RPG Student List

 

Jin LI

Doctor Candidate in Chemical and Biomolecular Engineering

Supervisor: Prof. Ping GAO

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Research Topic

Super-strong Thin/Ultra-thin High-voidage UHMWPE Films and the Extreme Reinforcement by Graphene

Abstract

Many efforts have been made in exploring 2D graphene’s ultimate reinforcement potential for polymer composites. Hitherto, the absence of freestanding polymer thin-films for the construction of ideal composite with full surface alignment of 2D graphene for direct mechanical property characterization has been a bottleneck for validating graphene’s reinforcement limit. In this thesis, freestanding biaxial-oriented super-strong nanoporous ultrahigh molecular weight polyethylene (UHMWPE) membranes with thicknesses of 80 nm to 200 nm were synthesized and investigated. Their maximum tensile strengths and ductilities reached the fabulous values of 1 GPa and 25%, respectively. Based on that, the top surface of the membrane was aligned by spanning a chemical vapor deposition (CVD) monolayer graphene. The assembled graphene/UHMWPE (GPE) porous membrane exhibited unprecedented tensile strengths much higher than stainless steel. The Young’s modulus and tensile strengths of the prepared GPE are in accordance with the upper-bound prediction by the classical theory of mixtures corroborating graphene’s maximum limit in mechanical property reinforcement. Besides, the toughening effect of graphene was also revealed by a six-fold crack-propagation-rate retardation. These findings may lead to the further breakthroughs of reinforce 2D polymer composites and corresponding applications.