Poly(lactic acid) green composites filled with linseed cake as an agricultural waste filler. Influence of oil content within the filler on the rheological behavior

The rheological behavior of poly(lactic acid) (PLA) composites filled with linseed cake (LC) has been investigated in relation to the amount of the filler and the fat content in the natural waste agricultural filler. Natural waste fillers characterized with 17.4 and 28.7 wt % content of linseed oil were incorporated in different amounts (5–40 wt %) into a polymeric matrix. The main task was to investigate the plasticization effect of PLA by oil residue present in LC which was used as a low‐cost filler in highly filled biocomposites. The application of oscillatory rheological measurements and capillary rheometry allowed to get a detailed description of the changes in the composites' rheological behavior in reference to the plasticizing effect caused by the oil that migrated from the filler. The rheological properties of composites with natural filler with high oil content were evaluated also with rheological tests related to processing properties: the torque rheometry and melt flow index. It has been proven that the application of natural fillers from the food industry with high oil content allows to produce highly filled thermoplastic composites with improved processing properties due to the lubricating and plasticizing effect of the oil on the PLA matrix.