 to 243℃.PIO-2 cured resin also exhibited good mechanical properties with tensile strength of 102 MPa,tensile modulus of 1.8 GPa,high break elongation of 10%,flexural strength of 142 MPa and flexural modulus of 3.1 GPa.