Thickness swelling and its relationship to internal bond strength loss of commercial oriented strandboard

Samples from two types of mixed hardwood oriented strandboard (OSB) and two types of southern pine OSB were tested to study thickness swelling (TS) and its relationship to internal bond (IB) strength loss of the products. The treatment conditions included four equilibrium moisture contents and 24-hour water soaking at room temperature. It was shown that both high humidity and water-soaking treatments led to significant TS for all materials tested. Residual IB strength for all OSBs decreased linearly with an increase in non-recoverable TS. Regardless of the way OSB absorbed moisture, there was an average IB strength loss of about 0.0138 MPa for every percent of non-recoverable TS in the specimens. In-plane density variation and non-uniform resin application due to curled flakes were found to play a significant role for the large TS and IB strength loss in these products.