Blends of thermoplastic starch and recycled polyvinylbutyral from automotive windscreens were investigated. Mechanically compatible blends are formed at low to intermediate starch content. However, scanning electron microscopy and dynamic-mechanical analysis revealed a phase-separated nature for all blend compositions investigated. Tensile properties are negatively affected by aging in a high humidity environment and they deteriorate rapidly when the samples are soaked in water. Synergistic property enhancement was observed for a compound containing 22% thermoplastic starch. It features a higher tensile strength, shows better water resistance, and is significantly less affected by aging. (c) 2006 Wiley Periodicals, Inc.