Processing of Natural Starch

Attempts have been made to process natural starch on standard equipment and existing technology known in the plastic industry. Since natural starch generally has a granular structure, it needs to be destructurized and modified before it can be melt processed fike a thermoplastic material (1). 

Granular starch can be added to a polymer in order to decrease the cost of the base polymer. Clearly, the use of granular starch makes the derivative more biodegradable (13). 

Furthermore, glycerol is not added to the mixture. This reduces the water absorbency of the final product (13). An example of a grafting compound is maleic anhydride (MA). An example of a good compatibilizer is poly(ethylene) (PE) containing approximately 5% MA which is commercially available and only slightly more expensive than pure poly (ethylene). 

When PE-y-MA is added to low density poly(ethylene) (LDPE)/ corn starch blends, the tensile strength and elongation at break of the blends are improved and the improvement was more pronounced at higher starch contents. 

Because the starch may be granular wheat or rice starch, this greatly reduces the cost of manufacturing the polymer. In addition, it greatly enhances the biodegradabUity of the mixture. 

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