Soy protein-based polymer nanocomposites

The incorporation of nanofillers into soy protein materials significantly enhances tensile strength and modulus, and in some cases, contributes to a simultaneous increase in strength and elongation. The decrease in tensile strength that results from plasticization, is therefore, to some extent recovered. Water absorption usually decreased with the incorporation of nanofillers. In addition, the unique properties of some nanofillers such as the electron conductivity of carbon nanotubes and the antiflammability of layered silicates, can be transplanted into soy protein based nanocomposites. The nanocomposite shows great potential for partly solving the two prevailing problems of low strength and water sensitivity, which greatly hamper the development and application of soy protein based plastics. It also contributes to the development of high performance/novel functionality soy protein based materials. Contrary to most cases with soy protein as matrix, one recent study focused on applying soy protein nanoparticle aggregates to modify styrene-butadiene elastomer. The results showed that compact soy protein nanoparticle aggregates interacted more strongly with the polymer matrix and dispersed more uniformly than crude soy protein, and hence produced better modulus retention for the nanocomposites. Without doubt, soy protein based fibres (such as textiles) and adhesives can be further improved in terms of mechanical or adhesion performance by incorporating the proper nanofiller. The single most important factor affecting the high performance of soy protein based nanocomposites is strengthening the interfacial adhesion between the soy protein matrix and nanofillers. Chemical modification on the nanofiller surface is expected to improve the miscibility between filler and soy protein matrix. Furthermore, grafted long polymer chains may penetrate the soy protein matrix to produce a "co-continuous phase" structure, where the interactions and entanglements between grafted polymer chains and soy protein chains contribute to stronger interfacial adhesion.