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Journal ArticleDOI

The effect of planing on the microscopic structure of Pinus radiata wood cells in relation to penetration of PVA glue

TL;DR: In this article, the authors examined the penetration of PVA glue by light microscopy and scanning and transmission electron microscopy on wood cells and found that the wood cells were greatly distorted and cell walls were extensively damaged, particularly at and near the glue line.
Abstract: wood cells and penetration of PVA glue was examined by light microscopy and scanning and transmission electron microscopy. After planing with dull knives the wood cells were greatly distorted and cell walls were extensively damaged, particularly at and near the glue line. In comparison, sharp knives caused much less damage to cell walls and the cells had a normal or near-normal appearance. These features are discussed in detail in relation to glue penetration and the performance of glue joints after planing with sharp and dull knives.
Citations
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Journal ArticleDOI
17 Feb 2017-Polymers
TL;DR: This article reviews the recent research published over the last few decades on the synthesis of bio-adhesives derived from such renewable resources as lignin, starch, and plant proteins and discusses techniques commonly used for evaluating the petroleum-based wood adhesives in terms of mechanical properties and penetration behavior.
Abstract: There has been a rapid growth in research and innovation of bio-based adhesives in the engineered wood product industry. This article reviews the recent research published over the last few decades on the synthesis of bio-adhesives derived from such renewable resources as lignin, starch, and plant proteins. The chemical structure of these biopolymers is described and discussed to highlight the active functional groups that are used in the synthesis of bio-adhesives. The potentials and drawbacks of each biomass are then discussed in detail; some methods have been suggested to modify their chemical structures and to improve their properties including water resistance and bonding strength for their ultimate application as wood adhesives. Moreover, this article includes discussion of techniques commonly used for evaluating the petroleum-based wood adhesives in terms of mechanical properties and penetration behavior, which are expected to be more widely applied to bio-based wood adhesives to better evaluate their prospect for wood composites application.

164 citations

Journal ArticleDOI
TL;DR: In this article, a number of factors determining the durability of structural adhesive joints have been identified and can be grouped in three categories: environment, materials and stresses, and the last category refers to the stresses to which the bond is subjected during or after exposure to service environment, affecting both longevity and residual strength.

160 citations

Journal ArticleDOI
TL;DR: In this article, the elastic modulus, hardness, and creep factor of wood cell walls in the interphase region of four different adhesive bonds were determined by nanoindentation, and it was concluded that damage and loss of elastic modulation to surface cells occurring during the machining of wood is recovered in MUF and PRF bond lines, whereas damage of cell walls persists in PVAc and PUR bond lines.
Abstract: The elastic modulus, hardness, and creep factor of wood cell walls in the interphase region of four different adhesive bonds were determined by nanoindentation. In comparison with reference cell walls unaffected by adhesive, interphase cell walls from melamine-urea-formaldehyde (MUF) and phenol-resorcinol-formaldehyde (PRF) adhesive bonds showed improved hardness and reduced creep, as well as improved elastic modulus in the case of MUF. In contrast, cell walls from the interphase region in polyvinylacetate (PVAc) and one-component polyurethane (PUR) bonds showed more creep, but lower elastic modulus and hardness than the reference. Considering the different cell-wall penetration behaviour of the adhesive polymers studied here, it is concluded that damage and loss of elastic modulus to surface cells occurring during the machining of wood is recovered in MUF and PRF bond lines, whereas damage of cell walls persists in PVAc and PUR bond lines.

96 citations


Cites background from "The effect of planing on the micros..."

  • ...In the case of wood adhesive bonds, the interphase consists of wood cell walls, which are often significantly damaged as a result of surface preparation (Singh et al. 2002), a phenomenon termed the mechanical weak boundary layer (Dunky and Niemz 2002)....

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  • ...For PVAc and PUR, no detectable penetration of adhesive into the wood cell wall was found (Buckley et al. 2002; Singh et al. 2002; Backman and Lindberg 2004; Gindl et al. 2004a,b)....

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Journal ArticleDOI
12 Dec 2018
TL;DR: A review of wood bond analysis methods can be found in this article, where the authors highlight recent developments in the analyses and understanding of wood bonds and highlight several challenges facing the wood bonding community.
Abstract: Understanding why wood bonds fail is an excellent route toward understanding how to make them better. Certifying a bonded product usually requires achieving a specific load, percent wood failure, and an ability to withstand some form of moisture exposure without excessive delamination. While these tests protect the public from catastrophic failures, they are not very helpful in understanding why bonds fail. Understanding failure often requires going beyond what meets the naked eye, conducting additional tests, probing the wood surface, the fracture surface, adhesive properties, and the interaction of wood and adhesive during bond formation and service. This review of wood bond analysis methods reviews fundamentals of wood bonding and highlights recent developments in the analyses and understanding of wood bonds. It concludes with a series of challenges facing the wood bonding community.

42 citations

Journal ArticleDOI
TL;DR: In this article, a study was conducted to examine the influences of primer treatment and other parameters, such as surface machining and press time on the bondability of ash, beech, oak, and Norway spruce.
Abstract: European hardwood species such as beech, oak and ash present a potential alternative to commonly used softwoods in glued engineered wood products. To date, mainly amino- and phenoplast adhesives are used for bonding these hardwoods, but some one-component polyurethane (1C-PUR) adhesives prove to offer an alternative when combined with a primer pretreatment. Therefore, a study was conducted to examine the influences of primer treatment and other parameters, such as surface machining and press time on the bondability of ash, beech, oak and—as a reference—Norway spruce. Delamination and block shear tests were conducted according to current European standards. Furthermore, information about bonding quality was gathered by means of microscopic glue line thickness measurements. The results suggest that the primer treatment is able to significantly enhance the bonding quality of hardwoods. The choice of the surfacing method causes some significant changes in the primer effectiveness. However, not all species were equally affected. The influence of the primer treatment on shear tests in a dry state was rather low throughout the series and only little significance was found. similar results were found after variations of the press time.

38 citations


Cites background from "The effect of planing on the micros..."

  • ...Singh et al. (2002) found that dull knives can cause an extensive subsurface damage with fractured and distorted cells on peripherally planed wood surfaces....

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References
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Journal ArticleDOI
TL;DR: A low-viscosity embedding medium based on ERL-4206 is recommended for use in electron microscopy and has a long pot life of several days and infiltrates readily because of its low viscosity.

12,930 citations


"The effect of planing on the micros..." refers methods in this paper

  • ...For transmission electron microscopy (TEM) small hand sections taken through the glue and the wood tissue were dehydrated in acetone and embedded in Spurr’s low viscosity resin (Spurr 1969)....

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Journal ArticleDOI
01 Jun 1999-Botany
TL;DR: Evidence for radial striations in the S2 region probably representing regions of alternating high and low lignin concentration is revealed, which may be the precursor to the helical cavities found in severe compression wood.
Abstract: The structure of tracheid cell walls in mild compression wood of Pinus radiata D. Don was examined by confocal laser scanning fluorescence microscopy (CLSM) and transmission electron microscopy (TE...

61 citations


"The effect of planing on the micros..." refers background in this paper

  • ...…layer appears intact, except for the presence of a large radial crack in the S2 layer, which may have developed in the region where a fine crack may have been initially present, a feature characteristic of mild compression wood tracheids in P. radiata (Singh and Donaldson 1999; tracheid D in Fig....

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Journal Article

41 citations


"The effect of planing on the micros..." refers background in this paper

  • ...Markierungsstrich ¼ 1 lm 337 planing (Jokerst and Stewart 1976; Stewart and Crist 1982; Murmanis et al. 1983)....

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  • ...Planing is one of the most commonly used machining methods, and it is therefore not surprising that the effect of planing on both wood surface and on the strength of glue joints has been extensively investigated (Jokerst and Stewart 1976; Stewart and Crist 1982; Murmanis et al. 1983; Naderi and Hernandez 1999)....

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  • ...…of the most commonly used machining methods, and it is therefore not surprising that the effect of planing on both wood surface and on the strength of glue joints has been extensively investigated (Jokerst and Stewart 1976; Stewart and Crist 1982; Murmanis et al. 1983; Naderi and Hernandez 1999)....

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Journal ArticleDOI
TL;DR: In this paper, conditions of broyage de bois d'epicea and de hetre font varier la taille, the forme et la structure des particules.
Abstract: Des variations des conditions de broyage de bois d'epicea et de hetre font varier la taille, la forme et la structure des particules. Le traitement mecanique influe aussi sur la structure interne de la paroi cellulaire. Dans cette etude, les coins des cellules et les lamelles moyennes ont ete les elements les plus resistants, alors que les parois secondaires 1 (S1) etaient ramollies dans la phase initiale. La couche S2 a ete fendue en lamelles de differentes epaisseurs. Une duree accrue de broyage augmente la quantite de particules globulaires sans structures visibles.

32 citations


"The effect of planing on the micros..." refers methods in this paper

  • ...In addition, the use of TEM, which has had limited application in wood fracture studies ( Maurer and Fengel 1992; Schmitt et al. 1996; Donaldson 1997) has greatly Fig. 3. Wood surface planed with sharp knives....

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  • ...In addition, the use of TEM, which has had limited application in wood fracture studies (Maurer and Fengel 1992; Schmitt et al. 1996; Donaldson 1997) has greatly Fig....

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Journal ArticleDOI
TL;DR: In this article, the authors examined Alder and Eucalypt wood before and after a chemical treatment by the Indurite process to increase the hardness of the wood in some respects.
Abstract: The woods of Alder and Eucalypt were examined by light microscopy before and after a chemical treatment by the Indurite process to increase the hardness of the wood. The pattern of wood cell impregnation for Alder differed significantly from Eucalypt in some respects. In Alder wood all cell types eg. vessels, fibres and rays, were impregnated in similar proportions. In comparison, in Eucalypt wood the impregnation material was largely confined to ray cells and the lumina of vessels; other cell types were either not impregnated or impregnated in very small numbers. Transmission electron microscopy of Alder and Eucalypt woods suggests that ultrastructural differences in the texture and porosity of pit membranes may be the main reason for the observed differences between these wood species with regard to their impregnability by the impregnation material used.

30 citations


"The effect of planing on the micros..." refers background in this paper

  • ...The importance of pit membrane porosity in liquid flow has also been demonstrated for a high molecular weight woodhardening material (Singh et al. 1999)....

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