Chemical modification of starch by reactive extrusion

Processes for chemical transformation of starch by extrusion processing (reactive extrusion, REX) are reviewed with a focus on non-food applications. The scope, advantages, limitations and specificity of various REX processes for are examined in this context. The processes covered include: the grafting of monomers from starch as single units, such as ring-opening of epoxides, esterification (with lactones, anhydrides, acids, halides or vinyl esters) phosphorylation and silylation; graft polymerization from starch by radical-induced grafting or the ring-opening polymerization of lactones; reactive compatibilization with polyesters and polyolefins by grafting to or from starch; crosslinking of starch with epichlorohydrin or by phosphorylation; and the degradation of starch thermally or catalyzed by acid or enzymes.