Towards balanced strength and toughness improvement of isotactic polypropylene nanocomposites by surface functionalized graphene oxide

Balanced stiffness and toughness is always the goal of high-performance general plastics for engineering purposes and the interfacial crystalline structure control has been proved to be an effective way to approach this goal. In this work, a kind of novel beta-nucleating agent (beta-NA) for isotactic polypropylene (iPP), one of the most rapidly developing general plastics, was supported onto the surface of octadecylamine functionalized graphene oxide (GO-D), and the effects of functionalized graphene oxide (GO) on the crystallization behavior, crystalline structures and mechanical properties of iPP composites were studied. The presence of the octadecyl chain changes the hydrophilic GO to be hydrophobic, and further supporting of beta-NA onto GO-D (GO-N) does not change its solubility in xylene. The hydrophobic nature of octadecyl chains on the GO-D and GO-N surfaces leads to improved interfacial adhesion with the non-polar iPP matrix. At the same time, GO-N exhibits high efficiency in inducing the formation of beta-crystals of iPP. The relative content of beta-crystals, k(beta), reaches a value as high as 73.6% at a loading of 0.1 wt% GO-N, resulting in a maximum increase in impact strength by almost 100% and a simultaneous improvement of the tensile strength by about 30%. This work provides a potential industrializable technique for high-performance iPP nanocomposites.