Processing and characterization of a sorghum stem-based fibre polymer composite for building insulation application

Agricultural residue-based fibrous (ARF) materials have been identified to be a commercially viable solution for energy-efficient building insulation application. ARFs have various advantages over synthetic fibers including environmentally friendly, light weight, low cost, and competent mechanical properties. Meanwhile, in many African countries including Botswana, the expertise to manufacture building insulators by using ARFs is scarce and consequently building insulation material is imported. Furthermore, undesirable characteristics of hydrophilic ARF such as poor mechanical properties, water absorption, poor thermal stability, and poor adhesion with hydrophobic polymers have posed challenges to the development and application of agricultural residue-based fibers reinforced polymer composites (ARFRPCs). Hence, the need to engage a critical literature review to identify appropriate surface medication methods, materials, and processing parameters to manufacture ARFRPCs for building insulation. This thesis investigates the production of building insulation composites by using ARF derived from sorghum stalk incorporated into polymeric matrices to develop local expertise and reduce importation. To achieve this goal, samples of ARF extracted via water retting technique and then treated for five and ten days using thermo-alkali and thermo-laccase surface modification techniques. Samples of ARRFPC from both treatments were manufactured by compounding ARF with recycled low 18 density polyethylene (rLDPE) and later on processed via compression moulding technique. The samples were then dried and cured in a conditioning room for 10 days. Analytical techniques such as water absorption, thermal conductivity tests, thermo-gravimetric analysis (TGA), Scanning Electron Microscope(SEM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) were engaged to provide insight into the thermal degradation, microstructural features, interfacial adhesion mechanisms as well as mechanical and chemical characteristics of the Agricultural residue-based fibrous (ARF) materials have been identified to be a commercially viable solution for energy-efficient building insulation application. ARFs have various advantages over synthetic fibers including environmentally friendly, light weight, low cost, and competent mechanical properties. Meanwhile, in many African countries including Botswana, the expertise to manufacture building insulators by using ARFs is scarce and consequently building insulation material is imported. Furthermore, undesirable characteristics of hydrophilic ARF such as poor mechanical properties, water absorption, poor thermal stability, and poor adhesion with hydrophobic polymers have posed challenges to the development and application of agricultural residue-based fibers reinforced polymer composites(ARFRPCs). Hence, the need to engage a critical literature review to identify appropriate surface medication methods, materials, and processing parameters to manufacture ARFRPCs for building insulation. This thesis investigates the production of building insulation composites by using ARF derived from sorghum stalk incorporated into polymeric matrices to develop local expertise and reduce importation. To achieve this goal, samples of ARF extracted via water retting technique and then treated for five and ten days using thermo-alkali and thermo-laccase surface modification techniques. Samples of ARRFPC from both treatments were manufactured by compounding ARF with recycled low 18 density polyethylene(rLDPE) and later on processed via compression moulding technique. The samples were then dried and cured in a conditioning room for 10 days. Analytical techniques such as water absorption, thermal conductivity tests, thermo-gravimetric analysis (TGA), Scanning Electron Microscope(SEM), X-Ray Diffraction(XRD), Fourier Transform Infrared Spectroscopy(FTIR) were engaged to provide insight into the thermal degradation, microstructural features, interfacial adhesion mechanisms as well as mechanical and chemical characteristics of the ARFRPC modified with thermo-alkali and thermo-laccase treatments at different time durations. Both thermo-alkali and thermo-laccase treated ARFRPCs were found to be stiff and well compacted. It was established that modified fibres improved the functional performance of the composites in comparison to untreated composites. Moreover, thermo-alkali reinforced ARFRPCs exhibited the most desirable mechanical characteristics with a tensile strength of 28.57 MPa, improved microstructure/interfacial adhesion, and reduction in porosity between the filler/matrix relative to untreated and thermo-laccase treated samples. The thermo-alkali treatment increased the interfacial bonding between the plastic and the fibrous filler for the composites as observed in SEM micrographs of the fractured surfaces of ARFRPCs. The thermal properties revealed that the thermal conductivity values ranging in between 0.223-030 W/m.K are higher than other commercially available insulation materials, such as glass fiber blanket (0.039 W/m.K), cork board (0.043 W/m.K) and expanded polystyrene (0.029 W/m.K) to mention few, but they are comparable to those obtained from ARFs reinforced polymer boards. Therefore, a conclusion is made that the composite materials produced in this study require extrusion moulding which is better suited to produce foamy insulation material, and a provisional application given the quality properties of the composite boards produced is wall and floor panelling applications in buildings.