Determination Of A Limit In Particle Concentration For Coalescence In Pa6/Hdpe Blends Under Extensional Flow

A limiting dilute concentration of the dispersed phase in polyamide-6 (PA6) and high-density polyethylene (HDPE) blends during extensional flow was detected. This limit concentration is explained in terms of coalescence phenomena. Blends of PA6/HDPE at different compositions and melt-drawn ratio were prepared using a twin-screw extruder with a rectangular slit at 250 degreesC. The rectangular sheets were cooled in water prior to being rolled with a suitable device. The extrusion velocity was maintained constant and the take up velocity was varied in order to obtain different states of deformation of the minor phase. The morphology results shown that at low take up velocity, the final state of deformation is independent of the dispersed phase composition. However, at high take up velocity the drop deformation increases with the composition. To determine a lower limit concentration, at which coalescence occurs, the average particle volume of the dispersed phase was evaluated. At the concentration range of 1 to 4 %vol. of PA6, the average volume of the particles remains constant (no coalescence) during the stretching process. However, at higher concentrations (> 5 %vol. of PA6) the coalescence process takes place and the volume increases with stretching.