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 or ''destructurized'' starch as a new type of material. The term ''destructurized starch'' has apparently been coined after the physically modified state of starch obtained by the disruption of the granular state, resulting in the loss of order and crystallinity. A brief literature review is presented which shows that, in the 1970's, starch containing low (10-30%) water contents was extruded at elevated temperatures to give a thermoplastic melt exhibiting no residual starch crystallinity. Differential scanning calorimetry studies of starch-g-polymethyl acrylate and blends of starch with poly (ethylene-co-acrylic acid) are also presented. These data indicate that these materials, prepared in the 1970's, also contain starch which was partially or completely destructurized. 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.