Blends of polyamide 6 (PA) with maleic anhydride-grafted styrene/(ethylene or butylene)/styrene
(SEBS-graft-MAH) block copolymer
Polimery 1997, No 9, 549
Binary PA 6— SEBS-graft-MAH blends were extruded in a Brabender single-screw extruder at 220°C and screw speed 50 min-1 by using (i) a standard extruder die and (ii) a specially designed homogenizing head (static mixer) fixed before the die and providing a shearing rate of 26.5 s-1, intended to compatibilize the blend mechanically. Blend morphology and crystallinity were examined by respectively scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Impact and tensile strengths, melt flow rate (MFR) and water absorption were measured. Blend structure and property data were related to blend composition and processing parameters. As the SEBS-graft-MAH proportion was raised, the impact strength (Fig. 1) increased, the tensile strength decreased (Fig. 2), the elongation at break increased (Fig. 3), crystallinity and m.p. fell (Figs. 8, 9) and so did MFR (Fig. 4) and water absorption (Fig. 7). SEM photomicrographs of fracture surfaces (Figs. 10, 11) revealed no spherical domains, a fact indicative of good compatibility of blend components. The mechanical compatibilization resulted in increased impact strength, enhanced continuity, higher viscosity and lower crystallinity.