Compatible blends of thermoplastic starch and hydrolyzed ethylene-vinyl acetate copolymers

• Published in: Carbohydrate polymers 2012-09, Vol.90 (1), p.34-40
• Main Authors: Da Róz, A.L., Ferreira, A.M., Yamaji, F.M., Carvalho, A.J.F.
• Format: Article
• Language: English
• Subjects: absorption; acetates; Applied sciences; Ethylene-vinyl acetate; Exact sciences and technology; Fourier transform infrared spectroscopy; glass transition temperature; glycerol; hydrolysis; Mechanical properties; Natural polymers; Organic polymers; Physicochemistry of polymers; Poly(ethylene-co-vinyl acetate-co-vinyl alcohol); Properties and characterization; scanning electron microscopy; starch; Starch and polysaccharides; thermogravimetry; Thermoplastic starch; thermoplastics; X-ray diffraction
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2012.04.055

► Compatible blends of thermoplastic starch and modified ethylene-vinyl acetate copolymers. ► The glass transition temperature of thermoplastic blends increased when blended with partially and completely hydrolyzed EVA. ► Water absorption of thermoplastic starch decreases when blended with hydrolyzed EVA. Ethylene-vinyl acetate copolymer (EVA) with 19% of vinyl acetate and its derivatives modified by hydrolysis of 50 and 100% of the initial vinyl acetate groups were used to produce blends with thermoplastic starch (TPS) plasticized with 30wt% glycerol. The blends were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, water absorption, stress–strain mechanical tests, dynamic mechanical analysis and thermogravimetric analysis. In contrast to the blends with unmodified EVA, those made with hydrolyzed EVA were compatible, as demonstrated by the brittle fracture surface analysis and the results of thermal and mechanical tests. The mechanical characteristics and water absorption of the TPS were improved even with a small addition (2.5wt%) of hydrolyzed EVA. The glass transition temperature rose with the degree of hydrolysis of EVA by 40 and 50°, for the EVA with 50 and 100% hydrolysis, respectively. The addition of hydrolyzed EVA proved to be an interesting approach to improving TPS properties, even when very small quantities were used, such as 2.5wt%.