The rapid rise of eucalyptus plantations causes problems in the handling of waste generated by their processing. Eucalyptus bark, unlike pine bark, is difficult to handle, store and eliminate. Therefore, its combustion in industrial boilers is unattractive, generating large volumes of bark in debarking plants with consequent hazard of fire by autoignition.
On the other hand, new regulations have been implemented regarding thermal insulation of houses in Chile. In parallel, and as a consequence of the above, the market for insulation panels is constantly growing, expanded polystyrene, polyurethanes, glass wool and rock wool being the main products of interest. Although these materials have good technical properties and low cost, their large environmental footprint is a problem.
The Fondef project ID14i10081 “Sustainable thermal insulation panel from Eucalyptus sp.bark” proposed to develop a panel prototype based on eucalyptus bark fibers with good thermal insulation properties, low ecological footprint, competitive prices and technical performance that meet Chilean construction sector demands. The work was conducted with companies Fulghum Fibres Chile S.A., Urbo Arquitectura y Construcción sustentable Eirl. and Módulos Wewfe Ltda.
In the first stage of this study, eucalyptus bark was characterized and different mechanical processing alternatives were evaluated to obtain a fibrous material suitable for manufacturing insulation panels. In the second stage, insulation panels were made with thus obtained fibrous material. In the third stage, different panel coatings were applied, (e.g., Kraft paper, OSB board or plywood, thermal aluminum and gypsum) in order to achieve improvements in thermal insulation, handling, applicability and water vapor permeability.
Rigid eucalyptus bark fiber panels (80-300 kg/m3), as well as flexible ones (25-100 kg/m3) were produced. They were characterized in terms of their thermal conductivity, thermal diffusivity, water absorption, water vapor permeability, resistance to mold attack and resistance to flame propagation in the horizontal direction. Comparisons were conducted in all tests with a commercial product (glass wool).
It was possible to define the most suitable operational conditions for the manufacture of insulation panels. Different alternatives for mechanical treatment of bark were evaluated, noting that milling in a hammer mill provides high fibers yield with low energy requirements. Pressing using saturated vapor reduces curing time and energy consumption during manufacturing. In addition, two types of anchoring agents were tested: bicomponent synthetic fibers and phenolic resin to produce flexible and rigid panels, respectively.
Due to their organic nature, the panels can be affected by fire, humidity and pathogens (molds/fungi). Incorporation of antifungal agents and flame retardants was thus evaluated.
We confirmed that lower densities, results in greater thermal insulation. Flexible panels achieved thermal conductivity values similar to that of glass wool, with densities varying between 25 and 100 kg/m3. But, bark panels, unlike glass wool, have a higher thermal inertia, which reduces temperature variations inside the house despite the fluctuations the outdoor temperature.
Both prototypes, rigid and flexible, can be used in a wide range of applications, from bare panels with different density in floors and exterior of house walls to sandwich-type panels for prefabricated houses and low-density flexible panels for interior walls and ceilings. The industrial-scale manufacturing process still needs to be optimized and validated as we pursue to license the developed technology. Tests must also be carried out under actual conditions of use, and the techno-economic and market feasibility should be evaluated.