Influence of MWCNTs and gamma irradiation on thermal characteristics of medical grade UHMWPE

Several techniques are available to characterize the influence of gamma-irradiation on structural parameters of polymers; among which thermal characterization is more often used. The present work is aimed to study the influence of multi walled carbon nanotubes (MWCNTs) and gamma-irradiation on polymer crystallinity, lamellar thickness, coefficient of thermal expansion (CTE) and thermal stability of UHMWPE. The chemically treated MWCNTs were homogenously dispersed in UHMWPE using a ball milling machine and compression moulded to make the nanocomposites with different concentration of MWCNTs. The nanocomposites were then gamma-irradiated at a dose rate of 2.5 kGy/h up to 25, 50, 75, 100 kGy irradiation doses. The results obtained from TGA studies revealed that the presence of MWCNTs improved the thermal stability and onset temperature of degradation of nanocomposites. The CTE of nanocomposites was decreased with an increase of MWCNTs concentration and irradiation dose. The reduction of thermal expansion of nanocomposites aids in minimizing the dimensional fluctuation of them. It is concluded that irradiation and the presence of MWCNTs in UHMWPE not only improved the thermal stability of the composites but also enhanced their crystallinity and lamellar thickness.