Over the last few years, there has been renewed interest in biodegradable plastics made from annually renewable, natural polymers such as starch (see Chapters 1, 2, 5 and 10). The fact that starch is receiving considerable attention is understandable, as it is totally biodegradable, is inexpensive compared to other biodegradable polymers, and is available in large quantities. However, starch-based materials and bio-plastics containing starch are only slowly being manufactured and marketed into consumer products, despite the advantages listed above. One reason for this is due to the hygroscopic nature of starch (Whisler and Hillbert, 1944). Starch that comes into contact with water can absorb water, thereby changing the properties of the starch-based material (Swanson et al, 1993). Even starch-based materials that do not come into direct contact with water can be affected by water. Changes in humidity affect the physical properties of starch (Perice, 1928; Lloyd and Kirst, 1963) and starch-based materials (Jasberg et al, 1992). Starch absorbs water under high humidity conditions and loses water under low humidity conditions. Since water is a good plasticizer for starch (Young, 1984; Donovan 1979), any change in the water content of the starch will change the properties of the starch-based article.
KeywordsInterfacial Tension Surface Free Energy Vinyl Alcohol Peel Test Peel Strength
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