Effect of moisture content and temperature on tension strength of fingerjoined black spruce lumber

To optimize product performance, the various parameters which can influence the complex fingerjointing process must be evaluated. Among key variables are the conditions of the lumber blanks including moisture content (MC) and temperature. Black spruce (Picea mariana (Mill) B.S.P.) 2- by 3-inch blocks at different MCs (12%, 16%, 20%, and green) were conditioned at several temperatures (?5?, 5?, 12?, and 20?C) prior to fingerjointing. Two types of adhesives were used in this study: polymer emulsion polyurethane (PEP) and a new fast-curing formulation of phenol-resorcinol-formaldehyde (PRF). All specimens were tested in tension after 24 hours of curing at room temperature to determine their ultimate tensile strength. Microscopic analysis of the adhesive bond was also carried out to explain differences between the various treatments. Results have shown that the operating envelope for PEP adhesive is between 12 percent and 16 percent and between 5?C and 20?C. It was also found that frozen lumber bonded better with PRF compared to PEP. Optimum MC for the PRF adhesive was found to be 16 percent. Highwood failure and a uniform glue penetration profile were associated with dry lumber (? 12%). High adhesive failure and a non-uniform glue penetration were generally observed with green lumber.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member