Published by De Gruyter

Volume 75 Issue 9

Issue of Holzforschung

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Contents
Journal Overview

Publicly Available September 1, 2021

Original articles

March 15, 2021

Specific heat capacity of wood between −140 and 50 °C in dry and wet state

Martin Nopens, Uta Sazama, Andreas Krause, Michael Fröba

Page range: 779-785

Abstract

Specific heat capacity of wood is an important material property for fundamental research and timber technology. However, the existing database for heat capacity values is limited, especially for data below 0 °C. Therefore, the aim of this study was to investigate the specific heat capacity of wood with different moisture contents (dry, below and above fibre saturation) in lower temperature. Beech ( Fagus sylvatica ) and scots pine ( Pinus sylvestris ) were investigated via differential scanning calorimetry (DSC), equipped with a liquid nitrogen-cooling device, using the sapphire standard. Specific heat capacity for beech and pine were linear within the investigated temperature region. Values above 0 °C are in agreement with existing literature. Both species showed similar results. Based on the obtained results the specific heat capacity for bound water was calculated. The presented results are an important step for increasing the database of wood heat capacity. These findings enable future research for calculating heat-flux, diffusion and moisture transfer in wood.

February 15, 2021

Growth behavior of wood-destroying fungi in chemically modified wood: wood degradation and translocation of nitrogen compounds

Lukas Emmerich, Maja Bleckmann, Sarah Strohbusch, Christian Brischke, Susanne Bollmus, Holger Militz

Page range: 786-797

Abstract

Chemical wood modification has been used to modify wood and improve its decay resistance. However, the mode of protective action is still not fully understood. Occasionally, outdoor products made from chemically modified timber (CMT) show internal decay while their outer shell remains intact. Hence, it was hypothesized that wood decay fungi may grow through CMT without losing their capability to degrade non-modified wood. This study aimed at developing a laboratory test set-up to investigate (1) whether decay fungi grow through CMT and (2) retain their ability to degrade non-modified wood. Acetylated and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) treated wood were used in decay tests with modified ‘mantle specimens’ and untreated ‘core dowels’. It became evident that white rot ( Trametes versicolor ), brown rot ( Coniophora puteana ) and soft rot fungi can grow through CMT without losing their ability to degrade untreated wood. Consequently, full volume impregnation of wood with the modifying agent is required to achieve complete protection of wooden products. In decay tests with DMDHEU treated specimens, significant amounts of apparently non-fixated DMDHEU were translocated from modified mantle specimens to untreated wood cores. A diffusion-driven transport of nitrogen and DMDHEU seemed to be responsible for mass translocation during decay testing.

February 11, 2021

Characterisation of compound middle lamella isolated by a combination of wet-beating, sedimentation, and methanol dialysis

Yasuyuki Matsushita, Taichi Fukumura, Dan Aoki, Kazuhiko Fukushima

Page range: 798-805

Abstract

A simple method was developed to isolate the compound middle lamella (CML) in its natural state using wet-beating, sedimentation, and methanol dialysis. The isolated CML fraction was characterised. The CML was isolated in 2.0% yield from the mature wood of Ginkgo biloba . Scanning electron microscopy (SEM) images of the isolated CML fraction showed the presence of flake-like structures. However, some small amounts of secondary wall substance was observed. The lignin content of the CML fraction was approximately 45%. Thioacidolysis reactions with the isolated CML fraction revealed that the lignin β - O -4 structure was scarce in the isolated fraction and that numerous structures with two or more consecutive condensed-type bonds were present. Results from the solid-state carbon-13 nuclear magnetic resonance ( 13 C NMR) experiments indicated that the CML fraction had low crystallinity, indicating low cellulose content. Liquid-state NMR analysis of the lignin from the CML fraction revealed the absence of p -hydroxyphenyl (H) units.

Review

March 18, 2021

A review of lignin hydrogen peroxide oxidation chemistry with emphasis on aromatic aldehydes and acids

Ajinkya More, Thomas Elder, Zhihua Jiang

Page range: 806-823

Abstract

This review discusses the main factors that govern the oxidation processes of lignins into aromatic aldehydes and acids using hydrogen peroxide. Aromatic aldehydes and acids are produced in the oxidative degradation of lignin whereas mono and dicarboxylic acids are the main products. The stability of hydrogen peroxide under the reaction conditions is an important factor that needs to be addressed for selectively improving the yield of aromatic aldehydes. Hydrogen peroxide in the presence of heavy metal ions readily decomposes, leading to minor degradation of lignin. This degradation results in quinones which are highly reactive towards peroxide. Under these reaction conditions, the pH of the reaction medium defines the reaction mechanism and the product distribution. Under acidic conditions, hydrogen peroxide reacts electrophilically with electron rich aromatic and olefinic structures at comparatively higher temperatures. In contrast, under alkaline conditions it reacts nucleophilically with electron deficient carbonyl and conjugated carbonyl structures in lignin. The reaction pattern in the oxidation of lignin usually involves cleavage of the aromatic ring, the aliphatic side chain or other linkages which will be discussed in this review.

Original articles

Open Access April 13, 2021

Fibre development in an intensified mechanical pulping process

Christer Sandberg

Page range: 824-837

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Abstract

Mechanical pulp for printing paper can be produced with a process that involve much less equipment and that require much lower specific energy compared to conventional processes. Even though common evaluation methods, e.g. handsheet testing, have shown that the pulp quality is similar for the simplified and the conventional processes, it is not known how fibre properties, at the microscopic level, is developed with the simplified process. In this mill scale study, the fibre properties attained with an “intensified” mechanical pulping process, consisting of single stage high consistency double disc refining followed by two stage low consistency refining and no reject treatment was investigated. The simplified process was compared to a process with a reject system. The simplified process rendered fibres with higher degree of fibrillation, higher share of axial splits, lower fibre wall thickness but slightly lower length than the conventional process. The fibrillar fines size distribution of the two processes was different. The conventional process generated more of small fibrillar fines which probably explains the higher tensile index at given density for that process. The results show that it is possible to simplify the production process for mechanical pulp and reduce the specific energy with over 700 kWh/adt.

January 28, 2021

Tensile properties of finger-jointed lumber under high-temperature and oxygen-free conditions

Kong Yue, Feng Wang, Weidong Lu, Zhongqiu Tang, Zhangjing Chen, Weiqing Liu

Page range: 838-846

Abstract

A model for engineered wood was developed that considers the parallel-to-grain tensile strength of finger-jointed lumber at high temperatures relevant to fire conditions. The finger-jointed lumber was composed of Douglas fir, larch, and poplar wood with phenol-resorcinol-formaldehyde (PRF) as an adhesive. The tensile properties of the finger-jointed lumber were evaluated at high temperatures under oxygen-free conditions, i.e. in a nitrogen atmosphere. A combination of chemical and thermal-physical property analysis of the PRF adhesive and microscopic observations on the glueline was used to discuss the reduction of tensile strength of the parallel-to-grain finger-jointed lumber at variable temperature. The results show that the tensile strength of the finger-jointed lumber decreased linearly with increasing temperature. The parallel-to-grain tensile strength of the PRF finger-jointed samples at 20 and 280 °C were 84 and 5% of the tensile strength of the solid wood at 20 °C, respectively. The thermal-physical properties and scanning electron microscopy analysis revealed that the pyrolysis intensity of the PRF adhesive was lower than that of the wood at 220 °C or higher.

Open Access March 15, 2021

Predicting strength of Finnish birch veneers based on three different failure criteria

Maximilian Pramreiter, Sabine C. Bodner, Jozef Keckes, Alexander Stadlmann, Florian Feist, Georg Baumann, Emad Maawad, Ulrich Müller

Page range: 847-856

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Abstract

The use of wood in high-performance composites based on laminated veneer products, plywood or wood hybrid elements thereof requires accurate prediction of strength of each individual ply. Previous research has shown that one dominating factor influencing the strength of birch veneers is the fibre orientation. The present study investigates the validity of the failure criteria after Tsai-Hill, Hoffmann and Kollmann for thin birch veneers under tensile loading. The fibre orientation in- and out-of-plane was measured by means of wide-angle X-ray scattering. Tensile strength and threshold values were determined in laboratory experiments. Pearson correlation between the predicted strength and actual strength ranged from 0.836 up to 0.883. Best correlation ( r = 0.883) was achieved for Kollmann using a combined angle between in- and out-of-plane fibre orientation. It was shown that the failure criteria commonly used for manmade fibre reinforced composites are also applicable for thin birch veneers.

Open Access April 5, 2021

Non-fluorine surface modification of acetylated birch for improved water repellence

Haiyan Yin, Maziar Sedighi Moghaddam, Mikko Tuominen, Andra Dėdinaitė, Magnus Wålinder, Agne Swerin

Page range: 857-868

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Abstract

In this work, a non-fluorinated surface treatment, i.e., hydrophobized silicone nanofilaments, was applied on both birch and acetylated birch wood samples via a gas-phase based reaction. A superhydrophobic behavior was observed on both the surface-modified samples as revealed by the static water contact angles (CAs) greater than 160°, also valid for samples prepared with the shortest reaction time of 1 h. The dynamic wettability behavior of the samples was studied by a multicycle Wilhelmy plate method. The surface-modified acetylated birch exhibited a pronounced enhanced water resistance, resulting in very low water uptake of 3 ± 1 wt% after 100 cycles, which was not only about 29 and 5 times lower than that of the non-surface-modified birch and acetylated birch, respectively, but also three times lower than that of the surface-modified birch. Moreover, the aesthetic appearance of the acetylated wood was maintained as the surface modification only resulted in a small color change. This work shows the potential of preparing super water-repellent wood by non-fluorinated surface modification.

February 25, 2021

Ultrasonic cavitation driven fabrication of organic solvent free lignin/prochloraz nano capsules to promote resistance to photolysis and rain wash, and provide extended release performance

Jingtian Chen, Miao Wang, Yong Qian, Shanyuan Tan, Huan Wang, Mingsong Zhou, Xueqing Que

Page range: 869-877

Abstract

Lignin is a natural macromolecular sun blocker and provides an ideal protection material for pesticides that have poor photostability. In this study, alkali lignin/prochloraz capsules (AL-P) were prepared via one-pot ultrasonic cavitation. The results demonstrated that the produced AL-P were uniform spheres with sizes of 170–375 nm. The prochloraz encapsulation efficiency (EE) and loading capacity (LC) reached as high as 91.8 and 98.5%, respectively. Adding a small of surfactant reduced the size of the capsules, but both EE and LC were decreased. AL-P exhibited excellent extended release performance. The cumulative release of AL-P in the first 45 h was 76.1% and continuous release was maintained after 96 h. The resulting AL-P have improved photostability under UV irradiation radiation. Finally, AL-P capsules were sprayed on the mango leaves and bananas to act as preservatives, AL-P capsules had stronger rain wash resistance and were better preserved demonstrating their industrial applicability. Together, organic solvent free AL-P capsules demonstrate a method to improve the efficiency of photosensitive pesticides.

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 9

Issue of Holzforschung

Frontmatter

Specific heat capacity of wood between −140 and 50 °C in dry and wet state

Abstract

Growth behavior of wood-destroying fungi in chemically modified wood: wood degradation and translocation of nitrogen compounds

Abstract

Characterisation of compound middle lamella isolated by a combination of wet-beating, sedimentation, and methanol dialysis

Abstract

A review of lignin hydrogen peroxide oxidation chemistry with emphasis on aromatic aldehydes and acids

Abstract

Fibre development in an intensified mechanical pulping process

Abstract

Tensile properties of finger-jointed lumber under high-temperature and oxygen-free conditions

Abstract

Predicting strength of Finnish birch veneers based on three different failure criteria

Abstract

Non-fluorine surface modification of acetylated birch for improved water repellence

Abstract

Ultrasonic cavitation driven fabrication of organic solvent free lignin/prochloraz nano capsules to promote resistance to photolysis and rain wash, and provide extended release performance

Abstract