Development of Cloisite20A-polyurethane nanocomposite coatings for thermomechanical performance

Cloisite 20A-polyurethane (C20-PU) nanocomposites were prepared using three processing schemes at different reinforcement levels (1, 2 and 3 wt%). The H-bonding chemistry of hard segments (HS) of PU and C20, leads to compartment effect in C20-PU thus varying the mechanical performance, as deduced from nanoindentation studies. Elastic nanocomposites (7.8 % - 60.6 % decrease in the plasticity index) and plastic nanocomposites (4.8 %–25.3 % increase in the plasticity index) are produced by switching the sequence of homogenizer (HSH) and ultrasonic bath (USB), either in tandem or independently. Polymer phase mixing morphology indicated by Fourier transform infrared (FTIR) and plasticity indices derived from nanoindentation, corroborate the active role of compartment effect in governing the properties and performance of PU and C20-PU nanocomposites. Dynamic mechanical analyzer (DMA) studies demonstrate that C20-PU nanocomposites are thermally and mechanically more robust than pure PU, with a >10 °C right shift in the glass transition temperature (Tg) along with a reduction in Tg peak intensities of nanocomposites. These findings articulate the interaction between PU chains and 2D nanofiller with improved thermomechanical properties.