Development of surface modified SiO2 nanoparticles incorporated clearcoats for automotive industry

Abstract

Evaluating organic-inorganic hybrid coatings containing modified nanoparticles may open up opportunities for the automotive industry. In this study, vinyltrimethoxysilane (VTMO) modified SiO₂ nanoparticles were synthesized to develop two-component High Solid (2K HS) hybrid clearcoats (CC) which require low-temperature curing. Hansen Solubility Parameters (HSP) and Design of Experiment (DOE) studies provided better optimization in terms of reaction parameters and suitable solvent prediction. Several characterization techniques like FTIR, SEM, and DLS techniques were performed to prove the successful modification of SiO₂ nanoparticles with silane agent, VTMO. HS Hybrid CC formulations were designed for the automotive industry with 1.75 and 3.00 phr (per hundred acrylic polyol resin) VTMO modified SiO₂ nanoparticles. Dynamic Mechanical Analysis (DMA) tests showed that toughness values increase with the nanofiller amount, in contrast to Young's modulus and yield strength due to the various interactions between nanofiller and the polyurethane polymer matrix. The free volume formed between VTMO ligands of the SiO₂ nanoparticles and the polymer matrix provides a low-density region which results in a decrease in time, temperature, and frequency dependent modulus values and glass transition temperature (T_g) of HS Hybrid CC system. Static and dynamic surface tension measurements, water uptake, and cure monitoring result that 1.75 phr nanofiller content in HS Hybrid CC enhances the performance of clearcoats significantly due to the formed low-density region between the nanofiller and the polymer matrix. However, further increase of the nanofiller causes agglomeration and consequently worse clearcoat performance. VTMO modified SiO₂ nanoparticles provide significant compatibility up to 1.75 phr and enhance the clearcoat performance in terms of mechanical strength for further usage in the automotive industry.