Non-biodegradable single use packaging are a serious environmental problem as it generates large amounts of waste and is generally not recycled. These packages, especially those made of expanded polystyrene, can be replaced by thermoplastic starch foams. These foams have the advantage of being from renewable sources and biodegradable. However, this material is hydrophilic and becomes unusable when it is exposed to water. Hydrophobizing starch comes as an alternative to make the foams more resistant to contact with water. The purpose of the modification is to exchange starch hydroxyl groups for less polar groups such as silane groups. In this work, two silanes were used for starch silylation: 3-chloropropyl trimethoxysilane and Methyltrimethoxysilane. The foams were made using four materials: modified starch, gelatinized starch, polyvinyl alcohol and water. Results from water absorption tests and mechanical tests show that foams absorb less water and become more resistant with the addition of silylated starch.