Poly(propylene)-grafted thermally reduced graphene oxide and its compatibilization effect on poly(propylene)–graphene nanocomposites

Abstract

Graphene is a nanofiller with outstanding mechanical, electrical, and gas barrier properties. However, graphene nanofillers suffer from poor dispersibility in polymer matrices, particularly in non-polar polymers. This paper reports the preparation and characterization of enhanced poly(propylene)/graphene nanoplatelet (PP)/(GNP) nanocomposites, using PP-grafted thermally reduced graphene oxide (TRGO) as a compatibilizer. We optimized the synthesis of the compatibilizers by controlling the temperature of the reduction of graphene oxide. Reduction reactions were carried out at 200 °C (TRGO2), 400 °C (TRGO4) and 600 °C (TRGO6). The crystallinity, crystallization temperature, and onset temperature of PP/GNP nanocomposites were all increased by the presence of the PP-g-TRGO compatibilizers in loadings of 0.1 wt%. The mechanical and gas barrier properties of PP/GNP nanocomposites were enhanced by the presence of only 0.1 wt% PP-g-TRGO compatibilizer. Among the three PP-g-TRGO compatibilizers used to prepare PP/GNP nanocomposites (PP-g-TRGO2, PP-g-TRGO4 and PP-g-TRGO6), those prepared using PP-g-TRGO6 exhibited superior electrical, mechanical and oxygen barrier properties. These results were attributed to high crystallinity, a strong interfacial interaction between GNPs and the compatibilized PP matrix, and the compatibilizer-enhanced dispersibility of the GNPs in the PP matrix. The superior performance of PP-g-TRGO6 in particular is suggested to occur because of the greater availability of strong π–π interactions between GNPs and the increased sp²-hybridised carbon content of TRGO6, relative to the other TRGO systems. The performance-enhancing effect of PP–TRGO6 was evident despite its lower TRGO content, compared to PP-g-TRGO2 and PP-g-TRGO4.