Thermoplastic corn starch/clay hybrids: Effect of clay type and content on physical properties

Thermoplastic corn starch (TPS) hybrids, plasticized with glycerol and reinforced with two types of clay (sodium montmorillonite and Cloisite® 30B), were prepared by melt-extrusion. Scanning electron microscopy was used to visualize extrudates morphology. The effects of clay content and of glycerol content on the physical properties of extrudates were evaluated. As determined by contact angle measurements and X-ray diffraction, the increase in glycerol content led to materials with higher hydrophilicity, and higher B-type crystallinity. Addition of clay resulted in hybrid materials with improved properties in relation to TPS alone, even after conditioning at a high relative humidity for 90 days. X-ray diffraction was also used to evaluate clay intercalation within the polymeric matrix, before and after conditioning. Soil burial biodegradation tests, carried out for TPS alone and for TPS/Cloisite 30B hybrids, and followed by weight loss measurements, revealed that biodegradation was enhanced for the hybrid materials in comparison with TPS.