Abstract
Rubber wood utilization in Nigeria has become a viable alternative because of over-exploitation of more durable species. The use of rubber wood in its native form has some disadvantages including dimensional instability, low durability and susceptibility to weathering in outdoor uses. However, it may be improved through chemical modification such as acetylation. In this study, we revealed the effectiveness of acetylation on the protection of rubber wood against weathering in terms of weight loss (WL), colour change, lignin degradation, and mechanical properties. Acetylation was carried out using two different reaction times to achieve weight percent gains (WPG) of around 7% and 10%. Understanding of the effect of acetylation and subsequent weathering on mechanical properties was enabled by analysing wood chemistry with Fourier transform infrared (FTIR) analysis and Raman spectroscopy. The mechanical tests of weathered unmodified and acetylated rubber wood revealed a decrease of tensile stiffness of the unmodified samples as a function of weathering time, while stiffness was retained for the acetylated samples. Weathered unmodified samples showed a bi-phasic stress-strain pattern with a high strain at breakage indicating a slippage of fibres under stress due to degradation of the middle lamella. This was hardly visible for acetylated samples. Thus, acetylation was shown to be effective for protecting rubber wood used in outdoor conditions.
Acknowledgements
We acknowledge Mr. Kehinde Olonisakin for his efforts of organising the procurement of rubber tree harvested during the field work in Nigeria. The kind efforts of Adrian Wick, Bachtiar Erik, Thomas Schnider, and Philippe Grönquist are well appreciated for their assistance in the workshop for sample preparation and valuable discussions in the course of this study.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: S.O. Olaniran acknowledges the Swiss Government Excellence Scholarship through the Federal Commission for Scholarships for Foreign Students for the financial support provided for this doctoral study (Grant Number: 2015.0612).
Employment or leadership: None declared.
Honorarium: None declared.
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