Effect of Primary Spruce Lamella Aging on the Bending Characteristics of Glulam Beams

Glued laminated (glulam) beams are used in the roofs, ceilings and walls of buildings as well as in bridges and towers. At present, with the limitation of tree harvesting, the production of glulam beams from recycled wood sources is implemented with the proviso that their mechanical properties and resistance to pests, fire and weathering will not be aggravated. This work deals with the primary effect of aging Norway spruce wood (Picea abies Karst. L.) lamellas on the moduli of rupture (MOR) and elasticity (MOE) in bending of three-layer glulam beams composed of sound and aged lamellas and polyurethane (PUR) glue. Three methods of lamella aging were used: (A) natural, lasting 60 years in the form of roof trusses with a greater or lesser degree of bio-attack by woodworm (Anobium punctatum De Geer); (B) artificial, caused by increased temperatures from 160 to 220 °C for 4 h; (C) artificial, caused by 2% water solutions of inorganic preservatives, namely, CuSO4 × 5H2O, ZnCl2, H3BO3 or (NH4)2SO4, for 28 days. The lowest MOR values were determined for glulam beams in which all three lamellas or two surface lamellas had a greater degree of bio-attack (60.5 MPa, a decrease of 25.9%) or were exposed to primary aging at 220 °C (62.6 MPa, a decrease of 23.3%). On the contrary, the exposure of lamellas to 160 or 180 °C did not significantly influence the MOR of beams (76.0–82.7 MPa, an average decrease of 1.6%). The MOE of glulam beams ranged from 7540 to 10,432 MPa without an obvious influence of the method of lamella aging or their location in the beams. Linear correlations between the MOR or MOE of glulam beams and the shear strength (σ) of glued joints, if both composite types consisted of similarly aged lamellas, were only slightly significant or insignificant

Effect of Primary Spruce Lamella Aging on the Bending Characteristics of Glulam Beams

Glued laminated (glulam) beams are used in the roofs, ceilings and walls of buildings as well as in bridges and towers. At present, with the limitation of tree harvesting, the production of glulam beams from recycled wood sources is implemented with the proviso that their mechanical properties and resistance to pests, fire and weathering will not be aggravated. This work deals with the primary effect of aging Norway spruce wood (Picea abies Karst. L.) lamellas on the moduli of rupture (MOR) and elasticity (MOE) in bending of three-layer glulam beams composed of sound and aged lamellas and polyurethane (PUR) glue. Three methods of lamella aging were used: (A) natural, lasting 60 years in the form of roof trusses with a greater or lesser degree of bio-attack by woodworm (Anobium punctatum De Geer); (B) artificial, caused by increased temperatures from 160 to 220 °C for 4 h; (C) artificial, caused by 2% water solutions of inorganic preservatives, namely, CuSO4 × 5H2O, ZnCl2, H3BO3 or (NH4)2SO4, for 28 days. The lowest MOR values were determined for glulam beams in which all three lamellas or two surface lamellas had a greater degree of bio-attack (60.5 MPa, a decrease of 25.9%) or were exposed to primary aging at 220 °C (62.6 MPa, a decrease of 23.3%). On the contrary, the exposure of lamellas to 160 or 180 °C did not significantly influence the MOR of beams (76.0–82.7 MPa, an average decrease of 1.6%). The MOE of glulam beams ranged from 7540 to 10,432 MPa without an obvious influence of the method of lamella aging or their location in the beams. Linear correlations between the MOR or MOE of glulam beams and the shear strength (σ) of glued joints, if both composite types consisted of similarly aged lamellas, were only slightly significant or insignificant

Bonding of Selected Hardwoods with PVAc Adhesive

The bonding of wood with assembly adhesives is crucial for manufacturing wood composites, such as solid wood panels, glulam, furniture parts, and sport and musical instruments. This work investigates 13 hardwoods—bangkirai, beech, black locust, bubinga, ipé, iroko, maçaranduba, meranti, oak, palisander, sapelli, wengé and zebrano—and analyzes the impact of their selected structural and physical characteristics (e.g., the density, cold water extract, pH value, roughness, and wettability) on the adhesion strength with the polyvinyl acetate (PVAc) adhesive Multibond SK8. The adhesion strength of the bonded hardwoods, determined by the standard EN 205, ranged in the dry state from 9.5 MPa to 17.2 MPa, from 0.6 MPa to 2.6 MPa in the wet state, and from 8.5 MPa to 19.2 MPa in the reconditioned state. The adhesion strength in the dry state of the bonded hardwoods was not influenced by their cold water extracts, pH values, or roughness parallel with the grain. On the contrary, the adhesion strength was significantly with positive tendency influenced by their higher densities, lower roughness parameters perpendicular to the grain, and lower water contact angles

Investigation into mechanical, surface and adhesive properties of date palm wood-polyolefin micro composites

Wood-plastic composites are composite materials made of wood fibre or other lignocellulosic materials and thermoplastic(s). Date palms are one of the potential replacements of insufficient timber sources in the Middle East and the Horn of Africa countries. Low density polyethylene (LDPE) was blended with date palm wood (DPW) (Phoenix dactylifera) powder to prepare composites with the concentrations of filler ranging from 10 to 70 wt. %. The Young´s modulus of the composites significantly increased with an increase in the filler content in the entire concentration range. The maximum value of 1933 MPa for the composite filled with 70 wt.% of the filler is approximately 13 times higher than that for the neat LDPE. The incorporation of DPW into the LDPE matrix led to a significant increase in the polarity of composites and to an increase in their adhesion to polar substrates.This contribution was supported by Ministry of Education of the Slovak Republic and Slovak Academy of Sciences, project VEGA, Grant No. 1/0570/17. This research was supported by the Slovak Research and Development Agency under the contracts No. APVV-16-0177, APVV-17-0583 and APVV-18-0378.Scopu

Selected Properties of Veneered Lightweight Particleboards with Expanded Polystyrene

The aim of this study was to improve the properties of lightweight particleboards by their veneering. The industrially produced wood particles, rotary-cut birch veneer, expanded polystyrene (EPS) granules and urea-formaldehyde (UF) resin were used to manufacture non-veneered and veneered boards in laboratory conditions. The boards were manufactured with different densities of 350, 450 and 550 kg/m3 and with various levels of EPS content 4, 7 and 10%. Boards without EPS granules as the reference were also manufactured. Bending strength (MOR), modulus of elasticity in bending (MOE), internal bond (IB) strength, thickness swelling (TS) and water absorption (WA) of lightweight particleboards were determined. This study confirmed that veneering of lightweight particleboards by birch veneer improved mechanical properties significantly. The MOR and MOE of veneered boards throughout the whole density range of 350–550 kg/m3 meet the requirements of the CEN/TS 16368 for lightweight particleboards types LP1 and LP2. The IB strength of veneered boards only with density of 550 kg/m3 meets the requirements of CEN/TS 16368 (type LP1). The MOR, MOE and IB of non-veneered boards also meet the requirements of CEN/TS 16368 (type LP1) except boards with density of 350 kg/m3 for MOR and MOE, and except densities of 350 and 450 kg/m3 for IB

The Effect of Diffusive Impregnation of Birch Veneers with Fire Retardant on Plywood Properties

Wood is a natural, organic material that cannot be exposed to high temperatures, fire, or heat, especially when wood or wood-based materials are used as construction elements. The fire-extinguishing composition of di-ammonium phosphate, ammonium sulfate, and ammonium bromide (DAB) was used to increase the fire-resistance of birch plywood. The effects of various parameters of diffusive impregnation of the veneer (temperature and concentration of impregnating solution, duration of impregnation) were investigated. Their dependence was linear for the temperature of impregnating solution, and logarithmic for concentration of impregnating solution and duration of impregnation. Increased retention of fire retardant improved plywood fire resistance. However, considering the quality of impregnation, energy costs, and plywood properties, the following parameters of wet veneer impregnation are recommended: a temperature of impregnating solution of 22 °C, concentration of 30%, and duration of impregnation of 8 min

Properties of Plywood Panels Composed of Thermally Densified and Non-Densified Alder and Birch Veneers

Ukrainian companies mainly use birch in the manufacture of plywood, but species, such as black alder, are not yet widely used in the manufacture of plywood due to their poorer properties. It is well known that thermal compression is often used to improve the properties of solid wood. Good lay-up schemes of veneer can maximize the advantages and minimize the disadvantages of these wood species, and generally improve the utility value of the plywood. This research aimed to develop plywood panels with two wood species and two types of veneer treatments in order to evaluate the influences of different lay-up schemes on the properties of the plywood. Five-layer plywood panels were formed with 16 different lay-up schemes using birch (Betula verrucosa Ehrh.) (B) and black alder (Alnus glutinosa L.) (A) veneers, which were non-densified (N) and thermally densified (D). The different lay-up schemes were used to identify opportunities to improve the mechanical and physical properties of the plywood by replacing the birch veneer in the plywood structure with an alternative alder veneer. The veneer sheets were thermally densified in a laboratory hot press at a temperature of 180 °C and pressure of 2 MPa for 3 min. The conducted study showed that the bending strength, modulus of elasticity and shear strength of mixed-species plywood (BD–AN–AN–AN–BD) increased by up to 31.5%, 34.4% and 16.8%, respectively, in comparison to those properties of alder plywood from non-densified veneer (AN–AN–AN–AN–AN), by positioning alder non-densified veneers in the core layers and birch densified veneers in the outer layers. Moreover, the surface roughness of plywood panels with outer layers of birch veneer was lower than that of panels with outer layers of alder veneer. It was shown that non-treated alder veneer, despite exhibiting somewhat lower strength properties than birch veneer, could be successfully used with proper lay-up schemes in the veneer-based products industry

Effect of Barrier Plasma Pre-Treatment on Polyester Films and their Adhesive Properties on Oak Wood

A barrier plasma, created at atmospheric pressure, was used to improve the surface and adhesive properties of polyester (PES) film with respect to wood using polyurethane adhesives. The modification of PES film surfaces using barrier discharge plasma is attractive for various applications. Plasma pre-treatment initiates and participates in grafting, polymerization, or cross-linking reactions on the PES surface. This method of surface modification is clean, dry, ecological, and very efficient. The enhancement of the wettability of the polyester film was necessary for promoting higher adhesion to wood with water-based adhesives. The treatment of polyester films by barrier plasma led to a considerable increase in the surface free energy of the film and subsequently an increase in the peel strength of the adhesive joint of PES film-oak wood with polyurethane adhesive