Progress 09/15/04 to 09/14/07
Outputs
OUTPUTS: This project had four research objectives. The first research objective was to improve the utilization of undervalued hardwood species by incorporating them into highly valued composite materials, such as Wood-Plastic Composites (WPC). The ability of triblock copolymers of styrene (S) and methyl methacrylate (MMA) to improve the wood/PS interface have been evaluated as a function of the copolymer architecture and thickness. Copolymer layers ranging from 50 nm to 300 nm have been tested. After adding copolymer to the interface, the fracture toughness varies with the copolymer architecture. Three different regions can be distinguished for both copolymers. A first region was delineated between 0 and 50 nm, the second one between 50 and 150 nm, and the last one between 150 and 300 nm. Results indicated that, due to its chemical composition (79 percent styrene), the SMS has a very high affinity for the PS homopolymer plate. At low copolymer thickness (i.e., until 50 nm), it is believed that the copolymer partly entangles into the PS plate, while the amount of MMA (nMMA) was not sufficient to adhere to the wood. No improvement in Gc was thus measured. When the copolymer thickness increased, nMMA increased at the copolymer/wood interface, hence amplifying the interaction possibilities with wood. The second research objective developed a novel process using high-intensity ultrasonication (HIUS) to isolate fibrils from cellulose fibers. The geometrical characteristics of the fibrils were investigated using polarized light microscopy (PLM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Fibrils degradation was evaluated by HIUS to further develop a new nano three-point bending method to measure the elastic modulus of single cellulose fibrils. The modulus of Lyocell fibrils with diameters from 150 to 180 nm was evaluated about 100 GPa and it decreased dramatically when the diameter was more than 180 nm. The third research objective conducted an experiment to measure the effect of temperature on the output of a moisture sensor system for lumber. Tests on sample boards were conducted measuring temperature at approximately 10 degree F intervals as the board cooled. Both temperature correction information and thickness correction information were incorporated into a general predictive model for moisture content determination. The fourth research objective resulted in the development of an automated real-time distributed data fusion system and a real-time genetic algorithm to predict the physical properties of wood-plastic composites (WPC). WPC manufacturers are a mix of large and small manufacturers from both the plastics and forest products industries. Research investigated material flow during extrusion and final material properties performance. The research defined genetic representation and genetic operations to predict the value of a single material property from parameter values acquired during real-time data acquisition from a number of sensors. PARTICIPANTS: Dr. Michael P. Wolcott from Washington State University colloborated on this research. Tim Stortz, T. Neimsuwan, W. Chen, Dr. J.W. Kim, Dr. Adam Taylor, Dr. Frank M. Guess, Dr. Nicolas Andre, Dr. R.V. Leon, from The University of Tennessee collaborated. TARGET AUDIENCES: Wood science community, wood composite manufacturers and adhesive formulators PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Ligno-cellulosic materials are not compatible with most commodity thermoplastics. A synthetic, block copolymer is being developed that optimizes hydrogen bonding efficiency with the wood and chain entanglement with a bulk matrix polymer. The use of efficient WPC coupling agents can increase the strength of the composite by over 200 percent and stiffness by 50 percent. Increased performance of the materials provides opportunity for expansion into new markets and applications such as automotive, packaging, structural, and liquid-crystals among others. Wood plastic composites are under-going continued market pressures from increasing oil and wood fiber costs. Processing efficiency will be essential for the long-term survival of this engineered wood plastic product. The genetic algorithm and neural network system to predict strength and discover unknown sources of variation could save from one to five percent in input costs during manufacturing. Savings will be realized from reduced target density given reductions in processing variation. This work developed a novel method to generate fibrils from natural cellulose fibers for polymer reinforcement to make bio-based nanocomposites, which may have great growth potential for renewable resource in automotive and building industries, especially in the applications where biocompatibility and environmentally responsible design and construction are required. This high-intensity ultrasound technique is an environmentally benign method and a simplified process that may make fiber isolation and chemical modification simultaneously. The measurement of the mechanical properties of single fibrils by AFM may evaluate the degradation of cellulose fibrils during the isolation and may be as one fundamental bridge to connect the properties of the fibrils as reinforcing material and the properties of the reinforced nanocomposites. The sensors being developed in this study is compatible with current computer controlled kiln systems and will provide the previously unattainable measurements of moisture contents above 30 percent. Use of these sensors will result in decreased drying time and energy consumption with reduced risk of degradation to the lumber. Drying is the most expensive and the most energy consumptive process in the manufacture of lumber. Potentially the use of these sensors could reduce drying energy used by up to 15 percent. The development of these sensors into a line speed moisture meter and a hand held moisture meter will allow initial screening and sorting of green lumber by moisture content. Initial sorting of green softwood lumber will reduce drying time and drying degradation.
Publications
- Moschler, W.W., G. R. Hanson, T. F. Gee, S. M. Killough, and J. B. Wilgen. 2007. Microwave moisture measurement system for lumber drying. Forest Prod. J. 57(10):69-74
- Moschler, W.W. and G. R. Hanson. 2007. Microwave Measurement System for Lumber Drying. In: Understanding and Modeling the Theoretical and Practical Aspects of Drying Solid Wood and Wood Based Materials. Proceedings of the 10th International IUFRO Division 5 Wood Drying Conference. Robert W. Rice, Editor. ISBN 978-1-934710-0. The University of Maine.
- Cheng, Q., S. Wang, D. Zhou, T. Rials and Y. Zhang. 2007. Lyocell-derived cellulose microfibril/nanofibril and its biodegradable nanocompsites. Journal of Nanjing Forestry University (4): 21-26.
- Cheng, Q. and S. Wang. 2007. Recent research on nanocomposites reinforced by natural micro/nanofibrils. China Forest Products Industry 34(3): 3-7 (in Chinese, English abstract).
- Cheng, Q., S. Wang, T. Rials. 2007. A testing method of mechanical property of single cellulosic fibrils using AFM. The 9th International Conference on Wood & Biofiber Plastic Composites May 21-23, 2007, Madison, Wisconsin. (In press)
- Cheng Q., S. Wang. 2007. Cellulose fibrils isolated from Lyocell fiber by a novel process and its reinforced PVA nanocomposites. International Symposium on Advanced Biomass Science and Technology for Bio-based Products, May 23-25, 2007, Beijing, China. (In press)
- Cheng, Q., S. Wang, T. Rials. 2007. Fibrils isolated from cellulose fibers by a novel method and its reinforced nanocomposites. Forest Product Society, 2007 Annual Meeting, June 10-13, Knoxville, TN. pp. 15. (Presentation).
- Cheng, Q., S. Wang, T. Rials. 2007. Biodegradable nanocomposites reinforced with cellulose fibrils. Technical Association of Pulp and Paper Industry (TAPPI) & Forest Product Society, 2007 International Conference on Nanotechnology for the Forest Products Industry, June 13-15, Knoxville, TN. pp.47 (Presentation).
- Cheng, Q., S. Wang, T. Rials. 2007. Fibril isolation and its reinforced nanocomposites from natural biomass. Forest Product Society, 2007 Annual Meeting, June 10-13, Knoxville, TN. pp34. (Poster).
- Cheng, Q., S. Wang, T. Rials. 2007. Biodegradable nanocomposites reinforced with cellulose fibrils. Technical Association of Pulp and Paper Industry (TAPPI) & Forest Product Society, 2007 International Conference on Nanotechnology for the Forest Products Industry, June 13-15, Knoxville, TN. pp 61 (Poster).
- Cheng, Q., S. Wang, T. Rials. 2007. Mechanical properties of single natural cellulose fibrils. Technical Association of Pulp and Paper Industry (TAPPI) & Forest Product Society, 2007 International Conference on Nanotechnology for the Forest Products Industry, June 13-15, Knoxville, TN. pp72. (Poster)
- Cheng, Q., S. Wang, T. Rials. 2007. Mechanical properties of single natural cellulose fibrils. The 9th International Conference on Wood & Biofiber Plastic Composites, May 21-23, 2007, Madison, Wisconsin. pp. 21 (Poster)
- Cheng, Q., S. Wang, T. Rials. 2007. A novel method to isolate fibrils from cellulose fibers and its reinforced PVA nanocomposites. The 9th International Conference on Wood & Biofiber Plastic Composites, May 21-23, 2007, Madison, Wisconsin. pp. 21 (Poster)
- Harper, D. P., Lee, S.-H., and Dadmun, M. 2006. Interactions between ps-pmma based block copolymers and wood derivatives. Paper presented at the 2006 AIChE Annual Meeting, San Francisco, CA.
- Perhac, D.G., T.M. Young, F.M. Guess and R.V. Leon. 2007. Exploring reliability of wood-plastic composites: stiffness and flexural strengths. International Journal of Reliability and Application. 8(2):153-173.
- Perhac, D.G. 2007. An applied statistical reliability analysis of the modulus of elasticity and the modulus of rupture for wood-plastic composites. M.S. Thesis. The University of Tennessee. 102p.
- Tingaut, P. N. Henry, T.G. Rials, D.P. Harper and M. Dadmun. 2007. Compatibilization of natural fibers with synthetic polymers using triblock copolymers as coupling agents. Macromolecular Bioscience. Submitted.
- Lee, S.H. and S. Wang. 2006. Thermal analysis and nano-mechanical properties of natural fiber or cornstarch-reinforced biodegradable biocomposites. ANTEC 2006. Charlotte, NC. May 7-11. Pp. 228-232.
- Lee, S., Y. Teramoto, S. Wang, G. Pharr and T.M. Rials. 2007. Nanoindentation of biodegradable cellulose diacetate-grafted-poly(L-lactide)s copolymers-Effect of molecular composition and thermal ageing on mechanical property. Journal of Polymer Science B 45: 1114-1121.
- Moschler, W.W. and G. R. Hanson. 2007. Microwave measurement system for lumber drying. Presented to IUFRO Division 5 Wood Drying Conference, Orono, Maine. August 29, 2007.
- Wang, S., Q. Cheng, T. Rials and S.-H. Lee. 2006. Cellulose microfibril/nanofibril and its nanocompsites. Proceedings of the 8th Pacific Rim Bio-Based Composites Symposium, edited by M.N.M. Yusoff et al. Nov. 20-23, 2006. Kuala Lumpur, Malaysia. Pp. 301-308 (ISBN 983-2181-87-9).
- Young, T.M., D.G. Perhac, F.M. Guess and R.V. Leon. 2007. Bootstrap confidence intervals for percentiles of reliability data for wood plastic composites. Forest Products Journal. In Press.
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Progress 01/01/05 to 12/31/05
Outputs
Several wood species and polypropylene species have been extruded with a small laboratory single screw extruder. The species include an oak, maple, pine, and yellow pine bark derivatives. Thermal analysis has been performed on the majority of these samples. Crystallization kinetics is being evaluated and reveals differences according to particle size and surface roughness. These differences are attributed to larger surface areas having higher degrees of nucleation. Twin-screw extrusion capabilities are being established currently for the preparation of composite materials. During the reporting period we have completed the design and construction of a high-resolution gravimetric analysis system to measure adsorption and desorption processes of wood under controlled relative humidity and temperature. Preliminary experiments have been conducted to confirm the instruments sensitivity by monitoring the sorption isotherms and kinetics for earlywood and latewood specimens. The
relationship between the chemical structure of acrylic-based resins was studied using chemical imaging methods developed in earlier work. Adhesive joints were prepared using urethane, epoxy, and polyester derived resins. Chemical imaging methods developed in previous research was applied to monitor diffusion and interphase thickness, particularly as influenced by viscosity of the formulation. Dynamic mechanical analysis is currently being used to further define interphase properties, and the impact of resin cure advancement. A heuristic algorithmic method using genetic algorithms with real-time distributed data fusion was developed to predict the internal bond of medium density fiberboard and the parallel elasticity index for oriented strand board. The system incorporated real-time lags and statistical estimates of 285 critical process parameters with data quality verification algorithms. Results of the genetic algorithm modeling system indicate predictions within 5% of the median
physical properties. Time-ordered residuals accurately detect trends and are normally distributed.
Impacts
Durability of wood-plastic composites is a large liability to manufacturers and a growing concern to the public, but is poorly understood for this novel material. Research has demonstrated that wood of varying morphology can direct the assembly of semi-crystalline thermoplastics, affording a point of control for this important characteristic. This development expands the potential for WPC's, which is growing at a rate of 20% annually and currently holds 25% of the $5 billion decking market.
Publications
- Guess, F.M., R.V. Leon, W. Chen and T.M. Young. 2004. Forcing a closer fit in the lower tails of a distribution for better estimating extremely small percentiles of strengths. International Journal of Reliability and Application. 5(4):129-145.
- Wang, S., P.M. Winistorfer and T.M. Young. 2004. Fundamentals of vertical density profile formation in wood composites - Part 3. MDF density formation during hot-pressing. Wood and Fiber Science. 36(1):17-25.
- Song, Ting. 2005. Electron-beam cured resins for wood composites. Master of Science Thesis, The University of Tennessee, Department of Material Science, July 2005.
- Chen, Weiwei. 2005. A reliability case study on estimating extremely small percentiles of strength data for the continuous improvement of medium density fiberboard product quality. Master of Science Thesis, The University of Tennessee, Department of Forestry, Wildlife, and Fisheries, December, 2005.
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