The properties of starch/styrene maleic anhydride (SMA)/ethylene propylene maleic anhydride (EPMA) were studied at a constant starch composition 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 extruder. 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, corresponding to the glass transitions of EPMA, starch and SMA. Tests showed injection moulding gave higher tensile strength compared to compression moulding, and tensile strength increased with SMA content. Gel permeation chromatography data indicated there was degradation during mixing. Blending using an extruder caused more degradation of starch in the blends than when a batch mixer was used. Both scanning electron microscopy 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 microscopy indicated the different morphologies of injection moulded samples at different locations in the mould.
- Maleated polymers
- Ternary blends