Open Access

ARTICLE

Synthetic Process of Bio-Based Phenol Formaldehyde Adhesive Derived from Demethylated Wheat Straw Alkali Lignin and Its Curing Behavior

by Yan Song^1,2, Zhixin Wang³, Xin Zhang⁴, Rong Zhang¹, Jinchun Li^1,2,*

1 Faculty of Materials Science & Engineering, Changzhou University, Changzhou, 213164, China
2 Jiangsu Key Laboratory of Environmentally Friendly Polymeric Materials, School of Materials Science and Engineering, Changzhou University, Changzhou, 213164, China
3 Organization Department of the Party Committee, Changshu Institute of Technology, Changshu, 215500, China
4 School of Petrochemical Engineering, Changzhou University, Changzhou, 213164, China

* Corresponding Author: Jinchun Li. Email:

(This article belongs to the Special Issue: Renewable and Biosourced Adhesives)

Journal of Renewable Materials 2021, 9(5), 943-957. https://doi.org/10.32604/jrm.2021.014131

Received 03 September 2020; Accepted 06 October 2020; Issue published 20 February 2021

Abstract

Lignin is a natural biopolymer with a complex three-dimensional network, commercially obtained from waste liquid of paper pulp and bioethanol production, and could be a candidate for preparation of environment-friendly bio-based polyphenol material. In the present work, the demethylated wheat straw alkali lignin (D-Lig), prepared by demethylation of wheat straw alkali lignin (Lig) using an in-situ generated Lewis acid, was used to synthesize bio-based phenol formaldehyde resin adhesive (D-LPF) applied in plywood. Effects of synthetic process’s factors, including lignin substitution for phenol, NaOH concentration and molar ratio of formaldehyde to phenol, on the bonding strength and free formaldehyde content of D-LPF were investigated in detail, and the optimum synthetic process of D-LPF was obtained as following: Lignin substitution for phenol 60%, NaOH concentration 5.0% and molar ratio of formaldehyde to phenol 2.0, and under the optimum reaction condition, the D-LPF presented lower free formaldehyde content (0.18%) and higher bonding strength (2.19 MPa), which was better than those of containing-lignin phenol formaldehyde resin adhesive(LPF). Additionally, the curing behavior of the adhesive was studied by differential scanning calorimetry (DSC) combined with gel time. It can be obtained that D-LPF resin adhesive had the shortest gel time, and fastest curing rate, compared with those of PF and L-PF resin adhesives. The curing kinetics data was fitted well by Kissinger model using non-isothermal DSC method, and the average activation energy value was 85.3 kJ/mol, slightly higher than that of commercial PF resin, while lower than that of LPF (90.2 kJ/mol). Finally, based on the analytical results of high temperature fourier transform infrared spectroscopy (FTIR), a possible curing mechanism of D-LPF was proposed.

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