Evaluation of relationships between particle orientation and thermal conductivity in bark insulation board by means of CT and discrete modeling

Thermophysical Properties of Larch Bark Composite Panels

The effects of using 100% larch bark (Larix decidua Mill) as a raw material for composite boards on the thermophysical properties of this innovative material were investigated in this study. Panels made of larch bark with 4–11 mm and 10–30 mm particle size, with ground bark oriented parallel and perpendicular to the panel’s plane at densities varying from 350 to 700 kg/m³ and bonded with urea-formaldehyde adhesive were analyzed for thermal conductivity, thermal resistivity and specific heat capacity. It was determined that there was a highly significant influence of bulk density on the thermal conductivity of all the panels. With an increase in the particle size, both parallel and perpendicular to the panel´s plane direction, the thermal conductivity also increased. The decrease of thermal diffusivity was a consequence of the increasing particle size, mostly in the parallel orientation of the bark particles due to the different pore structures. The specific heat capacity is not statistically significantly dependent on the density, particle size, glue amount and particle orientation.

Acoustic Properties of Larch Bark Panels

The potential of tree bark, a by-product of the woodworking industry, has been studied for more than seven decades. Bark, as a sustainable raw material, can replace wood or other resources in numerous applications in construction. In this study, the acoustic properties of bark-based panels were analyzed. The roles of the particle size (4–11 mm and 10–30 mm), particle orientation (parallel and perpendicular) and density (350–700 kg/m3) of samples with 30 mm and 60 mm thicknesses were studied at frequencies ranging from 50 to 6400 Hz. Bark-based boards with fine-grained particles have been shown to be better in terms of sound absorption coefficient values compared with coarse-grained particles. Bark composites mixed with popcorn bonded with UF did not return the expected results, and it is not possible to recommend this solution. The best density of bark boards to obtain the best sound absorption coefficients is about 350 kg/m3. These lightweight panels achieved better sound-absorbing properties (especially at lower frequencies) at higher thicknesses. The noise reduction coefficient of 0.5 obtained a sample with fine particles with a parallel orientation and a density of around 360 kg/m3.

Thermal and Mechanical Properties of Green Insulation Composites Made from Cannabis and Bark Residues

The objective of this paper was to investigate the technical feasibility of manufacturing low density insulation particleboards that were made from two renewable resources, namely hemp fibers (Cannabis sativa) and pine tree bark, which were bonded with a non-toxic methyl cellulose glue, as a binder. Four types of panels were made, which consisted of varying mixtures of tree bark and hemp fibers (tree bark to hemp fibers percentages of 90:10, 80:20, 70:30, and 60:40). An additional set of panels was made, consisting only of bark. The results showed that addition of hemp fibers to furnish improved mechanical properties of boards to reach an acceptable level. The thermal conductivity unfavorably increased as hemp content increased, though all values were still within the acceptable range. Based on cluster analysis, board type 70:30 (with 30% hemp content) produced the highest mechanical properties as well as the optimal thermal conductivity value. It is concluded that low density insulation boards can be successfully produced using these waste raw materials.

Bark Thermal Insulation Panels: An Explorative Study on the Effects of Bark Species

Tree bark is a byproduct of the timber industry which accrues in large amounts, because approximately 10% of the volume a log is bark. Bark is used primarily for low-value applications such as fuel or as a soil covering material in agriculture. Within the present study, thermal insulation panels made from larch, pine, spruce, fir and oak tree bark with different resins (urea formaldehyde, melamine formaldehyde, Quebracho, Mimosa) as a binder are discussed. Also, the properties of panels made from larch bark mixed with industrial popcorn are investigated. The physical-mechanical properties of the panels, which are dependent on panel density, bark species, resin type, resin content and particle size, are analyzed. The bark species has a minor effect on the mechanical characteristics of the panels, while the compression ratio is important for the panel strength, and hence, barks with lower bulk density are preferable. Under laboratory conditions, panels made with green tannin resins proved to have adequate properties for practical use. The addition of popcorn is a means to lower the panel density, but the water absorption of such panels is comparably high. The bark type has a minor effect on the thermal conductivity of the panels; rather, this parameter is predominantly affected by the panel density.