Polypropylene/graphene nanosheet nanocomposites by in situ polymerization: Synthesis, characterization and fundamental properties

This study investigates the synthesis, characterization and properties of isotactic polypropylene/graphene nanosheet nanocomposites (iPP/GNS). These nanocomposites were prepared by in situ polymerization using the metallocene complex rac-Me2Si(Ind)2ZrCl2 and methylaluminoxane (MAO) as cocatalyst. Homogeneous graphene nanosheet dispersions within the polymeric matrix were observed by TEM and XRD. The molecular characteristics of iPP, such as molecular weight, polydispersity and tacticity, were not affected by the presence of nanoparticles. The thermal properties investigated by DSC and TGA showed that graphene nanosheets significantly improved the matrix, increasing the crystallization and the degradation temperatures. From a mechanical perspective, there was an excellent balance between a significant increase in Young’s modulus and a slight reduction in the elongation at break. The reinforcing effect of graphene incorporation was confirmed by the increase of the storage modulus with nanosheet content. An enhancement of dimensional stability was also detected, and deformability was significantly smaller in the nanocomposites than in the homopolymer. Impedance measurements showed that the electrical conductivity increased by a factor of 108 compared to that of neat iPP.