Comparing hemp composites made with mineral or organic binder on thermal, hygric and mechanical point of view

Abstract

This study investigates the effect of the kind of binder on thermal, hygric and mechanical properties of hemp composites. Three binders are considered: a formulated hydraulic lime based binder, a prompt cement based binder and a peculiar bio-polymer: the Poly-Lactic Acid (PLA). The binder is coupled with hemp shiv to produce biocomposite. For each kind of binder, the specific manufacturing method is presented and discussed. The thermal properties of produced biocomposite are measured with a hot disk method at 23°C, 50%RH. The hygric characterization is based on the measurement of Moisture Buffer Value at 23°C. The mechanical behavior of composite under compression is analyzed. Thermal conductivities range from 0.08 to 0.16 W/(m.K), this allows to use these composites without added insulation layer. Following the classification given in the Nordtest report, the studied materials are very good or excellent hygric regulator. Performances are slightly higher with mineral binders. However, the compressive strength obtained with PLA binder are much higher than the ones with mineral binders.