Comparing the morphological evolution of reactive and nonreactive Polystyrene/Polypropylene polymer blends: Processing phase inversion

• Published in: Polymer engineering and science 2024-07, Vol.64 (7), p.3173-3187
• Main Authors: Ramakrishnan, Shashank, Lencar, Calin, Mohseni, Majid, Sundararaj, Uttandaraman
• Format: Article
• Language: English
• Subjects: Copolymers; Deformation; Energy requirements; Evolution; Industrial equipment; Maleic anhydride; Melt blending; Morphology; Pellets; Phase inversion; Phase shift; Polymer blends; Polymer industry; Polymer melts; Polymers; Polypropylene; polypropylene blends; Polystyrene resins; reactive polymer blending; Torque; Visualization
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.26759

This paper discusses the evolution of morphology in 80/20 (vol/vol) (polypropylene‐maleic anhydride)/polypropylene (PP)/(polystyrene‐oxazoline)/polystyrene (PS) reactive blends and nonreactive 80/20 PP/PS blends. For both the blends, the PS forms the continuous phase initially, traps the PP‐maleic anhydride or PP pellets within, and gradually deforms these pellets to lamellar sheets and elongated fibers. Eventually, the irregular domains of PP coalesce and invert to form the continuous phase in a transition known as the “processing phase inversion.” The nonreactive PP/PS blend needed much higher torque to be deformed from pellets to a viscoelastic melt than their reactive counterparts. Despite the significant differences in their processing energy, the reactive and nonreactive blends have similar morphologies during the inversion process. The changes in the structure of the blends were captured on video by a custom‐built visualization system and correlated with scanning electron microscopy of the fractured surfaces, along with monitoring the changes in the torque levels during the processing. The solid‐state properties of the minor phase were crucial for deforming the major phase pellets and, consequentially, the work required to process the blends. Due to a suppression of coalescence due to the presence of in situ formed copolymers at the interface of the PP/PS, a finer dispersion was obtained in the case of the reactive blend systems. Highlights Visualization of polymer melt blending. In situ reaction during processing. Processing energy requirements during blending. The morphology development of in situ reactive blends is compared with their nonreactive counterparts. The specific mechanical energy required to process these blends under different processing conditions is examined. The various rheological states that the blends undergo during the processing are visualized.