DEVELOPMENT OF STARCH-BASED PLASTICS - A REEXAMINATION OF SELECTED POLYMER SYSTEMS IN HISTORICAL-PERSPECTIVE

Recent patents in the starch-based plastics area have claimed melted o r ''destructurized'' starch as a new type of material. The term ''dest ructurized starch'' has apparently been coined after the physically mo dified state of starch obtained by the disruption of the granular stat e, resulting in the loss of order and crystallinity. A brief literatur e review is presented which shows that, in the 1970's, starch containi ng low (10-30%) water contents was extruded at elevated temperatures t o give a thermoplastic melt exhibiting no residual starch crystallinit y. Differential scanning calorimetry studies of starch-g-polymethyl ac rylate and blends of starch with poly (ethylene-co-acrylic acid) are a lso presented. These data indicate that these materials, prepared in t he 1970's, also contain starch which was partially or completely destr ucturized. Thus, although ideas and uses for destructurized starch in plastic items have proliferated in recent years, completely melted or ''destructurized'' starch had been conceived and used much earlier.