Location: Plant Polymer Research2016 Annual Report
The goal of this research project is to use a wide range of technological approaches in the utilization of agricultural byproducts and feedstocks to improve functionalities of protein/carbohydrate particles for elastomer, coating, agricultural, medical, and cosmetic applications. Over the next 5 years, we will focus on the following objectives: Objective 1: Enable the commercial production of new products based on functionalized particles for applications in elastomeric composites and latex coatings. Objective 2: Enable new commercial processes to produce marketable biochar particles for rubber composite filler applications. Objective 3: Enable the commercial production of new products based on nano- or micro-particles for controlled-release of chemicals. Objective 4: Enable the commercial production of new products based on biodegradable nanoparticles from starch, and expand their end-use applications. Objective 5: Enable the commercial production of new products based on micro-and nano-sized particles of lignin and cellulose.
The aim of this research is to develop biobased particle technologies that produce functional particles using renewable agricultural byproducts and feedstocks. The characteristics of the functional particles include size, shape, aggregate structure, and surface functionalities that can be changed for the particles to function as reinforcements in polymer matrices, hydrocolloids for modifying rheological and surface properties, and controlled-release vehicles for delivering chemicals. The outcome of this research will contribute to the utilization of voluminous byproducts generated by the biofuel and food industries, reduction of greenhouse gases responsible for climate change from carbon black production, and sustainability of the global economy. Currently, carbon black is the dominant filler in rubber products. Our previous research on biobased particles has produced natural rubber composites with useful mechanical properties. Further development will be on the regulation of particle connectivity and interface adhesion. Our masterbatch process will be extended to the rheology and films of latex coatings. Carbonized biomaterials as feedstock will also be developed as rubber filler with emphasis on the methods of biochar production to address performance, quality, and supply issues. We have produced nanoparticles of amylose complexes with steam jet cooking technology and will improve particle functionality for composite, coating, and medical applications. We will also develop nano-size cellulose/lignin for composite and cosmetic applications. For controlled-release applications using biobased particles, the functional particles to deliver chemicals, specifically pesticides, will be developed to solve wash-away issues and reduce pesticide consumption. The resulting technologies will be transferred to users who use these products.
For FY16, we have accomplished the development of modified natural rubber composites with soy nanoparticles, charcoal particulates from birch and elm hardwood, particles of starch-fatty acid complexes, and micro-/nano cellulose particles from corn stover for a variety of industrial elastomer, plastic, and coating applications. Our accomplishments are documented in peer-reviewed scientific publications. Demanding rubber applications require reinforcement fillers, which are currently dominated by carbon black produced by burning heavy oil. In this process, ~50% of the oil is converted to carbon dioxide. Renewable and environmentally-friendly fillers from agriculturally-derived particles can be used to replace carbon black. Natural rubber is a major rubber used in a variety of rubber products and has excellent mechanical properties compared to other rubbers. To evaluate compatibility between agricultural-based reinforcement particles and natural rubber, natural rubber was modified to include molecules that can interact with soy protein nanoparticles. A one-step process was developed to change a portion of natural rubber to become more compatible with soy protein nanoparticles. Soy protein nanoparticles were prepared by breaking up soy protein aggregates with different types of basic chemicals and processed at different temperatures for a certain time. They were further processed with different shearing force to further break up the larger particles into nano-sized particles. The mechanical properties including strength, stiffness, and toughness were measured. The results indicate the strength of rubber composites were improved substantially at higher stretched ratios. These results show that they have the potential to be used in a variety of molded rubber objects for damping applications. Our project objective is to make rubber composites for the tire industry that replace carbon black filler (fossil fuel-based) with biochar (from renewable biomass) as much as possible without detrimental effects to the final composite. To do this, in FY16 we worked with a collaborator to procure potential hardwood feedstocks that would be successful in producing biochar that met three major criteria: 1) at least 75% carbon (higher is better), 2) at most 5% ash (lower is better), and 3) an average particle size of less than 2 microns. Birch and elm are two hardwood feedstocks that are plentiful due to declining demand in the paper industry as the popularity of digital media increases. Biochars were made from these feedstocks that met all of the above criteria, and we are currently assessing the properties of biochar-filled rubber composites to evaluate how much carbon black we can successfully replace with these biochars. Production of biochar from these feedstocks can be scaled-up and research to transfer this technology to the tire industry is ongoing. Excessive use of synthetic pesticides has resulted in an increased risk of pesticide resistance, enhanced pest resurgence, toxicological implications to human health, and increased environmental pollution. To mitigate these problems, natural pesticides emerged as an alternative to the existing synthetic chemicals. Plant-derived essential oil products, in general, are minimum-risk natural pesticides. These oils show a broad spectrum of activity against pest insects and fungi that cause plant disease. However, these oils are so volatile that the spray effect does not last long. To extend the effective period as pesticide, encapsulation of essential oils was performed. Peppermint oil is one of the most frequently used natural pesticides. As a first trial system of this research, a major component of peppermint oil, was encapsulated in tiny particles made up of biodegradable molecules. The optimum condition for manufacturing these particles was investigated by varying several experimental conditions. After the encapsulation, the evaporation of essential oils was significantly retarded. This newly developed technique is being extended to other essential oils with proper modification. Films were prepared by combining water solutions of polyvinyl alcohol (PVOH) with solutions of starch complexes prepared from jet-cooked high amylose starch and the sodium salts of fatty acids, such as those obtained from plant-based oils. These water-soluble complexes are easier and more economical to prepare than water-insoluble nanoparticles prepared from starch complexes, and they could therefore have enhanced value for the commercial production of films. Films prepared from water-soluble starch complexes had tensile properties superior to comparable films prepared from uncomplexed corn starch, and some film properties exceeded those of films prepared from pure PVOH. Films prepared from starch complexes also showed increased resistance to the penetration of water. Spray drying water solutions of these starch complexes is more economical than freeze-drying, and spray drying conditions were developed to isolate these complexes from water solution. Water-soluble complexes were also prepared from jet-cooked high amylose starch and the water-soluble salts of commercially available fatty amines. Application of water solutions of these complexes to paper followed by treatment with a dilute solution of sodium hydroxide greatly increased the resistance of paper to the penetration of water. The positive charges on the amine salt complexes cause them to adhere to the cellulose fibers of paper. A second treatment with sodium hydroxide converts the complexed amine salt to insoluble amine and precipitates the amylose complexes from solution so they will more effectively inhibit the penetration of water and will not be easily washed off. Most methods currently used to increase the water resistance of paper use agents that biodegrade more slowly than starch and are not as safe. A method for the preparation of micro-/nano cellulose from corn stover was developed and optimized. In addition, the condition of the extraction such as acidity/basicity (pH), temperature, and heating time were determined. The temperature, pressure, and passing time of mechanical shearing using homogenizer were optimized. The properties of the micro-/nano cellulose are being tested, such as purity of the product (chemical components), mechanical properties of the films made by micro-/nano cellulose, and viscoelastic properties of the micro-/nano cellulose gels. The study of the form, size, and structure of the micro-/nano cellulose using transmission electron microscopy has been conducted through a collaboration with the school of medicine in a university in Illinois. A manuscript is in preparation. Our research contributes to the improvement of the environment, climate change, and product functionality. It also expands potential markets for agricultural materials.
1. Modified natural rubber reinforced with soy nanoparticles. Most rubber products for demanding applications required reinforcement filler to function in these applications. However, the most common reinforcement filler is carbon black produced by burning petroleum-based heavy oil that generates a significant amount of carbon dioxide in the process. ARS scientists in Peoria, Illinois, have produced useful natural rubber composites reinforced with soy-based nanoparticles by modifying a portion of natural rubber to improve the compatibility between natural rubber and soy nanoparticles. The development improves the strength of rubber composites at higher stretched ratios significantly. This development will have an impact on increasing the renewable content and replacing a large portion of carbon black in the manufacture of molded rubber products to improve the product functionality and environmental sustainability.
2. Identification of birch and elm as viable biochar feedstocks for carbon black substitution as rubber composite filler. The price of petroleum and its byproducts (such as carbon black) are projected to rise over time as demand increases, especially in rapidly growing markets like China and India. Additionally, the use of fossil fuels contributes to climate change. Biochar is a solid, granular, carbon-containing material made from renewable biomass. ARS scientists in Peoria, Illinois, have tested and confirmed a process for making biochar from birch and elm that contains at least 94% carbon and less than 5% ash. These feedstocks are plentiful due to decreased demand in the paper industry. Biochar with that level of carbon purity has been successful in replacing up to 20% of the carbon black filler in rubber composites that can stretch and absorb energy without breaking just as well or better than the carbon black control. With the sheer size of the carbon black market (roughly 1.2 million metric tons in 2015), replacing this fossil fuel-based commodity with renewable biochar would have a significant impact in reducing climate change and reducing our dependence on petroleum.
3. Encapsulation of peppermint oil to extend its effective time as natural pesticide. Peppermint oil works as a natural pesticide that provides a simple, inexpensive, and environmentally-friendly alternative for pest control; however, because of its volatility and immiscibility with water, the advantage and usefulness of peppermint oil as a pesticide is less appealing. ARS researchers in Peoria, Illinois have developed a technique for the encapsulation of peppermint oil in nanocapsules prepared from degradable materials to make the oil more easily dispersed in water and effective for a longer period of time. This encapsulation technique can be extended to other essential oils that work as natural pesticides. It will allow essential oils, as more effective natural pesticides, to be more appealing to customers and stakeholders.
4. Starch-containing polymer films with improved properties. Films prepared from poly(vinyl alcohol) are widely used commercially, however poly(vinyl alcohol) is expensive and biodegrades slowly, creating a need for high-quality films prepared from mixtures of poly(vinyl alcohol) and inexpensive, rapidly-biodegradable components. ARS researchers in Peoria, Illinois, have prepared water-soluble films with a good balance of physical properties from mixtures of poly(vinyl alcohol) and starch complexes prepared from the sodium salts of fatty acids and jet cooked high-amylose corn starch, and these films also show increased resistance to the penetration of water. This research will enable manufacturers to prepare films that are less expensive and more water resistant than the films currently prepared from 100% poly(vinyl alcohol), and these films will be more biodegradable and environmentally-friendly due to the high percentage of corn starch.
5. Preparation of micro-/nano-sized cellulose from an agricultural waste. Many agricultural residues including corn stover, soybean stover, sorghum stover, corn fiber, rice hulls, wheat straw, rice straw, and pennycress have little economic value other than for mulching back into the soil or for burning as fuel. Little research has been conducted on the use of these agricultural wastes for higher value polymer materials applications. ARS scientists in Peoria, Illinois, have developed a method to prepare micro-/nano-sized cellulose from corn stover for the first time. These cellulose filaments are very small with diameters in the range of 10-30 nanometers. The micro-/nano-sized celluloses are high value-added biopolymers and can be widely used in cosmetics, wound healing, drug delivery, and reinforcement of composites to increase the value of agricultural waste and facilitate its removal.
6. Paper with increased resistance to the penetration of water. Paper absorbs water rapidly and numerous chemical treatments have been used to reduce water absorption; however the chemicals used for this purpose are not biobased and biodegraded slowly. ARS researchers in Peoria, Illinois, have developed a method for increasing the water-resistance of paper by applying water solutions of starch complexes prepared from jet-cooked high amylose corn starch and water-soluble fatty amine salts, and then applying a dilute alkaline solution to precipitate the complex onto the paper fibers. Compared to the methods currently used, our method for increasing the water resistance of paper uses water-soluble, non-toxic materials that are environmentally safe and rapidly biodegradable.
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Jong, L. 2016. Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber. European Polymer Journal. 74:136-147.
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Peterson, S.C., Chandrasekaran, S.R., Sharma, B.K. 2016. Birchwood biochar as partial carbon black replacement in styrene-butadiene rubber composites. Journal of Elastomers and Plastics. 48(4):305-316.
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Selling, G.W., Utt, K.D., Finkenstadt, V., Kim, S., Biswas, A. 2015. Impact of solvent selection on graft co-polymerization of acrylamide onto starch. Journal of Polymers and the Environment. 23(3):294-301. doi: 10.1007/s10924-015-0714-y.
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Xu, J., Solaiman, D., Ashby, R.D., Garcia, R.A., Gordon, S.H., Harry-O'kuru, R.E. 2016. Properties of starch-polyglutamic acid (PGA) graft copolymer prepared by microwave irradiation - Fourier transform infrared spectroscopy (FTIR) and rheology studies. Starch 68:1-7. doi: 10.1002/star.201600021.