Pre-treatment and its effect on the thermal conductivity of natural lignocellulosic rice straw stubble waste boards: Analysis vis a vis potential for the civil engineering applications

Abstract

Once built, the residential or commercial building must maintain a temperature suitable for human comfort. Presently, according to an estimate, building energy consumption contributes about 40 % to global greenhouse gas (GHG) emissions. Thus, it is necessary to develop building materials that not only have low or zero carbon footprints during their production stage but also provide thermal insulation for buildings amidst variable climates. Among such materials, the use of straw waste boards can not only offer an opportunity to reduce the use of GHG-intensive materials but also provide excellent thermal insulation. The objective of the present work is to fabricate, characterize, and evaluate the thermal conductivity of composite boards made from rice (Oryza sativa) straw. The effect of water and alkali pre-treatment is also evaluated. Three different mass fractions (Mf) with 50 %, 60 %, and 70 % of straw by weight are considered, and three different matrix materials, viz., Polyethylene (PE), Polylactic acid (PLA), and epoxy resin, have been used. Among these, the epoxy matrix is found to be most suitable owing to its uniform dispersion, which leads to superior adhesion in the straw laminates. Subsequent morphological characterization techniques, such as energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), have been employed to evaluate the physicochemical structure changes of straw fibre and fibre boards. The microstructural characterization revealed that the alkali and water pre-treatment have a pronounced effect on the morphological properties of straw and composite boards. Thermal conductivity has been measured using the experimental setup based on the guarded hot plate method, and the lowest conductivity of heat is recorded in the order of 0.023 W/mK. The present research work attempts to demonstrate the development of a novel product using rice straw waste that can potentially replace/reduce the usage of EPS (Expanded Polystyrene) for building construction applications in the near future.