Starches alkali-treated

Hessian starch untreated/polyester-HSUNTR Hessian starch alkali treated/polyester-HSAL... 

Hessian starch alkali treated with mechanical constraint/polyester-HSALMC... 

The fractionation of acid- and alkali-treated starches has been reported,64 but the products are obviously degraded. Further work is, however, necessary on the use of alkaline solutions for fractionating starch. Pacsu10 maintains that the addition of an amylose precipitant to an alkaline dispersion... 

A general method for synthesizing starch-metal complexes with Ba, Ca, Sr, Be, Mg, Zn, Al, Fe, and Cu is given by a 1926 British patent,522 wherein alkali starches were treated with one or more metal salts. The cupric complex was reported to have disinfecting properties. 

When starch is treated with hot alkaline solutions, it behaves in the manner to be expected of a material composed of an alkali-labile fraction and an alkali-stable fraction. Starches from different sources vary in the relative amounts of these two components, and, therefore, starches can be characterized by their alkali lability. Alkali lability of a starch can be expressed as its alkali number, which is an empirical expression of the acids produced from the terminal, reducing group by the action of alkali. The alkali number (and, therefore, the alkali lability) increases progressively during acid hydrolysis. - Hence, the alkali number is an index of molecular size for linear molecules. 

Carboxyethyl)starch is also obtainable by treatment of starch with acrylonitrile in 10% aqueous NaOH solution at temperatures no higher than 60 °c,852-854 and hydrolysis of the nitrile group can be stopped at the carbamoylethyl group stage.855 The apparent viscosity of cyanoethyl starch decreased upon storage, whereas the shear rate significantly increases.856 This behavior is opposite to that of alkali-treated starch. 

Polysaccharides can be oxidized even by such a mild oxidant as atmospheric oxygen. The rate of oxidation is greatly enhanced by alkalies and by various heavy metal ions. Mild oxidations are beneficial when properly employed for producing new and useful properties in polysaccharides. As an example, starch is mildly oxidized by small amounts of bleaching powder to produce improved textile sizes. Atmospheric oxidation of alkali-treated cellulose reduces the chain length of commercial cellulose to the point where its xanthate can be dissolved in a strong alkaline solution and can be used... 

The mechanical properties and water absorption behaviour of composites made from a starch-based thermoplastic matrix in combination with alkali-treated sisal fibres were studied by Alvarez et al. (2003). The variables in their experiments were fibre percentage, temperature and process time. The selected matrix was Mater-Bi -Y (Novamont), a blend based on cellulose derivatives, starch and additives (Cyras et al, 2001). Composites were prepared by blending Mater-Bi -Y with fibres in a high-intensity mixer and then compression moulding the compounded material into panels. Mechanical tests showed that the tensile modulus more than doubled from 0.95 GPa to 2.2 GPa when the fibre content was increased from 0 to 15%. Fibre treatment with sodium hydroxide solution had no statistically significant effect on tensile modulus. Similarly, the flexural modulus increased from roughly 1.4 GPa to 2.8 GPa when Mater-Bi -Y was reinforced with 15% w/w sisal fibre but was not significantly increased when alkali-treated fibres were used. 

Resins are obtained by heating formaldehyde and starch under m rous conditions. A mbber-like product is claimed on heating starch and formaldehyde at 150-175 F under pressure in the presence of metallic magnesium. . Alkali-treated starch that has been reacted A dth formaldehyde under acidic conditions acts as an adhesiAre when subjected to heat and pressure . 

The effect of alkali treatment on molecular weight (compare with the case of the starch components) has been studied treating a 5% solution of rabbit-liver glycogen in 2 N sodium hydroxide, for 90 minutes at 100°, decreased the sedimentation constant (Sits X 1013) from 86 to 57 (that is, by 34%).237... 

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