Effect of multi-walled carbon nanotubes reinforcement and gamma irradiation on viscoelastic properties of ultra-high molecular weight polyethylene

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) has been used as a surface for acetabular in total joint replacements for the past 60 years. However, the performance of the implant is influenced by the increase in temperature because of the articulating motion and the contact asperities, which affects its longevity. The viscoelastic properties of multi-walled carbon nanotubes (MWCNTs) reinforced UHMWPE nanocomposites with respect to temperature and irradiation dose are not reported so far. Hence, an attempt was made to study the viscoelastic properties of UHMWPE by varying concentration of MWCNTs and intensity of irradiation dose. The test samples were subjected to sinusoidal loading in the temperature range of 30–80°C. Ultra-high molecular weight polyethylene nanocomposites were prepared at different concentrations of MWCNTs such as 0.5, 1.0, 1.5 and 2 wt-% using compression moulding process and the nanocomposites were subjected to ⁶⁰Co gamma irradiation up to 100 kGy dose. The viscoelastic characteristics of UHMWPE, such as storage modulus, loss moduls and damping factor of the irradiated nanocomposites, were studied in detail. It was observed that the storage modulus of the pure UHMWPE was increased by 139% with the addition of 2 wt-% MWCNTs; however, it was found to be reduced by 83% with 100 kGy irradiation doses. The damping factor and loss modulus of the nanocomposites were reduced by 27.3 and 71.6% with 2 wt-% of MWCNTs concentration, but both were increased with 100 kGy irradiation dose by 74.7 and 69% compared to virgin UHMWPE. It is concluded that the storage modulus reduced with the increase in temperature and also irradiation dose, which may lead to higher static deformation of material. However, the presence of MWCNTs would minimise the deformation and pave way for the better functionality of the material.

Keywords:

• UHMWPE
• MWCNTs
• Dynamic mechanical analysis
• Gamma irradiation

Acknowledgements

Authors acknowledge the funding support received from the Department of Science and Technology, India, IDP/Med/04/2009, M/s Ticona, Germany for kindly supplying the medical grade UHMWPE, M/s Microtrol Sterilization Pvt. Ltd., Bangalore. Authors also kindly acknowledge the assistance received from Technical staff of materials science laboratory, Department of Mechanical Engineering, Indian Institute of Technology Guwahati.