Investigation of the initial degradation stage and tensile strength of polylactide and its composites with eggshells

The degradation rate of the composite polylactide (PLA) – eggshell powder (ESP), depends on many factors. The main are porosity, particle distribution, the weight load of ESP and chain length, the microstructure of bio-based and biodegradable PLA polymer. Bio-additives introduced to polymer matrix may have an impact on mechanical properties of the composite. Natural bone structure inspires to design mimicry materials. Materials which combine inorganic and organic components are of highly complex structure. The paper focuses on the investigation of tensile strength and the initial stage of degradation of PLA and its composites with ESP in two media, i.e. H2O and PBS. ESP was obtained by grinding, stirring with mixture 14.5 wt.% NaOH and 85.5 wt.% ethanol, and drying. Samples containing: 0, 10 and 20 wt.% of ESP were prepared. Dumbbell-samples were made by injection molding, and their mechanical properties were measured. Tensile results suggest that Young’s modulus increased and tensile strength decreased as the amount of ESP is increased. Conductivity and pH of incubation media differed according to the material composition. SEM-EDS observations of PLA-ESP composites after fracture test were performed, and showed good adhesion between ESP and the polymer matrix. Influence of the incubation in H2O and PBS on PLA and PLA- -ESP composite surface degradation was checked. The PLA-ESP composites are characterized by a combination of unique properties, which may be suitable to use them as an eco-friendly packaging or medical material.