Improvement of the mechanical properties of PLA/coffee residue biocomposites from the liquor industry

Abstract

This work deals with the revaluation of coffee bean residues from the coffee liquor industry with the aim of developing eco-efficient composite materials with a polymeric matrix of polylactic acid (PLA). The coffee residue is incorporated in a proportion of 20% to the PLA by extrusion. After a grinding process, they are processed by injection to obtain standardized test pieces for their characterization. In order to improve the mechanical properties, as well as the toughness and compatibility between the biopolyester and the lignocellulosic particles of the coffee residue, two oligomers of lactic acid (OLA2 and OLA2mal functionalized with maleic anhydride) are added, together with the particles of the coffee residue during the extrusion process. These "Green composites" show that the incorporation of coffee residue particles from the manufacture of coffee liquor considerably increases the ductility of the samples analyzed by practically 280% due to their high content of oils present in the lignocellulosic residue. In addition, the incorporation of the OLA2 and OLA2mal oligomers contribute to improve the tensile strength of the composite materials studied, by 35% and 60%, respectively. These interesting results show the wide possibilities of this eco-efficient and sustainable material made of PLA and coffee residue. These are biodegradable materials, respectful of the environment and that allow the revaluation of coffee bean residues from the agri-food industry such as coffee liquor.