Interfacial strength and mechanisms of silicone resin composites reinforced with 2 different polyhedral oligomeric silsesquioxanes/carbon fiber hybrids

Grafting nanoscale reinforcement onto macrolevel carbon fiber (CF) surface is an efficient approach to improve interfacial strength and properties of composites. In the research, 2 different polyhedral oligomeric silsesquioxanes (POSS)/CF hybrids have been prepared by a facile 2-step method. Carbon fiber was grafted with aniline groups by aryl diazonium reaction using water as the reaction medium, and then separately functionalized with glycidyllsobutyl POSS (EP0418) or glycidyl POSS (EP0409) by the chemical bonding. Characterization of fiber surface structures before and after modification confirmed the covalent bonding nature between both kinds of POSS and CF. Atomic force microscopy images showed the uniform distributions of EP0418 or EP0409 modified on the fiber surface and the similar enhanced degree of surface roughness (89.3 and 88.7nm). Dynamic contact angle tests showed that EP0409-grafted CF (CF-g-EP0409) had lower contact angles and higher surface free energy than those of EP0418-grafted CF (CF-g-EP0418). Interfacial strength and hydrothermal aging resistance of composites enhanced significantly after POSS modification, especially for CF-g-EP0409 composites. Interfacial reinforcing mechanisms of composites reinforced with 2 different POSS/CF hybrids have also been analyzed and compared.