Submitted to: Polymer Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2004
Publication Date: May 15, 2004
Citation: Selling, G.W., Sessa, D.J., Palmquist, D.E. 2004. Effect of water and tri(ethylene)glycol on rheological properties of zein. Polymer. Available: http://authors.elseviere.com/sd/article/S0032386104003611. Interpretive Summary: New industrial markets need to be found for the corn protein (predominantly zein) produced from the corn refining and bioethanol industries. Historically the most successful commercial application of zein was in the fiber market where it was used as an alternative to wool. In its pure state, zein fiber had properties which did not meet the needs of the desired market. Some of these deficiencies were reduced through chemical modification and a commercial fiber (Vicara (TM)) was produced. With the growth of Orlon(TM), which had superior properties, the Vicara(TM) business eventually disappeared. The global market for wool and acrylic fiber is approximately 1.3 and 2.7 million metric tons per year respectively. A 1% penetration into these markets would allow the use of approximately 100 million pounds of zein. This new high value end use for a by-product of the bioethanol industry that is renewable and readily biodegradable would obviously greatly improve the economics of the corn processing industry. Other methods must be evaluated in order to both improve the physical properties of products made from zein and the ability to process zein. There is little information regarding the behavior of zein when processed. A torque rheometer was used to assess how various additives effect the processing of zein. These fundamental findings are essential to produce improved zein based fibers and other articles. This information will be useful to scientist in industry, academia and government who are interested in zein processing and products.
Technical Abstract: Before conducting larger scale studies utilizing zein on an extruder, it is necessary to carry out experiments on a torque rheometer. Water and tri(ethylene glycol) (TEG) are known plasticizers for zein, however, the effects these materials have on zein has not been studied using a torque rheometer. The amount of each plasticizer in zein was varied between 5 and 30%. The plasticizers were tested separately and in combination. It was demonstrated that water and TEG interact differently with zein. TEG was more effective on a molar basis. When the amount of water was above 10%, network formation occurred and the resulting torque increased exponentially with time. TEG will allow network formation at elevated temperatures. When TEG was used at lower temperatures, torque increased linearly with time. When TEG and water combinations were used to plasticize zein, the resulting rate of torque increase was dissimilar to that obtained when either plasticizer was used alone. Previously unobserved multiple state changes for zein mixtures were observed suggesting that under suitable conditions the formation of networks is an ongoing process. The energy of activation of flow was determined when using 20% TEG. A model was developed relating %water, %TEG, temperature and rpm with initial torque.