Resistant starch cross-linked starches

Polymers. AH nitro alcohols are sources of formaldehyde for cross-linking in polymers of urea, melamine, phenols, resorcinol, etc (see Amino RESINS AND PLASTICS). Nitrodiols and 2-hydroxymethyl-2-nitro-l,3-propanediol can be used as polyols to form polyester or polyurethane products (see Polyesters Urethane polymers). 2-Methyl-2-nitro-l-propanol is used in tires to promote the adhesion of mbber to tire cord (qv). Nitro alcohols are used as hardening agents in photographic processes, and 2-hydroxymethyl-2-nitro-l,3-propanediol is a cross-linking agent for starch adhesives, polyamides, urea resins, or wool, and in tanning operations (17—25). Wrinkle-resistant fabric with reduced free formaldehyde content is obtained by treatment with... 

In contrast to monophosphates, starch phosphate diesters contain cross-links between two or more starch chains. This covalent linkage in the granule produces a starch product which swells less but is more resistant to heat, agitation, and acid than natural starch. 

Woo, K. S. (1999). Cross-linked, RS4 type resistant starch preparation and properties. PhD Thesis. Kansas State University Manhattan, KS. 

As in the case of aU other polymers, the cross-linking of starch causes an increase in the chemical and mechanical resistance as well as a decrease in the solubility. The... 

Seidel C, Kulicke WM, Hes C, Hartinatm B, Lechner MD, Lazik W (2001) Influence of the cross-linking agent on the gel structure of starch derivatives. Starch 53 305-310 Xie X, Lin Q (2004) Development of physicochemical characterization of new resistant citrate starch from different com starches. Starch 56 364-370... 

Granular starch has been cross-linked with phosphate by reaction of an aqueous alkaline suspension at pH 8-12 with 0.005-0.25% phosphorus oxychloride [15] (reaction 7.15). If starch granules are treated with 1% or higher concentrations of phosphorus oxychloride, the granules become very resistant to gela-tinization. Trimetaphosphate has also been used to produce phosphate cross-linkages [15] (reaction 7.16). Phosphorylation of 0-6 is predominant, and that of 0-3 is minimal [19]. 

The utilization of TPS for the production of biodegradable plastics has increased and has been the object of several studies in the last decade. However, TPS has two main drawbacks namely its water affinity and its poor mechanical properties. To overcome these problems, the addition of other materials to TPS is necessary. In order to increase its water resistance, TPS has been blended with synthetic polymers and modified by cross-linking agents such as Ca and Zr salts. Substances such as waxes and lignin have also been tested to decrease the water uptake of starch-based materials. TPS s mechanical properties have usually been improved by addition of synthetic polymers, such as ethylene-acryhc acid and ethylene-vinyl alcohol copolymers. Another approach requires the use of natural fibers and mineral fillers. The inclusion of reinforcing fillers such as fibers could, however, enhance the degradation of thermoplastic starch because of the increase in the melt viscosity [79-81]. 

---