Starch plastic production

Starch-plastic composites contain a mixture of two very different types of materials (/) hydrophobic, petrochemical-derived polymers (PE, EAA) known to be highly resistant to degradation by living organisms, and (i7) a hydrophilic, natural polymer (starch) that is easily broken down by a wide array of organisms. In the process developed by Otey (3), these fundamentally incompatible materials are forced into an intimate mixture during production of the plastic film. Since... 

At this point little is known about the interrelationships between composition, structure, starch-degradation and physical disintegration properties of starch-plastic composites. Continued work towards development of a laboratory assay for biodegradability will eventually result in the establishment of a sufficient database to elucidate these relationships, allowing development of a host of starch-containing plastic products for both existing and new markets. 

For starch-Bionolle compound production process, we obtain data of product yield and mixing ratios of Bionolle, starch, plasticizer, and water from actual site data provided by Showa Denko. Data of electric power consumption for kneading process are taken from actual site data from Showa Denko. 

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beet, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications. 

Other molds are used in various industrial processes. For example, Aspergillus terreus is used to manufacture icatonic acid, which is used in plastics production. Other molds are used in the production of alcohol. For example, Rhizopus, which can metabolize starch into glucose, directly ferments the glucose to give alcohol. Other molds are used in the manufacture of cheeses, flavorings and chemical additives for foods. 

Biodegradable plates, knives, forks, and leaf bags can be made by molding or extrusion of starch plasticized with 10% water.66 After use, the materials could be composted. A mixture of benzylated wood and polystyrene can be extruded easily.67 The properties of the product are comparable with those of poly(styrene). 

Currently, materials derived directly from starch by physical processing or by continuous chemical modification, as in reactive extrusion, are considered the most promising options for bio-based plastic production, particularly on economic grounds. A brief historical view of such starch-based materials is offered in the next section. 

The global demand for bioplastics was estimated at 0.36 million tonnes, which is equivalent to 0.2 % of the annual petrochemical plastic production (Thompson et al. 2009). PHA accounted for about 10 % of the bioplastic market which is currently dominated by poly(lactic acid) and other starch-based biopolymers (Barker et al. 2009). Based on the statistics, in order to fulfill the PHA market demand... 

Flux of Molecules within a Porous Plastic Matrix. The flux of starch digestion products and en2ymes in a porous plastic matrix can be treated as analogous to solute movement in a soil matrix, llie transport of starch-digestion products and the enzyme in the plastic matrix and the solutes of soil solutions are both examples of solute movement in a porous body. Solute movement in soil... 

Enzyme Assays. Starch digestion from blends by porcine a-amylase (Sigma) was determined by measuring soluble product formation by the phenol-sulfuric acid method (12). Incubations were conducted in 20 mL of 0.05 M phosphate buffer (pH 7.0) containing 8 pieces of 1 x 2 cm starch-plastic blend and 2 /iL mL merthiolate to inhibit microbial catabolism of digestion products (13). Merthiolate did not inhibit en2yme activity or interfere with product assays. Sufficient enzyme was added to give a 100 to 200 units mL solution. Incubation temperature was 35° C. Mixtures were shaken at 50 to 70 rpm on a rotary shaker. 

The mathematic model provides a reliable means to predict the starch release kinetics of controlled release formulations made from starch plastic blends. The predicted release of starch digestion products from the blends as a function of time was plotted in Figure 5a and Figure 5b. Correspondence between model-derived values and experimental results was excellent in nearly all cases. 

The work presented here constructed a general model of starch-plastic blends as potential controlled release formulations. This model provided a practical method of predicting the kinetics of the starch digestion and product release from starch-plastic blends, thus the kinetics of pesticide release is predictable if the pesticides are either adsorbed or covalently bonded to the starch. The model was developed for starch-plastic blends. It should be adaptable to other blends of incompatible polymers, so long as one of the polymers is susceptible to enzymatic l drolysis. 

Based on the mechanisms of enzyme hydrolysis of starch and the diffusion processes of enzyme and the starch digestion products in the plastic matrix, the following assumptions were made (a) the diffusion of both the enzyme and the products in the plastic matrix obeys the Pick s first law, (b) the diffusion coefficient is constant throughout the matrix during the reaction, (c) the hydrolytic reactions take place only inside the hydrophobic plastic matrix, and (d) the reaction between the enzyme and the substrate is a modified Michaelis-Menten type and the product (P), will competitively inhibit the enzyme activity ... 

There is an increasing demand for many plastic products used in packaging to be biodegradable. Difficulties have been encoimtered in producing starch-based pol5rmers by hot melt extrusion. The molecular structure of the starch is adversely affected by the shear stresses and temperature conditions needed to plasticize the starch. 

This chapter reviews the general context of starch as a material. After a survey of the major sources of starch and their characteristic compositions in terms of amylase and amylopectin, the morphology of the granules and the techniques applied to disrupt them are critically examined. The use of starch for the production of polymeric materials covers the bulk of the chapter, including the major aspect of starch plasticization, the preparation and assessment of blends, the processing of thermoplastic starch (TPS), the problems associated with its degradation and the preparation of TPS composites and nanocomposites. The present and perspective applications of these biodegradable materials and the problems associated with their moisture sensitivity conclude this manuscript. 

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