Improvement of scratch and abrasion resistance properties of automobile paint
Authors:   , Mohanty Debasmita 
Published: June 2023

The automobile paint industry normally consumes petro-based feedstock as the raw material, which is non-renewable and emits a higher amount of volatile organic compound (VOC), that pollutes the environment. This study focuses on the use of ecofriendly castor oil (CO) as a substitute for petro-based feedstocks; while synthesizing polyurethane (PU)-based automobile coats. The novelty and objective of this work is paints derived from bio-based CO as a substitute for petro-based feedstocks.CO is a nonedible oil, hence it does not affect the food chain. Paints derived are with fewer VOCs, thus having a less detrimental effect on the environment and is cost-effective. Modified castor oil (CO) based polyurethane (PU)/nano-silica (NS)/titanium pigment (TP) hybrid coating with an organic-inorganic covalent bond was synthesized by the in-situ polymerization method. Aminopropyl tri-ethoxy silane (APTES) modified NS particles along with TP were added to the PU matrix at various wt. %. Thermal, mechanical, and chemical resistance properties of the coating samples were significantly enhanced with the addition of NS and TP. Char residue, Glass transition temperature, pencil hardness, Young’s modulus, water contact angle (WCA), crosssectional density, cross-cut tape adhesion %, abrasion % increased from 0.29%, - 24.5ºC, 2H, 251MPa, 77.61º, 0.16mol/m3 , 65±5%, 0.040% to 1.26%, 1.94ºC, 3H, 1199MPa, 88.89º, 2.4mol/m3 , 93±2% and 0.016% with addition of modified NS particles along with TP particles. Paint formulation with 0.5 wt% NS and 0.2 wt% TP was optimized to be applicable as an automobile base coat and its characteristic properties can be comparable with a commercial base coat (BC). An acrylate-PU/NS hybrid coating was developed, which was derived from CO-based polyol. CO was modified by employing a process that includes epoxidation, followed by transesterification, and acrylation to synthesize the required polyols, which is used for acrylate-PU paint synthesis via the in-situ polymerization process. Triallyl isocyanurate (TI) modified NS particles were incorporated with the paint matrix by the ultrasonication method to enhance the paint properties. Experimental findings revealed that with the incorporation of NS particles, char residue, Young’s modulus, abrasion resistance, and cross-cut adhesion % increased by 71.31%, 42%, 0.28%, and 5% respectively. Also, glass transition temperature, pencil hardness, nanoindentation depth, water contact angle (WCA), and cross-linking density were increased from -12.16 ºC, 2H, 3300 nm, 81.71 º, and 0.90 mol/m3 to 1.65 ºC, 3H, 2000 nm, 92.26 º, and 1.78 mol/m3 respectively. The UV-visibility spectra, haze, transmittance, and gloss parameter showed the enhanced optical properties of the paint samples. PU/NS composite coating developed showed equivalent properties as that of the commercial clear coat. Epoxy/PU composite applicable as automobile sealer was synthesized by the ultrasonication mixing process. TI-modified NS particles were incorporated into the blend to enhance the characteristic properties. Structural properties of the composite were studied using FTIR spectra. Char residue %, glass transition temperature, crosslinking density, and WCA were observed to increase from 3.10%, 50.60 °C, 0.98 mol/m3 , and 85.63 ° to 4.55%, 73.76 °C, 3.75 mol/m3 , and 91.45 ° respectively after incorporation of NS. The impact strength, tensile strength, and fracture toughness of the blend were studied to increase after NS reinforcement. The epoxy-PU/NS nanocomposite developed fulfilled the parameters of automobile sealer.