Structure and Properties of Starch/Poly(Vinyl Alcohol) Foams

Abstract

Expanded polystyrene foam (EPS), nonbiodegradable, is widely available and extensively employed in packaging. Starch foams were an alternative biodegradable material to replace EPS. This research aimed to prepare one‐step hot mold baked starch/poly(vinyl alcohol) (PVA) foams composed primarily of cassava starch (CS) and corn starch (CO) and minor amounts of PVA (up to 5 wt%). CS/PVA batters demonstrated stronger viscoelastic properties at elevated temperatures than CO/PVA batters due to more pronounced gelatinization. CS and CO batters with 1 wt% PVA showed the highest storage modulus ( G′ max ≈ 4.55 and 2.46 MPa, respectively), but decreased cell foam interior. The increase in PVA decreased G′ max due to PVA acting as a polymeric plasticizer. With 5 wt% PVA, the foam density of CS decreased by 10.53%, but that of CO increased by 23.08%. The swelling in water (6 h) of CS and CO foams with 5 wt% PVA decreased by ≈ 49.60% and 38.61%, respectively. The addition of 5 wt% PVA did not improve the flexural strength and flexural toughness of both foams, but significantly improved the flexural modulus of CS foams by ≈ 52.85%. Within 6 months, CS foams with 3 wt% PVA were completely degraded in soil; however, CO foams with all PVA content remained.