Phenol-formaldehyde resins with suitable bonding strength synthesized from "less-reactive" hardwood lignin fractions
No Thumbnail Available
Access rights
openAccess
URL
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This publication is imported from Aalto University research portal.
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
Other link related to publication (opens in new window)
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
Other link related to publication (opens in new window)
Date
2020-02-01
Department
Major/Subject
Mcode
Degree programme
Language
en
Pages
Series
Holzforschung
Abstract
The substitution of phenol by lignin in phenol-formaldehyde (PF) resins is one of the most promising end uses of lignin valorization. Lignin from grasses and softwood has been the focus of the studies in this field as they present a higher number of theoretical reactive sites for resin synthesis. Herein we examined the composition and chemical reactivity of "less-reactive" hardwood lignin fractions and their performance in PF resins, synthesized by substituting 50 wt% of the phenol with lignin. Before resin synthesis, the samples were hydroxymethylated and the maximum formaldehyde consumption was recorded. By doing so, we observed that hardwood fractions consumed formaldehyde close to the theoretical calculation, whereas the reference softwood lignin consumed only about of the theoretical value. In the resin synthesis, we added formaldehyde to the formulation according to the measured maximum formaldehyde consumption. Thus, low values of free formaldehyde in lignin-PF (LPF) resins were achieved (<0.23%). Moreover, the resin bonding strength displayed similar performance irrespective of whether the LPF resins were made with softwood or hardwood lignin (range of 3.4-4.8 N mm-2 at 150°C and 45-480 s of press time). Furthermore, we concluded that hardwood kraft lignins present no disadvantage compared to softwood lignins in PF resin applications, which have significant practical implications.Description
Keywords
formaldehyde consumption, kraft, phenolic resins, reactive sites, technical lignin
Other note
Citation
Lourençon, T V, Alakurtti, S, Virtanen, T, Jääskeläinen, A S, Liitiä, T, Hughes, M, Magalhães, W L E, Muniz, G I B & Tamminen, T 2020, ' Phenol-formaldehyde resins with suitable bonding strength synthesized from "less-reactive" hardwood lignin fractions ', Holzforschung, vol. 74, no. 2, pp. 175–183 . https://doi.org/10.1515/hf-2018-0203