Films prepared from poly(vinyl alcohol) and amylose-fatty acid salt inclusion complexes with increased surface hydrophobicity and high elongation

Authors: Fanta, George; Felker, Frederick; Selling, Gordon

Submitted to: Starch
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2016
Publication Date: 3/16/2016
Publication URL: http://handle.nal.usda.gov/10113/62510
Citation: Fanta, G.F., Felker, F.C., Selling, G.W. 2016. Films prepared from poly(vinyl alcohol) and amylose-fatty acid salt inclusion complexes with increased surface hydrophobicity and high elongation. Starch. 68:1-11.

Interpretive Summary: Starch is widely used as a component in biodegradable plastics and films because it is inexpensive, renewable, and biodegrades rapidly. However, plastics and films prepared from pure starch do not have the strength, flexibility, and ease of processing required for many applications. Although poly(vinyl alcohol) (PVOH) has been blended with starch to overcome these disadvantages, PVOH is more expensive than starch and has a lower rate of biodegradation. For practical applications, it is therefore necessary to maximize the amount of starch in these mixtures while still retaining the desirable properties of PVOH. In this investigation, we have found that complexes of starch prepared from inexpensive fatty acids by the widely-used, economical, industrial process of steam jet cooking have water solubility greater than un-complexed starch. These complexes can be blended with PVOH in large quantities to provide films with good physical properties and in some cases with enhanced elasticity.

Technical Abstract: In this study, water-soluble amylose-inclusion complexes were prepared from high amylose corn starch and sodium salts of lauric, palmitic, and stearic acid by steam jet cooking. Cast films were prepared by combining the amylose complexes with poly(vinyl alcohol)(PVOH) solution at ratios varying from 100:0 to 0:100. Films produced using these complexes had advantages over films prepared using uncomplexed starch. While in general the PVOH starch complex films had slightly lower tensile strength, some formulations had small improvements in elongation relative to the PVOH control. Contact angles of water droplets applied to film surfaces showed that incorporation of as little as 20% amylose complex yielded films with increased hydrophobicity. Microscopy of iodine-stained films prepared from the amylose-sodium palmitate complex showed that the films separated into a starch-rich phase and a continuous unstained background of PVOH. A phase inversion was observed with 60% complex. The presence of the amylose complex in both phases of the dried films may contribute to the high contact angles observed at low concentrations of the complex. This approach enables production of PVOH films having significant levels of biobased materials, a good balance of physical properties, and greatly increased surface hydrophobicity relative to the PVOH control.