Composites of Cysteamine Functionalised Graphene Oxide and Polypropylene

Abstract

Abstract Cysteamine functionalised reduced graphene oxide (rGO) was grafted to polypropylene-graft-maleic anhydride (PP-g-MA) and subsequently melt blended with PP. The covalent bridging of rGO to PP-g-MA via the cysteamine molecule and co-crystallization are routes to promoting interfacial interactions between rGO and the PP matrix. A rheological percolation threshold was achieved for a nanofiller loading between 3 wt% and 5 wt%, but none detected for the composites prepared with un-functionalized rGO. At low loadings (0.1 wt%), functionalized rGO is well dispersed in the PP matrix, an interconnecting filler-filler, polymer-filler and polymer-polymer network is formed, resulting in increased tensile toughness (1 500%) and elongation at break (40%) relative to neat PP. Irrespective of whether the rGO was functionalised or not, it had a significant effect on the crystallization behavior of PP, inducing heterogeneous nucleation, increasing the crystallisation temperature (Tm) of PP by up to 10°C and decreasing the crystalline content (Xc) by ∼30% for the highest (5 wt%) filler loading. The growth of the monoclinic a-phase of PP is preferred on addition of functionalised rGO and b crystal growth suppressed.