A BIOGRADABLE STARCH-BASED COATING TO WATERPROOF HYDROPHILIC MATERIALS

In this work, the efficiency of starch acetylation to reduce water sen sitivity of hydrophilic materials was investigated. Starch acetate was either included in foamed starch trays and/or used to coat these tray s, wheat gluten based films or paper sheets. The water sensitivity of these foamed trays (quantity and kinetics of water uptake) is shown to decrease when starch acetate content of the foam increases. The coati ng of the hydrophilic trays with starch triacetate is detailled. The b iodegradability of the coating was also unambigously demonstrated. Wha tever the nature of the foam, the coating allowed in all cases to slow down the water uptake but best results were obtained in the case of a coated foam prepared with a starch-starch acetate blend. The coating of wheat gluten films was tested with disappointing results because of chemical incompatibility between wheat gluten and starch acetate. In the case of paper sheet coating, the efficiency in water sensitivity r eduction increased with the thickness of the coating film. However, th e water sensitivity of this coated paper remained higher than paper co ated with polyethylene (with a similar coating thickness).