Starch acetate solubility

Starch acetates may be characterized, in part, by (1) acetyl content, (2) solubility, (3) behavior in solution, (4) optical rotation, (5) fusion temperature, and (6) mechanical properties. 

The solubility of a starch acetate is dependent upon (a) the acetyl content (b) the average degree of polymerization of the starch and... 

It should be observed that slight depolymerization or incomplete acetylation of the starch acetate molecule leads to products possessing a much wider degree of solubility. For example, at low acetyl values (0-26%), starch acetates are said to be water-soluble. -" However, if the starch molecules are undegraded, it is probable that the water-soluble range does not extend to products containing more than fi-15% acetyl groups. 

Staudinger and Husemann determined the osmotic pressure of solutions of a potato starch acetate which had been fractionated into four parts by precipitation of its chloroform solution with ether. The molecular weights of the fractions ranged from 45,000 to 275,000. All of the fractions were soluble in chloroform, but fractions of low molecular weight were also soluble in acetone. For various concentrations of solute in either chloroform or acetone, the osmotic pressure did not increase in direct proportion to the solute concentration, but the deviation from van t Hoff s law was the smallest in the case of the acetone solutions. Osmotic pressure measurements on amylose and amylopectin tri-acetates dissolved in tetrachloroethane have been made by Meyer and co-workers, who have deduced molecular weights for these substances of approximately 78,000 and 300,000, respectively (see above discussion of the purity of these fractions). 

Common starch esters include the acetates. High d.s. starch acetates have been formed by using acetic anhydride with either sodium acetate or pyridine catalysts at 90-100 °C [158,159,160]. The major use of starch acetates have been in the study of the stmctures of amylose and amylopectin after acid hydrolysis. Acetylation of granular starch in aqueous suspension by acetic anhydride at pH 10-11 is used to produce low d.s. starch acetates that are primarily used for the stabilization of their viscosity and for their water-soluble clarity. The acetylation decreases the hydrophilic character and increases the hydrophobic character of starch. The major uses of starch acetates is in the paper industry for surface sizing to give improved print quality, uniform porosity, surface strength, and resistance to various solvents [161]. 

The solubility of starch acetates depends on the d.s. and the d.p. Starch acetates of 10-15% are soluble in water at 50-100 °C and are insoluble in organic solvents. Starch acetates of 40% or more are soluble in aromatic hydrocarbons and halogenated aliphatic hydrocarbons. 

Acetylation of starch, which is commonly done with acetic anhydride and can reach a D.S. between 2 and 3. Highly acetylated starches are soluble in organic solvents and become insoluble in water. They are used for their capability to form films and coatings. 

Use Plasticizer for cellulose acetate intermediate for antioxidants, special starches, oil-soluble phenolic resins pour-point depressors and emulsion breakers for petroleum oils and some plastics synthetic lubricants insecticides industrial odorants motor-oil additives. 

C, whereas the com starch derivative only turned brown at this temperature. Further allylation led to diallyl ethers.748-752 For this purpose, an acetone solution of starch acetate in a 50% solution of NaOH containing allyl bromide was boiled or heated in an autoclave at 80 °C. These procedures were then improved by using either butanone and KOFI753 or 1,4-dioxane and NaOH.754 Di-O-allyIstarch is a soft, gummy product that is soluble in most of organic solvents except for aliphatic hydrocarbons. This solubility is lost after exposure of diallyl starch to air.748 It can also be hardened by the addition Co(II) octanoate or Co(II) naphthenate.755... 

Starch acetates may have low or high DS. The industrial importance of low DS acetates results from their ability to stabilize aqueous polymer sols. Low DS acetates inhibit association of amylose polymers and reduce the association of the longer outer chains of amylopectin. These properties are important in food applications. Highly derivatized starches (DS 2—3) are useful because of their solubility in oiganic solvents and ability to form films and fibers. 

The reaction of polysaccharides ivith aldehydes to give cross-linked products has been known and exploited industrially for some time. Starch acetals may also be prepared by a method that does not give rise to cross-links and involves treatment of starch with a cyclic vinyl ether, 3,4-dihydro-2H-pyran, to give a tetrahydropyran-2-yl derivative (16). At low levels of substitution, the acetals are water-soluble, at... 

High DS starch acetates are used to create brittle films and molded products. These have had little application, due to the economic superiority of cellulose acetates. In general, specific gravity and melting temperature both decrease with an increase in acetylation (45). Highly acetylated starches above 15% acetyl content (DS approximately 0.7) are soluble in water at 50° to 100°C and insoluble in organic solvents. When the acetyl content reaches 40% (DS approximately 2.5), the derivatized starch is soluble in aromatic hydrocarbons, ketones, and glycol ethers. 

Extruded starch foam is produced by the flash generation of steam as the starch leaves the die (49,50). Foam packaging peanuts, as a replacement for polystyrene, can be made by extruding starch acetate or hydroxypropylated starch and water (Fig. 2). A commercial example is EcoFoam, a water-soluble extruded hydroxypropylated starch foam manufactured by National Starch and Chemical Co. 

Starch Derivatives. The most important ester is starch acetate it is obtained according to the same method as that leading to cellulose acetate. The gradual substitution of acetate groups for hydroxyls decreases the hydrophilic-ity of modified starch even at low degrees of modification, the hydrosolubility in hot water disappears and products with D.S.> 1.5 become soluble in organic solvents. 

Shogren RL, Biswas A. 2006. Preparation of water-soluble and water swellable starch acetates using microwave heating. Carbohydr Polym 64 16-21. 

The dialdehyde groups are highly reactive, leading to dicarboxylic groups by further oxidation, to dihydroxymethyl starch by reduction, to inter- or intramolecular hemialdalic or hemiacetalic forms. Dried dialdehyde starch is soluble only in boiling water or in solutions of sodium acetate or sodium borate at 60 °C. 

Starch acetates lose their water-swelling and pasteforming properties when DS increases. With up to 15% acetyl groups, they are still swellable in water at 50-100 °C at 40% acetyl content, they are only soluble in organic solvents, such as acetone, tri-chloromethane and aromatic hydrocarbons. Such peracetylation is best reached in homogeneous-phase reactions after dissolution of the starch in N-... 

---