An investigation on the possible use of coffee silverskin in PLA/PBS composites

The production of degradable packaging materials is a task that can be no longer postponed. Moreover, high amounts of agricultural wastes are landfilled without any recycling. In this research, the possibility to formulate particulate composites made of biopolymers filled with coffee waste with acceptable physical and mechanical characteristics that will degrade is investigated. The addition of this agricultural waste, by reducing the requested amount of biopolymer, can decrease the overall price of the material presently the main limiting factor to the use of biopolymers in the packaging industry. Silverskin, the integument of coffee beans discarded during the roasting process, after a milling step, is added up to a 30 wt% either to polylactic acid (PLA) or to a blend of PLA and polybutylene succinate. The filler can be homogeneously dispersed in both systems. The data shows that the silverskin filler increases the elastic modulus but decreases the tensile strength of the material and helps the development of crystal phase in the matrix. The thermal stability and the hydrophobicity of the materials stay almost unchanged on filler addition. Moreover, data shows that the addition of silverskin increases the materials susceptibility to microbial attack.

Automated summary

This research investigates the possibility of formulating degradable packaging materials using coffee waste as a filler. By adding coffee silverskin filler, the required amount of biopolymer is reduced, resulting in a lower material cost. However, the addition of filler also affects some material characteristics, such as increasing the elastic modulus, decreasing the tensile strength, and increasing susceptibility to microbial attack.