Borate and Adhesives: Can They Work in Harmony?

Scientists at the Forest Products Laboratory (FPL) are continually honing their expertise on all things cross-laminated timber (CLT) and this time, they’re digging deeper to learn how preservatives can protect and enhance this handy material.

Borate, an environmentally friendly preservative, has been proven effective in shielding decay and termite damage, while also protecting CLT’s aesthetic appearance, making it a suitable treatment for interior residential applications. But researchers from the Lab’s Durability and Wood Protection Research unit and Michigan State University are wondering how far borate can go if a sticky situation comes into play.

The project, which began in January 2018, aims to discover how well borate can protect CLT against termites, fungal decay and fire when it teams up with adhesives.

Fire test samples. Top, Class I fire-retardant coating; bottom, borate-treated spruce.

Researchers are currently studying how borate will change the surface properties of CLT.  They plan to compare how adhesive formulations interact with CLT that is treated with borate with that which is left untreated.  The wood will be analyzed using various spectroscopy methods. After measuring the adhesive properties of both polyurethane and phenolic glues, researchers will construct small-scale samples of CLT from borate-treated wood and a range of adhesive formulations.  The strength of these formulations will be tested when they are applied to a selection of treated and untreated CLT.

A borate spray solution will also be developed and applied to various CLT samples, where it will then be observed under conditions like fire, termites, and fungal decay. By the conclusion of the project in 2020, researchers hope to further understand how preservative-treated CLT performs under stress, especially when exposed adhesive is involved.

To learn more about this study and how borate and adhesives coexist, read the full Research in Progress report.