Mechanical performance of biodegradable hemp shivs and corn starch-based biocomposite boards

Abstract

For the production of traditional building materials, excavated natural resources are used. The production process of such materials requires high-energy demands, wherefore, high amounts of CO2 gases, which have a great impact on climate change, are emitted. Only a small part of such materials is effectively recycled and reused. Generally, they are transported to landfills, which rapidly expand and may pollute the soil, groundwater and air. Currently, a great attention is paid to the production of novel building materials. The aim is to use as less excavated materials as possible and replace them by natural renewable resources. Therefore, the recycling and utilisation at the end of life cycle of such materials would be easier and generation of waste would reduce. This way, the efforts of switching to circular economy are being put. One of the approaches – wider application of vegetable-based raw materials (cultivated and uncultivated agricultural plants). The usage of fibre hemp shives (HS) as an aggregate and corn stach (CS) as a binding material allows development of biocomposite boards (WPCs) which could contribute to the solution of the before mentioned problems. Bio-sourced materials combined with a polymer matrix offer an interesting alternative to traditional building materials. To contribute to their wider acceptance and application, an investigation into the use of wood-polymer composite boards is presented. In this study, biocomposite boards for the building industry are reported. WPCa are fabricated using a dry incorporation method of corn starch and HS treatment with water at 100 °C. The amount of CS and the size of the HS fraction are evaluated by means of compressive, bending and tensile strength, as well as microstructure. The results show that the rational amount of CS, independently on HS fraction, is 10 wt.%. The obtained WPCs have compressive stress at 10% of deformation in the range of (2.4–3.0) MPa, bending of (4.4–6.3) MPa and tensile strength of (0.23– 0.45) MPa. Additionally, the microstructural analysis shows that 10 wt.% of CS forms a sufficient amount of contact zones that strengthen the final product. The obtained average density (~319–408 kg/m3) indicate that, according to European normative document EN 316, WPCs can be classified as softboards and used as self-bearing structural material for building industry. Based on the requirements, WPCs can be applied in dry and humid conditions for the internal and external uses without loading (EN 622-4, section 4.2) or as load-bearing boards in dry and humid conditions for instantaneous or short-term load duration (EN 622-4, section 4.3).