Fixed-angle rotary shear as a new method for tailoring electro-mechanical properties of templated graphene-polymer composites

A capillary-driven particle-level templating technique was utilized to distribute graphite nanoplatelets (GNPs) into specially constructed architectures throughout a polystyrene matrix to form multi-functional composites with tailored electro-mechanical properties. By precisely controlling the temperature and pressure during a melt compression process, highly conductive segregated composites were formed using very low loadings of graphene particles. Since the graphene flakes form a honeycomb percolating network along the boundaries between the polymer matrix particles, the composites show very high electrical conductivity but poor mechanical strength. To improve the mechanical properties, a new processing technique was developed that uses rotary shear through pre-set fixed angles to gradually evolve the honeycomb graphene network into a concentric band structure over the dimensions of the sample. An experimental investigation was conducted to understand the effect of GNP loading as well as rotary shear angle on the mechanical strength and electrical conductivity of the composites. The experimental results show that both the electrical and mechanical properties of the composites are significantly altered using this very simple technique, which allows rational co-optimization of competing mechanical and electrical performance as appropriate for a given target application.