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Polymers 2018, 10(6), 651; https://doi.org/10.3390/polym10060651

Effects of Sulfuric Acid on the Curing Behavior and Bonding Performance of Tannin–Sucrose Adhesive

1
Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, China
2
College of Furnishings and Industrial Design, Nanjing Forestry University, Nanjing 210037, China
3
College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
4
Laboratory of Sustainable Materials, Research Institute for Sustainable Humanosphere, Kyoto Univeersity, Gokasho, Uji, Kyoto 611-0011, Japan
5
College of Material Science and Engineering, Nanjing Forestry University, Nanjing 210037, China
*
Authors to whom correspondence should be addressed.
Received: 12 May 2018 / Revised: 8 June 2018 / Accepted: 8 June 2018 / Published: 11 June 2018
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Abstract

The development of biomaterials-based adhesives is one of the main research directions for the wood-based material industry. In previous research, tannin and sucrose were used as adhesive to manufacture particleboard. However, the reaction conditions need to be optimized. In this study, sulfuric acid was added to the tannin–sucrose adhesive as a catalyst to improve the curing process. Thermal analysis, insoluble mass proportion, FT-IR, and solid state 13C NMR were used to investigate the effects of sulfuric acid on the curing behavior of tannin and sucrose. Thermal analysis showed weight loss and endotherm temperature reduced from 205 and 215 to 136 and 138 °C, respectively, by adding sulfuric acid. In case of the adhesive with pH = 1.0, the insoluble mass proportion achieved 81% at 160 °C, which was higher than the reference at 220 °C. FT-IR analysis of the uncured adhesives showed that adding sulfuric acid leads to hydrolysis of sucrose; then, glucose and fructose converted to 5-hydroxymehthylfurfural (HMF) and levulinic acid. Dimethylene ether bridges were observed by FT-IR analysis of the cured adhesives. The results of solid state 13C NMR spectrum indicated that 5-HMF participated in the curing process and formed methylene bridges with the C8 position of the resorcinol A-rings of tannin, whereas dimethylene ether bridges were detected as a major chemical chain of the polymer. Lab particleboards were produced using 20 wt % resin content at 180 °C and 10 min press time; the tannin–sucrose adhesive modified with sulfuric acid to pH = 1.0 exhibited better performance than the unmodified tannin–sucrose adhesive; the properties of the boards fulfilled the requirement of Japanese Industrial Standard (JIS) A5908 type 15. View Full-Text
Keywords: natural adhesive; tannin; sucrose; sulfuric acid catalyst; curing behavior; particleboard natural adhesive; tannin; sucrose; sulfuric acid catalyst; curing behavior; particleboard
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Zhao, Z.; Miao, Y.; Yang, Z.; Wang, H.; Sang, R.; Fu, Y.; Huang, C.; Wu, Z.; Zhang, M.; Sun, S.; Umemura, K.; Yong, Q. Effects of Sulfuric Acid on the Curing Behavior and Bonding Performance of Tannin–Sucrose Adhesive. Polymers 2018, 10, 651.

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