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  4. Tuning Polyphenols for Thermosetting Wood Adhesives: Class ‘A1’ Non-Isocyanate Polyurethanes from Condensed Tannins
 
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June 2025
Journal Article
Title

Tuning Polyphenols for Thermosetting Wood Adhesives: Class ‘A1’ Non-Isocyanate Polyurethanes from Condensed Tannins

Abstract
This study aimed to develop nonisocyanate polyurethane (NIPU) wood adhesives from Quebracho condensed tannins (CT). Following the carbonation of CTs with dimethyl carbonate, condensation with multifunctional amines delivered two distinct NIPU formulations: TANIPU-DA when hexamethylene diamine (DA) was used and TANIPU-DA-TD when successively using DA and hexamethylenetetramine (TD). For both TANIPUs, urethane formation was confirmed with Fourier-transform infrared (FTIR), viscosity measurements, and size exclusion chromatography (SEC). Gelation and vitrification were evidenced with DMA in the 120-150 °C and the 160-220 °C ranges, respectively. TANIPU-DA-TD wood-bonded assemblies reached a lap shear strength exceeding 10 N/mm2, qualifying TANIPU-DA-TD as a class ‘A1’ wood adhesive according to European standards. TANIPU-DA and TANIPU-DA-TD achieved relatively high wet strengths of 2.5 ± 1.3 and 3.8 ± 1.2 N/mm2, respectively. This study demonstrates that tannin-based NIPUs can meet the dry bonding strength requirements for wood adhesives, suggesting a viable, more environmentally friendly alternative to traditional formaldehyde- and isocyanate-based wood adhesives.
Author(s)
Sivasankarapillai, Gopakumar
Universität Freiburg
Arsène , Bikoro Bi Athomo
Universität Freiburg
Schmiedl, Detlef  
Fraunhofer-Institut für Chemische Technologie ICT  
Pizzi, Antonio
Laborie, Marie-Pierre
Journal
Journal of agricultural and food chemistry  
Open Access
File(s)
Download (4.99 MB)
Rights
CC BY 4.0: Creative Commons Attribution
DOI
10.1021/acs.jafc.5c02453
10.24406/publica-4848
Additional link
Full text
Language
English
Fraunhofer-Institut für Chemische Technologie ICT  
Keyword(s)
  • adhesive class

  • condensed tannins

  • derivatization

  • nonisocyanate polyurethane

  • polycondensation

  • shear bond strength

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