Submitted to: Journal of Applied Polymer Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2003
Publication Date: 8/1/2003
Citation: Fanta, G.F., Felker, F.C., Salch, J. 2003. Graft polymerization of acrylonitrile onto starch-coated polyethylene film surfaces. Journal of Applied Polymer Science. v. 89. p. 336-339. Interpretive Summary: When plastic films are immersed in hot, dilute solutions of starch prepared by steam jet cooking, a thin layer of starch is deposited on film surfaces as the starch solutions are allowed to cool. Although the amount of deposited starch is so small that it is barely visible, these coatings greatly enhance the compatibility of the films with aqueous systems. We have now discovered that these starch coatings may be modified by graft polymerization with acrylonitrile. These starch-polyacrylonitrile (i.e., Orlon) copolymers adhere tightly to polyethylene film surfaces and cannot be completely removed, even when water-wet films are vigorously rubbed. Water-compatible coatings on plastic film surfaces help reduce static build up, alter friction and adhesion properties, improve absorption of water-based dyes and inks, and enhance the compatibility of the film with body fluids. Moreover, the graft polymerized films curl when dry and return to their original shape when they are re-wet. These films can thus be considered to be a type of stimulus-responsive polymer. This research will enable producers to alter the surface properties of plastics, thereby expanding the number of end use applications for their products. The research will also benefit American farmers by providing new markets for surplus starch.
Technical Abstract: When starch-coated polyethylene (PE) films were allowed to react with acrylonitrile in the presence of ceric ammonium nitrate initiator, graft polymerization occurred to produce starch-polyacrylonitrile (PAN) coatings that contained about 25% grafted PAN, by weight. The graft copolymer coatings adhered tightly to PE film surfaces. When the coatings were wet with water and the surfaces were vigorously rubbed, less than 20% of the coating was removed. The fact that grafted coatings were not removed with boiling water provided further evidence for their strong adherence. When starch was removed from the coating by acid hydrolysis, residual PAN grafts still remained adsorbed on the PE surface. Since the grafted coating was completely removed by treatment with refluxing 0.7 N sodium hydroxide, there is apparently no chemical bonding between starch-PAN graft copolymer and PE. Dimensional changes associated with the evaporation of water from these PAN-grafted coatings caused the films to curl during drying. Since the final shape of these coated films depends upon the presence or absence of water in the surrounding environment, these films may be considered to be a type of stimulus-responsive polymer.