Abstract
Corn starch and zein mixtures (4 : 1 dry weight) were extruded and injection-molded in the presence of plasticizers (glycerol and water). Tensile strength and percentage elongation of the molded plastics were measured before and after 1 week of storage under a dry or humid condition (11 or 93% RH). With 10–12% glycerol and 6–8% water, injection-molded plastics had relatively good tensile properties (20- to 25-MPa tensile strength and 3.5–4.7% elongation). But while exposed to dry conditions (11% RH), the molded plastics lost weight (0.5–1.5% in 7 days) and became very brittle, with significant decreases in tensile strength and elongation. Partial replacement (5–10%) of starch with a maltodextrin (average DE 5) reduced the glass transition and melting temperatures of the starch-zein mixture as well as the dry storage stability. Using potato starch instead of corn starch significantly improved the dry storage stability of the injection-molded starch-zein plastics (18- vs 11-MPa tensile strength). Anionic corn starches with a maleate or succinate group (DS<0.01) produced injection-molded plastics with improved tensile properties and storage stability. Plastics prepared from the starch maleate and zein mixture retained the strength during 1 week of dry storage without a significant change (26-MPa tensile strength and 3.7% elongation after 1 week of storage).
Similar content being viewed by others
References
F. Wittwer and I. Tomka (1987) U.S. Patent 4673438.
J.-P. Sachetto, M. Egli, and H. Zeller (1988) GB 2214919A.
E. T. Cole and R. Daumesnil (1988) GB 2214920A.
G. Lay, J. Rehm, R. F. Stepto, and M. Thoma (1989) European Patent Application 0327505 A2.
C. Bastioli, V. Bellot, L. Del Giudice, G. Del Tredici, R. Lombi, and A. Rallis (1990) PCT WO 90/10671.
I. Tomka and S. Schmidlin (1990) PCT WO 90/01043.
G. Lay, J. Rehm, R. F. Stepto, M. Thoma, J.-P. Sachetto, D. Lentz, and J. Silbiger (1992) U.S. Patent 5095054.
R. Nakatsuka, S. Suzuki, S. Tanimoto, and E. Funatsu (1978) U.S. Patent 4076846.
S. Lim and J. Jane (1993) in M. Yalpani (Ed.),Carbohydrates and Carbohydrate Polymers, Analysis, and Biotechnology, Modification, Antiviral, Biomedical and Other Applications, ATL Press, Mount Prospect, IL, pp. 288–297.
K. J. Zeleznak and R. C. Hoseney (1987)Cereal Chem. 64 121–124.
I. A. Wolff, H. A. Davis, J. E. Cluskey, L. J. Gundrum, and C. E. Rist (1951)Ind. Eng. Chem. 42(4), 915–919.
J. Muetgeert and P. Hiemstra (1958) U.S. Patent 2822581.
T. F. Protzman, J. Wagoner, and A. H. Young (1967) U.S. Patent 3344216.
C. G. Caldwell (1949) U.S. Patent 2,461,139.
ASTM (1992)Annual Book of ASTM Standards D 638-86, American Society of Testing and Materials, Philadelphia, PA. pp. 216–226.
T. G. Fox and P. J. Flory (1950)J. Appl. Phys. 21 581–591.
M. Gordon and J. S. Taylor (1952)J. Appl. Chem. 2 493–500.
J. J. M. Swinkels (1985)Starch 37(1), 1–5.
M. J. Gidley and P. V. Bulpin (1989)Macromolecules 22 341–346.
S. Lim and P. A. Seib (1993)Cereal Chem. 70(2), 137–144.
S. Lim, T. Kasemsuwan, and J. Jane (1994)Cereal Chem. In press.
Author information
Authors and Affiliations
Additional information
Journal paper No. J-15561 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2863.
Rights and permissions
About this article
Cite this article
Lim, S., Jane, J. Storage stability of injection-molded starch-zein plastics under dry and humid conditions. J Environ Polym Degr 2, 111–120 (1994). https://doi.org/10.1007/BF02074779
Issue Date:
DOI: https://doi.org/10.1007/BF02074779