Development of a new method to evaluate chain entanglements density in low entangled UHMWPE and UHMWPE/Graphene nanocomposites

Several methods such as oscillatory rheometry, by following modulus build up, and solid state nuclear magnetic resonance (NMR) have been introduced to investigate entanglement density of polymers. In this study, we developed a new method to evaluate entanglement density in ultra-high molecular weight polyethylene (UHMWPE) using dynamic mechanical thermal analysis (DMTA). DMTA tests were conducted on films and drawn tapes made from low entangled UHMWPE and UHMWPE nanocomposites
containing graphene nano-sheets. In this study, the relation between α-transition temperature and entanglement density was investigated. DMTA results confirmed that as the content of entanglements increased, the chain mobility decreased and the α-transition moved to higher temperatures. It was found that the drawn tapes show a modulus increase with temperature in DMTA due to the tendency of the UHMWPE chains to return to its undrawn state.