Simultaneously improving the thermal stability, flame retardancy and mechanical properties of polyethylene by the combination of graphene with carbon black

Abstract

A novel combination of graphene nanosheets (GNSs) with carbon black (CB) was demonstrated to significantly improve the thermal stability, flame retardancy and mechanical properties of linear low density polyethylene (LLDPE). The temperature at the maximum weight loss rate of LLDPE under an air flow was dramatically increased by 94.3 °C, and the peak value of the heat release rate of the LLDPE nanocomposite measured by a cone calorimeter was obviously reduced from 1466 to 297 kW m⁻² (by 80%). According to the results from rheological tests and structural characterization of residual chars, the improved thermal stability and flame retardancy of LLDPE were partially attributed to the formation of a percolated network structure by GNS and CB in the LLDPE matrix, and partially to the accelerated oxidation crosslinking reaction of LLDPE radicals catalyzed by CB and GNS. More importantly, although both GNS and CB were commercial and used without any pre-treatments, LLDPE nanocomposites incorporating both the nanofillers showed much higher mechanical properties compared to neat LLDPE, especially Young's moduli which was improved by 219%. This was ascribed to good dispersions of two nanofillers and strong matrix–nanofiller interfacial interactions.