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Influence of Thermo-Pressing Conditions on Insulation Materials from Bamboo Fibers and Bone Glue

Building insulation materials form the thermal envelope of a building and reduce heat transfer. They are part of the complex structural elements of a wall or a roof. Consequently, insulation materials are indispensable parts in the design and construction of buildings.

Bamboo is a sustainable material and its products are considered as building materials for the same uses as timber: floors, ceiling, wall, and building envelopes in both exterior and interior design elements. Moreover, bamboo materials have great advantages including low cost and attractive aesthetic appearance; they are therefore an ideal alternative to traditional materials for sustainable building.

Researchers at Université Savoie Mont Blanc, Vietnam National University and Ton Duc Thang University manufactured novel, environment friendly insulation fiberboards from bamboo fibers and protein-based bone glue using thermo-pressing on a heated hydraulic press. They investigated the relationship between thermal conductivity and density, the amount of proteins, humidity levels, and moisture content variation in their study.

The thermal conductivity of the specimens was determined with a TCi Thermal Conductivity Analyzer using method of Modified Transient Plane Source (MTPS) at 25 °C, and it was installed inside the RH-Box (Fig. 1). 

  

Fig. 1. The photographs of specimens and thermal conductivity measurement inside RH-Box at 25 °C.

The specimens tested (50 ± 1 mm) were pre-conditioned at 57% RH and 25 °C until reaching a constant mass. First, the thermal conductivity of these specimens was assessed at 57%RH, followed by 75%RH; the thermal conductivity was regularly measured until reaching a constant mass. After reaching a constant mass at 75%RH, these specimens were evaluated at 33%RH; the thermal conductivity was also regularly measured until reaching a constant mass. This measurement was repeated in three cycles for each relative humidity level (33% and 75%). The thermal conductivity variation could be measured according to the density, relative humidity and moisture content variation of the materials.

  

Fig. 2. Thermal conductivity functions with amount of glue (a) and density (b) of bamboo fiberboards at 57% RH and 25 °C

Fig. 3. Evolution of thermal conductivity during three cycles between 75% and 33% RH at 25 °C inside RH-Box.

Fig. 4. Evolution of thermal conductivity with moisture content variations for the fiberboards at 25 °C (RH: 57%→ 75%).

In conclusion, the thermal conductivity of bamboo fiberboards at different glue ratios is fairly low, varying between 0.0582 and 0.0812 (W.m−1K−1) at 25 °C and 57%RH. Thermal conductivity is a function of relative humidity and moisture content.

Information source: D. Nguyen, et al., Influence of Thermo-Pressing Conditions on Insulation Materials from Bamboo Fibers and Proteins Based Bone Glue (2018)

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