The patented HefCel is an enzymatically-fibrillated nanocellulose type that has unique properties. When mixed with inorganic nano-scale pigments, it can be spray- or brush-coated on wood-based materials. The coating reduces the access of oxygen to the surface, and acts as an effective fire retardant treatment.
After the manufacturing process, HefCel has a consistency of 25% and an appearance of moldable paste. The processing is significantly more cost-efficient compared to mechanically prepared nanocellulose, and no harmful chemicals are needed in the process.
HefCel can be used in wood coatings without any binder chemicals, as it has an inherent adhesion to wooden surfaces. It also adheres to particles such as fillers. A HefCel-coating is breathable in terms of moisture, but it forms an airtight film, which slows down the spread of fire on the surface.
The lab-scale trials using HefCel together with various amounts of selected nanoscale pigments have shown promising fire retardant properties (see the image). The coating thickness has varied from 100 microns to 300 microns. The coating can be applied layer-by-layer or as a single treatment to create the protective layer.
Based on our preliminary experiments at VTT, the coating is also very resistant to abrasion. The coatings are opaque, so they add a light colour on the coated surface. To date, sawn and planed planks and various types of plywood have been coated with HefCel.
Top: The cross section of three spray coated layers applied on wood. Image: Tiina Pöhler.
Bottom: The fire-retarding effect of the HefCel-based coating. Exposure time to fire tested according to ISO 11925-2. Flame contact time 30 sec. Image: Paula Bergqvist.
For detailed information, please contact
Tomi Erho, Principal Scientist, tel. +358 40 1768 840, Tomi.Erho@vtt.fi
Vesa Kunnari, Senior Scientist, tel. +358 40 7036 189, Vesa.Kunnari@vtt.fi