Comparative Study on Polyamide 6 Toughness using Multiple Melt-Kneading Techniques

In the present work, we tried to toughen polyamide 6 (PA6) by blending a small amount of low molecular-weight polyethylene (LMWPE). We obtained the PA6/LMWPE blends with different morphologies using multiple melt-kneading methods such as the uniaxial melt-kneading, the eight-axial screw melt-kneading, and the high shearing method. As a result, it was elucidated that the LMWPE was homogeneously and finely dispersed by using the eight-axial melt-kneading method. On the other hand, we found that for high shearing method the LMWPE was finely dispersed to a degree close to the compatible system. The result of the three-point bending test showed that the PA6 was brittle fractured, but it changed to ductile fracture when a small amount of LMWPE was blended. Also, the fracture displacement was extensively improved. The results of the comparison by the melt-kneading methods revealed that the toughness of the PA6 was improved even by adding a small amount of LMWPE (about 2%) when they were blended using the eight-axial screw melt-kneading machine. The cross-sectional observation in the bending test showed that voids were produced from the LMWPE. We elucidated that the production of voids was induced with low stress by adding fragile LMWPE, resulting in the improvement of the bending toughness. Moreover, we found that the LMWPE needs to be finely dispersed with an appropriate particle size in order to exhibit ductile properties.