Location: Plant Polymer ResearchTitle: Properties of Starch-Poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) Graft Copolymers Prepared by Reactive Extrusion Author
Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2015
Publication Date: 6/5/2015
Publication URL: http://handle.nal.usda.gov/10113/5852177
Citation: Willett, J.L., Finkenstadt, V.L. 2015. Starch-poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) graft copolymers prepared by reactive extrusion. Journal of Applied Polymer Science. 132(33). DOI: 10.1002/app.42405.
Interpretive Summary: ARS scientists have produced new biobased materials by using the natural properties of starch and chemically bonding them to other polymers. These polymers modified with starch are called starch-graft-copolymers. These starch-graft-copolymers can be made in solution, which generates a great deal of solvent waste. Alternatively they can be produced in the solid state (minimal solvent) using a twin-screw extruder. Extrusion processing is the most economical method for processing materials as it avoids the use of large amounts of solvent. Polyethylene is processed using extrusion techniques. Reactive extrusion is a type of extrusion where the desired chemistry takes place inside the extruder. he reaction occurs very quickly – minutes instead of hours.Our starch-graft-copolymers were prepared in a continuous process by reactive extrusion in a twin-screw extruder. The starch-graft-copolymers are responsive to their environment and can be used to replace other commercially available super absorber polymers currently being used in the marketplace. This work is of interest to farmers of commodity crops and companies that produce starch products. This process addresses the growing need to develop biobased materials to provide new markets for agriculture and reduce dependence on nonrenewable resources.
Technical Abstract: Graft copolymers of starch with acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were prepared by reactive extrusion in a twin-screw extruder. The weight ratio of total monomer to starch was fixed at 1:3, while the molar fraction of AMPS in the monomer feed ranged from 0 to 0.119. Monomer to polymer conversions were 85% or greater, with grafting efficiencies of 68% (highest AMPS content) to 85% (no AMPS). Absorbency in distilled water at pH 7 increased linearly with the mole fraction AMPS in the grafted polymer, while absorbencies in 0.9% NaCl were independent of AMPS content. When swollen in water/ethanol mixtures, swelling decreased gradually with increasing ethanol volume fraction, followed by a large decrease over a narrow ethanol concentration. This behavior is similar to that observed for AMPS-acrylamide gels. The swelling properties suggest these graft copolymers may have applications as responsive materials.