Density related properties of bark insulation boards bonded with tannin hexamine resin

Building owners are increasingly interested in a healthy and sustainable living environment, which is a trend favoring ecological building materials with outstanding structural physical parameters. Insulation boards from particles of larch bark (Larix decidua Mill.) bonded with a formaldehyde-free tannin resin were pressed and evaluated for their mechanical and physical properties. It could be shown that light (target density 250 kg/m³) boards can be pressed, and their thermal conductivity is low (0.065-0.09 W/(mK)). With regard to mechanical characteristics, the influence of panel density was studied, and it was found that a certain compaction (ρ ≥ 400 kg/m³) is necessary to meet the requirements of the relevant standard. Interestingly, the resin amount did not influence the mechanical board properties as strongly as expected, and panel density is the most important variable in this respect. The study proved that tree bark cannot only be used for substantially upgraded insulation panels but can also be bonded with a formaldehyde free tannin resin.