Location: Plant Polymer Research2012 Annual Report
1a. Objectives (from AD-416):
The long-term objective of this project is to develop processes to enhance the conversion of cereal crops and residues into value added polymers, demonstrate the useful properties and applications of these biobased materials, reduce dependence on petroleum and increase utilization of environmentally friendly renewable resources. Objective 1: Develop technologies that enable commercially viable products composed of lipid and amylose or modified starch complexes with novel micro- and nano-sized spherulitic morphologies; Objective 2: Develop reactive extrusion-based technologies that enable commercially viable graft co-polymers from starches and lignocellulosics; Objective 3: Develop novel chemical and thermal processes that enable the commercially viable production of derivatives of starches, lignins, and lignocellulosics; Objective 4: Develop novel biocatalytic processes to produce commercially viable derivatives of starches, lignins, and/or lignocellulosics.
1b. Approach (from AD-416):
New biobased products and sustainable processing technologies are needed to replace industrial and consumer products made from petroleum based feedstocks. This project focuses on making polymeric materials with a variety of useful applications from starch and associated low cost coproducts of corn processing and harvesting. In order to accomplish this, modified biopolymers with new or improved properties need to be prepared and processing technologies which are more efficient, i.e. use safer or less solvent, are faster, have more complete reaction and fewer byproducts need to be developed. Specific objectives for this project include: 1) prepare novel spherulitic starch-polymer composites via jet-cooking; 2) prepare starch graft copolymers with controlled structure by reactive extrusion and evaluate applications; 3) prepare modified starches, celluloses, and lignins with novel structures via processing with ionic liquids, microwaves, and autoclave heating; and 4) prepare new starch and lignin graft copolymers as well as polyglutamic acid and polyhydroxyalkanoates by enzymatic and microbial catalysis. Overall, this research will lead to biobased polymer products which will have new or improved properties, have lower cost, are more environmentally friendly and thus will be more acceptable to consumer markets.
3. Progress Report:
Water-soluble complexes were prepared by adding water solutions of sodium palmitate to hot, jet-cooked dispersions of high-amylose corn starch and normal food grade corn starch. The viscous properties of these complexes were similar to those of some high-priced natural gums. The use of these complexes as replacements for guar gum in hydromulching applications is being evaluated. Composites prepared by freeze-drying aqueous mixtures of styrene-butadiene latex and amylose-sodium palmitate complex were molded into starch-reinforced plastics with good physical properties. Water-solutions of starch-stabilized silver nanoparticles were prepared by adding silver nitrate to aqueous solutions of starch-sodium palmitate complex and then reducing the complexed silver salt to metallic silver. Silver nanoparticles are currently of interest due to their antibacterial properties. Jet cooked high amylose corn starch was also used to prepare poly(methyl acrylate) graft copolymers that had improved properties relative to controls. Starch-lignin graft copolymers were prepared and their structures were characterized by infrared and other techniques. The flocculation activities, water solubility index, and water absorption index were also measured. The rheological properties of starch-lignin graft copolymers are being conducted continually. Starch-lignin compositions were prepared and studied. This research conducted under a Non Funded Cooperative Agreement between ARS and the State University of New York, Binghamton, NY. Currently we are using dynamic light scattering (DLS) to investigate the behavior of plant polysaccharides in ionic liquid. This technique has rarely been used before to study dissolution in ionic liquid. For wood and other plant materials, ionic liquids have an advantage in serving as suitable solvent media. We looked at wheat and barley straw in order to add value to these agricultural waste materials. We have successfully converted them to methyl cellulose, with yields ranging from 25-72%. Methyl cellulose is a well known material that is being used in agriculture as a binder, film former, as additives in adhesives, protective coatings, cosmetics, and toiletries. We are exploring the radical initiated graft polymerization reaction of acrylamide with starch in dimethyl sulfoxide (DMSO). When the reaction is carried out in water, there is on average one polyacrylamide graft of molecular weight 485,000 per 2300 glucose units (approximately three grafts per starch polymer). When the reaction is carried out in DMSO, there is on average one polyacrylamide graft of molecular weight 48,000 per 260 glucose units (approximately 25 grafts per starch polymer). We expect dramatically different rheological properties between the resulting products and this testing has begun.
1. High elongation starch. Articles made using starch typically are brittle with relatively low elongation. ARS, Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, have found that by using steam to cook starch (jet cooking), followed by chemically attaching a different polymer to it, a novel material is produced with excellent properties. By having the starch chemically attached to the polymer, the starch serves as a reinforcing agent that provides higher elongation and strength. This technology will be beneficial to the producers of corn starch by generating another revenue stream for their product. It will also be beneficial to polymer producers interested in producing high elongation biodegradable products.
2. Improved starch based materials. ARS scientists in the Plant Polymer Research Unit at the National Center for Agricultural Utilization Research have prepared polymer grafted starch materials (starch having another polymer bound to it) with a vastly different architecture. One of the methods to modify starch is to place polymers having different compositions onto the starch (“polymer grafts”). Traditional polymer grafting of starch placed two or three of these new polymers onto starch. Using the newly modified technology, starch has been produced having 20 to 40 of these polymer grafts attached to the starch. These new modified starches will benefit water purification or paper production industries as well as enhancing the value of farmers that produce high starch crops.
3. Improved synthesis of methyl cellulose. ARS, Plant Polymer Research Unit scientists at the National Center for Agricultural Utilization Research in Peoria, IL, have discovered a microwave-assisted fast method of making methyl cellulose, a valuable product used as a thickener in food and cosmetic products. This discovery will benefit industrial chemical manufacturers, among others to save time and energy during the production of methyl cellulose. In the end this method will help us to convert agricultural waste materials, such as corn fiber, corn stover, rice hulls, wheat straw, etc. to value added methyl cellulose.
Shogren, R.L., Peterson, S.C., Evans, K.O., Kenar, J.A. 2011. Preparation and characterization of cellulose gels from corn cobs. Carbohydrate Polymers. 86(3):1351-1357. DOI: 10.1016/j.carbpol.2011.06.035.