Analysis of a liquid-assisted molding process for coating microchannels with an ultraviolet curable polymer

Injection molding can be altered to form hollow parts by partially pre-filling a mold with polymer melt and then injecting a gas into the mold before cooling. The gas will core the center section and in the process force melt into the unfilled portions of the mold. This process is called gas-assisted injection molding (GAIM) and is a thoroughly studied polymer processing technique. Liquid-assisted molding follows the same principles as GAIM, except the coring fluid is a liquid of low viscosity. Liquid-assisted molding of an ultraviolet (UV) curable polymer can be used to coat microchannels, the benefit of which being a smooth and circular cross-section. Presented here are experiments of the controlled microchannel flow of a long, immiscible liquid thread through a viscous UV curable polymer. The roles of channel geometry and bubble velocity are discussed for square, rectangular, and circular microchannels. Finally, a quasi-analytical model for calculating the Newtonian coating fluid thickness, when the coring fluid is driven by a constant pressure, was developed using the equation for Poiseuille-like flow within a square channel. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers