Development of green adhesives for fiberboard manufacturing, using okoume bark tannins and hexamine – characterization by ¹H NMR, TMA, TGA and DSC analysis

Abstract

Okoume wood is widely known for having an excellent unwinding capability. This hardwood species was used for tannin extraction in order to formulate for the first time tropical hardwood, an eco-friendly adhesive. The tannins were extracted from the bark, then mixed to hexamine for hardening. The system obtained showed high values of the elasticity modulus (3681 MPa; 3752 M Pa; 3894 MPa; 3971 MPa) according to the thermomechanical analysis. A good cohesive index of ≥80% and ≥60% based on standard NF EN 314-1 and NF EN 314-2. ¹H NMR analysis was used to understand the reactivity between Okoume tannins and hexamine and also to compare the reactivity with hexamine of tannins extracted from different Okoume barks. Thermal stability control revealed advanced thermal degradation of the adhesive system.

Keywords:

• Adhesive
• bio-based
• hexamine
• tannins
• Okoume

Acknowledgments

We gratefully acknowledge Société Equatoriale de Déroulage (SED) for its generous collaboration in providing wood material.

Disclosure statement

The authors declare that this work is no in conflicts with any interest.

Additional information

Funding

This work was supported by the Gabonese National Agency of Fellowships (ANBG) of the Gabonese Government under the PhD grant program [grant number 1405035]. We thank University de Pau et des Pays de l’Adour (UPPA) for the material support and financial support offered by the [ANR-10-EQPX-16] Xyloforest (Xylomat; Mont-de-Marsan).