Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2008
Publication Date: 4/7/2009
Citation: Mukhopadhyay, S., Onwulata, C.I., Thomas, A.E. 2009. Thermo mechanical and surface morphology of reactively-mixed starch-protein composite. Meeting Abstract. Abstract 97Session 15 Interpretive Summary:
Technical Abstract: Plastic polymers derived mostly from refined crude-oil products, are currently regarded as unsustainable, and are fluctuating widely in costs. There is an increasing demand for finding renewable and sustainable sources for plastics. Agricultural materials such as proteins and starch are both renewable and can be thermoformed into bioplastics. Proteins and starch, although highly biodegradable, are often difficult to process individually into bioplastics as starch may degrade prior to the melting stage, and proteins exhibit low mechanical strength. Experiments were conducted using a mixture of 40% whey protein isolate (WPI) and 30% starch, with water and aqueous solutions of either Acetic Acid (AA) or Citric Acid (CA) 30% (w/w) to form composites. The composites were mixed with roller blades in a torque rheometer for 45 min at the preset initial temperatures of 35 deg C and 70 deg C. At the completion of reactive mixing, the thermoformed composite pastes were molded into ASTM D4065 strips in a Carver press for 30 min at 121 deg C. The mechanical properties indicate that the presence of mono- and poly- basic organic acids increased crosslinking of starch and protein. The storage modulus of the composites was found to be a function of the concentration of organic acids in the mix. Results indicate an increasing trend of storage modulus of the bioplastic as the AA concentration in the matrix increased. There was a 27.5% increase in storage modulus from 636 MPa for the control sample with no added AA to 862 MPa at 3.75% AA. Molded products mixed at 70 deg C performed better than those mixed at 35 deg C. Reactively extruded DBP can be used as adjunct polymers for specific products. The properties of crosslinked starch and protein composites can be tailored to specific needs by controlling the proportion of the protein or starch.