Transparent polysiloxane/POSS hybrid coatings on polycarbonate for enhanced abrasion resistance and hydrophobicity

Abstract

Siloxane coatings can be applied via simple and low-cost sol-gel process, exhibit high mechanical strength and abrasion resistance, making them suitable for wide range of industrial use. However, acquiring high optical transparency and maintaining mechanical properties while providing functional properties, like hydrophobicity, remain a challenge. In this study, highly transparent and abrasion resistant coatings with improved hydrophobicity and enhanced elastic recovery were developed by combining both organic and inorganic precursors, TEOS (tetraethyl orthosilicate), GPTMS (3-glycidyloxypropyl trimethoxysilane) and Amino-functional Polyhedral Oligomeric Silsesquioxane (POSS). The effect of precursor ratios on the optical properties, such as transmittance, haze and yellowness index, as well as the mechanical properties, including hardness, young's modulus, elasticity and abrasion resistance of hybrid organic-inorganic siloxane coatings deposited on polycarbonate via flow-coating was examined. Chemical, morphological, optical and mechanical analyses of the coatings were done by FTIR, XPS, UV/vis spectroscopy, hazemeter, optical and confocal microscopy, contact angle, Taber abrasion, pencil hardness and nanoindentation. We achieved minimal haze of 0.44 % and a high optical transmittance of ∼83 % within the 400 nm to 700 nm wavelength range, and haze was increased only to 0.93 % after 1000 cycle of Taber abrasion. Also, water contact angles increased to ∼112° after inclusion of Amino-POSS molecules. These findings indicate that the developed hybrid organic-inorganic siloxane coatings show significant potential as transparent and abrasion-resistant multifunctional coatings.