Cellulose whiskers separated from commercially available microcrystalline cellulose (MCC) and polylactic acid (PLA) were used to develop novel nanostructured biocomposites by compounding extrusion. MCC was treated with N , N -dimethylacetamide (DMAc) containing lithium chloride (LiCl) in order to swell the MCC and partly separate the cellulose whiskers. The suspension of whiskers was pumped into the polymer melt during the extrusion process. Different microscopy techniques, thermogravimetric analysis, X-ray diffraction and mechanical testing were used to study the structure and properties of the whiskers and composites. The results showed that DMAc/LiCl can be used as swelling/separation agent for MCC but seems to cause degradation of the composites at high temperature processing. The structure of composites was made up of partly separated nanowhiskers when PEG was used as processing aid. The mechanical properties of nanocomposites were improved and compared to reference material the elongation to break was increased about 800% for one material combination. The future studies will be focused on process optimization, dispersion of nanowhiskers and finding a more suitable pumping medium to avoid thermal degradation of the composite. Udgivelsesdato: December ; Cellulose whiskers separated from commercially available microcrystalline cellulose (MCC) and polylactic acid (PLA) were used to develop novel nanostructured biocomposites by compounding extrusion. MCC was treated with N , N -dimethylacetamide (DMAc) containing lithium chloride (LiCl) in order to swell the MCC and partly separate the cellulose whiskers. The suspension of whiskers was pumped into the polymer melt during the extrusion process. Different microscopy techniques, thermogravimetric analysis, X-ray diffraction and mechanical testing were used to study the structure and properties of the whiskers and composites. The results showed that DMAc/LiCl can be used as swelling/separation agent for MCC but seems to cause degradation of the composites at high temperature processing. The structure of composites was made up of partly separated nanowhiskers when PEG was used as processing aid. The mechanical properties of nanocomposites were improved and compared to reference material the elongation to break was increased about 800% for one material combination. The future studies will be focused on process optimization, dispersion of nanowhiskers and finding a more suitable pumping medium to avoid thermal degradation of the composite.