Orientation effect in the crystallization of polymer blend during extrusion

The processing during extrusion can be done either in the steady or transient state. In the first case, all components are added continuously in the extruder and the machine produces great quantities of mixed compound. In the transient state, the polymer that will form the matrix is fed continuously in the extruder and all other components are added as a single or multiple pulse. The mixed material exits the extruder after its residence time and can be collected. This technique is very convenient when only small amounts of reactants are available, but needs a good knowledge of the residence time distribution RTD curve at that processing condition. At the Laboratório de Processamento de Polímeros, DEMa/UFSCar has been developed and constructed an in-line optical detector with polarized light adapted at the exit of a Werner&Pfleiderer ZSK30 extruder which can follow the extrusion of crystalline particles dispersed in a molten polymer matrix. The aim of this work is to evaluate the flow effect in the crystallization of a dispersive semicrystalline phase in a matrix of melted polymer using the new optical equipment, to establish the optimal processing conditions in the crystallization of the semi-crystalline phase at the extruder exit. A molten flow of polystyrene with solid crystalline particles of PA6, has been used as model blend. In order to calibrate the optical detector, films of PS/PA6 blend have been prepared. The calibration was done using the PS/PA6 films at various concentrations which were inserted in the slit-die at room temperature and measuring the signal From these results a linear relationship between voltage signal of optical detector and concentration of the PA6 dispersed phase has been obtained. In the next part of the work , PS/PA6 or PP/PA6 blends with the optical detector taking data inline, will be extruded using conveniently chosen processing conditions including temperature profile, screw configuration, screw speed and output. Initially a processing window will be defined experimentally in order to fix the limiting conditions to get crystallization during the extrusion through the die exit. From these results one or two conditions closed to the centre of the processing window will be set, samples will be collected, quickly cooled and analysed, using a variety of experimental techniques including polarized infrared spectroscopy, scanning electron microscopy SEM, X-Ray diffraction, etc.