Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2015
Publication Date: 3/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62512
Citation: Selling, G.W., Byars, J.A., Utt, K.D. 2016. Rheological studies on the reaction of zein with polyethylenemaleic anhydride. Cereal Chemistry. 93(2):145-149.
Interpretive Summary: Previously in this lab it was found that zein can be modified with a reactive polymer (called PEMA) to provide an article with improved strength and reduced sensitivity to liquids. Zein is a protein component that is the main co-product from bio-ethanol production. By developing higher valued products using this material, the economics of the bio-ethanol industry will improve. Zein has been modified using various reactive chemicals to provide improved articles; however, these chemicals will often require significant investment to be handled safely. We have that by using a reactive polymer, polyethylene maleic anhydride, zein can be modified in solution and provide articles that are stronger and less sensitive to liquids that usually dissolve zein. However, in order to utilize this technology, the rate at which the chemistry proceeds must be understood. Many reaction variables were changed in order to fully understand this chemistry. This information will be beneficial to manufacturers involved in the production of ethanol from corn as well as those companies interested in producing biobased (zein) articles that can compete with articles made using petroleum based ingredients.
Technical Abstract: There continues to be interest in developing solvent-resistant articles from biobased renewable materials to successfully complete with petro-chemical products. It was previously shown that reaction of zein with polyethylenemaleic anhydride (PEMA) provides articles that are solvent-resistant. The gelation kinetics for the reaction of PEMA with zein was investigated rheologically to better understand this chemistry. The reaction of the nucleophilic groups on zein with the anhydrides on PEMA is the main cause for the gelation reaction. The gelation time was defined as being the point when the elastic modulus (G') and viscous modulus (G") cross. In this work, the rate of reaction, in terms of time to gelation, was studied in N,N-dimethylformamide solution for which the amount of PEMA, the reaction temperature, and the overall reaction concentration were varied. Exponential relationships were found between the gelation time and % PEMA, temperature, and % solids, as well as between elastic modulus with either % PEMA or % solids. The concentration of PEMA had the largest impact on gelation time, for which going from 2.5% PEMA to 6% PEMA reduced the gelation time from 63,114 to 1,576 s. The temperature dependence of this gelation reaction was well described by an Arrhenius plot with an apparent activation energy of 50.5 kJ/mol.