Elaboration of light composite materials based on alginate and algal biomass for flame retardancy: preliminary tests

Alginate-based composites prepared by incorporation of bentonite into alginate or algal hydrogels show promising properties in terms of thermal degradation (mass-loss rate curves under epiradiator irradiation). They can be used as coating agent or as structured materials. Alginates characterized by high guluronic acid content are more efficient for retarding the ignition of tested materials after calcium gelation. Brown seaweed can be directly used for preparing composite blocks with clay; a pretreatment for partial extraction of alginate was introduced in the preparation of the composite material. In order to achieve a better control of drying procedures (with low apparent density, limited shrinking), another kind of composite was successfully elaborated by the incorporation of freeze-dried alginate/bentonite beads into an alginate matrix. Algal biomass (a renewable resource, which requires less processing than when using pure alginate) can be used for the green manufacturing of promising flame-retardant materials (associated to bentonite). Freeze-dried alginate/bentonite beads incorporated in alginate hydrogels show interesting thermal degradation properties allied to low-density characteristics.