Starch Destructurization in Presence of Synthetic Polymers

Starch can undergo a thermoplastic transformation up to destructurization in the presence of different synthetic polymers to satisfy a broad spectrum of market needs. Destructurized starch composites can reach starch contents higher than 50%. 

With some of these polymers, a real complexation of single helical amylose with the polymer backbone can happen, which gives rise to supramolecular stmctures characterized by V-type crystallinity. This sort of modified amylose crystallinity is the same mentioned in section 2.4.4 and has been widely studied with small molecules such as alcohols, glycerol, dimethylsulphoxide, fatty acids, or iodine [66]. 

Complexation of starch by macromolecules can give rise to even more stable complexes playing an important role on the final properties of the starch-based polymer. Unlike amylose, the majority of amylopectin does not interact with the complexing agent and remains in its amorphous state. 

In the following paragraphs, a resume of the state of the art related to starch destructurization with synthetic polymers will be made. 

Otey has studied the interactions between ethylene-acrylic acid copolymer (EAA) and gelatinized starch since 1977 [77-83]. 

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Usually, starch destructurization in presence of synthetic polymers, gives rise to Vh and Eh structures (always a V-type one). The latter is especially obtained with high mechanical stress and low moisture content [129]. 

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