环氧基POSS处理碳纤维对聚酰亚胺复合材料性能的影响

Effect of Carbon Fiber Treated with POSS on Properties of Polyimide Composites

以均苯四甲酸酐（PMDA）、间苯二胺（m-PDA）为单体制备出高黏度的聚酰胺酸（PAA）,然后采用环氧基多面体低聚倍半硅氧烷（POSS）并辅以2-乙基-4-甲基咪唑固化剂对碳纤维（CF）进行表面处理,再将其与已制备的PAA经载玻片涂膜高温固化制得聚酰亚胺/碳纤维（PI/CF）复合材料,通过FIIR、拉曼光谱、XRD、SEM研究了改性碳纤维对PI/CF复合材料性能的影响。研究表明：POSS的接枝改性增加了CF表面的粗糙度和无序程度,固化剂2-乙基-4-甲基咪唑的加入进一步促进了接枝过程,大量POSS接枝并固化于CF表层,使CF表层粗糙度进一步增加,进而改善了CF与PI基体的界面黏合力和相容性。拉曼光谱研究表明,改性前后CF拉曼光谱经分峰拟合得到的具体参数,涂覆改性后CF的R值有所提升,从2.57提升到2.91,以咪唑作为促进剂处理后R值提升至3.18,提升了23.7%。La值从1.71 nm降至1.38 nm。力学性能分析表明,相比接枝前的CF,接枝处理可明显提高PI/CF复合材料的力学性能,添加3%CF并以POSS涂覆处理,拉伸强度和弹性模量分别较改性前提升了11.1%和6.1%,而涂覆POSS并辅以咪唑固化促进剂改性后拉伸强度和弹性模量分别较改性前提升了24.3%和12%,但是断裂伸长率却有所下降。

First of all, high viscosity polyamic acid（PAA） was prepared by using phthalic anhydride（PMDA） and m-phenylenediamine（m-PDA） as mono system. Then, epoxy polyhedral oligomeric silsesquioxane（POSS） and 2-ethyl-4-methyl imidazole curing agent were used for surface treatment of carbon fiber（CF）. Polyimide/carbon fiber（PI/CF） composites were prepared by high temperature curing with polyamide acid（PAA） coated with glass. The effects of modified carbon fibers on the properties of polyimide/carbon fiber（PI/CF） composites were studied by FIIR, Raman spectroscopy, XRD and SEM. The results show that： the surface roughness and disordered degree of carbon fiber are increased by the graft modification of epoxy polyhedron oligosilane polysiloxane（POSS）. The addition of 2-ethyl-4-methyl imidazole further promotes the grafting process. A large number of POSS are grafted and solidified on the surface of CF. The surface roughness of CF is further increased, and the interfacial adhesion and compatibility of carbon fiber and PI matrix are improved. The Raman spectra shows that： the specific parameters of the Raman spectra of the carbon fibers before and after modification are obtained by peak fitting. The R value of the modified carbon fibers increases from 2.57 to 2.91. After imidazole is used as an accelerator, the R value increases to 3.18 and increases by 23.7%. The La value drops from 1.71 nm to 1.38 nm. The analysis of mechanical properties shows that the mechanical properties of PI/CF composites are obviously improved by grafting compared with CF before grafting. The tensile strength and modulus of elasticity are increased by 11.1% and 6.1%, respectively, with the addition of 3%CF and POSS coating. The tensile strength and modulus of elasticity are increased by 24.3% and 12%, respectively, when the POSS is coated with imidazole curing accelerators, but the elongation at break decreases.