Effect of Plasticizers on Morphology, Mechanical Properties and Water Absorption of Wheat Gluten and Epoxidized Natural Rubber Blend

Wheat gluten (WG) plastics are inherently brittle and sensitive to water. In this research, wheat gluten was blended with epoxidized natural rubber containing 50 mol% epoxide group (ENR-50) to improve flexibility and water resistance of WG plastics. Three plasticizers (i.e. glycerol (Gly), polyethylene glycol (PEG) and dioctyl phthalate (DOP) were used to enhance polymer chain mobility and process ability of WG phase in the blends. Differential scanning calorimetry (DSC) was used to evaluate plasticizing efficiency of plasticizers on WG. The DSC result revealed that an excellent plasticizer for WG was glycerol which could remarkably reduce glass transition temperature (Tg) of WG. Furthermore, effect of plasticizer types and contents (0, 10, 20 and 30wt% with respect to protein weight) on morphology, mechanical properties and water absorption of the WG/ENR blends was investigated. It was found that an enhancement in ductility and impact strength of the blends was observed with increasing plasticizer content. Among the plasticized WG/ENR blends, the glycerol-plasticized blend provided better homogenous morphology and superior results in tensile and impact properties. On the other hand, the Gly-plasticized WG/ENR blend showed a low water resistance compared with the blends plasticized with PEG and DOP as well as the unplasticized WG/ENR blend.