Assessment of Structural Differences between Water-Extracted and Non-Extracted Hydro-Thermally Treated Spruce Wood by NIR Spectroscopy

Carmen-Mihaela Popescu,Takuma Genkawa,Nanami Zeniya,Kaoru Endo,Eiichi Obataya,Miyuki Matsuo-Ueda

doi:10.3390/f12121689

Carmen-Mihaela Popescu, Takuma Genkawa + Show 4 more

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https://doi.org/10.3390/f12121689

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Journal: Forests	Publication Date: Dec 2, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: University of Tsukuba, Nagoya University

Abstract

Sitka spruce wood samples were subjected to different conditions of hydro-thermal treatment by varying the relative humidity (RH) and period of exposure at a constant temperature of 120 °C. Near infrared (NIR) spectroscopy, principal component analysis (PCA) and two dimensional correlation spectroscopy (2D-COS) were employed to examine the structural changes which occur in the wood samples during the applied treatment conditions and to quantify the differences between non-extracted and water-extracted wood specimens after the treatment. Modifications were dependent on the amount of water molecules present the medium and also on treatment time. Higher variations were observed for samples treated at higher RH values and for longer periods. At the same time, it was also observed that during the hydro-thermal treatment a high amount of extractives remain in the wood structure, extractives which vary in quantity and composition. PCA and 2D-COS made it possible to discriminate modifications in the wood samples according to treatment time and relative humidity. Non-extracted and water-extracted samples were also examined to identify the sequential order of band modification.

Highlights

Wood, a natural composite material, is used in many applications, but due to its structural features and depending on the environmental conditions, it can be degraded
The modifications induced by the hydro-thermal treatments in the structure and content of non-extracted and waterextracted Sitka spruce wood are reflected in the Near infrared (NIR) bands intensities, maxima and width
Sitka spruce wood samples were treated at 120 ◦ C using different values (0, 35, 60, 80 and 91%) of relative humidity during treatment

Summary

Introduction

A natural composite material, is used in many applications, but due to its structural features and depending on the environmental conditions (humidity, temperature and biological agents), it can be degraded. In order to understand wood degradation mechanisms taking place under natural environmental conditions (during material service life), many researchers have simulated accelerated ageing by using biodegradation factors, such as soft, brown and white rot fungi or termites [4,5,6]; thermal and hydro-thermal ageing [7,8,9] or weathering and UV light exposure [10,11]. As close as possible, natural ageing conditions, a certain amount of water should be added in the degradation medium, because natural ageing takes place at moderate relative humidity.

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