不同偶联剂对介孔分子筛MCM-41的表面修饰及对MCM-41/环氧树脂性能的影响

使用2种硅烷偶联剂(KH550和KH792)对介孔分子筛MCM-41进行表面改性,采取氮气吸附-脱附、FTIR和TGA等进行表征,并采用原位聚合法制备了MCM-41/环氧树脂复合材料,研究了偶联剂种类和MCM-41用量等对复合材料固化过程及性能的影响。结果表明:硅烷偶联剂可与MCM-41表面的硅羟基反应,在分子筛内外表面接枝上功能化基团。经表面修饰的MCM-41比表面积下降为原来的1/5,KH550在MCM-41表面接枝率仅为KH792的一半。KH550与MCM-41外表面反应得更充分,KH792对MCM-41孔道内壁的修饰效果更强。固化动力学结果表明:KH792的功能化基团有伯胺和仲胺,与环氧树脂具有更高的反应活性,但不利于环氧大分子进入孔道,仅以球形粒子的形式添加在环氧树脂中;KH550表面修饰的MCM-41可使环氧大分子进入孔道内形成互穿结构。KH550表面修饰体系更多体现出MCM-41多孔的特征,形成了有机-无机互穿结构的复合体系,大幅度提高了储能模量和玻璃化转变温度。KH792表面修饰体系则呈常规球形纳米粒子的特征,其储能模量和玻璃化转变温度较纯环氧树脂有所提高但幅度不大。

Surface modification of different coupling agents on mesoporous molecular sieve MCM-41 and effects on properties of MCM-41/epoxy

Two kinds of silane coupling agents (KH550 and KH792) were applied to modify the surface of mesoporous molecular sieve MCM-41, and thus measurements including N₂ adsorption-desorption, FTIR and TGA etc, were employed to characterize. The MCM-41/epoxy composite was prepared by in-situ polymerization method and the influences of coupling agent kinds and MCM-41 content on curing process and properties of composite were explored. The results show that the silane coupling agent could react with silicon hydroxyl of MCM-41 surface and thus the functional group is grafted to the internal and external surface of molecular sieve. The specific surface area of surface modified MCM-41 decreases to the one fifth of neat MCM-41 and the KH550 grafting ratio on surface of MCM-41 is just half of that in KH792.The reaction between KH550 and MCM-41 external surface is more ample and KH792 has more sufficient modification effect on internal wall of MCM-41 pore channel. The curing kinetics results show higher reaction activity of KH792 containing functional groups of the primary and secondary amine but hindering the epoxy macromolecule move into pore channel and thus MCM-41 is added as spherical particle in epoxy while the epoxy macromolecule could move into KH550 surface modified MCM-41 pore channel forming the interpenetrating structure. KH550 surface modified system improves the storage modulus and glass transition temperature greatly because the character of porous effect appears and organic-inorganic interpenetrating structure composite system forms. The character of KH792 surface modified system shows the conventional spherical nano particle and thus storage modulus and glass transition temperature have slight improvement compared to pure epoxy.