作者机构:
[何啸宇; 左迎峰; 吴义强] College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China;Key Laboratory of Bio-Based Material Science and Technology, Northeast Forestry University, Ministry of Education Harbin, 150040, China;[张彦华; 顾继友] Key Laboratory of Bio-Based Material Science and Technology, Northeast Forestry University, Ministry of Education Harbin150040, China
通讯机构:
[Wu, Y.] C;College of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, China
期刊:
Wood Science and Technology,2018年52(4):971-985 ISSN:0043-7719
通讯作者:
Wu, Yiqiang
作者机构:
[Wu, Yiqiang; Guo, Xin] Cent South Univ Forestry & Technol, Coll Mat Sci & Engn, Changsha 410004, Hunan, Peoples R China.;[Guo, Xin] Cent South Univ Forestry & Technol, Coll Sci, Changsha 410004, Hunan, Peoples R China.;[Yan, Ning] Univ Toronto, Fac Forestry, 33 Willcocks St, Toronto, ON M5S 3B3, Canada.
通讯机构:
[Wu, Yiqiang] C;Cent South Univ Forestry & Technol, Coll Mat Sci & Engn, Changsha 410004, Hunan, Peoples R China.
摘要:
Heat modification is an effective method of reducing the hygroscopicity of wood. To gain a detailed understanding of water adsorption mechanism of heat-treated wood, the molecular interaction between the adsorbed water and heat-treated wood was studied via micro-FTIR spectroscopy. The micro-FTIR spectra of heat-treated wood exhibited a typical change in the chemical groups resulting from the heat treatment. In addition, the micro-FTIR spectra at different relative humidity levels confirmed the chemical sites at which the heat-treated wood adsorbed the water. A component band analysis of these difference spectra revealed three component peaks that were assigned to strongly, moderately, and weakly hydrogen-bonded water, respectively. Based on this variation of these three types of adsorbed water, the water adsorption process of heat-treated wood was divided into three different sections. Furthermore, the structure of the water adsorbed in these three sections was demonstrated. The results of this study provide a valuable insight into the state of water present in heat-treated wood.
摘要:
In this work, we applied a fast and simple method to synthesize cellulose nanocrystal (CNC) aerogels, via a hydrothermal strategy followed by freeze drying. The characteristics and morphology of the obtained CNC-g-AA aerogels were affected by the hydrothermal treatment time, volume of added AA (acrylic acid), and the mass fraction of the CNCs. The formation mechanism of the aerogels involved free radical graft copolymerization of AA and CNCs with the cross-linker N,N′-methylene bis(acrylamide) (MBA) during the hydrothermal process. The swelling ratio of the CNC-g-AA aerogels was as high as 495:1, which is considerably greater than that of other polysaccharide-g-AA aerogels systems. Moreover, the CNC-g-AA aerogels exhibited an excellent methyl blue (MB) adsorption capacity and the ability to undergo rapid desorption/regeneration. The maximum adsorption capacity of the CNC-g-AA aerogels for MB was greater than 400 mg/g. Excellent regeneration performance further indicates the promise of our CNC-g-AA aerogels as an adsorbent for applications in environmental remediation.
摘要:
Urea-formaldehyde (UF) resin is one of the most widely used adhesives in wood-based composites. The major concerns of the resin utilization are free formaldehyde release and poor water resistance. In this study, based on life cycle assessment (LCA) analysis, a “greener” adhesive composed of UF resin and cottonseed meal was successfully prepared via a common synthetic process of pure UF resins. The raw materials (urea and formaldehyde) of UF resins were replaced by cottonseed meal with up to 40% on weight basis. The effect of the cottonseed meal on the rheological property, mechanical strength, chemical structure, thermal stability, and glue line features of these “greener” adhesives was investigated. The adhesive showed an improved mechanical strength as compared to pure UF resins in the tensile shear strength of bonded wood specimens, especially on the water soaked strength. It also showed similar chemical structures, thermal stabilities, and even better rheological properties than pure UF resins. Cottonseed meal resulted in good dispersions in these adhesives with up to 30% portion. It acted as a reinforcement for the adhesive other than a filler or an additive. This “greener” adhesive improved the performance of pure UF resins while retained its outstanding features, suggesting the feasibility of using it as UF resins in current manufacturing lines for wood-based composites is there.
摘要:
Cellulose nanofibrils (CNFs), disintegrated from natural fibers, are promising alternatives in wastewater purification for the porous structure and numerous hydroxyls. The pristine CNFs aerogel has limited mechanical strength and are vulnerable to collapse when exposed to water. In this work, eco-friendly and recycled CNFs aerogel adsorbents were successfully prepared using cellulose nanofibrils (CNFs), which cross-linked by poly(vinyl alcohol) (PVA) and acrylic acid (AA). The combination of PVA and AA endowed CNFs aerogel strong three-dimensional porous structure and desirable adsorption properties. The heavy metal ions were adsorbed on the CNFs-PVA-AA (CPA) adsorbents efficiently and the maximum adsorption capacities for Cu2+ and Pb2+ approached 30.0 mg/g and 131.5 mg/g, respectively. The CPA adsorbent also showed excellent reusability and their adsorption capacities maintained 89% and 88% for Cu2+ and Pb2+ after 5 repeated uses. The adsorption of these heavy metal ions were confirmed to follow pseudo-second-order kinetic and Langmuir isotherm model. The functions of C = O and -OH were the major adsorption sites. Chemical adsorption combined with the porous physical adsorption made the CPA to be excellent adsorbent for the removal of heavy metal ions in wastewater.
摘要:
Although hydrogel electrolytes have attracted considerable attentions due to high water retention and low leakage, their vulnerability and low conductivity still pose challenges in large-scale applications. In this work, a mechanically strong and highly conductive poly (acrylic acid) (PAA) electrolyte reinforced by cellulose nanofibrils (CNFs) is developed via versatile blending followed by polymerization. As a result of physical entanglement and hydrogen bonding, the mechanical strength of the PAA electrolyte is enhanced from 0.656 to 1.875 MPa at a CNF loading of 3 wt%, and the dimensional swelling is suppressed to half of its original level. The ionic conductivity of the composite electrolyte is improved by 100% due to excellent ion-transfer paths created by the hydroxyl groups exposed on the surfaces of CNFs. Furthermore, the CNF/PAAs exhibit preferable elasticity and flexibility with the maximum elongation at break reaching greater than 600%. These electrolytes are able to maintain the initial ionic conductivity even after being stretched to 100% elongation for 500 circles. After assembling with an air cathode and an aluminum anode, the as-prepared Al-air battery show good discharging performance, demonstrating promises for applications in portable and flexible electronic devices. (c) 2018 Elsevier Ltd. All rights reserved.
作者机构:
[邓凌峰; Qin, Yu-Kun; 彭辉艳; 连晓辉; 吴义强] School of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha;410004, China;[邓凌峰; Qin, Yu-Kun; 彭辉艳; 连晓辉; 吴义强] 410004, China
通讯机构:
[Deng, L.-F.] S;School of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, China
摘要:
In situ micro-Fourier transform infrared (FTIR) spectra of a typical cellulose nanofiber (CNF) film (i.e., CNF with cellulose I structure) were collected within the full relative humidity (RH) range from 0% to 90%. Red shifts of two peaks at 1036 and 1204cm(-1) and the variation of different spectra indicated the chemical adsorption sites for adsorbed water. From component band analysis of the spectral range of 2900-3700cm(-1), three component peaks at 3293, 3397, and 3543cm(-1) were due to strongly, moderately, and weakly hydrogen-bonded water. The signatures of these three types of hydrogen-bonded water were then observed to rise with an increase in RH. Based on growth regularities of these three types of hydrogen-bonded water, the water adsorption process of CNF film was divided into three stages; most of the water absorbed in these three stages was demonstrated to be CNFHOHCNF, WATERHOHWATER, and five-molecule tetrahedral structure, respectively.