|Ph.D Student||Haba Yafit|
|Subject||Reactive Extrusion of PVC/Monomer Systems: Process|
Development and Characterization of
|Department||Department of Chemical Engineering||Supervisor||Professor Emeritus Moshe Narkis|
Reactive extrusion is a plastic processing method where an extruder is used as a chemical reactor for the continuous synthesis and modification of polymers, at elevated temperatures.
The current research describes a method to obtain polymer blends by the absorption of a liquid solution of monomer, initiator, and a crosslinking agent in suspension type porous polyvinyl chloride (PVC) particles, forming a dry blend. These PVC/monomer dry blends are reactively polymerized in a twin-screw extruder at an elevated temperature (180ºC) to obtain an in-situ polymerization in the melt state of various blends: PVC/polystyrene (PVC/PS), PVC/polymethyl methacrylate (PVC/PMMA), PVC/polyvinyl acetate (PVC/PVAc), PVC/polybutyl acrylate (PVC/PBA) and PVC/polyethylhexyl acrylate (PVC/PEHA). Reactively extruded PVC/PMMA and PVC/PVAc blends are transparent and form single phase morphology, while reactively extruded PVC/PS, PVC/PBA and PVC/PEHA blends are not transparent and two discrete phases are observed.
The properties of the reactively extruded PVC based blends are compared to physical PVC blends at similar compositions. The morphology of the reactively extruded and physical PVC based blends is characterized using scanning electron microscopy, energy dispersive spectroscopy and small angle x-ray scattering; tensile mechanical and dynamic mechanical properties are measured using an Instron machine and dynamic thermal mechanical analysis, respectively; melt rheology properties are measured using parallel plates rheometer; thermal stability is characterized using thermal gravimetric analysis; molecular characterization is obtained using both solution and solid state nuclear magnetic resonance.