Studies on reactive compatibilisation of polyamide 6/poly(butylene terephthalate) blends by low molecular weight bis-oxazoline

Polyamide 6 (PA) was blended with poly(butylene terephthalate) (PBT) in the 80/20 wt/wt ratio, either with or without addition of small amounts (0.2 or 0.4 phr) of 2,2′-(1,3-phenylene)-bis(2-oxazoline) (PBO). The reactions of PBO with blend components were studied by Fourier transform infra red spectroscopy (FT-IR), solubility behaviour of the products in formic acid and rheological measurements. PA/PBT blends were prepared in a co-rotating twin-screw extruder and characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The static tensile properties, and impact strength of the blends were tested. The results indicate that the reactions of PBO with free carboxyl end groups of PA and PBT occur, at least in part, to form PA-co-PBO-co-PBT copolymers acting as effective compatibilisers for these blends. However, PBO reacts more rapidly with PBT than with PA, probably due to the lower molar mass and/or the more uniform distribution of the reactive oxazoline groups of PBT.