Starch component polymers

The viscosity of polymer solutions has been considered theoretically by Flory,130 but although this theory has been applied to cellulose esters,131 no applications have yet been made in the case of the starch components. Theoretical predictions of the effect, on [17], of branching in a polymer molecule have been made,132 and this may be of importance with regard to the viscometric behavior of amylopectin. 

Non-mutant normal) reserve and transitory starch granules are composed primarily of amylose and amylopectin. Amy lose is essentially a linear polymer consisting of (1—4)-linked a-D-glucopyranosyl units. Amylopectin is a branched polymer of a-D-glucop-yranosyl units primarily linked by (1—>4) bonds with branches resulting from (1—6) linkages. Properties of these two major starch components are summarized in Table 3.1. 

The physical state of starch during extrusion can be considered to change from a partially crystalline polymer to a polymer melt which is homogenized by shear. Extrusion may also decrease the molecular size of starch components, which is observed from decreased melt viscosity (Lai and Kokini 1991), and obviously a decreased molecular size results in a decreased glass transition temperature of the extmdate. The dramatic decrease of pressure that occurs as a viscous, plasticized melt exits the die may allow an extremely rapid loss of water, expansion of the melt and cooling to an amorphous solid state. 

Guy and Home (1998) report a detailed study of expansion as a function of barrel exit conditions. Firstly they note that even under conditions where melting of crystallites of starch should be complete, if shearing conditions are low, expansion is limited to 1-1.5 ml.g specific volume. This implies that for high expansions, the starch must not only be gelatinised but that its component polymers must be exuded into the continuous mass. 

Achayuthakan, R, Suphantharika, M., and Rao, M. A. 2006. Yield stress components of waxy com starch-xanthan mixtures effect of xanthan concentration and different starches. Carbohydr. Polym. 65 469-478. 

Starch is a condensation polymer made up of hundreds of glucose monomers, which split out water molecules as they chemically combine. Starch is a member of the basic food group carbohydrates and is found in cereal grains and potatoes. It is also referred to as a polysaccharide, because it is a polymer of the monosaccharide glucose. Starch molecules include two types of glucose polymers, amylose and amylopectin, the latter being the major starch component in most plants, making up about three-fourths of... 

C.A. Teaca, R. Bodirlau, I. Spiridon, and N. Tudorachi, Multi-component polymer systems comprising modified starch microparticles and different natural fillers, in Program of the European Polymer Federation Congress (EPF 2013), June 16-21, Pisa, Italy, P2-160, p. 42 (2013). 

The starch component of the Fantesk starch-oil composite can vary in its chemi-cal/structural properties (amylose, amylopectin, waxy) as well as in the type of crop source (corn, potato, rice, etc). Likewise, the oil component of the Fantesk starch-oil composite can have a variety of chemical/structural properties, compositions, and end uses. Over the years, Fantesk starch-oil composites of various combinations of starch and oil have been prepared and investigated for a variety of food and nonfood applications, including cosmetics, pharmaceuticals, polymers, coatings, and lubricants [4, 30-33]. 

Crystalline starch beads can be used as a natural filler in traditional plastics [3]. They have been particularly used in polyolefins. When blended with starch beads, polyethylene films biodeteriorate upon exposure to a soil environment. The microbial consumption of the starch component leads to increased porosity, void formation, and loss of integrity of the plastic matrix. Generally, starch is added at fairly low concentrations (6-15 wt%). The total disintegration of these materials is obtained using transition metal compounds, soluble in the thermoplastic matrix, used as pro-oxidant additives to catalyze the photo and thermo-oxidative processes [4]. These products belong to the first generation of degradable polymers that biodeteriorate more than mineralize to CO2 and H2O in a time... 

Although both starch components behave similarly with regard to water absorption, in the case of high ambient moisture levels amylose absorbs greater amount of water than amylopectin because the crystallization reduces water absorption by the hydrophilic polymers [17, 44, 53, 54]. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Biodegradation studies of starch blends have not been conclusive where a nondegradable synthetic polymer has been the blend component probably biodisiategration would be a better term to describe these polymers. The principal deficiencies of products based on this chemistry, aside from the incomplete biodegradation, are water-sensitivity of manufactured articles, and the balance of this and biodegradation with the starch level ia the product. 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aUphatic polyesters with inorganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibiUty of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and biodegradabihty is attempted. Starch and additives have been evaluated ia detail from the perspective of stmcture and compatibiUty with starch (214). 

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