A heat transfer analysis of injection molding of fiber-reinforced poly(m-xylylene adipamide)

In this paper, we present in a first time a methodology used to determine the thermophysical properties and the crystallization kinetics of a thermoplastic reinforced composite (MXD6). A specific instrumented device was developed to allow the molding of the polymer in conditions as close as possible to those met in the injection process. Measurements during molding are used by two inverse problems to compute the thermal conductivity in melted and solid phases and the kinetic parameters. The estimated values of thermal conductivity are compared to a model based on the orientation of the fibers through the thickness. Results from kinetics are compared to literature one. Heat transfers are then studied during the injection by using an instrumented mould. It is shown that during filling the heat transport term in the flow direction is negligible in front of transfer between the part and the mold. Then transfers are modelled within the thickness of the part by solving the energy equation coupled with the crystallization kinetic. The effects of pressure and shearing are introduced in the kinetic model through empirical acceleration functions. Results show that the shear seems to have no influence on the thermal contact resistance at the interface between the mould and the composite.