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INVESTIGATOR: Lim, H.; Morrell, JE, J.; Wan, HU, .

PERFORMING INSTITUTION:
FOREST AND WILDLIFE RES CENTER
MISSISSIPPI STATE, MISSISSIPPI 39762

CYCLODEXTRINS AS AGENTS FOR IMPROVED PROTECTION METHODS OF ORIENTED STRAND BOARD WOOD COMPOSITES

NON-TECHNICAL SUMMARY: The goal of this proof-of-principle study is to examine the feasibility of using cyclodextrins for stabilization of volatile and leachable biocides for wood composites protection. The need for such improvement is seen in a forecasted significant increase of composites in multi-story housing construction and need for improvement of the current composite protection methods for long-term outside exposures.Cyclodextrins are inexpensive, non-toxic cyclic oligosaccharides that have already found applications in industry. By increasing thermal stability of volatiles, and covalently binding to wood, they have already been proven as potential components of cellulose protection in the paper and packaging industry. In addition to minimizing the deficiencies of volatile and dissolvable compounds, amphiphilic cyclodextrins are also expected to decrease moisture absorptivity of wood enhancing panel mechanical properties.This study will examine all major aspects of wood treatment with cyclodextrin modified preservatives relevant for industrial applications by (1) incorporating biocides into cyclodextrins and treating wood wafers/boards, (2) studying penetration of preservatives into wood structures, (3) testing mechanical properties of boards, (4) examining preservative resistance to leaching, and (5) evaluating board susceptibility to fungal decay. Though the study encompasses one volatile (allyl isothiocyanate) and one water soluble biocide (borate), the knowledge gained will be transferable to broader spectra of comparable preservatives.This project aligns with the Program's goal of Sustainable Use of Natural Resources. It combines approaches of chemistry, microbiology, and materials science to develop the next generation of engineered products while reducing toxic wood disposed material, and decreasing use of heavy metal preservatives.

OBJECTIVES: The long-term goal of the proposed study is to contribute to advancement of environmentally-friendly protection methods of wood composites from fungal degradation. The goal of this proof-of-principle study is to examine the feasibility of using cyclodextrins for stabilization of volatile and leachable biocides for wood composites protection. In particular, the objectives of the study are:1. Production of cyclodextrin allyl isothiocyanate (CD-AITC) and cyclodextrin borates (CD-B) through two approaches: a) complexation before impregnation, and b) simultaneous complexation and wood impregnation in supercritical carbon dioxide2. Impregnation of wood wafers and board manufacturing3. Examination of penetrability of preservation into wood structure4. Measurement of boards' mechanical strength5. Evaluation of resistance to leaching and water repellency6. Examination of resistance of treated composites to decay by fungi

APPROACH: Production of CD-AITC and CD-BComplexes of AITC and borates with cyclodextrin will be prepared through already established procedures. Succinctly, CD-B will be obtained through refluxing the mixture of β-CD and boric acid for 18 h [1]. Upon evaporation of the solvent, the final product will be separated by centrifugation and washed. CD dissolved in 10% ethanol will be mixed with AITC (1:1), and precipitate washed by 30% ethanol [2]. Thin layer chromatography and FTIR will be used for confirmation of formation of CD-AITC and CD-B, respectively.Impregnation Impregnation with preservatives will be performed on wafers and on pre-fabricated boards through four different procedures:Citric acid-modified wafer treatment with aqueous solutions of CD-BCitric acid-modified wafer treatment with ethanol solutions of CD-AITCIn situ complexation of AITC and β-CD in citric acid-modified wafers in ScCO2In situ complexation of AITC and β-CD and treatment of boards in ScCO2Wood (southern yellow pine) wafers will be modified with 1.2 M citric acid and initially treated with five (2-30%) concentrations CD-B and CD-AITC solutions with and without presence of 0.25 M monosodium phosphate. Solutions with minimal concentrations of CD-B and CD-ATIC that yield maximum equilibrium weight gain will be used in further experiments.As the encapsulation of AITC into CD in supercritical carbon has not been optimized and/or reported yet, we will initially test for optimum parameters of pressures, temperatures, and time, using the same molar ratio of AITC, CD, and citric acid used in the previous steps. The best ScCO2 method inclusion parameters will then be used for concurrent preservative encapsulation and treatment of wafers with the optimum concentrations of CD-AITC and for treatment of pre-manufactured boards.Differences in treatment levels, i.e. weight gain, will be used for assessing the amount of preservative in the wood.Board manufacturingTwo types of pine wafers will be used for making boards - treated and untreated at 10% MC. The boards 5x5x0.5 inches (12.5 in3) will be made by incorporating 4% MDI resin into wafers, and pressed under 600 psi at 120°C for 10 minutes. The final panel density will be 40 lb/ft3.Penetrability of preservatives into wood structure of wafers will be estimated by bulking, i.e. estimate of volume change of dry wafers before and after treatment. The volume will be determined by buoyancy force in mercury.Mechanical strength of boards will be determined by measuring internal bond in accordance with ASTM D1037 [3].Resistance to leaching and water repellency Three board replicates of each treatment will be evaluated for water repellency by determining rate of swelling at 95% relative humidity. Leaching through weathering will be performed according to [4]. Leaching, expressed as a weight loss will be determined after 700 h of light exposure as a difference in freeze-dry weight before and after weathering period.Resistance of treated composites to decay by fungi will be done according to modified AWPA E-22 standard [5]. Two replicates for each selected treatment will be exposed to brown rot fungus (Gloeophyllum trabeum) and other two to white rot fungus (Trametes versicolor) for four weeks. Compression strength will be measured and resistance to fungal attack determined by percent strength loss for each treatment sample group as compared to the strength loss of untreated-and-unexposed samples.Statistical analysisDifferences in effectiveness of treatment will be statistically analyzed using ANOVA Tukey HST test.REFERENCES:1. Bhat, S. and S. Chandrasekaran, Oxygenation of alkenes with t-BuOOH catalysed by β-cyclodextrin borate. Tetrahedron Letters, 1996. 37(20): p. 3581-3584.2. Zhang, Q.F., Z.T. Jiang, and R. Li, Complexation of allyl isothiocyanate with β-cyclodextrin and its derivatives and molecular microcapsule of allyl isothiocyanate in β-cyclodextrin. European Food Research and Technology, 2007. 225(3-4): p. 407-413.3. ASTM, D1037.-. Standard test methods for evaluating properties of wood-base fiber and particle panel materials. 2012, ASTM International: West Conshohocken, PA.4. Feist, W.C., R.M. Rowell, and W.D. Ellis, Moisture sorption and accelerated weathering of acetylated and methacrylated aspen. Wood and Fiber Science, 1991. 23(1): p. 128-136.5. AWPA, E22-09: Standard Accelerated Laboratory Method for resting the efficacy of preservatives against wood decay fungi using compression strength. 2009, American Wood Protection Association.

PROGRESS: 2016/01 TO 2018/12
Target Audience:Our project was discussed with wood composites industry representatives during 2017 and 2018 Mississippi State University Department of Sustainable Products Annual Advisory Board Meeting and was well perceived. The graduate student employed on the project presented the research outcomes at 3 international and 1 domestic conferences/meetings, which were attended by researchers, industry representatives, graduate students, and engineers. Changes/Problems:The supercritical CO2 (ScCO2) treatment on OSB could not be performed since the Co-PI (who was affiliated with Oregon State University) moved to Australia. The budget allocated for the GRA's travel to the ScCO2 facility was spent to support GRA attending an international conference presenting the outcomes of this project, as well as conducting an additional study on using cyclodextrins to encapsulate essential oils for wood treatments. What opportunities for training and professional development has the project provided?Dr. Yunsang Kim participated in this research as a co-major supervisor of the GRA, Ms. Lili Cai. - The GRA became more familiar with the use of ultraviolet spectroscopy under the supervision of Dr. Yunsang Kim. - The GRA got a better understanding of using Differential scanning calorimetry under the supervision of Dr. Yunsang Kim. The Principal Investigator, Dr. Hyungsuk Lim, and the GRA, Ms. Lili Cai participated in conferences and meetings. - The PI attended World Conference in Timber Engineering 2018. Seoul, Korea, 2018 - The GRA attended and presented at AWPA's 114th Annual Meeting. Seatle, WA, USA, 2018 - The GRA attended and presented at 2018 SWST/JWRS International Convention, Nagoya, Japan, 2018 How have the results been disseminated to communities of interest?The GRA, Ms. Lili Cai presented the research outcomesat 2018 AWPA's 114th Annual Meeting. Seatle, WA and at 2018 SWST/JWRS International Convention, Nagoya, Japan. The poster presentation at the SWST conference got an honorable mention award. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

IMPACT: 2016/01 TO 2018/12
What was accomplished under these goals? Major activities completed; - Confirmation and production of β-cyclodextrin allyl isothiocyanate (βCD-AITC) and β-cyclodextrin borates (βCD-B) complexes - Evaluation of antifungal and leaching performance of βCD-AITC in wood - Evaluation of antifungal and leaching performance of βCD-B and βCD-AITC in Oriented Strand Board (OSB) panels, which involved following activities: a) production of OSB panels after confirming necessary manufacturing parameters, and b) measurements of physical and mechanical properties of the OSB panels - Application of the proposed research approach in forming βCD-essential oil (EO) complexes for wood protection purpose Specific objectives met; - All the proposed objectives, except Objective 1b), were met to different levels during the reporting period. Significant results achieved, including major findings, developments, or conclusions - βCDs enhance solubility and decrease the volatility of AITC (mustard oil). - Based on mass loss and scanning electron microscope / energy-dispersive X-ray results, the βCD-AITC complexes protected solid wood against brown and white rot fungi. - Increases of the inclusion yield of AITC in βCD would improve wood protection performance. - OSB panels composed of 5% and 10% βCD-AITC preservatives in a powder form met the internal bond (IB) strength criteria in BS EN 300 standard. - Regardless of exposure to leaching cycles, βCD-AITC treated OSB panels at both concentration levels had mass loss less than 10% against brown rot fungi. - βCD-B hydrolyzed during the leaching cycles, which made them only effective against fungi at dry conditions. Key outcomes or other accomplishments realized - βCDs could potentially be used as carriers of antimicrobial compounds. - The feasibility of using Methyl-β-cyclodextrins (MβCD) as carriers for essential oils was confirmed, which is beyond the scope of the proposed research. - MβCD had a higher encapsulation efficacy for eugenol, trans-cinnamaldehyde, carvacrol, and thymol, as compared to linear compounds, and restrained their volatility.

PUBLICATIONS (not previously reported): 2016/01 TO 2018/12
1. Type: Journal Articles Status: Published Year Published: 2019 Citation: Cai, L., Jeremic, D., Lim, H., Kim, Y., 2019. beta-Cyclodextrins as sustained-release carriers for natural wood preservatives. Ind. Crops Prod. 130, 42â48. https://doi.org/10.1016/j.indcrop.2018.12.061
2. Type: Journal Articles Status: Other Year Published: 2019 Citation: Cai, L., Jeremic, D., Cosovic, B., Kim, Y., Lim, H., 2019. beta-Cyclodextrin-Allyl Isothiocyanate Complex as a Natural Preservative for Strand-based Wood Composites (tentative title) (under preparation)
3. Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Cai, L., Jeremic, D., Lim, H., Kim, Y., 2018 Effect of beta-cyclodextrins/allyl isothiocyanate complexes on fungi resistance of southern yellow pine. AWPAâs 114th Annual Meeting. Seatle, WA.
4. Type: Conference Papers and Presentations Status: Accepted Year Published: 2018 Citation: Cai, L., Lim, H., Kim, Y., Jeremic, D., (November 6, 2018). "Fungi Resistance of Oriented Strand Board Treated with beta-cyclodextrins / Allyl Isothiocyanate Inclusion Complexes." Oral Presentation. 2018 SWST/JWRS International Convention, Nagoya University, Nagoya, Japan.
5. Type: Theses/Dissertations Status: Under Review Year Published: 2019 Citation: Cai, L. 2019. beta-Cyclodextrins as agents for improved protection methods of wood and oriented strand board wood composites (PhD dissertation), Mississippi State University, Mississippi, MS, USA.

PROGRESS: 2017/01/01 TO 2017/12/31
Target Audience:The project has been presented as poster presentations in two international conference. The recruited graduate student was introduced to the knowledge about wood deterioration and preservation, wood chemistry, chemometrics and new analytical techniques necessary for this project. Changes/Problems:We have decided to use β-cyclodextrins derivatives, methyl-β-cyclodextrins (3.5 times more expensive) and hydroxypropyl-β-cyclodextrins (2 times more expensive), instead of β-cyclodextrins which was originally proposed; thewater solubility of β-cyclodextrins has found to betoo low to treat wood strands. What opportunities for training and professional development has the project provided?The graduate research assistant (GRA)was trained to use the DSC and was introduced to the courses of wood preservation, wood chemistry, chemometric and statistics. The GRA has attendedtwo internal conferences where the personnel was exposed to the newest research and had chances to meet with the leading researchers around the world. Throughoutweekly meetings with the PI, the personnel got trained on project management as well as research plan development. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?We plan to determinethe concentration levels of the preservative solutions which would provide optimum fungi resistances. Prior to OSB panel construction, we will explore how the preservatives affect the curing behavior of the resin. Once the OSB panels are manufactured successfully with acceptable IB strength properties, we will conduct soil block tests with the leached and unleached samples. We also plan to send the graduate research assistantto Oregon State University to investigate the super critical treatment method.

IMPACT: 2017/01/01 TO 2017/12/31
What was accomplished under these goals? Major activities completed: During the reproting period, we have completed the following tasks under Objective 1, 2, and 3. 11B NMR and 1H NMR were used to conform βCD/B complexes and the appearance of a new chemical shift indicated the B-O-C was formed. 1H NMR and 12CNMR were used to conform βCD/AITC complexes and upfield of the chemical shifts indicated AITC was encapsulated in the cavity of βCD. Preliminary study on the effect of βCD/AITC complexes on the fungi resistance properties of southern yellow pine has been conducted by following AWPA E10 standard and the results indicated β-cylodextrin/allyl isothiocyanate complexes can be used as potential water-borne wood preservatives. The manufacturing parameters for Oriented Strand Board (OSB) was set. Two type pf preservatives: βCD/AITC complexes and βCD/B complexes, were added in powder form in the OSBmanufacuturing process and the internal bonding of the panel was obtained. Data collected: NMR was used to characterize βCD/B and βCD/AITC complexes by using DMSO-D6 as solvent. The results were compared to those ofpure βCD, boric acid, and AITC to confrim the formation of the complexes. Discussion of results: For the NMR confirmation, further work need to be done to clarify how much boric acid or AITC was attached or included in βCD. The soil block test on the fungi resistance test of βCD/AITC indicated higher concentration of the preservatives should be used to research a desired performance. The IB test indicated the preservatives interfere the curing behavior of pMDI resin and the interactions is ongoing by TGA/DSC methods. Key outcomes or other accomplishments realized: Preliminary results obtained.

PUBLICATIONS: 2017/01/01 TO 2017/12/31
1. Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Cai, L., Jeremic, D., Kim, Y., Lim, H. (Poster presentation) ?Effect of ?-cyclodextrin/Boric Acid Complexes on Setting Behavior of pMDI Resin in Oriented Strand Board Production? at 2017 11th International Conference on Wood Adhesives Student Poster Competition with 1st place.
2. Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Cai, L., Jeremic, D. (Poster presentation) ?Wood preservation by ?-cyclodextrin/boric acid complexes? at 2017 71st Forest Product Society International Convention Student Poster Competition with 2nd place.

PROGRESS: 2016/01/01 TO 2016/12/31
Target Audience:During the reporting period, our project was discussed with wood composites industry representatives during our Annual Board Meeting and was well perceived. The graduate student employed on the project has been introduced not only to the new analytical techniques necessary for the project, also to the area of wood composites manufacturing process and statistics. Changes/Problems:The delay in the project start may affect the deadline of delivery of final project objectives. What opportunities for training and professional development has the project provided?A student hired on the project has obtained knowledge on UV-Vis spectrometry, and FTIR and NMR spectroscopy, through in-lab training. The student has also been introduced to the Multivariate statistical analysis, namely Principal Components Analysis and Multivariate Curve Resolution methods, and took a course on biocomposites manufacturing. In addition, the student has learnt about safe laboratory practices, and proper lab notebook maintenance. The student met with the supervisor on weekly basis, which taught the student time management approaches by weekly planning and reporting. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?We plan to proceed with wood treatments and board testing upon NMR confirmation of the structures of the complexes. We also plan to send a student to Oregon State University to perform the in-situ complexation in supercritical carbon-dioxide during the Fall term of 2017.

IMPACT: 2016/01/01 TO 2016/12/31
What was accomplished under these goals? Impact of the project: An increased use of wood for mid-rise multi-family and mixed-use buildings in recent years forecasts substantial growth of wood products industry in the near future. This urges for revision and improvement of wood protection practices, as there is currently no reliable wood protection method for wood composites exposed to wet conditions over long periods of time. In many cases, when the leaks in the buildings are not discovered, hazardous fungi can develop mycotoxins, and cause serious health issues. According to EPA, as high as one-half of all structures have been estimated to be damp and therefore potential environment for molds and allergies. World Health Organization in their 2011 report titled "Environmental burden of disease associated with inadequate housing" that "asthma onset in (European) children attributable to indoor "mould" in their living environment is approximately 12% and that attributable to "dampness" is approximately 15%". In addition to the mold, wood decaying fungi can cause a substantial damage to the mechanical properties of the wood, causing therefore a need for a full replacement of the structural components. The long-term goal of this project is to develop an improved biocidal protection method for wood composites. This particular study addresses improvement of disadvantages of two wood protection systems: (1) vaporization of fumigants, and (2) leaching of water borne preservatives. Both of these products are complexed within a molecule of a sugar, cyclodextrin, which is believed to be able to bind allyl isothiocyanate (fumigant) and borate (salt used in water solution) and therefore improve their preservative properties. Major activities completed: The study involves six distinctive objectives. As the initial step, we are producing complexes of cyclodextrin allyl isothiocyanate (CD-AITC) and cyclodextrin borates (CD-B). For this particular objective we are taking two approaches: a) complexation before impregnation, and b) simultaneous complexation and wood impregnation in supercritical carbon dioxide. Upon preparing the material, we will examine penetrability of preservation into wood structure and impregnate wood wafers and manufacture boards, which accounts for the second and third objective of this study, respectively. The boards will be tested for mechanical strength and then subjected to water to accomplish the fourth and fifth objectives of the study: measurement of boards' mechanical strength, and evaluation of resistance to leaching and water repellency. Finally, we will examine resistance of treated composites to decay by fungi. During the reporting period, we have completed one part of the Objective 1, the most cumbersome effort in this study. Both cyclodextrin allyl isothiocyanate (CD-AITC) and cyclodextrin borates (CD-B) have been complexed, and analysis on UV-Vis and FTIR are indicating successful effort. We are currently performing NMR analysis to decipher the chemical structure of CD-B (never confirmed before), as well as to confirm the AITC-CD newly formed bonds. Data collected UV-Vis product assessment of CD-AITC complex Samples of CD, and allyl isocyanate, as controls, and newly formed CD-AITC were examined on UV-Vis. The CD complex was firstly treated with hexane, to extract AITC from CD cavity. The obtained results indicated that the hexane supernatant contained both CD and AITC characteristic peaks. Although the extraction was not fully accomplished, the presence of both peaks indicates complexation of the product. FTIR products examination The FTIR analysis included both CD-B and CD-AITC along with control CD, B, and AITC samples. Similarly, the presence of bonds characteristic for both the CD and the corresponding protectant indicated that the complexes have been successfully formed. Discussion of results: Considering that the project funding started in March 3, 2016 and the student started working in June 2016, we believe that we have made progress as planned, with expected initial results. Key outcomes and other accomplishments realized: Starting material prepared.

PUBLICATIONS: 2016/01/01 TO 2016/12/31
No publications reported this period.