PROPERTIES OF TERNARY BLENDS OF STARCH AND MALEATED POLYMERS OF STYRENE AND ETHYLENE-PROPYLENE RUBBER

The properties of starch/styrene maleic anhydride (SMA)/ethylene propy lene maleic anhydride (EPMA) were studied at a constant starch composi tion of 60% by weight. The synthetic polymer content was 40% of total weight and contained 30, 20 and 10% SMA by weight, the rest being EPMA . Blends were made in a batch mixer as well as continuously in an extr uder. The water absorption data showed that samples made by extrusion have less water resistance than samples made in a batch mixer. Dynamic mechanical analysis indicated three distinct glass transitions, corre sponding to the glass transitions of EPMA, starch and SMA. Tests showe d injection moulding gave higher tensile strength compared to compress ion moulding, and tensile strength increased with SMA content. Gel per meation chromatography data indicated there was degradation during mix ing. Blending using an extruder caused more degradation of starch in t he blends than when a batch mixer was used. Both scanning electron mic roscopy and optical microscopy showed that some starch was not melted during blending though the number and average size of unmelted starch granules decreased with decreasing SMA content. Scanning electron micr oscopy indicated the different morphologies of injection moulded sampl es at different locations in the mould. Copyright (C) 1996 Elsevier Sc ience Ltd.