Impact of thermal treatment on bonding performance of UF/PVAc formulations

Costa, Nuno; Ferra, João; Martins, Jorge; Coelho, Catarina; Pereira, João; Cruz, Paulo; Magalhães, Fernão D.; Carvalho, Luísa

doi:10.1179/2042645314y.0000000075

Cited by 2 publications

(2 citation statements)

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“…Although boiled logs can be applied to modify the surface characteristics of veneers, to the best of our authors' knowledge, this method is unsuitable for woods that were produced from community forest or industrial plantation forest because the value of wood density is around low (0.24-0.56 g cm −3 ) and medium (0.56-0.72 g cm −3 ) classes (Abdurachman and Hadjib 2009). In addition, thermal treatment on wood at high temperature in the range of 180-250°C could retard and even impair penetration of glues because of the decrease in wettability and surface inactivation by oxidation of wood bonding sites (Costa et al 2014), which is due to the compounds formed in the chemical transformations above 180°C (Esteves and Pereira 2009).…”

Section: Introductionmentioning

confidence: 99%

“…However, environmental requirements, such as stringent formaldehyde emission regulations (Carvalho et al 2012), have forced producers to use an alternative adhesive, and one of them is polyvinyl acetate (PVAc) adhesive. PVAc adhesives are widely used and chosen (Král et al 2015) because they are ready-to-use, short setting time, flexible joint, easy to clean, long storage life (Costa et al 2014), odorless, and nonflammable (Uysal 2005). The growing interest in the use of PVAc adhesives in the wood-based industry is due to the health hazards associated with formaldehyde-based adhesives (Kim and Kim 2006), which are inexpensive when compared with formaldehyde-based adhesives (Paris 2000), various materials can be bonded, and nontoxic (Kim et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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Improved strength properties of LVL glued using PVAc adhesives with physical treatment-based Rubberwood (Hevea brasiliensis)

et al. 2020

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The properties of the laminated veneer lumber (LVL) composed of the boiled veneer of Rubberwood (Hevea brasiliensis) using polyvinyl acetate (PVAc) adhesives in various cold-pressing time and various conditioned time with loaded and unloaded were studied. Five-ply LVL was produced by boiling veneer at 100°C for 90 min as pretreatment and cold-pressing time at 12 kgf cm−2 for 1.5, 6, 18, and 24 h then conditioned at 20°C and 65% relative humidity (RH) with loaded (12 kgf cm−2) and unloaded for 7 days as physical treatment. Especially for the delamination test, the specimens were immersed at 70 ± 3°C for 2 h and dried in the oven at 60 ± 3°C for 24 h; then, the specimens were solidified at room temperature (20°C and 65% RH) with loaded (12 kgf cm−2) and unloaded for 7, 10, 12, and 14 days. To determine the performance of LVL, the density, moisture content (MC), delamination, modulus of elasticity (MOE), modulus of rupture (MOR), horizontal shear strength, and formaldehyde emission tests were conducted according to the Japanese Agricultural Standard (JAS 2008) for structural LVL. The MOE and MOR values were significantly influenced by the physical treatment, however, neither to horizontal shear strength nor to formaldehyde emission. The best performance of LVL has resulted from unloaded LVL with cold-pressed time for 18 h; the MOE and MOR values were 9,345.05 ± 141.61 N mm−2 and 80.67 ± 1.77 N mm−2, respectively. The best value of the horizontal shear strength was obtained from the LVL with 18 h cold-pressing time and conditioned with loaded (13.10 ± 1.47 N mm−2) and unloaded (12.23 ± 1.36 N mm−2). The percentage of delamination values decreased with an increase in the cold-pressing time and conditioning time. The lowest value of delamination (19.06%) was obtained from the LVL with 24 h cold-pressing time and conditioned with loaded for 14 days. Except the delamination test, all other properties fulfilled the JAS.

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Section: Introductionmentioning

confidence: 99%