Screw Extrusion as a Scalable Technology for Manufacturing Polylactide Composite with Graphene Filler

The use of carbon nanomaterials as fillers in the process of obtaining polymer composites by extrusion poses many problems.The high agglomeration ability and low bulk density of carbon nanomaterials do not allow to easy production of composites characterized by very good dispersion of the filler in the polymer matrix, which is required to obtain a high-quality product.The advantage of this type of fillers is that the improvement of the composite properties can be achieved even at a low degree of filling.In this article, we describe a method for obtaining polylactide composites with a nanofiller in the form of graphene nanoplatelets.To overcome the difficulties associated with the use of graphene, we divided the process of obtaining composites into two stages.In the first stage, we made a masterbatch containing 25 wt.% graphene, from which, in the second stage, we obtained target composites containing from 0.1 to 2 wt.% graphene.A twin-screw extruder was used in both stages.The tested filling levels had no significant impact on the recorded processing parameters.The composites obtained by the described method are characterized by good dispersion of graphene.However the graphene agglomerates can be observed in the polymer matrix.Composites were tested by SEM, FTIR, DSC and MFR methods.Mechanical tests such as static tension, three-point bending, impact strength showed that the addition of 0.5 wt.% of graphene improves tensile strength by 10%, Young's modulus by 19% and both flexural strength and flexural modulus by 15%.The carbon filler has an impact on crystallization process of the polymer matrix by acting as a nucleating agent.