Compatibiliser activity and morphology stability during twin-screw extrusion and injection moulding of compatibilised blends

Abstract

The influence of screw speed, agitator configuration, and compatibiliser, namely maleated polypropylene (mPP), during twin-screw extrusion upon the morphology, dispersion stability, and properties of polyamide-6/polypropylene (PA6/iPP) blends has been investigated. For mPP contents of 2.4 vol% and greater, the number average domain diameters measured in the extruded compound, D n(ex), were found to decrease to a limiting value at the specific mechanical energy input, S e, around 0.07 kW h kg −1, when S e was controlled by the screw configuration and screw speed. For mixing energies greater than 0.07 kW h kg −1, the domain size was principally determined by the ratio of specific interfacial area, S ext, between the PA and iPP phases to the estimated volume fraction of in situ formed copolymer, φ c; S ext /φ c ≈45 μm −1. The difference, Δ D n, between D n(ex) and the average domain diameter measured in the cores of the samples after injection moulding, D n(m), was calculated: Δ D n=| D n(ext)− D n(m)|. It was found that Δ D n∝ D n(ext); i.e. larger droplets in the extrudate underwent the greatest changes in dimension in the subsequent moulding process.