Susceptibility of thermo-hydro-treated birch plywood to mould and blue stain fungi

ABSTRACT

In this study, mould and blue stain susceptibility, capillary water uptake (CWU) and microstructural properties of two thermo-hydro-treated (THT) birch plywood products A and B were investigated. Plywood A represented a THT industrial plywood glued with a phenol formaldehyde (PF) adhesive. Plywood B represented panels from THT veneers glued with a PF film. The THT regimes were (temperature, °C/time, min): 150/10, 150/50, 160/10 and 160/50. Both THT plywood products and untreated samples were resistant to mould and blue stain growth in 1 month of exposure in laboratory and outdoor conditions. A statistically significant correlation between fungal growth in laboratory and outdoor conditions for plywood products A and B was not found (P > .05). Artificial weathering of both plywood products provided adverse fungal growth results compared to the natural weathering test outdoors. The fungal growth on plywood A and B samples mutually strongly correlated (P < .05) only in the outdoor test. Plywood B samples demonstrated a much lower CWU than plywood A, obviously because of microstructural changes, including densification, and type of glue used. Lower CWU of THT plywood in comparison with untreated samples did not provide clear evidence on inhibition of fungal growth.

KEYWORDS:

• Thermo-hydro treatment (THT)
• moulds
• blue stain
• susceptibility
• birch plywood

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support of the European Regional Development Fund project “Plywood from thermally modified veneer with improved durability properties” No. 2014/0018/2DP/2.1.1.1.0/14/APIA/VIAA/040 and the National Research Programme (ResProd) Project No. 3 “Biomaterials and products from forest resources with versatile applicability” is gratefully acknowledged.