Effect of Bio-Based Monomers on the Scratch Resistance of Acrylate Photopolymerizable Coatings

International audiencePhotopolymerizable clear coatings based on bio-sourced acrylates, dedicated to the protection of polycarbonate substrates, were studied. The bio-sourced compounds were not based on triglycerides but were smaller, industrially available molecules similar to classical petro-based monomers. Their polymerization kinetics was studied by photo-DSC and was shown to allow high acrylate conversions even at 25 degrees C. Closely related coatings enriched in alkyl segments, or in monoacrylates to decrease the crosslinking density, were compared. The material composition affects its nanomorphology deduced from X-ray diffraction. Although these changes in composition can slightly shift the mechanical relaxation, it remains wide, and the elastic modulus remains high (>10(8) Pa) for all the tested materials. Microscratch experiments highlighted the efficiency of all the new coatings in terms of protection against scratches. Incorporating a monoacrylate, particularly isobornyl acrylate, can improve the scratch resistance especially in terms of critical load (up to 175% increase compared with a classical petro-based coating)