Dissipative particle dynamics simulations on powder clearcoat melts, aqueous nanogels and core-shell lattices

COMP 262

Michael P. Makowski, makowski@ppg.com1, Loukas I. Kioupis1, and Kaliappa Ragunathan, ragunathan@ppg.com2. (1) Applied Scientific Computing, PPG Industries, 4325 Rosanna Drive, Allison Park, PA 15101, (2) Automotive Refinish Synthesis, PPG Industries, 4325 Rosanna Drive, Allison Park, PA 15101
Dissipative particle dynamics (DPD) simulations have been used to study two applications important to the coatings industry. First, DPD methods were carried out on automotive powder clearcoat formulations with different flow additives to determine the mechanisms leading to poor appearance and surface roughness. The purpose of this study was to investigate the miscibility of the different components in the powder melt phase and to simulate the dynamics of phase separation during the curing process. We explored the possibility that during powder melt and coalescence, regions of high concentration of crosslinker are formed on the surface, which in turn results in large surface tension gradients. Our results helped explain recent experimental studies using surface profilometry showing that surfaces initially become very smooth during cure, but at later times become very rough. The role of flow additives is also discussed and the morphology of the system is studied at different stages of the curing reaction. A second DPD study will be discussed whose objective was to determine the intrinsic properties of new "reverse latex" nanogels and core-shell lattices to determine how modifications in synthetic methods, degree of neutralization, co-monomer composition, polymer architecture and solvent packages affected performance properties in waterborne coatings applications.