Non-terminal behavior as a finger print to follow droplet deformation

Abstract

It is well-established that rheology can trace structural dynamics and conjectures the forming/formed morphology. The objective of this work is to trace the droplet deformation via conducting fiber spinning process. In this regard, two types of polymer blends Polypropylene (PP)/Polyamide6 (PA6) and Polypropylene/Polytrimethylene terephthalate (PTT) with various ratios (99/1, 94/6, 90/10, and 80/20) were melt-blended on co-rotating twin screw extruder and thereafter, were spun. Scanning electron microscopy (SEM) images represent a droplet and fibrillar morphologies for as-extruded samples and spun blend fibers respectively. Unlike PA6 as dispersed phase, PTT droplets in PP/PTT blend system shows improved spinnability. Linear melt viscoelastic data were gathered by performing rheological approaches in linear region. Conducting frequency sweep at 240°C is revealed a terminal behavior for Gʹ and a Newtonian plateau for η* at low frequencies. However, at 195°C dynamic rheological data pertinent to fibers represent a non-terminal trend for Gʹ and viscosity upturn at low frequencies respectively. These distinguishable characteristics can be considered as spinnability of droplets which reflect fibrillation mechanism, and fibrillar growth can be followed by scanning the viscoelastic responses at low frequency region which enhanced upon fibril growth. According to SEM and rheological test results, PTT, as an engineering plastics, manifests higher capability of forming nano fibrils.