Submitted to: Polymer International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/2010
Publication Date: 3/23/2011
Citation: Selling, G.W., Woods, K.K., Biswas, A. 2011. Electrospinning formaldehyde cross-linked zein solutions. Polymer International. 60(4):537.
Interpretive Summary: This research further demonstrates that solvent resistant zein fibers can be produced where the chemical treatments take place before spinning. By carrying out the chemical reactions before spinning, the overall safety of an industrial process is improved. Zein is a major component in the co-products of the bio-ethanol industry. Techniques are being developed to economically extract and purify zein from these streams in order to use the zein in higher value products. The main historical use for zein was in fibers, where it had to be chemically modified using formaldehyde. In these processes, the zein was treated with formaldehyde both before and after fiber formation. It is expensive to safely utilize formaldehyde post-fiber production. Developing routes to produce formaldehyde treated zein fibers where the chemical processing takes place before fiber production demonstrates that post-chemical treatments are not necessary. In order to carry out this process in the lab, a small scale fiber production system was used. This technique is called electrospinning where electricity is used to make fibrous mattes using zein solutions that had been treated with formaldehyde. The resulting fibers did require an additional heat treatment in order to become solvent resistant. It was found that the fibers produced were stronger than control. In addition, it was found that how the zein protein wound back and forth in the fiber changed with formaldehyde treatment. These results demonstrate that solvent resistant zein fibers can be produced where the chemistry is performed pre-fiber production and provide support for continuing research in the area of producing zein based fibers.
Technical Abstract: In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as the cross-linking reagent before spinning. The cross-linking reaction was carried out in either acetic acid or ethanolic-HCl where the amount of cross-linking reagent was between 1 and 6%. Reactions were carried out at various times and temperatures. When carried out in acetic acid, the maximum amount of formaldehyde that could be used was 1.5% as gelation occurred at higher levels. In ethanolic-HCl, 6% formaldehyde could be incorporated into zein. All solutions were successfully electrospun producing predominantly ribbon and round fibers; morphology was strongly dependent on solvent and spinning solids. The formaldehyde cross-linked zein fabrics had double the tensile strength of control fibers. SDS-PAGE analysis clearly showed cross-linking has occurred. Electrospun fibers from all zein-formaldehyde treated solutions required an additional heating step in order to be resistant to dissolution in acetic acid, a known very good solvent for zein.