Radial variation in bonding performance of preservative-treated wood within Pinus elliottii trees and its relationships with wood density and adhesive penetration

Abstract

Pinus elliottii wood from different radial locations within trees was used to prepare two-layer preservative-treated wood joints with alkaline copper quaternary preservative and emulsion polymer isocyanates (EPI) or resorcinol-phenol-formaldehyde (RPF) adhesives. The radial variations in shear strength and wood failure percentage were analyzed. Radial variations in wood density and average penetration depth (AP) of adhesives were investigated to establish relationships between shear strengths and characteristics of bonded joints. The shear strengths of EPI- and RPF-bonded joints showed similar increasing trends from pith to bark, and they varied in ranges of 2.92 to 8.13 MPa and 2.03 to 7.12 MPa, respectively. The wood failure percentage of EPI joints (93% to 100%) had no significant differences in all the radial locations, but that of RPF joints (60% to 100%) showed a clear decreasing trend from pith to bark. High positive linear correlations were found between the shear strengths and wood density, and Pearson’s correlation coefficients for EPI and RPF were 0.934 (p < 0.01) and 0.931 (p < 0.01), respectively. Wood density is a very important factor influencing radial variations of bonding strengths. The correlation between the AP and shear strength was not significant at the 0.05 level.

The Effect of Inorganic Preservatives in the Norway Spruce Wood on Its Wettability and Adhesion with PUR Glue

“…Their strength and stability depend on many factors, especially on: (1) physicochemical characteristics of a glue, i.e., its molecular weight, viscosity, surface tension, pH-value; (2) type of wood and physicochemical properties of its surface, i.e., porosity, moisture content, surface tension, pH-value; (3) technological conditions of gluing, i.e., amount of glue, open time, pressing diagram-temperature, pressure and time and (4) curing mechanism of glue, e.g., polycondensation of phenolic resins or amino resins, polyaddition of epoxy resins, polymerization of acrylates or isocyanates, separation of water or other liquid types from polyvinylacetate dispersions, etc. [2][3][4][5][6][7][8].…”

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

“…The final quality of glulam beams is influenced by many factors: (1) the wood species, whether it is used in its natural state or after chemical, thermal, mechanical or biological modifications, and what are its typical structural characteristics and properties, e.g., the density and porosity, the type and amount of extractives, the pH value, roughness, free surface energy, moisture content at bonding, tension and compression strengths, elasticity, and resistance to pests, fire and weathering; (2) the glue type and its physical-chemical characteristics, e.g., the molecular weight, viscosity, surface tension, chemical reactivity, resistance to water and total durability; and (3) the technology of gluing, e.g., the spread rate of glue and its open time and the pressing diagram used [7][8][9][10][11][12][13][14]. The applicability of structural glulam beams depends mainly on their mechanical properties and resistance to biological damage, fire and weathering.…”