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Abstract:This work contributes to the development and characterization of the corrosion resistance and antifriction properties of high performance polyurethane (PU)/graphene (Gr) composite coating. In this study, PU composite coatings containing 0, 2, 4 and 8 wt.% of Gr were prepared and evaluated using various corrosion and mechanical tests, namely electrochemical impedance spectroscopy, salt spray tests, cross-cut tape tests and dynamic mechanical analysis. Antifriction properties of the coatings were evaluated using a tribometer with a ball-on-disc mode at room temperature. The corrosion resistance and adhesion property of the PU coatings were found to be enhanced by adding 4 and 8 wt.% of Gr. The coefficient of friction revealed that the antifriction properties of the PU/Gr composite coatings were 61% lower than those of the conventional coating when the Gr content was increased to 8 wt.%.

In the context of emerging methods to control particle organization in particle-matrix composite materials, we explore, using finite element analysis, how to modulate the material bulk mechanical stiffness. Compared to a composite containing randomly distributed particles, material stiffness is enhanced 100-fold when filler particles are aligned into linear chains lying parallel to the loading direction. In contrast, chains aligned perpendicular to that direction produce negligible stiffness change. These outcomes reveal how zigzag chains, which provide intermediate results, can modulate stiffness. The stiffness decreases gradually with increasing zigzag angle θ over a range spanning two orders of magnitude.

Elastomers are used as dielectric layers contained between the parallel conductive plates of capacitors. The introduction of filler particles into an elastomer changes its permittivity ε. When particle organization in a composite is intentionally varied, this alters its capacitance. Using numerical simulations, we examine how conductive particle chains introduced into polydimethylsiloxane (PDMS) alter ε. The effects of filler volume fraction ψ, interparticle d and interchain spacing a, zigzag angle θ between adjacent particles and overall chain orientation, particle size r, and clearance h between particles and the conductive plates are characterized. When filler particles are organized into chainlike structures rather than being just randomly distributed in the elastomer matrix, ε increases by as much as 85%. When particles are organized into chainlike forms, ε increases with increasing ψ and a, but decreases with increasing d and θ. A composite containing smaller particles has a higher ε when ψ<9% while larger particles provide greater enhancement when ψ is larger than that value. To enhance ε, adjacent particles must be interconnected and the overall chain direction should be oriented perpendicular to the conductive plates. These results are useful for additive manufacturing on electrical applications of elastomeric composites.