Thermal and acoustic characteristics of novel thermal insulating materials made of Eucalyptus Globulus leaves and wheat straw fibers

A novel research about using dried Eucalyptus Globulus leaves (EGL) as a biodegradable natural thermal insulating and sound absorbing material for building walls is presented. The EGL is used as leaves alone or hybrid with wheat straw fibers. Cornstarch is used as a binder for the leaves or for the hybrid specimens. Two bound specimens are made; one used leaves alone with the binder and the other used wheat straw alone. Four more hybrid specimens are made with different densities and compositions. Thermal conductivity coefficients are determined at different temperatures for all specimens. In addition to that, sound absorbing coefficient and three bending moment tests are obtained for the bound specimens. Scanning electron microscopy (SEM), Fourier transformation Infra red (FT-IR) spectral analysis, Thermo-gravimetric analysis, differential scanning calorimetry and moisture content are conducted for the leaves. Results show that the average thermal conductivity of the dried leaves is in the range 0.045–0.055 W/mK for a temperature range from 10 to 60 °C, respectively and the upper value of the hybrid specimens is about 0.065 W/mK at the maximum temperature of 60 °C. Sound absorbing coefficient has values greater than 0.5 in the range of frequency between 500 to 1600 Hz for most specimens. Thermo-gravimetric analysis shows that the leaves are stable up to 210 °C and the moisture content of the leaves is 16% at the environment conditions of Riyadh. These results ensure the promising effect of using Eucalyptus Globulus leaves as a new thermal insulating and sound absorbing material for buildings which have low environmental impact by using renewable natural resources for thermal insulation in buildings rather than the synthetic insulation materials.