国产精品国产自产 I 96亚洲精品久久久蜜桃 I 涩视频在线 I 翔田千里精品久久一区二 I 337p日本欧洲亚洲大胆 I 字幕日韩视频一区二区 I 日韩偷拍一区二区 I 免费一级大片 I 九九久久精品国产av片国产 I 午夜福利92国语 I 国产免费97 I 波多野结衣福利视频 I 男人和女人在羞羞视频 I 久久精彩视频 I 忘忧草社区中文字幕www I 日韩影视一区二区三区 I 青青av I 国产av熟女一区二区三区 I 亚洲日韩片无码中文字幕 I 懂色av一区二区三区四区 I 国产伦人人人人人人性 I 91亚洲黄色 I 人妻丰满熟妇av无码区免 I 中文字幕人成人乱码亚洲电影 I 大伊人久久 I 免费人成在线观看网站品爱网 I 黄色三级免费片 I 我看午夜视频 I 性欧美色图 I 日韩三级一区二区

A benzo five-membered heterocyclic rigid chain polymer containing two nitrogen atoms. It is generally made by aromatic polyamine and diphenyl phthalate through polycondensation and cyclization. The reaction can be carried out in a molten state or in a strong polar solvent. The thermal stability of aromatic PBI in nitrogen is more than 500 ℃. The introduction of flexible groups or side groups can improve the solubility, but the thermal stability is reduced. Trade name Celazole PBI. Poly m-phenylene bibenzimidazole plastic has a thermal deformation temperature of 430 ° C, a limiting oxygen index of 58, a compressive strength of 410 MPa, a tensile strength of 165 MPa, a flexural strength of 227 MPa, a friction coefficient of 0.27 with steel, a dielectric constant of 3.3, radiation resistance, Excellent resistance to boiling water, solvents and chemicals. It can be used as high-temperature-resistant adhesives and high-performance composite materials. It is widely used in aerospace, chemical machinery, petroleum mining, automobiles and other fields, and fiber fabrics are used as protective clothing against fire and atomic radiation.