Studying the role of polysiloxane additives and nano-SiO2 on the mechanical properties of a typical acrylic/melamine clearcoat

Effects of conventional polysiloxane additives and nano-SiO2 on the mechanical properties of an automotive acrylic/melamine clearcoat (CC) are studied. Clearcoats formulations were prepared by addition of different concentrations of polysioloxane additives (with different modifications) and hydrophobic nano-SiO2 particles. Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) and atomic force microscope (AFM) were utilized to evaluate the effects of nano-SiO2 and polysiloxane additives on the surface properties of the CCs. The mechanical properties of the surface and the bulk of the CCs were studied by nano-indentation and tensile tests, respectively. Results showed that polysiloxane additives can mostly affect the mechanical properties of the surface of the CC. Additives with shorter side chains and therefore higher surface activity caused higher changes on the surface properties the CC. Unlike conventional polysiloxane additives, the nano-SiO2 particles mainly influenced the mechanical properties of the bulk of the CC.

► Polysiloxane additives can improve the mechanical properties of clearcoat surface.
► Nano-SiO2 can improve the mechanical properties of surface/bulk of the clearcoat.
► Polyether modified additives improve the bulk properties greater than fluorocarbon.
► Polysiloxane additives show both plastisizering and hardening behaviors in clearcoat.
► Nano-SiO2 can affect the curing behavior of the clearcoat.