The bond strength development of coconut wood in relation to its density variations

ABSTRACT

This study examines the influence of density variations in coconut palm wood (Cocos nucifera L.) on bond strength development using three types of adhesives: urea formaldehyde (UF), melamine urea formaldehyde (MUF), and polyvinyl-acetate (PVAc). A special testing device called Automated Bonding Evaluation System (ABES) was used to investigate the bond strength development between coconut veneers as a function of adhesive type, wood density (moisture content of 10%), pressing time, and bond-temperature development. Coconut wood density was shown to greatly affect the bond line. The bond strength of medium-density material (600–700 kg/m³) was lower than that of high-density material (900–1,000 kg/m³). Interestingly, the medium-density coconut veneers achieved higher bond strength with shorter pressing times, while the high-density coconut veneers reached better results with longer pressing times. Moreover, the bond strength improved by increasing the hot-pressing time resulting in higher bond-line temperatures. A comparison was made between coconut wood and beech wood for similar bonding parameters.

KEYWORDS:

• Coconut palm wood
• coconut veneer
• beech veneer
• adhesive bonding evaluation system (ABES)
• bond strength

Acknowledgements

The authors gratefully acknowledge the Institute of Wood Science, Universität Hamburg (UHH), and the German Federal Thünen Institute of Wood Research (TI) for the available research equipment and financial support. We would like to express our sincere thanks to Dr. Dieter Fink of Applikatio Freiburg, Dr. Ralph Lehnen (TI), Daniel Hasemann (UHH), and Barlas Oran (Karadeniz Technical University Trabzon, Turkey) for their valuable suggestions and support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

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Additional information

Funding

This work was supported by the Institute of Wood Science, University of Hamburg, Germany, and the German Federal Thuenen Institute of Wood Research, Germany.