基于粉末微波发泡法制备超轻质聚酰亚胺泡沫的结构与性能

Structures and Properties of Lightweight Polyimide Foam Based on Powdered Precursor Process by Aid of Microwave

以3,3′,4,4′-二苯甲酮四羧基二酐和4,4′-二氨基二苯醚为主要原料,采用简单高效的粉末微波发泡法制备了一系列超轻质开孔柔性聚酰亚胺泡沫,克服了液相发泡法易掉渣的不足。泡沫密度6~200kg/m^3可调,厚度1~400mm可调,最大宏观尺寸可达1000mm×1000mm。对泡孔结构和性能进行了测试,分析了发泡原理,探究了高温下材料的拉伸、隔热和真空出气性能。结果表明,泡沫玻璃化温度达265℃、5%失重温度达560℃;随着密度由6kg/m^3增加至60kg/m^3,泡沫开孔率由99.1%降低至95%,拉伸强度由0.08MPa增加至0.92MPa,150℃时泡沫拉伸强度几乎不变;室温热导率则表现为先降低后增加的趋势,热端温度250℃,泡沫热导率均小于0.1W/(m·K);150℃的真空质量损失仅为0.947%,远低于液相发泡法的泡沫。

A series of polyimide foams using 3,3’,4,4’-benzophenone tetracarboxylic dianhydride and 4,4’-oxydianiline as main materials were fabricated by a facile and effective powdered precursor process with aid of microwave which has the advantage over liquid foaming process of no-dregs. In this case, polyimide foams can be produced in apparent densities of 6~200 kg/m^3, thickness of 1~400 mm, and dimension of 1000 mm×1000 mm. Then, the foaming mechanism, cell morphologies and properties were investigated in detail. Importantly, their thermal insulation, tensile performance and vacuum outgassing at high temperature were also illustrated. It is found that polyimide foams have Tg of 265 ℃ and 5% mass loss temperature of 560 ℃. The open cell content decreases from 99.1% to 95%, and the tensile strength increases from 0.08 MPa to 0.92 MPa when the apparent density increases from 6 kg/m3 to 60 kg/m3. Notably, the tensile property hardly decreases at 150 ℃. While the thermal conductivities decrease and then increase with foam densities. Moreover, and the thermal conductivities at 250 ℃ are lower than 0.1 W/(m·K) for all polyimide foams. In addition, the vacuum mass loss is 0.947% at 150 ℃, which is far below the value of polyimide foams based on the liquid foaming process.