ABSTRACTstudies of ~he morphology of extruded polyrner blend syst~ms have shawn that it is feasible to produce a laminar structure of an ethylene vinyl-alcohr-l copolymer (EVOH) dispersed phase in a po1yprapylene (PP) m~trix phase. The laminar structure forms in the core of the extrudate when a 5lit die 1s incorporated into the extrusion process.Morphological studies, including a study of morphology d~vel opment inside the die and studies of the effect of processing conditions on the morphology of the final product, :evealed that the laminar structure is a resul t of die design. Processing conditions influence main1y the shape and dimensions of the laminnr core region of the extrudate.Oxygen permeation tests have shown that the blend e:,hibits lower oxygen permeability than pure PP, when EVOH is incorporated as a dispersed phase into the system. Oxygen transmission rates obtained with a blend system can be as low as those obtained with a mUlti-layer coextrusion product, although only at h~gh EVOH concentrations. Comparison of experimental data with theoretical permeation predictions shows that, up to 20wt% EVOH, the reduction in oxygen transmission rate is on1y minor, and follows the prediction for a homogeneous system. At 25wt%, a considerable decrease in oxygen transmission rate is noticeable, and the tr'end for higher EVOH contents is towards the behavior of a multi-layer system .

A detailed study was carried out to understand the dynamics of pressure variations at different points in the injection-molding system. Thus, hydraulic, nozzle, and cavity pressures were evaluated, in addition to the pressure gradient in the cavity. Both steps and pseudorandom binary sequences (PRBS) were employed to obtain and compare dynamic models describing these variables. Subsequently, these models were employed to evaluate and select optimal controllers for the different variables.

varying lateral resolutions is proved. Finally, measured and numerically simulated orientation tensors are compared for one of the regions.