Characterization on the Copolymerization Resin between Bayberry (<i>Myrica rubra</i>) Tannin and Pre-Polymers of Conventional Urea–Formaldehyde Resin

Jinda Peng; Xinyi Chen; Jun Zhang; Hisham Essawy; Guanben Du; Xiaojian Zhou

doi:10.3390/f13040624

Forests (Apr 2022)

Characterization on the Copolymerization Resin between Bayberry (<i>Myrica rubra</i>) Tannin and Pre-Polymers of Conventional Urea–Formaldehyde Resin

Jinda Peng,
Xinyi Chen,
Jun Zhang,
Hisham Essawy,
Guanben Du,
Xiaojian Zhou

Affiliations

Jinda Peng: Yunnan Provincial Key Laboratory of Wood Adhesives and Glued Products, Southwest Forestry University, Kunming 650224, China
Xinyi Chen: Yunnan Provincial Key Laboratory of Wood Adhesives and Glued Products, Southwest Forestry University, Kunming 650224, China
Jun Zhang: Key Laboratory for Forest Resources Conservation and Utilisation in the Southwest Mountains of China, Southwest Forestry University, Ministry of Education, Kunming 650224, China
Hisham Essawy: National Research Centre, Department of Polymers and Pigments, Cairo 12622, Egypt
Guanben Du: Yunnan Provincial Key Laboratory of Wood Adhesives and Glued Products, Southwest Forestry University, Kunming 650224, China
Xiaojian Zhou: Yunnan Provincial Key Laboratory of Wood Adhesives and Glued Products, Southwest Forestry University, Kunming 650224, China

DOI: https://doi.org/10.3390/f13040624
Journal volume & issue: Vol. 13, no. 4
p. 624

Abstract

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By focusing on the disadvantages of weak water resistance and high formaldehyde emission of urea–formaldehyde resin (UF), this research provides a new method to overcome these shortages of UF resin by using tannin for partial substitution of urea. Furthermore, plasma pretreatment of wood was introduced to strengthen the bonding performance of plywood. The investigation of the chemical structure of UF resin and tannin–urea–formaldehyde resin (TUF) were performed with Fourier transform infrared spectroscopy (FT-IR) and solid-state 13C nuclear magnetic resonance (13C NMR). The results of investigations confirmed the joining of tannin into the resin structure, which may enhance structural rigidity of TUF adhesives and improve hydrolysis stability. Then, thermal performance of UF resin and TUF resins were tested by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The DSC results indicated that the curing temperature did not change significantly. However, the TG analysis showed that the thermal stability of TUF resin was considerably improved. In bonding performance test, tannin–urea–formaldehyde resin (TUF) revealed an excellent water resistance, comparable to UF resin and can fulfill the standard requirement for plywood (Type II according to the Norm GB/T 17657-2013). It is interesting that the shear strength of wood specimens, bonded with TUF6 resin, after low-pressure cold plasma equipment (CLP plasma) and jet type atmospheric low-temperature plasma (JTLP plasma) treatment, reached 0.80 MPa and 0.85 MPa, respectively, after being soaked in boiling water for 3 h. In addition, most of the bonded plywood samples with TUF resin exhibited a lower formaldehyde emission, especially those prepared at 70 °C and 1.5 h, in which the formaldehyde emission amount could be reduced by approximately 39%.

Published in Forests

ISSN: 1999-4907 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Science: Botany: Plant ecology
Website: http://www.mdpi.com/journal/forests/

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