Optimization of screw design on fiber breakage and dispersion in injection molded bamboo-fiber-reinforced polypropylene

Injection molding of fiber-reinforced thermoplastics (FRTP) leads to fiber breakage and in tum deterioration of mechanical properties of the molded parts. In this paper, we propose an effective screw geometry for improving both fiber dispersion and residual fiber length. By evaluating four types of screws by investigation of the molded specimens, we found that the screw geometry in the compression zone had a dominant effect on the residual fiber length, and that choosing the proper geometry for the melting and mixing process was the most important factor for improving both fiber dispersion and residual fiber length. The screw improves both properties at the same time owing to the appropriateness of its geometry for both the melting and mixing zone. Our experimental observations were compared with the results of flow analysis and consistency was observed.