Reactive compatibilization of nylon 6/styrene-acrylonitrile copolymer blends. Part 1. Phase inversion behavior

The phase morphology and phase inversion behavior of nylon 6 (PA)/styrene-a crylonitrile (SAN) compatibilized blends have been studied using an imidize d acrylic polymer (IA) and a styrene/acrylonitrile/maleic anhydride terpoly mer (SANMA) as compatibilizers. PA/SAN blends can be considered as a simple r version of industrially important PA/ABS blends; therefore, this study is useful for the better understanding of the morphology development for PA/A BS blends with compatibilizers. Compared to binary blends of nylon 6 and SA N, addition of IA causes the phase inversion composition to shift to a high er nylon 6 volume fraction; whereas, addition of SANMA slightly changes the phase inversion composition to a lower nylon 6 volume fraction. The use of IA results in a significant increase of the nylon 6 phase viscosity due to the in situ formation of graft polymers during the melt processing; wherea s, the addition of SANMA only slightly increases the nylon 6 phase viscosit y. The significant change in the nylon 6 to SAN25 viscosity ratio due to th e formation of PA-IA graft polymer may be partially responsible for the shi ft of the phase inversion composition observed as addition of IA. The metho d of the mixing also affects the phase inversion composition. The compositi on range where the nylon 6 forms a continuous phase extends to a lower nylo n 6 volume fraction for blends mixed in an extruder compared to those prepa red in a Brabender. The stabilization of blend morphology by Formation of g raft copolymers was studied for compositions near phase inversion as well a s at compositions away from this region. Accordingly, it has been shown tha t IA does not stabilize the morphology near the phase inversion composition , but it is very effective at compositions where either of the components f orms a clearly defined dispersed phase. The factors affecting the critical composition where phase inversion occurs have been established. (C) 2000 El sevier Science Ltd. All rights reserved.