Structural Elucidation and Mechanical Behavior of Cryogenically Treated Ultra-High Molecular Weight Poly-ethylene (UHMWPE)

The present work discusses the enhancement of mechanical properties, namely wear and impact resistance, of ultra-high molecular weight poly-ethylene (UHMWPE), exposed to cryogenic treatment under different conditions. The cryogenic temperature was found to play a vital role in the structure and properties of UHMWPE, whereas − 140 °C for a soaking period of 12 h was found to enhance the specific wear rate by 48% and 35% in dry and lubricated condition, respectively, while the impact strength increased by 175%, without hampering its structural stability. This finding contradicts the popular belief that a minimum 24 h of cryo-treatment at − 185 °C is essential to bring out the necessary changes in any polymer. Conversely, cryogenically treating the polymer at − 185 °C weakens and deteriorates the material, while lower temperature (− 80 °C) demonstrates to be insufficient to induce the desired cryo-structural modifications. The FTIR and XRD analysis revealed that the mechanical properties enhancement in UHMWPE is credited to the cryo-structural rearrangement of highly dense carbon backbone, which in turn reduces the inter-chain distance and brings the adjacent crystalline segments closer to each other, thereby increasing the crystallinity as well.