Published by De Gruyter

Volume 75 Issue 3

Issue of Holzforschung

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Contents
Journal Overview

Publicly Available March 4, 2021

Review

August 17, 2020

A review on life cycle assessments of thermally modified wood

Kévin Candelier, Janka Dibdiakova

Page range: 199-224

Abstract

This review compiles various literature studies on the environmental impacts associated with the processes of thermal modification of wood. In wood preservation field, the wood modification by heat is considered as an ecofriendly process due to the absence of any additional chemicals. However, it is challenging to find proper scientific and industrial data that support this aspect. There are still very few complete studies on the life cycle assessment (LCA) and even less studies on the environmental impacts related to wood heat treatment processes whether on a laboratory or on an industrial scales. This comprehensive review on environmental impact assessment emphasizes environmental categories such as dwindling of natural resources, cumulative energy intake, gaseous, solid and liquid emissions occurred by the thermal-treated wood industry. All literature-based data were collected for every single step of the process of wood thermal modification like resources, treatment process, transport and distribution, uses and end of life of treated wood products.

Original articles

Publicly Available August 27, 2020

Mechanisms of liquid imbibition in Douglas-fir inferred from ¹H nuclear magnetic resonance methods

Dang Mao Nguyen, Sabine Care, Denis Courtier-Murias, Meng Zhou, Philippe Coussot

Page range: 225-236

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Abstract

This study aims at identifying the mechanisms of oil and water imbibition in heartwood and sapwood of Douglas-fir through a combination of original experiments with magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) relaxation measurements for oil and free water, and deformation measurements for bound water. Experiments by weighing are performed to verify whether the imbibition process is also consistent with Washburn law. All the results are discussed taking into account the structure of wood (tubular tracheids closed at their tips, but possibly connected to each other via open pits on the side faces) and the preparation of samples. The observation of relatively fast oil flow imbibition confirms that sapwood exhibits a connected hydraulic network through which a liquid can a priori flow and climb along the structure. However, the spontaneous water imbibition is strongly damped by its very poor wetting when in contact with cell-walls only partially saturated with bound water, so that the diffusion of bound water control the uptake dynamics. However, due to preferentially closed pits, the heartwood does not exhibit a continuous hydraulic network and water essentially penetrates into wood by diffusion through the cell walls.

Open Access August 17, 2020

Evaluating internal condition of hardwood logs based on AR-minimum entropy deconvolution combined with wavelet based spectral kurtosis approach

Feng Xu, Yunfei Liu, Xiping Wang, Brian K. Brashaw, Lon A. Yeary, Robert J. Ross

Page range: 237-249

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Abstract

The aim of this research was to explore the potential of acoustic impact test to evaluate the condition of hardwood logs in regard to internal decay, void, crack and defect ratio using an acoustic signal separation and enhancement algorithm. Longitudinal acoustic signals were obtained from 15 logs of four hardwood species through acoustic impact testing. The defect components were separated from the acoustic response signals and enhanced based on the autoregressive minimum entropy deconvolution (AR-MED) method, and from which the kurtosis was derived and used as the global feature parameter for evaluating the internal condition of logs. Compared with the acoustic velocity obtained directly from the original signal, the kurtosis was deemed to be a more powerful predictor of log defect ratio with higher coefficient of determination ( R 2 = 0.89) and was not affected by log species. To identify the type of defects, a complex Morlet wavelet-based spectral kurtosis (SK) method was proposed. The research results indicated that the SK can not only determine the type and primary and secondary major defects, but also be able to identify those that were not detectable by global acoustic parameters.

August 19, 2020

Comprehensive study on the effects of process parameters of alkaline thermal pretreatment followed by thermomechanical extrusion in sugar liberation from Eucalyptus grandis wood

Pablo Doménech, Paloma Manzanares, Cristina Álvarez, Mercedes Ballesteros, Aleta Duque

Page range: 250-259

Abstract

A combination of alkaline thermal pretreatment followed by thermomechanical extrusion was studied as a novel sequential pretreatment process for an effective breakdown of the lignocellulosic structure of Eucalyptus grandis wood (EW). The first step was studied by analysing the influence of two factors: the NaOH-to-dry biomass ratio or NaOH loading (NaOH/DM) and the liquid-to-solid ratio (L/S). Optimization of these two parameters provided good results in terms of enzymatic hydrolysis at 5% (w w −1 ) solids loading, obtaining a total sugar concentration of 24.9 g L −1 and a total sugar production of 36.9 g 100 g −1 raw EW after pretreating the biomass at 20% NaOH/DM and L/S = 1/1. The second step of extrusion, when followed by a final washing step, provided a significant increase in glucose and xylose production when working at 10% NaOH/DM. For a soda loading of 20%, there was a clear improvement in sugars conversion yield after extrusion and washing: 71% for glucan conversion and 89% for xylan.

August 17, 2020

Influence of thermal modification and extraction techniques on yield, antioxidant capacity and phytochemical profile of chestnut (Castanea sativa Mill.) wood

Immacolata Faraone, Daniela Russo, Maurizio D’Auria, Maria Roberta Bruno, Paola Cetera, Luigi Todaro, Luigi Milella

Page range: 260-268

Abstract

Numerous investigations on the antioxidant properties of different plant tissue extracts are available in literature, but few studies on the effect of thermally modified wood on secondary metabolites were carried out up to now. This study highlights the influence of the thermal modification of Castanea sativa Mill. wood on total content of antioxidant compounds and consequently on its antioxidant activity. In addition, a chemical profile by Gas Chromatography–Mass Spectrometry (GC–MS) of the extractives was carried out. Wood of chestnut, thermally modified at 180 °C for 3 h, was used to obtain wood meal which was subjected to different extraction techniques, as maceration extraction (ME), ultrasound assisted extraction (UAE) and accelerated solvent extraction (ASE). The total content of principal antioxidant compounds, such as polyphenols, flavonoids and tannins, as well as the evaluation of antioxidant capacity by using different in vitro assays were determined. Relative Antioxidant Capacity Index (RACI), which is used to compare all antioxidant parameters, has also been applied. The study demonstrated a positive influence on chemical compounds present in C. sativa Mill wood originating from the thermal modification process. Thus, is possible to consider thermal modification as a promising strategy to improve the antioxidant activity of chestnut wood extractives.

September 4, 2020

Enhancing the mechanical and water resistance performances of bamboo particle reinforced polypropylene composite through cell separation

Dan Ren, Xuexia Zhang, Zixuan Yu, Hankun Wang, Yan Yu

Page range: 269-280

Abstract

It is frequently observed that bamboo particle composites (BPCs) do not show higher mechanical performances than the corresponding wood particles composites (WPCs), although bulk bamboo is much stronger than wood in mechanical performances. Herein this phenomenon was demonstrated from the cell compositions in the applied bamboo particles. To address that, a simple method to physically separate bamboo fibers (BFs) and bamboo parenchyma cells (BPs) from a bamboo particle mixture was developed. Polypropylene (PP) composites with pure BFs, BPs, a mixture of BFs and BPs (BFs + BPs), wood particles (WPs) as fillers were prepared. The flexural and dynamic mechanical properties, water absorption, and thermal properties were determined. The BF/PP composites showed the best mechanical performances (MOR at 35 MPa, MOE at 2.4 GPa), followed by WP/PP, (BF + BP)/PP, and BP/PP. They also exhibited the lowest water absorption and thickness swelling. Little difference was found for the thermal decomposition properties. However, a lower activation energy of BF/PP compared with BP/PP implied an uneven dispersion of BFs and weaker interfacial interaction between BF and PP. The results suggest that the mechanical performances and water resistance of bamboo particle/polymer composites can be significantly improved through cell separation. However, interface modification should be applied if higher performances of BF/PP composites are required.

August 31, 2020

Decay, insect, and termite resistance of wood modified with epoxidized vegetable oils

Gaye Kose Demirel, Ali Temiz, Sabrina Palanti, Nasko Terziev

Page range: 281-287

Abstract

Samples of Scots pine sapwood were treated with epoxidized linseed and soybean oils to improve decay, insect and termite resistance of wood. Non-epoxidized (raw) linseed and soybean oils were included as reference treatment in the study. In the epoxidation process, hydrogen peroxide was used to open double bounds, and acetic acid was added as a catalyst. Two retention levels, Ret A (80–140 kg m −3 ) and Ret B (170–270 kg m −3 ), two impregnation methods (full cell and empty cell) and emulsion technique were used. Samples treated with epoxidized oils had significantly lower mass losses than untreated samples while epoxidized oils showed higher mass losses than unepoxidized oils for Coniophora puteana and Trametes versicolor according to EN 113 for decay test. By adding boron, fungicidal properties were introduced to the treatment. All the vegetable oils showed 100% the mortality rate against larvae of Hylotrupes bajulus according to EN 47. Moreover, leached wood samples treated with oils also showed 100% larvae mortality. Additionally, termite testing based on EN 117 revealed 100% Reticulitermes lucifugus mortality for all leached oil treated samples.

August 10, 2020

Silver electrochemical treatment of bamboo and its effect on decay fungi

Zehui Ju, Qian He, Tianyi Zhan, Haiyang Zhang, Lu Hong, Suxia Li, Liangsong Chen, Xiaoning Lu

Page range: 288-301

Abstract

In this study, a simple and effective method for preparing bamboo with high fungal resistance was first proposed. Flattened moso bamboo ( Phyllostachys pubescens ), which is a perishable species, was connected to a silver plate and exposed to a high-voltage electrostatic field (HEVF). The method was based on HEVF excitation of a silver plate to produce silver ions and facilitate in situ impregnation of bamboo. Silver ions were present in the forms of Ag(0), Ag(I) and Ag(III) and reacted with bamboo functional groups under HVEF treatment. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis showed that compared to those of untreated bamboo, the O/C ratio and OH content of treated bamboo were lower, the number of CHO groups decreased, the number of CO groups increased, and silver interacted with the hemicellulose and lignin of bamboo. The concentration of silver ions increased with increasing treatment time and voltage. The silver ions were nanocrystalline, and the average particle size was 50 nm. The mass loss and moisture content of the treated bamboo decreased significantly after exposure to decay fungi. Therefore, in situ impregnation of silver with HVEF was a simple and effective method to improve the durability of bamboo materials.

About this journal

Objective
Holzforschung (HF) is an international scholarly journal that publishes cutting-edge research on the biology, chemistry, physics and technology of wood and wood components. High quality papers about biotechnology and tree genetics are also welcome. Rated year after year as one of the top scientific journals in the category of Pulp and Paper (ISI Journal Citation Index), Holzforschung represents innovative, high quality basic and applied research. The German title reflects the journal's origins in a long scientific tradition, but all articles are published in English to stimulate and promote cooperation between experts all over the world. Ahead-of-print publishing ensures fastest possible knowledge transfer.

Topics

Biology, chemistry, physics and technology of wood and wood components
Biotechnology and tree genetics

Article formats
Original articles, Reviews, Short notes

> Information on submission process

Volume 75 Issue 3

Issue of Holzforschung

Frontmatter

A review on life cycle assessments of thermally modified wood

Abstract

Mechanisms of liquid imbibition in Douglas-fir inferred from 1H nuclear magnetic resonance methods

Abstract

Evaluating internal condition of hardwood logs based on AR-minimum entropy deconvolution combined with wavelet based spectral kurtosis approach

Abstract

Comprehensive study on the effects of process parameters of alkaline thermal pretreatment followed by thermomechanical extrusion in sugar liberation from Eucalyptus grandis wood

Abstract

Influence of thermal modification and extraction techniques on yield, antioxidant capacity and phytochemical profile of chestnut (Castanea sativa Mill.) wood

Abstract

Enhancing the mechanical and water resistance performances of bamboo particle reinforced polypropylene composite through cell separation

Abstract

Decay, insect, and termite resistance of wood modified with epoxidized vegetable oils

Abstract

Silver electrochemical treatment of bamboo and its effect on decay fungi

Abstract

Mechanisms of liquid imbibition in Douglas-fir inferred from ¹H nuclear magnetic resonance methods