Micromechanical properties of the interphase in pMDI and UF bond lines

Stöckel, Frank; Konnerth, Johannes; Moser, Johann; Kantner, Wolfgang; Gindl‐Altmutter, Wolfgang

doi:10.1007/s00226-011-0432-0

Cited by 30 publications

(15 citation statements)

References 24 publications

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“…The mechanical properties of pure cured UF located in the bondline were quite different from that in wood cell walls. In agreement with earlier research (Stöckel et al 2012), cured UF located in the adhesive bondline showed lower modulus (8.43 GPa) and higher hardness (0.63 GPa) compared with the wood cell wall, with a modulus of 15.71 GPa and hardness of 0.51 GPa, which justified the classification of UF as an adhesive with distinctly stiff and brittle characteristics. The results showed that the reduced elastic modulus and hardness of cell walls containing UF, including exposed cell walls (Er = 18.10 GPa, H = 0.54 GPa) and fully filled cell walls (Er = 17.68 GPa, H = 0.54 GPa), were significantly higher than those of reference cell walls situated far away from the bondline.…”

Section: Nanoindentation -Micromechanical Properties Of Cell Walls Wisupporting

confidence: 91%

“…5, the surface tissues embedded in the UF including exposed cell walls and fully filled cell walls presented light greenish to yellowish color, which was different from the color of UF and reference cell walls. This suggests that UF had penetrated into wood cell walls, which has been demonstrated in other studies (Stöckel et al 2012). With increasing penetration depth, UF content in both lumens and walls declined.…”

Section: Confocal Laser Scanning Microscopy -Microstructure Of Cell Wsupporting

confidence: 79%

“…Nanoindentation (NI), an important method for measuring the micromechanical properties of materials, has been used to determine the penetration behavior of adhesives indirectly by measuring the mechanical properties of cell walls in the interphase region (Liang et al 2011;Zhang et al 2015). Studies show that the penetration of UF into cell walls would considerably influence their mechanical properties (Stöckel et al 2010(Stöckel et al , 2012. It is generally believed that cell walls with more UF will present higher elastic modulus and hardness.…”

Section: Introductionmentioning

confidence: 99%

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Microstructural and Micromechanical Characterization of Modified Urea-Formaldehyde Resin Penetration into Wood

Qin

Lin

2015

BioResources

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Characterization of the adhesive penetration behavior in wood is highly desired for optimizing the manufacturing processes and product properties. In this study, modified urea-formaldehyde (UF) adhesive was used to prepare glued laminated timber (Cryptomeria fortunei Hooibrenk). The depth of gross penetration was measured by fluorescence microscopy (FM), which showed the UF passed through 1.5 to 3.5 earlywood tracheids (with an average penetration depth of 88.95 ± 27.49 μm) or 0.5 to 4.0 latewood tracheids (with an average penetration depth of 36.39 ± 15.14 μm). In addition, the distribution of cell wall penetration was observed clearly by confocal laser scanning microscopy (CLSM). The adhesive was found to diffuse into the cell walls of surface tissues embedded in the UF. To verify the results from CLSM, the mechanical properties of cell walls with and without adhesive penetration were measured through nanoindentation (NI). The reduced elastic modulus of exposed cell walls (18.10 GPa) was roughly equal to that of fully filled cell walls (17.68 GPa) but significantly greater than that of reference ones (15.71 GPa). The hardness showed a similar variation trend for these three types of cell walls. Combining the three techniques, both the microstructure and micromechanics of the adhesive penetration behavior can be quantitatively identified in a complementary manner.

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Section: Nanoindentation -Micromechanical Properties Of Cell Walls Wisupporting

confidence: 91%

Section: Confocal Laser Scanning Microscopy -Microstructure Of Cell Wsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Microstructural and Micromechanical Characterization of Modified Urea-Formaldehyde Resin Penetration into Wood

Qin

Lin

2015

BioResources

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“…Most conventional wood composite panels are currently produced using a formaldehyde based resin as the binder. There are many studies focusing on finding methods to limit formaldehyde emission and improve the properties of conventional wood composites (Stockel et al 2012, Valenzuela et al 2012. Wood-plastic composites (WPCs) offer the best homogeneity as well as higher resistance to biological deterioration agents, water and moisture, and therefore, can be substituted for solid wood in today's building structures and industrial applications if certain structural limitations are addressed.…”

Section: Introductionmentioning

confidence: 99%

Study on the effects of wood flour geometry on physical and mechanical properties of wood-plastic composites

Khonsari

Taghiyari

Karimi

et al. 2015

Maderas, Cienc. tecnol.

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The present study is focused on the effects of the shape and size of Fagus orientalis wood flour on physical and mechanical properties of HDPE based wood plastic composites (WPC). Variables included two mesh sizes (20 and 60), as well as five different contents of ground shavings (0, 25, 50, 75, and 100%) mixed with sawdust; totally 10 treatments. HDPT content was 40% in all formulations. Panels were compression molded and physical and mechanical tests were carried out in accordance with ASTM D2240 standard specifications. Results showed that mesh size can only significantly affect the hardness in the studied wood-plastic composites. On the other hand, increasing the proportion of the ground shavings possessing higher aspect ratio (l/d) increased both flexural strength and hardness. This increasing effect however was not observed for ground shavings beyond 50%. It was also concluded that while the addition of ground shavings up to 50% could improve the mechanical properties, higher proportions would reduce some of the properties, particularly the impact strength. In was concluded that the panel made of 50% wood flour combined with 50% ground shavings exhibited overall suitable properties for most applications.

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“…A blow occurs when excess moisture in the board explosively evaporates at temperatures greater than 100 °C, once pressure is released. Furthermore, for urea-formaldehyde (UF) resin, there is a limitation of MC level (Papadopoulos 2007, Stockel et al 2012. Therefore, rapid transfer of heat to the core section of the mat, and polymerization of resin, has always been a challenge.…”

Section: Introductionmentioning

confidence: 99%

Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF)

Taghiyari¹,

Norton²

2015

iForest

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© iForest -Biogeosciences and Forestry IntroductionThe harvested wood of fast-growing trees is not usually suitable for the furniture industry; however, they provide a sustainable source for paper and composite-manufacturing industries, and natural regeneration would help the process (Ruprecht et al. 2012, Maresi et al. 2013). Wood-composite panels offer the advantage of a homogeneous structure which may be important for many design purposes (Valenzuela et al. 2012). Due to the low thermal conductivity coefficient of wood (Taghiyari et al. 2013a), some studies have so far been carried out to decrease the maximum pressing time or increase the heat-transferring rate to the core section of the mat (Lehmann et al. 1973, Taghiyari et al. 2013b. Hot press time is dependant on the thickness of the composite mat, press temperature, closing rate, and most importantly, moisture distribution throughout the mat (Doost-Hoseini et al. 2013, Taghiyari et al. 2013b). There is a limit to moisture content of the mat because of two main reasons: (i) increase in the hotpress time; and (ii) occurrence of blows in wood-composite panels. A blow occurs when excess moisture in the board explosively evaporates at temperatures greater than 100 °C, once pressure is released. Furthermore, for urea-formaldehyde (UF) resin, there is a limitation of MC level (Papadopoulos 2007, Stockel et al. 2012. Therefore, rapid transfer of heat to the core section of the mat, and polymerization of resin, has always been a challenge.Many areas of science have used nanotechnology to enhance the effectiveness of materials at nano scales. Heat-transferring property of metal nanoparticles (Khojier et al. 2012) and mineral nanofibers (Haghighi Poshtiri et al. 2013) was reported to improve some properties in solid wood as well as wood-composite materials. However, little study has so far been carried out to practically investigate the effects of different nano-materials in wood-composite panels. The present research project was therefore conducted to study the effects of silver nanoparticles as well as different hot-press times on the hardness of medium-density fiberboards. The relations between the hardness and some physical properties of the panels were investigated as well. Materials and methods Specimen preparationWood fibers were obtained from the Sanaye Choobe Khazar Company (MDF Caspian Khazar, Amol, Iran). The fibers were a mixture of beech, alder, maple, hornbeam, and poplar from forests of the Gillan province (Amol, Iran). The raw materials were free from fungi deterioration. This material was used to prepare boards that were 16 mm thick and had a density of 0.68 g cm -3. A laboratory hot press produced by the Mehrabadi Machinery Mfg. Co. (Tehran, Iran) was used to prepare test specimens. The size of the hot plates was 50 × 50 cm. The total nominal pressure applied by the hot plates was 160 bars at a fixed plate temperature of 150°C. Hot-pressing continued for 6, 8, and 10 minutes. Urea-Formaldehyde resin (UF) was supplied from Pars Chemical Industries ...

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Micromechanical properties of the interphase in pMDI and UF bond lines

Cited by 30 publications

References 24 publications

Microstructural and Micromechanical Characterization of Modified Urea-Formaldehyde Resin Penetration into Wood

Microstructural and Micromechanical Characterization of Modified Urea-Formaldehyde Resin Penetration into Wood

Study on the effects of wood flour geometry on physical and mechanical properties of wood-plastic composites

Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF)

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