Chemical structures, rheological and physical properties of biopolyols prepared via solvothermal liquefaction of Enteromorpha and Zostera marina biomass

Abstract

In this work, liquefied biomass from the Baltic Sea was used for the preparation of rigid polyurethane (PUR) foams. The biomass contained 10 wt% of Enteromorpha macroalgae and 90 wt% of Zostera marina seagrass characterized by a high content of cellulose. The influence of time, temperature and the type of solvent on the efficiency of the liquefaction process and properties of biopolyols was determined. Obtained materials were analyzed in terms of chemical structure, rheological properties, thermal stability and basic physical and mechanical properties. It was found that optimal parameters for liquefaction of used biomass were: temperature of 150 °C, reaction time of 6 h and a solvent mixture containing glycerol and poly(ethylene glycol) in ratio of 50:50 (biopolyol 50G50P_150). Under these conditions, 78 wt% of biomass was liquefied and resulting biopolyol was characterized by a hydroxyl number of 650 mg KOH/g. Depending on the used solvent mixture and the liquefaction temperature, biopolyols showed the character of Newtonian or non-Newtonian liquids. Rigid PUR foams were obtained by substitution of petrochemical polyol with 10, 20 and 30 wt% of biopolyol. It was found that the addition of biopolyol to foams’ formulations did not cause significant changes in their chemical structure, while mechanical strength and thermal stability were enhanced. The presented study confirms that biomass from the Baltic Sea can be used for the synthesis of biopolyols and rigid polyurethane foams.