Versuche zur Behandlung von Holz mit monomerem Formaldehyd-Gas unter Verwendung von Gamma-Strahlen

Burmester, Arno

doi:10.1515/hfsg.1967.21.1.13

Cited by 12 publications

(3 citation statements)

References 3 publications

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“…The lack of inelastic deformation in dry heat-treated wood hinders the relaxation of stresses created by external loads, resulting in the built-up of high stress concentrations and a brittle failure of the material. Creation of additional covalent bonds within the cell wall matrix without de-polymerization of wood constituents by treatments of wood with cross-linking agents [64] or by incorporation of a rigid, three-dimensional corset of thermosetting resin such as melamine formaldehyde [65] result in a very similar change in mechanical performance during bending, i.e. in a significantly increased brittleness.…”

Section: Mechanical Behaviormentioning

confidence: 99%

The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

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Rautkari

2018

Polymer Degradation and Stability

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Loss in strength and ductility is a major drawback for the heat-treatment of solid wood. Previous studies focused mainly on the de-polymerization of cell wall constituents as a cause and the importance of the preferential removal of hemicelluloses. This study tested the hypothesis that the mechanical behavior of wood is additionally affected by re-polymerization reactions within the cell wall matrix during heat-treatment. This was achieved by comparing changes in chemical composition, FT-IR spectra, and mechanical properties of Scots pine sapwood that was heattreated in either dry state in superheated steam or in wet state using pressurized hot water. Although preferential de-polymerization of hemicelluloses was evident for both heat-treatment techniques, the analysis of the chemical composition and FT-IR spectroscopy indicated additional re-polymerization reactions within the cell wall matrix of dry heat-treated wood. The consequent formation of covalent bonds and cross-links increased the resistance against compression loads and hindered inelastic deformation during bending. This resulted in an additional reduction in bending strength and strain energy density of dry compared to wet heat-treated wood. Repolymerization reactions during heat-treatments of wood in dry state were suggested as the main cause for the brittle failure under bending loads, while the effect of hemicellulose-removal on brittleness was much smaller than stated previously.

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Section: Mechanical Behaviormentioning

confidence: 99%

The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

Altgen

Uimonen

Rautkari

2018

Polymer Degradation and Stability

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“…Still, the main contribution in EMC reduction was attributed to cross-linking. Even low levels of FA treatment significantly reduced the EMC of wood ( Burmester 1967 ;Minato and Norimoto 1985 ;Minato and Yano 1990 ;Minato 1993 ). At a weight percent gain (WPG) of 3.5%, the EMC level was reduced by approximately 50% compared with W untr ( Yasuda et al 1995 ), owing to the reduction in swelling in the presence of air moisture due to the cross-linking of polymers.…”

Section: Introductionmentioning

confidence: 99%

Effects of acetylation and formalization on the dynamic water vapor sorption behavior of wood

Himmel¹,

Mai

2014

Holzforschung

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The dynamic water vapor sorption of untreated, acetylated (W ac ), and formaldehyde-treated (W FA ) Scots pine ( Pinus sylvestris L.) sapwood was studied in a dynamic vapor sorption apparatus to assess the effects of cell wall bulking and cross-linking. Both modifications resulted in a considerable reduction of reduced equilibrium moisture content (EMC R ), the corresponding equilibrium times, and hysteresis in the hydroscopic range of wood. Acetylation reduced the adsorption and desorption of water at each given relative humidity (RH) step from 0% to 95% RH, whereas formalization affected the sorption behavior of wood solely above 20% RH. From 20% to 95% RH, the EMC ratio of W FA to its control steadily decreased, whereas the EMC ratio of W ac was still constant in this RH range. Below 20% RH, the sorption behavior of W ac was governed by hydroxyl blocking, whereas that of W FA was hardly influenced compared with the control. Above 20% RH, the sorption behavior of W ac was solely determined by cell wall bulking, whereas that of W FA was governed by the increased matrix stiffness due to the cross-linking of cell wall polymers.

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“…Formaldehyde tends to form networks as it is bifunctional [41]. According to Burmester [42] as well as Rowell [43], treatment of wood with formaldehyde alone leads to a considerable embrittlement of the wood. Reasons for this are cross-linking and hydrolysis of cellulose.…”

Section: Influence Of Modification Agentsmentioning

confidence: 99%

Tensile and Impact Bending Properties of Chemically Modified Scots Pine

Bollmus¹,

Beeretz²,

Militz³

2020

Forests

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This study deals with the influence of chemical modification on elasto-mechanical properties of Scots pine (Pinus sylvestris L.). The elasto-mechanical properties examined were impact bending strength, determined by impact bending test; tensile strength; and work to maximum load in traction, determined by tensile tests. The modification agents used were one melamine-formaldehyde resin (MF), one low molecular weight phenol-formaldehyde resin, one higher molecular weight phenol-formaldehyde resin, and a dimethylol dihydroxyethyleneurea (DMDHEU). Special attention was paid to the influence of the solution concentration (0.5%, 5%, and 20%). With an increase in the concentration of each modification agent, the elasto-mechanical properties decreased as compared to the control specimens. Especially impact bending strength decreased greatly by modifications with the 0.5% solutions of each agent (by 37% to 47%). Modification with DMDHEU resulted in the highest overall reduction of the elasto-mechanical properties examined (up to 81% in work to maximum load in traction at 20% solution concentration). The results indicate that embrittlement is not primarily related to the degree of modification depended on used solution concentration. It is therefore assumed that molecular size and the resulting ability to penetrate into the cell wall could be crucial. The results show that, in the application of chemically modified wood, impact and tensile loads should be avoided even after treatment with low concentrations.

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Versuche zur Behandlung von Holz mit monomerem Formaldehyd-Gas unter Verwendung von Gamma-Strahlen

Cited by 12 publications

References 3 publications

The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

The effect of de- and re-polymerization during heat-treatment on the mechanical behavior of Scots pine sapwood under quasi-static load

Effects of acetylation and formalization on the dynamic water vapor sorption behavior of wood

Tensile and Impact Bending Properties of Chemically Modified Scots Pine

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