Study on phase compatibility and water resistance of thermoplastic starch foams coated with flexible poly(L-lactide)-b-polyethylene glycol-b-poly(L-lactide) bioplastics

Abstract

Thermoplastic starch (TPS) foams can be produced by compression molding of gelatinized potato starch. The main disadvantage of these TPS foams is very poor water resistance which can be solved by coating them with hydrophobic polymers. In this work, TPS foams were coated with poly(L-lactide)-b-polyethylene glycol-b-poly(L-lactide) (PLLA-PEG-PLLA) by a dip coating method and compared to foams coated with PLLA. TPS foams coated with PLLA-PEG-PLLA showed better phase compatibility between foam surfaces and coated films than did those coated with PLLA. The water resistance of coated TPS foams increased with the PLLA-PEG-PLLA concentration. However, longer PEG blocks reduced water resistance of the TPS foams. Tensile tests found that the TPS foams coated with PLLA-PEG-PLLA were more flexible than those coated with PLLA. Thus, the TPS foams coated with PLLA-PEG-PLLA have potential to be used as starch-based foams with good water resistance and phase compatibility between foam surfaces and coated films.