Progress 10/01/16 to 09/30/21
Outputs
Target Audience:The 2021findings were disseminated, through publicationand conference presentation, tothe academic research and products development communities working in the areas of biobased materials and products. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project in 2021 has provided research training to a researcher and an undergraduate student through their participation in generating the reported output. How have the results been disseminated to communities of interest?Research results were disseminated through scientific publication and conference presentation. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Co-products from bioprocessing residues are an emerging focus to enable the viability of a cellulosic sugar platform. Various co-production opportunities are possible based on what we currently know about converting lignin, the major component in the solid waste stream of enzymatic saccharification (enzymatic process of breaking polysaccharides down into sugars). While lignin is widely known as a natural binder, our preliminary findings suggest that residual xylan plays a key role in interacting with polycarboxylic acid crosslinkers when utilizing saccharification residues for wood adhesive applications. Xylan is the major hemicellulose in hardwood (and grasses), and it is recoverable from kraft (alkaline) pulping. Understanding the reactions between xylan and polycarboxylic acids would help direct strategies for future utilization of hardwood biomass wastes. The knowledge gained from this study could also lead to opportunities for modifying other polysaccharides, and even lignin from plants. These, combined, have the impact of increasing revenues through value adding of solid residues from biomass processing. This impact, in turn, could improve the commercial viability of the main product stream, such as fuels and chemicals from cellulosic sugars. For 2021, efforts to discern the heat-activated bonding properties of xylan hemicellulose (Objective 1) was extended to testing integrity of wet films made of xylan-containing saccharification residues of lignocellulosic biomass. The material was mechanically fibrillated, formed into films, pressed with or without heat, and then evaluated for their wet tensile strength to infertheir (self) bonding performance. This effort, which was published in the same year (2021), revealed that heat activation (hotpressing) drastically improved wet tensile strength of the films (compared to pressing without heat); such hydrolytically stable bonds could not be attributed to densification nor merely the hydrogen bonding effects. Supplementary to this finding about heat-activated self-bonding, a follow-up study was conducted to remove hemicelluloses and lignin prior to hotpressing. The component removal was confirmed using mid-infrared spectroscopy for vibrational bands characteristic of the chemical components. Tensile tests, upon 24-hour water soaking of the films, revealed that hotpressing prior to soaking improved the wet strength retention (relative to dry condition) of the control film from 5% to about 30%. The heat-induced wet strength retention did not change significantly with partial lignin removal, but it dropped (from 30%) to 14% upon hemicellulose removal.This result verifies the adhesion properties of the hemicellulose component in lignocellulosic materials for their heat-activated bonding capability, thus offering insights into adhesive applications in utilizing biomass wastes. The knowledge gained earlier (2017) for Objective 2 (ductility improvement) in modifying polysaccharide materials via a non-crosslinking approach was applied to efforts for addressing Objective 3 (inducing carboxyl functionality). In lieu of the adipic acid reported in 2017, another bifunctional carboxylic acid, i.e., maleic acid, was used for treating cellulosic paper films. Mid-infrared spectroscopy revealedester or/and carboxyl groups on the treatedpaper substrates (water rinsed).The carboxyl groups (intended species on the substrate) became evidenced after the treated paper was rinsed instead with sodium hydroxide which transformed the groups to carboxylatesdistinguishable under infrared spectroscopyfrom the ester groups (indicating occurence of chemical attachment). The same effects were observed when citric acid,a trifunctional carboxylic acid, was used as the treating compound. Interestingly, no ester bond formation or attachment of carboxyl groups were detected when acetic acid,a monofunctional carboxylic acid, was used. This supports the concept of cyclic anhydrides as the intermediate for the esterification reaction, necessitating at least two carboxylfunctionalities to allow chemical attachment via ester bonds to the (hydroxyls of) polysaccharide substrates. By comparing the intensities of the carboxylate bands between maleic acid and citric acid treatments conducted at the same temperature (180 C) and dosage (in moles), it could be estimated that the carboxyl group in the maleic-acid treated sample was 38% of that detected in citric-acid treated samples, but the ester amount of the former was considerably lower, at a merely 8% of that found in citric acid treatment. This favorably suggests carboxyl functionalizing of the paper substrates enabled by maleic acid treatment without significantly causing crosslinking (ester linkage) of the substrate. This outcome signifies the potential of sparing the functionalized samples from the side effect of increased brittleness (addressed in Objective 2). Moreover, treatment condition studies revealed that the amount of carboxyl groups induced by maleic acid treatment reached a plateau at 160 C, thereby suggesting a route toward optimization. Collectively, the outcome of this project led to improved understanding of the value-adding (e.g., carboxyl functionalization) strategies for polysaccharides. Thus it has the impacts of enabling new opportunities for producing biobased materials and adhesives for more effective utilization of plant biomass wastes. Such opportunities include xylan- (also lignin-) containingnanofiber products, hence contributing to the high priority issue of "technological advancements (biotechnology, nanotechnology, and geospatial technology), productivity, and forest applications" identified in the McIntire-Stennis Cooperative Forestry Research Program (McIntire-Stennis RFA-508, 2021).
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Yang, H.-S., F. J. Liew, J. Kaffenberger, N. C. A. Seaton, O. Kwon, J. S. Schilling, and W. T. Y. Tze. 2021. Binderless films from lignin-rich residues of enzymatic saccharification. Biomass and Bioenergy 153: 106214.
DOI: 10.1016/j.biombioe.2021.106214
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2021
Citation:
Chen, H.-C. and W. T. Y. Tze. Resin-free fiberboard from lignin-containing cellulosic nanofibers. Poster (virtual) presented in American Chemical Society Spring 2021 Conference, Apr 5-30, 2021
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Progress 10/01/19 to 09/30/20
Outputs
Target Audience:The target audiences reached were the academic research (including graduate students) and products development communities working in the areas of biobased materials and composites. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Research results were disseminated through oral presentation and publication in refereed journals. What do you plan to do during the next reporting period to accomplish the goals?For the next reporting period, continued efforts will be focused on incorporating carboxylic functional groups on paper formed by micro-nanofibrillated plant biomass (Objective 3).
Impacts
What was accomplished under these goals?
# Co-poducts from bioprocessing residues are an emerging focus to enable the viability of a cellulosic sugar platform. Various co-production opportunities are possible based on what we currently know about converting lignin, the major component in the solid waste stream of enzymatic saccharification (enzymatic process of breaking polysaccharides down into sugars). While lignin is widely known as a natural binder, our preliminary findings suggest that residual xylan plays a key role in interacting with polycarboxylic acid crosslinkers when utilizing saccharification residues for wood adhesive applications. Xylan is the major hemicellulose in hardwood (and grasses), and it is recoverable from kraft (alkaline) pulping. Understanding the reactions between xylan and polycarboxylic acids would help direct strategies for future utilization of hardwood biomass wastes. The knowledge gained from this study could also lead to opportunities for modifying other polysaccharides, and even lignin from plants. These, combined, have the impact of increasing revenues through value adding of solid residues from biomass processing. This impact, in turn, could improve the commercial viability of the main product stream, such as fuels and chemicals from cellulosic sugars. # Previously (2019), the conversion of xylan-containing solid wastes was enabled through acquired understanding of their reaction with polycarboxylic acid modifiers (Objective 1). Subsequent efforts in 2020 were channeled to understanding the influence of residual xylan in such biomass on the ease of fibrillation, which could lead to magnified interactions and bonding that further enable materials and adhesive applications. Results showed that fibrillation is facilitated by xylan residing in the plant biomass. This major outcome is an addition to our previous conclusion that the presence of in situ cellulose is critical in enabling fibrillation. For the 2020 study, the cellulose influence was circumvented by keeping its fraction similar in the plant biomass, but the xylan fraction was reduced through a controlled dilute acid treatment. The material, upon defibrillation, exhibited a higher surface area and water retaining capacity if some xylan remained in it before wet milling (grinding). For example, when the xylan content was about 10 wt%, the surface area of the fibrillated material was 170 square meter per gram, with 1430% water retained based on its dry mass, after a moderate grinding of -50 micrometer stone clearance. This degree of fibrillation was at least two times of that obtained from xylan-poor (~1 wt%) feedstock using the same grinding protocol. In this regard, xylan is judged to promote swelling of lignocellulosics in water so that wet milling could more effectively induce their defibrillation. This acquired understanding has the implications of shaping future strategies for selecting and treating bioprocessing solid wastes for valorizations that involve defibrillation. # Supplementary to the outcome mentioned above, efforts (published in 2020) were also made to better understand the fibrillation effects of cellulosic nanomaterials on their utilization. Compared to the crystalline form (cellulose nanocrystals), the fibrillated from of cellulose nanomaterials was reported to require a lower dosage of merely 2 wt% to effectively reinforce an artwork restoration polymeric material(by at least 2.5 times in stiffness and strength). This was made possible due to its relative ease of network percolating in the composite. Nanofibrillation also enhanced the specific surface area over that of (the starting) pulp fiber, resulting in a higher capacity of binding to enzymes; the immobilization improved the lifetime of enzymes to as much as 27 folds for use in biotransformation catalysis. This acquired know-how signifies a useful strategyfor developing high performance biocatalysts to intensify bioprocessing, while utilizing cellulosic solid wastes. # Building on our previously established knowledge in using adipic acid (Objective 2), we applied the bi-functional polycarboxylic acid to modify, with the aid of heat treatment, paper films made of fibrillated cellulosic elements (Objective 3). The modified paper film was compared against films heat-treated with citric acid (a tri-functional polycarboxylic acid) for tensile performance. Results showed that the citric-acid treatment stiffened the paper sample (by at least 50%) due to crosslinking effects. In contrast, the stiffness of bi-functional polycarboxylic acid-treated paper film was not altered considerably. While this latter outcome suggests attachment of one of the two carboxylic functionality onto the fibrous film, the desired (expected) carboxylation afforded by the unreacted, second carboxylic acid groups would need to be verified. This verification is planned for 2021.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Chen, H.-C., W. T. Y. Tze, and F.-C. Chang. 2020. Effects of nanocellulose formulations on physicomechanical properties of Aquazol-nanocellulose composites, Cellulose 27:5757-5769.
- Type:
Journal Articles
Status:
Published
Year Published:
2020
Citation:
Dai, G., W. T. Y. Tze, B. Frigo-Vaz, N. C. Mancipe, H.-S. Yang, M. C. Branciforti. And P. Wang. 2020. Nanofibrillated cellulose-enzyme assemblies for enhanced biotransformations with in situ cofactor regeneration. Applied Biochemistry and Biotechnology 191:1369-1383.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2020
Citation:
Tze, W. T. Y. Utilizing solid wastes from bioprocessing of wood for materials and adhesive applications. Invited talk (virtual) for the Wood Science and Engineering Graduate Seminar, Oregon State University. Dec 2, 2020.
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:The 2019 findings were disseminated, through publicationand conference presentations, tothe academic research and products development communities working in the areas of biobased materials and composites. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?Research results were disseminated through scientific publication and conference presentations. What do you plan to do during the next reporting period to accomplish the goals?For the next reporting period, continued efforts will be focused on investigating bonding with/of xylan-containing materials (Objective 1). Efforts will also be made on incorporating carboxylic functional groups on paper formed by micro-nanofibrillated plant biomass (Objective 3).
Impacts
What was accomplished under these goals?
# Co-products from bioprocessing residues are an emerging focus to enable the viability of a cellulosic sugar platform. Various co-production opportunities are possible based on what we currently know about converting lignin, the major component in the solid waste stream of enzymatic saccharification (enzymatic process of breaking polysaccharides down into sugars). While lignin is widely known as a natural binder, our preliminary findings suggest that residual xylan plays a key role in interacting with polycarboxylic acid crosslinkers when utilizing saccharification residues for wood adhesive applications. Xylan is the major hemicellulose in hardwood (and grasses), and it is recoverable from kraft (alkaline) pulping. Understanding the reactions between xylan and polycarboxylic acids would help direct strategies for future utilization of hardwood biomass wastes. The knowledge gained from this study could also lead to opportunities for modifying other polysaccharides, and even lignin from plants. These, combined, have the impact of increasing revenues through value adding of solid residues from biomass processing. This impact, in turn, could improve the commercial viability of the main product stream, such as fuels and chemicals from cellulosic sugars. # We reported, in 2018, that citric acid (a tricarboxylic acid) improved significantly the wet bond strength between xylan-containing saccharification residues and wood substrates, while adipic acid, with the absence of the third carboxylic functionality, did not contribute as remarkably to wet bond strength retention. The 2018 findings also validated the existence of crosslinking in samples of wood bonded with such saccharification residues and citric acid. One major outcome in 2019 was proving that the reduction of the hydrophilic functional groups is not the key contributing factor in wet bond strength improvement. To illustrate, there was merely a 13% reduction in water uptake (upon 24-hour soaking) forthe citric acid-modified, xylan-containing saccharification residues, compared to the case without an additive. This reduction amount is small considering the 275% improvement in wet bond strength. The result therefore allows the reasoning that it is crosslinking, not the reduction of hydrophilic groups, that plays a direct role in wet strength improvement of citric acid-assisted bonding of wood when using xylan-containing saccharification residues as the adhesive. This verification constitutes the key outcome related to Objective 1, on the stability of bonding between saccharification residues and wood substrates, thereby paving the way for utilization of xylan in wood adhesive applications. # Efforts in 2019 also involved expanding the beneficial effect of crosslinking to enhancing wet performance of lignosulfonates, a side product from acid pulping of wood. Fiber spun from this lignin-based polymer with citric acid blended, followed by a heat treatment, showed a 40% reduction in moisture uptake when exposed to high humidity (95% relative humidity).In contrast, the spun lignosulfonate fiber undergoing the same heat treatmentbut without crosslinking (citric acid) was observed to dissolveat high humid environments. Thus, this finding (presented in conference) suggests the possibility of controlling the dissolution of water-soluble wood-based polymers usingcitric acid crosslinking. This improved know-how signifies a useful strategyfor enabling material applications of biomass wastes and also expanding the humidity range of their use. # As demonstrated in 2017 for Objective 2 (ductility improvement),bifunctional carboxylic acids could be used to modify properties of polysaccharide materials possibly via a non-crosslinking approach. This knowledge gained will be expanded to inducing carboxylic functionality onto wood-basednanofiber, which is scheduled for investigation in the next year under Objective 3. Meanwhile, efforts (published 2019) were made to better understand the fibrillation process of hardwood particles, a likely form of solid residues from wood processing, to possibly allow tailoring of specific surface area and viscosity for conversion into value-added products. In addition, fibrillated solid residues of saccharification, at 45 wt% filler content, were also shown (presented in conference) to reduce by half the moisture uptake of poly(vinyl alcohol), a water-soluble polymer, at 98% relative humidity.The fibrillated residues also reduced the stiffness loss of the humidity-exposed materials from 50% (no filler) to 20%. Overall, efforts in 2019 resulted in improved understanding of a potential valorization strategy for utilizing plant biomass wastes for adhesive and material applications.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Tze, W. T. Y., S.-H. Wang, H.-C. Chen, and F.-C. Chang. Crosslinking and carbonization of electrospun lignosulfonate fiber. Poster presentation in the 2019 TAPPI International Conference on Nano for Renewable Materials, Chiba, Japan. Jun 3-7, 2019.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Chen, H.-C., W. T. Y. Tze, and F.-C. Chang. Effects of nanocellulose formulations on hygroscopic and mechanical properties of Aquazol/nanocellulose biocomposites. Poster presentation in the 2019 TAPPI International Conference on Nano for Renewable Materials, Chiba, Japan. Jun 3-7, 2019.
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Branciforti, M. C., H.-S. Yang, I. Hafez, N. C. A. Seaton, and W. T. Y. Tze. 2019. Morphological and rheological behaviors of micro-nanofibrillated NaOH-pretreated aspen wood. Cellulose Journal 26:4601-4614.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2019
Citation:
Tze, W. T. Y. and H.-S. Yang. Wet strength properties of poly(vinyl alcohol)-microfibrillated wood composites. Poster presentation in the 6th Global Conference on Polymer and Composite Materials, Bangkok, Thailand. Jul 8-11, 2019.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:Research and products development communities in both academic and industrial sectors in the areas of wood products. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided training for PhD student Islam Hafez, who took part in the biobased adhesive studies. How have the results been disseminated to communities of interest?Research results were disseminated through conference presentation and publication. What do you plan to do during the next reporting period to accomplish the goals?For the next reporting period, continued efforts will be focused on investigating the stability of bonding between the saccharification residues and wood substrates (Objective 1). Efforts will also be made on the polycarboxylic modification of xylan-containing materials (Objective 2).
Impacts
What was accomplished under these goals?
# Co-products from bioprocessing residues are an emerging focus to enable the viability of a cellulosic sugar platform. Various co-production opportunities are possible based on what we currently know about converting lignin, the major component in the solid waste stream of saccharification (process of breaking polysaccharides down into sugars). While lignin is widely known as a natural binder, our preliminary findings suggest that residual xylan plays a key role in interacting with polycarboxylic acid crosslinkers when utilizing saccharification residues for wood adhesive applications. Xylan is the major hemicellulose in hardwood (and grasses), and it is recoverable from kraft (alkaline) pulping. Understanding the reactions between xylan and polycarboxylic acids would help direct strategies for future utilization of hardwood biomass wastes. The knowledge gained from this study could also lead to opportunities for modifying xylan and other polysaccharide-based materials. These, combined, have the impact of increasing revenues through value adding of biomass processing/harvesting residues. This impact, in turn, could improve the commercial viability of the main product stream, such as fuels and chemicals from cellulosic sugars. # For 2018 activities, the findings reported earlier (2017) on the wood bonding capability of xylan (Objective 1) were extended to the testing of residual xylan (remaining) in the solid residues from enzymatic saccharification of hardwood. Two types of residues were compared - one was pretreated with alkali at moderate temperature (to retain most xylan), and the other one pretreated with dilute acid (to remove xylan). The cellulose (more precisely, glucan) in both samples were then enzymatically hydrolyzed to the maximum extent. Infra-red spectroscopy revealed that the sample from alkali pretreatment (i.e., containing xylan) has a larger amount of hydroxyl groups, suggesting favorable criteria in allowing wood bonding and also reacting with the polycarboxylic acid crosslinker. This inference corroborates the stronger wood bonding capability observed for such residues compared to the one from acid pretreatment, with or without the addition of citric acid (a tricarboxylic acid). Focusing on the reaction with citric acid, condutometric titration studies revealed that two-third of the carboxyl groups in the acid was consumed in reacting (via esterification) with hydroxyls of the saccharification residues. This observation supports the published mechanism that two carboxyl groups of a citric acid molecule first combine to become a cyclic anhydride which in turns react with hydroxyl groups forming an ester bond; the third carboxyl could not make the pair for forming the cyclic anhydride intermediate and it therefore remains unreacted. As such, the key outcome for 2018 under this objective was the increased understanding of the mechanism of wood bonding by a lignocellulose-based adhesive with polycarboxylic acid as an adhesion promoter. # On the effect of longer-chain polycarboxylic acid (related to Objective 2), adipic acid was tested in the bonding of wood by saccharification residues, with citric acid as the reference additive. Adipic acid has four methylene groups in its linear molecule and one carboxyl functionality at each of the two ends. Since it is a dicarboxylic acid, the "cyclic anhydride intermediate" mechanism dictates that each molecule of adipic acid could only form an ester bond with saccharification residues, but the second carboxyl group would remain unattached; in other words, no crosslinking is anticipated. When blended into saccahrification residue for bonding to wood substrates, adipic acid at the same dosage level (in mole per gram of residue) as citric acid did not improve the wet strength of the bonding upon 24-hour soaking. When the adipic acid dosage was increased to 2x of that of citric acid, a 50% improvement by average in wet strength was noted, attributable to its hydrophobic methylene group. Such bonding improvement, however, is not as remarkable as that attained (275% improvement) with citric acid addition to saccharification residues for wood bonding, in which crosslinking is allowed. These results demonstrate the significance of crosslinking in enhancing wet performance. Thus, the second key outcome for 2018 was the gain of knowhow in enhancing wet performance of bioproducts using a polycarboxylic acid. # It can be concluded from the findings for Objectives 1 and 2 that appropriate anhydrides if used or facilitated could modify biomass substrates to enhance their end-use performance, paving the way for our later-year efforts related to Objective 3 (introducing carboxyl groups). Meanwhile, through a collaborative project (publication listed), acetic anhydride was employed to surface-chemically modify plant fibers (kenaf) - substituting their polar hydroxyl groups while introducing the less polar acetyl groups. Test results show that due to improved compatibility and the resulted favorable interaction, injection-molded composites made of these modified fibers and poly(lactic acid) plastic exhibited a 70% lower absorption of water (800 hours; ~35-day soaking) and 17% improvement in tensile strength compared to the case of no-treatment.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Chung, T.-J., J.-W. Park, H.-J. Lee, H.-J. Kwon, H.- J. Kim, Y.-K. Lee, W. T. Y. Tze. 2018. The improvement of mechanical properties, thermal stability, and water absorption resistance of an eco-friendly PLA/kenaf biocomposite using acetylation. Applied Sciences 8:376; doi:10.3390/app8030376
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2018
Citation:
Hafez, I., H.-S. Yang, W. T. Y. Tze, and F.-C. Chang. Utilizing saccharification residues for wood adhesive. 107 Forest Resource Sustainability Development Conference, Taipei, Taiwan
- Type:
Journal Articles
Status:
Under Review
Year Published:
2019
Citation:
Branciforti, M. C., H.-S. Yang, I. Hafez, N. C. A. Seaton, and W. T. Y. Tze. Morphological and rheological behaviors of nanofibrillated NaOH-pretreated aspen wood. Cellulose Journal.
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:The 2017 findings were disseminatad, through publicationand conference presentations, tothe academic reaserch and products development communities working in the areas of biobased materials including biopolymer. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided research training to an undergraduate student (Fletcher Gilbertson) who participated in the reported study as part of his Undergraduate Research Opportunity (UROP) experience. The student is currently applying for graduate school. The project has also provided training for PhD student Islam Hafez, who took part inthe adhesive studies. How have the results been disseminated to communities of interest?Research results were disseminated through conference presentation and the University of Minnesota Digital Conservancy (open access) to reach the broad communities of interest. What do you plan to do during the next reporting period to accomplish the goals?For the next reporting period, continued efforts will be made on the crosslinking study of citric acid and xylan in wood bonding (Objective 1). Efforts will also be focused on the polycarboxylic crosslinking of xylan-glucomannan films (Objective 2).
Impacts
What was accomplished under these goals?
# Tasks for this project were formulated to examine the use of polycarboxylic acids for modifying properties of hardwood biomass. While lignin is widely known for its adhesive nature, our preliminary findings suggest that (residual) xylan could play a key role in interacting with polycarboxylic acid crosslinkers when utilizing biomass for wood adhesive applications. Xylan is the major hemicellulose in hardwood (and grasses). Understanding the reactions between xylan and polycarboxylic acids would help direct strategies for future utilization of hardwood biomass wastes. The knowledge gained from this study could also lead to new opportunities for producing polymeric materials in addition to biobased adhesives. These, combined, bring the impacts of increased biomass values through co-products and improved commercial viability of the main product stream, such as fuels and chemicals from cellulosic sugars. # The major outcome in 2017 is the gain of knowledge in improving the wet performance of xylan-based polymeric films using citric acid as a biobased, polycarboxylic crosslinker (Objective 2). Xylan can be cast into continuous films if it is mixed with chitosan, a polysaccharide derived from the chitin shells of shrimps or crabs. The wet tensile strength of the films exhibited a 40% increase as the citric acid dosage in the formulation was increased from 0 to 0.4 mmol for every gram of polymer (xylan/chitosan mixture). Chemical functional groups resulted from the crosslinking reaction were identified through infrared spectroscopy. Based on the 24-hour soaking test, the crosslinked films were noted to contain 40% less water than the control (films without citric acid), signifying an improved water resistance. In dry condition, the film became slightly less brittle if the citric-acid crosslinker in the formulation was partially substituted with adipic acid; however, additional work would be needed to verify the significance of the improved ductility. # In addition to the aforementioned, as an initial step to understand the role of xylan in wood bonding (Objective 1), xylan extracted from hardwood was used as a "model" wood adhesive cured with citric acid. The shear strength of the wood lap joint specimens turned out to be, on average, 87% of that of the adhesive system consisting of saccharification residues and citric acid. This finding agrees with the hypothesized role of xylan in contributing to the previously established wood bonding capabilities of saccharification residues. The second outcome in 2017 is thus the expansion of an accumulating knowledge base related to the bonding mechanisms involved (hence to be accentuated) when utilizing saccharification residues for wood adhesive applications.
Publications
- Type:
Other
Status:
Published
Year Published:
2017
Citation:
Gilbertson, F J. R., and W. T. Y. Tze. 2017. Improving wet performance of chitosan-xylan bioplastic using a biobased additive. UROP paper, University of Minnesota Digital Conservancy. http://conservancy.umn.edu/handle/11299/184271.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2017
Citation:
Gilbertson, F J. R., I. Hafez, and W. T. Y. Tze. 2017 Crosslinking of chitosan-xylan films: Effects of citric acid on wet strength and influence of adipic acid on film ductility. Poster presentation in the 2017 University of Minnesota Undergraduate Symposium, Minneapolis, MN. Apr. 20, 2017
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