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Rheological Studies on the Reaction of Zein with Polyethylenemaleic Anhydride

Gordon W. Selling, Jeffrey A. Byars, Kelly D. Utt
Cereal chemistry 2016 v.93 no.2 pp. 145-149
activation energy, anhydrides, gelation, modulus of elasticity, reaction kinetics, temperature, viscoelasticity, zein
There continues to be interest in developing solvent-resistant articles from biobased renewable materials to successfully complete with petrochemical 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.