Progress 07/01/20 to 06/30/22
Outputs
Target Audience:The target audiences I reached out during the project include: (1) I reached the scientists (Dr. Hui Li, Dr. Karl Englund) at the Composite Materials and Engineering Center of Washington State University and cooperated on the wood sample preparation and property testing. (2) I reached the industrial person (Todd R. Miller from Hexion Inc.) and academical researcher (Dr. Matthew Schwarzkopf from InnoRenew CoE in Slovenia) to discuss about my research and comparison of different technologies on wood densification. (3) I reached the Rubicon Foundation in Seattle of Washington State to talk about my research and they provided me the cottonwood samples for my research in this project. (4) I attended the 2022 Annual International Conference and presented my research findings to the attendees to increase my research impact. (5) It's worth noting that the developed wood products samples could be exhibited in tradeshow in this field to reach more audience and study the public awareness of this value-added wood products through structured interviews and questionnaires. Changes/Problems:Due to the limited time and resources available, especially the covid disruption, a detailed economic analysis of the developed value-added wood products cannot be performed.A detailed the cost analysis of the HTM wood was recommended in the future to promote the development of this valued-added wood product. In addition, it's worth noting that the developed wood products samples could also be exhibited in tradeshow in this field to reach more audience and study the public awareness of this value-added wood products through structured interviews and questionnaires. What opportunities for training and professional development has the project provided?1) This project offered me the opportunities to work with my mentors (Dr. Kent Wheiler and Dr. Anthony Dichiara) and they provided valuable guidance and strong support and training to carry out the proposed research. 2) Through this project, I was able to continue to assist my supervisors in managing the lab, mentor graduate students, give guest lectures, and organize seminars as well as workshops. 3) This project provided the opportunities for me to cooperate with the researchers at the Composite Materials and Engineering Center of Washington State University and improved my research capabilities. 4) This project provided me the opportunity to attend the Annual International Conference of Forest Products Society and presented my research results at the conference. By this meeting, I discussed my research with other scientists from all over the world in this field. How have the results been disseminated to communities of interest?Due to the travel restriction by the Covid, the interactions with communities of interest were largely limited. Most of the meetings, seminars, and workshops were held online, but I was still actively interacting with the researchers in the filed to discuss the research results of this project remotely. Fortunately, I attended the in-person meeting of the 2022 Annual International Conference of Forest Products in Madison, Wisconsin. They conference attendees showed a large interest in my research and was aware that my research could promote the use of more valued-added wood products using locally sourced wood species. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1. Preparation of wood materials, chemicals, and supplies The collected wood materials and required supplies are shown in the progress report in 2021. 2. Chemical pretreatment The specific chemical pretreatment process was shown in the progress report. To achieve full infiltration of wood by the chemicals, the thickness of wood samples was set to 10 mm. 3. Effect of chemical pretreatment on wood structure and properties After the wood samples were chemically pretreated, the cellulose content decreased very slightly, while a large amount of hemicellulose and lignin was removed. The different treatment durations (3, 6, 9 h) hadn't made significant difference on the changes of the chemical components.The thermogravimetric (TG) curve of the chemically pretreated wood shifted to lower temperature, indicating that the wood thermal stability was lowered by the pretreatment. The "shoulder", ascribed to hemicellulose degradation under inert atmosphere and overlapped with the main peak, almost disappeared after the pretreatment, which was in accordance with the chemical changes. Other wood species including poplar, Eucalyptus, and cotton wood showed similar results that were not shown here. 4. HTM modification 1) Effect of pre-steaming treatment The hot compressing treatment of wood was performed by a computer-controlled hydraulic press with oil-heated platens (3 by 3 ft.) at the Composite Materials and Engineering Center of Washington State University (see details in the progress report in 2021). 2) Effect of temperature The kiln-dried wood samples of different species were pre-steamed for 1 h and hot-compressed by half of its original thickness in the radial direction under different temperatures (140 - 180 °C). The Western hemlock, Eucalyptus, and poplar wood was successfully compressed to the target thickness at different temperatures without visual defects . The cottonwood was compressed successfully at lower temperatures (140, 160 °C), while it charred at higher temperature (180 °C). In addition, the mechanical performance of HTM modified wood exhibited different trend with an increasing temperature, dependent on different wood species. The HTM modified Western hemlock showed significantly improved mechanical properties with increased temperatures, while the HTM modified eucalyptus wood reached the maximum mechanical performance at around 160 °C. For the modified Eucalyptus wood, the MOE was improved with an increasing temperature, while the MOR peaked at 160 °C and declined when the temperature increased further. 3) Effect of chemical pretreatment The imagesweretaken from the natural and modified poplar wood.Upon hot compressing at high temperature, the wood cell lumina was closed entirely. The modified wood had the fully collapsed wood cells that were tightly intertwined and densely packed together. As a result, the density of wood increased, and its porosity decreased after the hydro-thermo-mechanical modification. The dimensional changes of the modified wood were measured after the samples were conditioned at the temperature of 20 °C and the relative humidity of 65% for one week. All four wood species showed the same trend, with significantly reduced dimensional changes of the modified wood that was chemically pretreated, compared to the HTM modified wood without chemical pretreatment. However, there was no significant difference in the dimensional changes of wood among different chemical pretreatment time. The flexural tests were conducted to analyze the strength characteristics of the HTM modified wood . Compared to the untreated wood, the mechanical performance was improved with the HTM modification, and even better if the wood was chemically pretreated before the HTM process. All four wood species showed similar trend. As a result, the combined process of HTM modification with the chemical pretreatment was a great way to better utilize the wood, especially the underutilized and low-quality wood. 5. Techno-economic analysis of HTM wood? Thermally modified wood is used throughout Europe, and its use is growing in the U.S. There is currently only one production facility in the Northwest, recently installed in Montana featuring state-of-the-art machinery, to produce thermally modified wood. Transporting local species to distant processing plants is not economically feasible. Establishing and expanding the processing capacity of these value-added wood products using locally sourced and abundant wood species are highly desirable. Here, I'm going to give a brief overview on the research of the market and manufacturing cost of the HTM wood, facilitating the commercialization of the developed valued-added technology in this study.The HTM wood is a new wood product under investigating and there is no large-scale commercial production. Due to the limited time and resources available, especially the covid disruption, a detailed market investigation cannot be performed, but some insights can be obtained by reviewing the market and economic analysis of thermally modified (TM) wood since the HTM wood can be thought of as a special type of the TM wood. During the past two decades, the TM wood has achieved technical maturity and commercial success worldwide especially in Europe. However, the TM wood is developing relatively slow in the United States. One of the main technical barriers to limit its application is the loss in strength properties and increased brittleness of the TM wood compared to the natural wood. The increased mechanical performance by hydrothermal compression process in this study could be great remedy to overcome the shortcomings of the TM wood and even perform much better in terms of physical and mechanical properties. Therefore, the HTM wood can be not only used in decking, siding, or outdoor furniture, but also used to produce structural wood products such as wood beams or columns in the growing wood building market. In addition, the level of awareness of the TM wood among the public is still low. So, different promotion methods such as internet presence, social media, tradeshows, etc., should be used to increase the public awareness and reputation of these value-added wood products. The major attributes of the HTM wood promoted include eco-friendliness, sustainability, dimensional stability, "local" nature, exotic appearance, and competitive price. The production of the HTM wood is a combined process of chemical pretreatment and hydro-thermo-mechanical compression. Although lots of research has been done on chemical pretreatment, thermal modification, and wood compression separately before, the research on the combined treatments to process wood is quite new. It's a very complex process to calculate the manufacturing cost of the HTM wood, including raw materials, capital, labor, energy, delivery, etc., which are highly dependent on the location, wood species, and energy price. Due to the limited time and resources, a full cost analysis of the HTM wood was not achievable in this study, but an estimated cost could be obtained. The cost of the pressured treated softwood was within $200 per m3. The wood compression treatment cost can be estimated from the similar compression process of CLT manufacturing. It was estimated that the cost of compression for CLT was about $50 per m3. So, the estimated total cost of manufacturing the HTM wood was about $250 per m3. A detailed the cost analysis of the HTM wood was recommended in the future to promote the development of this valued-added wood product.
Publications
- Type:
Journal Articles
Status:
Submitted
Year Published:
2022
Citation:
Kunlin Song, Hui Li, Kent Wheiler, Anthony Dichiara, Indroneil Ganguly. Structural and mechanical properties of chemical pretreated Western hemlock. Wood Science and Technology. 2022.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2022
Citation:
Kunlin Song, Hui Li, Kent Wheiler, Anthony Dichiara, Indroneil Ganguly. Structure-property relationships of hydro-thermo-mechanically modified wood. Materials and Design. 2022.
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Progress 07/01/20 to 06/30/21
Outputs
Target Audience:(1) I reached the scientists (Dr. Hui Li, Dr. Karl Englund) at the Composite Materials and Engineering Center of Washington State University and cooperated on the wood sample preparation and property testing; (2) I reached the industrial person(Todd R. Miller from Hexion Inc.) and academical researcher (Dr. Matthew Schwarzkopf from InnoRenew CoE in Slovenia) to discuss about my research and comparasion of different technologies onwood densification; (3) I reached the Rubicon Foundation in Seattle of Washington State to talk about my research and they provided me the cottonwood samples for my research in this project. Changes/Problems:(1) The structure and property tests for the hydro-thermo-mechanically (HTM) modifed wood were postponed due to the lab close and travel restriction imposed by the Covid. They will be performed in the second year (7/1/2021 - 6/30/2022) of this project. (2) An amount of $5000 fund was transferred from the fund for supplies and materials to the fund for travel. Because some wood samples were donated the research partners and all the experiments could be performed using the currently available equipment or facilities, some of the fund was transferred to support the travel to Washington State University to perform wood sample hot-compressing and mechanical testing. What opportunities for training and professional development has the project provided?(1) This projectoffered me the opportunities to work with my mentors (Dr. Kent Wheiler and Dr. Anthony Dichiara) and they provided valuable guidance and strong support and training to carry out the proposed research. (2) This project provided the opportunities for me to cooperate with the scientists at the Composite Materials and Engineering Center of Washington State University and improved my research capabilities. How have the results been disseminated to communities of interest?Due to the travel restriction impposed by the Covid, the interactions with communities of interest were largely restricted. But I had lots of discussion about my research results with people who I have interacted, such as Rubicon Foundation (who provided me some of wood samples). What do you plan to do during the next reporting period to accomplish the goals?(1) Finish the structure and properties testing of HTM modifed wood produced previously; (2)Conduct a techno-economic-assessment of commercial production of the HTM modified wood products; (3) Publish a peer-reviewed journal article with the research results from this project; (4) Attend the 75th Annual International Conference ofForest Products Society and present the results from this project.
Impacts
What was accomplished under these goals?
The abundant and lower value wood including western hemlock, poplar, cottonwood, and eucalyptus were modified by an innovative, efficient, and sustainable technologycombining chemical pretreatment and hydro-thermo-mechanical (HTM) processes. Different parameters including wood sample moisture content, hot-compressing temperature and time, chemical pretreatment time, etc.associated with this treatment were studied to achieve the optimal processing condition for improving the wood quality and value of these wood species. The developed wood processing technologies could be highly potential to increase the use of underutilized wood species, improve forest health, andprovide new economic opportunities in rural and timber-dependent communities. 1. Preparation of wood materials, chemicals, and supplies Kiln dried untreated Western hemlock (Tsuga heterophylla) lumber (88 (T) × 37 (R) mm) was purchased from a Dunn Lumber store in Seattle, WA. The yellow poplar (Liriodendron tulipifera) lumber (118 (T) × 30 (R) mm) was sourced from a local hardwood lumber store (Crosscut Hardwoods, Seattle, WA, United States). The cottonwood (Populus trichocarpa) lumber (varied size) was kindly supplied by the Rubicon Foundation. The Eucalyptus (Eucalyptus urograndis) lumber (varied size) was supplied by Composite Materials & Engineering Center at Washington State University. Selected straight lumbers (i.e., no crook, twist or bow) with minimal slope of grain and no wane were used in this project. Each piece of lumber will be cut into three matching specimens of identical dimensions, which will be randomly selected for the control samples without any treatments, hydro-thermo-mechanical (HTM) treated samples, and HTM modified samples with the chemical pretreatment, respectively. The purchased chemicals and supplies for this project were listed in the financial report. 2. Chemical pretreatment of wood materials The general procedure to chemically process the wood samples of four species is followed. First, wood samples were immersed in an aqueous solution of 2.5 M NaOH and 0.4 M Na2SO3 and boiled for 3, 6 or 9 hours. By varing the treatment time, modified wood with different degree of lignin removal was expected. Then, the residual chemicals in the wood were removed by boiling deionized water for at least three times. Finally, the samples were air dried prior to structure and property characterization or further mechanical compression. The chemical solution for pretreating the wood samples was completely clear before boiling and became black after boiling for about 3 hours, due to the lignin removed from the wood. The treatment time varied from three to nine hours to study the degree of lignin removal and penetration depth of chemicals through different direction of wood. The wood sample dimension in this experiment was 120 mm (Longitudinal) × 40 mm (Tangential) × 35 mm (Radial). The chemicals infiltrated into the wood from surfaces and the flow path is mainly through the longitudinal direction because of the anisotropic characteristics of wood. The center of wood was unreachable by the chemicals and looked obviously different from the surrounding area. Compared to untreated samples, the penetration depth of chemicals increased with longer treatment time, but there was still a small area in the center that was not penetrated by the chemicals even after boiling for 9 hours. To achieve full infiltration of wood by the chemicals, the thickness of wood samples decreased to 10 mm in the subsequent experiments. 3. HTM treatment of wood materials 1) Effect of pre-steaming treatment The hot compressing treatment of wood was performed by a computer-controlled hydraulic press with oil-heated platens (3 by 3 ft.) at the Composite Materials and Engineering Center of Washington State University. The wood samples were placed between two smooth metal plates, which were loaded onto the lower press plate. The upper press plate was lowered to gently touch the metal plate holding the samples without applying any pressure. The press was then heated and the wood samples were compressed to the determined thickness when the temperature reached the set temperature (120-180 °C). After compression, the wood samples were conditioned at the temperature of 20 °C and the relative humidity of 65% for at least one week prior to further property testing. To study the effect of steaming on the shape recovery of compressed wood, some wood samples were pre-steamed for 1 hour prior to compression. Both the pre-steamed and control wood samples were compressed at the same temperature of 160 °C and compression ratio of 50%. Subsequently, the compressed wood samples were subject to soaking in water for 2 hours, steaming for 2 hours or left in air without any further treatment, respectively. After these treatments, it was found the pre-steaming treatment could reduce the shape recovery of compressed wood, especially under the condition of re-moistening. In addition, the applied maximum pressure could be largely reduced to compress the wood to the specified thickness when the samples were pre-steamed sufficiently. As a result, all subsequent samples subject to hot compressing were pre-steamed. 2) Effect of hot-temperature The kiln-dried wood samples of different species were pre-steamed for 1 h and hot-compressed by half of its original thickness in the radial direction under different temperatures (140 - 180 °C). The Western hemlock wood was successfully compressed to the target thickness at different temperatures without visual defects. The cottonwood was compressed successfully at lower temperatures (140, 160 °C), while it charred at higher temperature (180 °C), probably due to the accelerated thermal decomposition under the condition of pre-steaming, high moisture content in the center of wood samples, and high-temperature compressing. In addition, the mechanical performance of HTM modified wood exhibited different trend with an increasing temperature, dependent on different wood species (Figure 5). The HTM modified Western hemlock showed significantly improved mechanical properties with increased temperatures, while the HTM modified eucalyptus wood reached the maximum mechanical performance at around 160 °C. Based on these results, the temperature of 160 °C was chosen to process the wood samples in the subsequent studies.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2021
Citation:
Kunlin Song, Kent Wheiler, Anthony Dichiara. Structural and mechanical properties of hydro-thermo-mechanically modified western hemlock. Wood Science and Technology. 2021. (in submitting)
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