High Starch Polymer

A substantiaUy completely biodegradable high starch composition has been developed. A poly(vinyl alcohol) (PYA) is made compati- 

Fiber/[%] MMT/[%] Weight loss/[%] 30 d 60 days after 90 days 

The elasticity enhancer is made from a mixture of polyols, polyglycol and water. Suitable polyols include glycol, propanediol, glycerol, or sorbitol. 

The stabilizing agent is synthesized from PVA, ethylene vinyl alcohol, ethylene acrylic acid and poly(methyl methacrylate). An example of a formulation of a stabilizing agent is given in Table 5.2. 

Three examples of high starch compositions are given in Table 5.3. 

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The manufacturing process uses a relatively simple technology. It does not require capital-intensive equipment. The high starch polymer film can be made by using conventional plastic film extruders. The entire operation is cost-effective and makes the large-scale industrial production readily feasible (8). 

C. J. Bemu. High temperature stable modified starch polymers and well drilling fluids employing same. Patent EP 852235,1998. 

Molecular Structure. Most starches consist of a mixture of two polysaccharide types amylose, an essentially linear polymer, and amylopectin, a highly branched polymer. The relative amounts of these starch fractions in a particular starch are a major factor in determining the properties of that starch. 

Films of starch-EAA blends were prepared by either casting aqueous dispersions or by dry fluxing both the polymers.133 Cast films were relatively transparent, flexible and stable on immersion in water. In contrast, the dry blended materials were opaque at starch levels greater than 30% and had poorer tensile properties at high starch contents. No plasticizers were needed to prepare flexible films. Starch-EAA films have also been prepared by extrusion.134... 

During the same period, commercialization of thermoplastic starch polymer blends was pursued by Novamont, a division of the Ferruzzi Group of Italy.162-172 Their products, marketed under the trade name Mater-Bi, are typically comprised of at least 60% starch or natural additive and hydrophilic, biodegradable synthetic polymers.64,165 It is stated that these blends form interpenetrated or semi-interpenetrated structures at the molecular level. Properties of typical commercial formulations have properties similar to those in the range of low- and high-density PE. Blends of Mater-Bi products with biodegradable polyesters have been claimed for use as water impervious films.173... 

The beta-amylases (EC3.2.1.2) used are enzymes of barley and yeast that act on the non-reducing ends of starch molecules and produce maltose in the beta form from the starch polymers. These enzymes are used to produce high-maltose syrups. Although beta-amylase converts linear chains completely to maltose, the enzyme cannot cleave branch points and the yield of maltose from amylopectin11 (see Chapter 7) is only 55% of the molecule. 

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