Development of sunflower-based insulation materials coated with glycerol esters to prevent microbial growth

It is now well known that, under specific environmental conditions, building materials may be the target of microbial proliferation. Their growth leads to the deterioration of both materials and indoor air quality (indirectly induced by the release of airborne microbial contaminants, including spores, fragments, toxins, mVOC, etc.). As bio-based building materials usually contain cellulose or derivatives, they are likely to be much more sensitive to such degradations. However, very few studies have shown precise hygrometric conditions that allow microbial growth and spread on this type of material. Glycerol esters are valuable by-products of agroindustry. Previous works have highlighted their significant antimicrobial effect. They are commonly used in the food industry as antimicrobial agents. They could be used as well to protect bio-based materials from microbial colonization. It would be an eco-friendly alternative, consistent with human health, to the classic ways of protecting bio-based materials against microorganisms. Two types of insulation bio-based materials were designed from sunflower stalk particles. A “light” type was casted from pith and a “denser” one was casted from extruded bark, i.e. the depithed stalk. Physical, thermal and hygric performances of the insulating panels were assessed (density, thermal conductivity, water vapor permeability and vapor sorption isotherm). Minimum inhibitory concentrations (MIC) of glycerol esters on two fungal strains were evaluated. Then, the antimicrobial properties of the coated materials were investigated under severe conditions favoring microbial growth.