4193198 - Impact of mechanically-accelerated chemical degradation of entangled linear rubbery polymer melts on upcycling processes

Polymer upcycling requires applying catalytic knowledge to highly entangled and transport-limited polymer melts to deconstruct polymer molecules; effective processes will require understanding the impact of molecular weight and structure on rheology. In this work, shear-induced polymer chain scission is quantified to inform the design of processes for pre-treatment of polymers for catalytic upcycling. Flow-induced scission in entangled polymer melts is poorly understood and critical flow conditions for chain scission have not been identified. We focus on the impact of simple shear flow and its duration and strength on overall chain scission in entangled polymer melts and conduct a detailed analysis of the nature of the shear type and history, specifically considering the impact of work applied by shear flow. The level of scission scales with work applied by shear flow. Increasing temperature accelerates the scission process, suggesting that shear flow induced scission is an activated process. Superposition of isothermal curves (scission versus work, strain, stress) was possible with horizontal shifting and shift factors, , were found to follow and Arrhenius dependance with and activation energy of approximately 110 kJ/mol. Results strongly suggest that shear accelerates chemical degradation through tension along chain backbones, and we hope that polymer physics will allow this to be better understood.