Effect of γ-Irradiation on Thermal Properties of MWCNTs Reinforced HDPE

Abstract

Crosslinking by gamma irradiation is a key technique employed in industrial and medical application of polymers to improve their mechanical and thermal properties. The objective of the present work is to investigate the effect of gamma irradiation on thermal properties of high density polyethylene (HDPE) reinforced with multiwalled carbon nanotubes (MWCNTs). The chemically treated MWCNTs were coated on HDPE pellets using nanofluid based deposition technique under continuous stirring, which were processed in an injection moulding machine to obtain nanocomposites having 0.25, 0.50, 0.75 and 1.0 wt% of MWCNTs. The nanocomposites thus obtained were exposed to γ-irradiation in the presence of air at 50 and 100 kGy doses. Thermal characterization of nanocomposites was studied using DSC, TGA and TMA techniques. The results obtained from the DSC studies revealed that the melting point of nanocomposites was not significantly influenced by the presence of MWCNTs, while γ-irradiation resulted a marginal change. The crystallinity of the nanocomposites was increased from 37.4 % for unirradiated HDPE to 55.8 % for 1.0 wt% and 100 kGy irradiated sample, which corresponds to 49 % enhancement. The onset temperature of degradation of nanocomposites was found to be influenced by both MWCNTs and irradiation dosage, which was increased by 16 °C for 100 kGy irradiated 1 wt% nanocomposite compared to unirradiated pure polymer. It is also found that the dimensional stability of the nanocomposites was increased by the reinforcement of MWCNTs. It is concluded from the above studies that thermal properties of nanocomposites are significantly influenced by the irradiation process and the concentration of MWCNTs.