Optimization of Thermal Conductivity vs. Bulk Density of Steam-Exploded Loose-Fill Annual Lignocellulosics

Abstract

Lignocellulosic biomass (LCB)-based thermal insulation materials available in the market are more expensive than conventional ones and consist mainly of wood or agricultural bast fibers which are primarily used in construction and textile industries. Therefore, it is crucial to develop LCB-based thermal insulation materials from cheap and available raw materials. The study investigates new thermal insulation materials from locally available residues of annual plants like wheat straw, reeds and corn stalks. The treatment of raw materials was performed by mechanical crushing and defibration by steam explosion process. Optimization of thermal conductivity of the obtained loose-fill thermal insulation materials was investigated at different bulk density levels (30–45–60–75–90 kg m−3). The obtained thermal conductivity varies in range of 0.0401–0.0538 W m−1 K−1 depending on raw material, treatment mode and a target density. The changes of thermal conductivity depending on density were described by the second order polynomial models. In most cases, the optimal thermal conductivity was revealed for the materials with the density of 60 kg m−3. The obtained results suggest the adjustment of density to achieve an optimal thermal conductivity of LCB-based thermal insulation materials. The study also approves the suitability of used annual plants for further investigation towards sustainable LCB-based thermal insulation materials.

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed

“…That phenomena could be explained by a large amount of soluble sugars providing nutrients for mold fungi [25]. The most potential soluble sugars of raw LCB used in this study is the content of hemicelluloses that varied in range of 24-30% [23]. The highest resistance to fungi growth of reed raw LCB could be associated to the natural plant growing conditions in water.…”

“…The obtained SEP and TMP materials were mechanically foamed by a self-made device through a system of two rotating cylinders (900 rpm) coupled with stainless steel wires as described in [23]. The procedure was performed at least 3x to separate and homogenize the obtained fiber mass making it fluffy and suitable for application as loose-fill thermal insulation material.…”

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed

“…The negative effect of higher sugar contents against molds was shown on wood–plastic composites made of different wood types [ 16 ]. The soluble sugars of raw LCB used in this study with the most potential for mold is the content of hemicelluloses, which varied in range of 24–30% [ 29 ]. The highest resistance to fungi growth of reed raw LCB could be associated with the natural plant growing conditions in water.…”

“…The obtained SEP and TMP materials were mechanically foamed by a self-made device through a system of two rotating cylinders (900 rpm) coupled with stainless steel wires, as described in [ 29 ]. The procedure was performed at least 3× to separate and homogenize the obtained fiber mass making it fluffy and suitable for application as loose-fill thermal insulation material.…”