Storage stability of injection-molded starch-zein plastics under dry and humid conditions

S. Lim, J. Jane

Research output: Contribution to journalArticle

24 Citations (Scopus)

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).

Original languageEnglish
Pages (from-to)111-120
Number of pages10
JournalJournal of Environmental Polymer Degradation
Volume2
Issue number2
DOIs
Publication statusPublished - 1994 Apr

Keywords

  • Starch-zein plastic
  • anionic starch
  • injection-molding
  • storage stability

ASJC Scopus subject areas

  • Environmental Science(all)
  • Polymers and Plastics

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