端羧基液体氟橡胶的合成及固化性能

Synthesis and cure properties of liquid fluoroelastomer with carboxyl end group

以高相对分子质量偏氟乙烯(VDF)-六氟丙烯(HFP)-四氟乙烯(TFE)共聚物为原料,采用一步氧化降解法制备了低相对分子质量的端羧基液体氟橡胶,以六亚甲基二异氰酸酯三聚体为交联剂对其进行交联固化,确定了合成条件,通过傅里叶变换红外光谱和核磁共振表征了端羧基液体氟橡胶,并研究了固化产物的物理机械性能和热性能。结果表明,以KOH为碱时,随着KOH用量的增加,液体氟橡胶的相对分子质量降低(数均分子量较低值为2 200),羧基含量增加,产率可达到98%;随着NCO/COOH(摩尔比)的增加,固化产物的拉伸强度先增加后降低,扯断伸长率先降低后增加,当NCO/COOH为1.20时,固化产物的物理机械性能较好,在800℃时其残炭率为35%,较端羧基液体氟橡胶有所提高。

The carboxyl-terminated liquid fluororubbers with low relative molecular mass were prepared by one-step oxidative degradation of high relative molecular mass vinylidene fluoride （VDF）-hexafluoropropene （HFP）-tetrafluoroethylene （TFE）copolymer and were characterized by Fourier fransform infrared spectroscopy and nuclear magnetic resonance.The carboxyl-terminated fluororubbers were cured with 1,3,5-triazine-2,4,6 （1H,3H,5H）-trione,1,3,5-tris （6-isocyanatohexyl） and the mechanical and thermal properties ofthe cured products were investigated.The results showed that with increasing the amount of KOH,the number average molecular weight of liquid fluororubbers decreased （the minimum was 2 200）,the content of carboxyl groups increased,and the yield reached 98％.With increasing NCO/COOH （mole ratio）,tensile strength first increased and then decreased,while elongation at break went the other way around.When the NCO/COOH was 1.20,the all-round mechanical properties of the cured product were the better,and the carbon residue of cured product at 800 ℃ was 35％,higher than that of the uncured.