In the upcoming CSA Standard 112.9 – Standard Specification for Evaluation of Adhesives for Structural Wood Products (Exterior Exposure), the percentage of block shear wood failure under dry and wet (vacuum-pressure and boil-dry-freeze) test conditions is one of the required performance criteria.
It is well known that the percentage wood failure normally correlates well to bond strength in block shear testing for phenol-resorcinol-formaldehyde (PRF) adhesives that have been traditionally used in the manufacture of engineered wood products. However, it has been noted that some new adhesives could yield strong bond strength but fail the wood failure test, or yield opposite results. This project will focus on the characterization of adhesive penetration into wood and the bonding mechanism (chemical bonding vs. other bonding).
This project will: develop a technique to quantitatively measure the degree of adhesive penetration into wood substrate as influenced by glue type, wood condition and bonding process; characterize the chemical interaction between adhesive and wood; correlate adhesive penetration with wood failure and shear strength; and assess the suitable wood failure criteria for structural adhesive performance in terms of adhesive categories.