Progress 09/01/08 to 08/31/10
Outputs
OUTPUTS: Based on a novel two-step reactive extrusion technology, we were able to produce poly(ethylene terephthalate) PET/high density polyethylene (HDPE) microfibrillar blends and subsequently to introduce wood fibers into the blends created wood plastic composite with improved mechanical performances. A US patent has been applied for that describes a process that separates chromated copper arsenate (CCA) from spent CCA-treated wood. Copper, chromium, and arsenic components as well as a detoxified wood product are recovered for recycling. The process covers not only the separation of CCA from wood but also the recycling of both CCA and a detoxified wood product that results from the process. It is based on the use of microwave heating, wood liquefaction, and wastewater treatment and, therefore it offers numerous technical options for improvements to the constituting process in both technique and processing equipment. The microwave reactor and liquefaction temperature is much lower than the releasing point of arsenic, and the process is easily controlled. PARTICIPANTS: Qinglin Wu, Professor, School of Renewable Natural Resources, LSU AgCenter; Yong Lei, Postdoc Researcher, School of Renewable Natural Resources, LSU AgCenter; C Piao, Assistant Professor, Calhoun Research Station, LSU AgCenter; CJ Monlezun, Professor, Department of Experimental Statistics, LSU AgCenter; TF Shupe, Professor, School of Renewable Natural Resources, LSU AgCenter TARGET AUDIENCES: wood plastic composite manufacturers, plastics recycler, general public wood preservation industry, treated wood recycling industry, utility industry PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
High-melting-temperature poly(ethylene terephthalate) (PET) was successfully introduced into wood plastic composites through a two-step reactive extrusion technology. Wood flour was added into pre-prepared PET/high density polyethylene (HDPE) microfibrillar blends (MFBs) in the second extrusion at the temperature for processing HDPE. Addition of 25% in situ formed PET microfibers obviously increased the mechanical properties of HDPE, and more significant enhancement by the in situ-formed recycled PET microfibers was observed for the recycled HDPE. Adding 2% E-GMA improved the compatibility between matrix and microfibers in MFBs, resulting in further enhanced mechanical properties. The subsequent addition of 40% wood flour did not influence the size and morphology of PET microfibers and improved the comprehensive mechanical properties of MFBs. The wood flour increased the crystallinity level of HDPE in the compatibilized MFB in which PET phase did not crystallize. The storage modulus of MFB was greatly improved by wood flour. The technology provides a way for using recycled engineering plastics for wood plastic composite manufacturing. CCA-treated wood is first extracted in a microwave reactor in the presence of acid solutions (i.e., acetic acid, oxalic acid, and phosphoric acid) and the combination of these acids at a temperature of 70 - 160 C (step1). This treatment solvates or dissolves CCA into an acid solution and this acid-extracted CCA solution can then be easily drained off through a filter and separated from the wood (step 2). To this solution, precipitants or complex agents for the hazardous elements (Cr, Cu and As), such as Ca(OH)2 or phosphoric acid (in the case where it was not used in the acid extraction), are added and the solution is agitated and then allowed to form sedimentation (step 3). The sediment, which contains Cr, Cu, and As, is then separated from the solution by centrifugation or filtration. By this process, more than 99% of the Cu, Cr, and As are removed. As the fourth step, the CCA-bearing sediment is regenerated by adding a concentrated inorganic acid such as sulfuric, nitric, or phosphoric acid, and can be reused as recycled CCA. For the fifth step, the recovered acid solution can be reused in the process without further treatment. As the sixth step, the wood liquefaction reagents are added to the microwave reactor containing the CCA-free-wood and reacts at 120 - 150 0C to convert the spent wood into a thick liquid with molecular weights ranging from several hundreds to several thousands. Finally, the liquefied wood solution is concentrated to a desirable concentration to be used as a bio-based raw material for the preparation of polymer materials, such as polyurethanes and phenolic adhesives. In this study, a dual acid system was found to be optimal, consisting of phosphoric acid from 0.5-3.5 (wt.%) and acetic acid (0.5-2.0) (wt.%). The metal recovery rate of As, Cr, and Cu was over 99% for most of the various experimental variables combinations.
Publications
- Lei, Y., and Q. Wu. 2010. Wood plastic composites based on recycled high density polyethylene and poly(ethylene terephthalate) microfibillar blends. Bioresource Technology, 101:3665-3671.
- Piao, C. C. J. Monlezun, T.F. Shupe. 2009. Glueline bonding performance of decommissioned CCA-treated wood. Part I: Without retreatment. Forest Products Journal. 59(7/8):36-42.
|
Progress 09/01/08 to 08/31/09
Outputs
OUTPUTS: Research in wood plastics composites focused on introducing high-melting-temperature poly(ethylene terephthalate) (PET) into wood plastic composites through a two-step reactive extrusion technology. Wood flour was added into pre-prepared PET/high density polyethylene (HDPE) microfibrillar blends (MFBs) in the second extrusion at the temperature for processing HDPE. Addition of 25% PET microfibers obviously increased the mechanical properties of HDPE, especially the tensile modulus which was increased by about 134%. Adding 2% E-GMA improved the compatibility between matrix and microfiber in MFBs, resulting increased mechanical properties. The subsequent addition of 40% wood flour did not influence the size and morphology of PET microfibers, and improved the comprehensive mechanical properties of MFBs. The wood flour increased the crystallinity level of HDPE in the compatibilized MFB in which PET phase did not crystallize. The storage modulus of MFB was greatly improved by wood flour. Research for the treated wood recycling project has focused on development of novel chemical means to detoxify and/or recover mixed preservative-treated wood waste and development of value-added engineered wood products from decommissioned CCA-treated wood. Regarding wood preservative detoxification/recycling, past work has focused on chromated copper arsenate (CCA), oil-borne pentachlorophenol (penta), and creosote. Hydrothermal treatment (HT) was applied to samples treated with these three wood preservatives on an equal mass basis. During HT treatment, creosote-derived hydrocarbon residues in the decommissioned treated wood were recovered and of the wood mass itself was transformed (95%) into a mixture of hydrocarbons including substituted benzenes, phenolics, and light PAHs. The metals from the CCA-treated wood were partially recovered (up to 48-88%) either in an acidified aqueous phase or as scale on the internal walls of the reactor. Some arsenic was likely transformed to arsine gas, which could be trapped and recovered under basic conditions. Penta was dechlorinated and removed to below detection limits. The HT process also resulted in the generation of industrially useful mixed hydrocarbons with substantial reduction in substrate mass. Thus, the preservative-treated wood as a hazardous waste was transformed into a complimentary mixture of liquid products. Creosote and CCA were recovered, and penta was degraded. Research on the development value-added engineered wood products from decommissioned CCA-treated wood included an investigation of the gluability of CCA treated utility pole wood plies cut from decommissioned southern pine (Pinus spp.) utility poles. Two surface treatment methods (priming and incising) were evaluated for their efficacy in improving the bonding performance of decommissioned utility pole wood and untreated virgin wood. Effects of CCA retention and distribution on glue-line shear strength and delamination were investigated. Results showed that CCA reduced glue-line shear strength. Incising had a marginally positive effect on glue-line shear strength and delamination. PARTICIPANTS: Qinglin Wu Todd Shupe TARGET AUDIENCES: wood composite industry/treated pole industry PROJECT MODIFICATIONS: none
Impacts
PET and HDPE are used extensively in packaging materials, and their annual rates of growth of production and consumption steadily increase. Combining PET and PE can yield unusual properties. With the price of petroleum soaring, plastic wastes are becoming of more interest as an inexpensive source of raw materials. The developed technology of making in-situ HDPE/PET microfibrillar blends through reactive extrusion at the processing temperature for PET, and then combining them with wood flour through the second extrusion at the processing temperature for HDPE led to a strong composite building material. The treated wood project is still underway and the true impact has yet to be realized. However, the potential economic and environmental impacts of this project are substantial. Disposal is generally considered the "Achilles heel" of the preservative-treated wood industry. Since approximately half of all southern pine lumber is preservative-treated, a strong wood preservation industry is vital for the overall wood industry as well as forest landowners. Processes that economically and environmentally recycle spent treated wood waste, have the potential to strengthen the wood preservation industry, enhance rural economic development, and enhance environmental stewardship by extending the service life of wood in service, reducing the demand for timber, and lessening the amount of treated wood sent to landfills. One Louisiana wood preservation facility has estimated the potential impact of this research to his facility to be between $1-$5 million per year.
Publications
- Lei, Y., and Q. Wu. 2009. Wood plastic composites based on recycled high density polyethylene and poly(ethylene terephthalate) co-blend matrix. Bioresource Technology, Accepted. (IF=4.45) Catallo, W.J. and T.F. Shupe. 2008. Hydrothermal treatment of mixed preservative-treated wood waste. Holzforschung. 62(1):119-122.
- Pan, H., C.Y. Hse, R.P. Gambrell, and T.F. Shupe. 2009. Fractionation of heavy metals in liquefied chromated copper arsenate (CCA)-treated wood sludge using a modified BCR-sequential extraction procedure. Chemosphere. 77:201-206. Piao, C. Charles J. Monlezun, T.F. Shupe. 2009. Glueline bonding performance of decommissioned CCA-treated wood. Part I: Without retreatment. Forest Products Journal. 59(7/8): in press.
- Lei, Y., Q. Wu, and Q., Zhang. 2009. Microfibrillar composites based on recycled high density polyethylene and poly(ethylene terephthalate): morphological and mechanical properties. Composite Part A 40:904-912.
|