硅烷偶联剂修饰下SiO2-甲基乙烯基硅橡胶分子界面的粘结性

Adhesion of SiO2-methyl vinyl silicone rubber molecular interface modified by silane coupling agents

纳米SiO2掺杂已经成为提升甲基乙烯基硅橡胶(MVSR)性能的有效方法,但是纳米SiO2容易发生团聚现象,将其直接掺到MVSR基体中时,纳米SiO2难以在MVSR基体中分散,从而造成SiO2-MVSR分子界面粘结效果不佳、分子界面存在缺陷等不利影响,进而无法实现提升MVSR性能的目的。为了提升SiO2-MVSR分子界面的粘结性,使纳米SiO2在MVSR基体中更易分散,本文构建了未修饰和KH550、KH560、KH570、KH792四种硅烷偶联剂修饰下的SiO2-MVSR分子界面模型,并对模型进行结构优化和分子动力学计算。通过比较不同模型中分子界面的结合能、粘结深度和粘结热稳定性的变化规律,从分子结构角度分析硅烷偶联剂修饰下SiO2-MVSR分子界面粘结性提升的原因。研究表明:提升SiO2-MVSR分子界面粘结性的关键在于优选硅烷偶联剂的非水解基团,当非水解基团中与MVSR分子链相同的化学键占比越大,包含电负性较强原子的数量越多时,修饰后SiO2-MVSR分子界面粘结性的提升效果就越好,同时,硅烷偶联剂较长的链长与较大的相对分子质量也会对粘结性的提升起到一定帮助。

Nano-SiO2 doping has become an effective way to improve the performance of methyl vinyl silicone rubber(MVSR).However,nano-SiO2 is easy to agglomerate.When it is directly mixed into MVSR matrix,nano-SiO2 is difficult to disperse in MVSR matrix,resulting in poor adhesion effect of SiO2-MVSR molecular interface,defects in the molecular interface and other adverse effects,so that the purpose of improving MVSR performance cannot be achieved.In order to improve the adhesion of SiO2-MVSR molecular interface and make nano-SiO2 more easily dispersed in MVSR matrix,this paper constructed the SiO2-MVSR molecular interface models that unmodified and modified by KH550,KH560,KH570 and KH792,and carried out structural optimization and molecular dynamics calculation.By comparing the adhesion energies,adhesion depths and adhesion thermal stabilities of the molecular interface in different models,the reason for the improvement of the adhesion of SiO2-MVSR molecular interface modified by silane coupling agents was analyzed from the perspective of molecular structure.The results show that the key to improve the adhesion of SiO2-MVSR molecular interface is to select the non-hydrolytic group of the silane coupling agents.When the proportion of the same chemical bond between the non-hydrolytic group and MVSR molecular chain is larger,and the number of more electronegative atoms is more,the effect of improving the adhesion of SiO2-MVSR molecular interface is better.At the same time,the longer chain length and larger relative mo-lecular weight of silane coupling agent will also help to improve the adhesion.