Studies of mold filling and curing in the reaction injection molding process

Abstract

K m' m " iii " N = average protein concentration in resin at any time t , = initial solution protein concentration, mg/gm = initial resin protein concentration, mg/gm = final or equilibrium solution protein concentration, = final or equilibrium resin protein concentration, = protein concentration in solution at resin-solution in-= protein concentration in resin at resin-solution interface, = protein concentration in the solution that would be mg/gm mg/gm w / g m terface, mg/gm mg/gm equilibrium with the average particle concentration C at any time, mg/gm = protein concentration in resin that would be in equilibrium with bulk solution concentration, mg/gm = diffusion coefficient of protein in solution, cmz/s = diffusion coefficient of protein in r z i n , cm2/s = fractional conversion defined by (C(o) -C ) / ( c ( o ) = solution side mass transfer coefficient, cm/s = resin side mass transfer coefficient, cm/s = overall mass transfer coefficient defined by Eq. 1, cm/s = overall mass transfer coefficient defined by Eq. 20, cm/s = slope of a chord between a point defined by (C*, c) and a point at the intersection of aJne drawn from any operatin_g point (C, C ) with a slope equal to -k/k -C(m)) = (g-g / ( C = -C*) = ( C , -C * ) / ( C , -C ) = flux of protein, mg/cm2-s T O t = time, s V v 6 = effective resin particle radius, cm = amount of solution in stirred vessel, gm = amount of resin in stirred vessel, gm = effective solution film thickness, em A model is developed for pressure rise, extent of reaction and temperature changes during filling and curing in thin rectangular molds for the reaction injection molding (RIM) process. The predictions of the model are shown to be in good agreement with experimental results obtained for several intrumented molds using polyurethane RIM chemical systems. The relevant dimensionless groups are identified. Criteria for good mold filling are developed.The RIM process is a fairly new polymer processing method (Wood, 1974; Prepelka, 1979). Building on automotive success, it is moving into broader markets via improved systems which can give custom molding capability. The technique is still essentially an art and the trial and error approach employed in production often can not cope with variations in resin proper-J M. Castro 1s presently with the

Effect of carbon nanofibers on the cure kinetics of unsaturated polyester resin: Thermal and chemorheological modelling

“…The relationship between viscosity and the degree of reaction in the interval before the gel point during isothermal cure, was described by using the empirical model developed by Castro and Makosco [36] and previously adopted for UP matrices for fiber reinforced composites [3]:…”

“…Then, a phenomenological model is used to obtain the kinetic parameters of the cure process adopting a mathematical approach previously proposed for fibre reinforced UP matrices [3]. The kinetic model is then combined with an empirical rheological model proposed by Castro and Macosko for polyurethane systems [36] and successfully applied to describe the chemorheology of unsaturated polyester systems by Kenny and coworkers [3].…”

Principles of polymer processing modelling

“…This requires coupling the mechanical and thermal equations everywhere in the cavity. Moreover this "thin layer" approximation is not able to capture the "fountain flow" effect at flow front (Castro and Macosko [17]; Mavridis et al [18]). In order to capture such 2016) phenomena and to account for complex mold geometry as the one presented figure 2, 3D viscous compressible modeling is required (Haagh et al [19]; Silva et al [20]).…”

Reaction injection molding: Analyzing the filling stage of a complex product with a highly viscous thermoset

“…The modeling of RIM has been described previously (e.g., 3,4,7,8). Since we do not add anything to this modeling, it will only be outlined briefly in this section.…”

“…These models have been implemented in computer codes to simulate injection molding processes and to enable product designers to predict flow front advancement, pressure buildup, temperature distribution, and, in some cases, thermal and flow-induced stresses (2)(3)(4)(5).…”