The impact of hot-water-treated fibre hemp shivs on the water resistance and thermal insulating performance of corn starch bonded biocomposite boards

This paper reports a novel type of biocomposite boards based on different fractions fibre hemp shivs as an aggregate and corn starch as a binding material for thermal insulation applications. It is shown that different fractions of hemp shivs have density varying from 81 to 96 kg/m(3), while the thermal conductivity ranges from 0.0505 to 0.0616 W/(m.K). The addition of corn starch from 10 to 50% increases the density of hemp shivs based biocomposite boards from 319 to 374 kg/m(3), and the lowest thermal conductivity is obtained for the fraction 2.5/5 mm, that is in the range of (0.0605-0.0630) W/(m.K). Based on the results obtained, two prediction models are suggested. The first one describes the thermal conductivity dependence on biocomposite board density and the second one - the dependence of biocomposite board density on the amount of corn starch added. It is as well shown that a mechanical treatment (additional shredding) has an impact on water absorption and swelling in thickness of biocomposite boards. Shredded hemp shivs lead to an average swelling in thickness of 10.7% and short-term water absorption - 4.92 kg/m(2), while non-shredded ones the respective values of 27.8% and 5.72 kg/m(2).