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Abstract: In the present work, a dynamic thermo-mechanical analysis technique has been used to investigate the effect of pre-heat treatments on the visco-elastic properties of Ultra-High Molecular Weight Polyethylene (UHMWPE) as a function of frequency and temperature. These properties include storage modulus (E′) and loss modulus (E″). The UHMWPE specimens were pre-heated at 50, 80 and 100°C for periods of 2 and 4h, respectively. The effect of these pre-heat treatments on the quasi-static mechanical properties (Young''s modulus, yield strength, fracture strength, ductility and micro-hardness) has also been investigated. Finally, the degree of crystallinity of the UHMWPE has been measured as a function of pre-heat treatment time and temperature. The results show a strong dependence of most of these properties on the degree of crystallinity which is a function of pre-heat treatment temperature and duration. [Copyright &y& Elsevier]

In recent work, we demonstrated the successful fabrication of core-shell nanofiber composites with enhanced tensile, surface wetting and cytocompatibility properties via coaxial electrospinning using PLA and PVA. It has been shown that core/shell-structured PLA/PVA nanofiber mat has the hydrophilic benefits of PVA and the attractive biological properties of PLA. In this paper, we present detailed mechanical evaluation of the electrospun coaxial nanofiber mats under static, dynamic and creep loading. The core/shell-PLA/PVA nanofibers showed nearly 233% and 150% increase in tensile strength and ductility, respectively, compared to pristine PLA. Dynamic loading tests were employed to study the viscoelasticity of the coaxial core-shell composite nanofibers at various temperatures and frequencies. The results of the storage and loss moduli of the coaxial nanofibers suggested strong physical interaction between the PLA and PVA layers, that contribute to the observed good mechanical behaviour. The better creep resistance of the coaxial PLA/PVA nanofibers under axial loading compared to the pristine materials provides further evidence for the physical interaction between the two constituent materials. A simple linear viscoelastic model is used to quantify the evolution of creep strain in pristine and coaxial materials. This research may help to understand the physical relation between the observed viscoelastic behaviour and the internal structure of coaxial core/shell nanofibers of PLA and PVA. [ABSTRACT FROM AUTHOR]