A Rheological Study of Isotactic Metallocene-Based Polypropylene Resins and the Mathematical Modeling of the Melt Spinning Process-Edición Única

Abstract

A comprehensive rheological study of metallocene-based isotactic polypropylene resins was conducted and the materials were processed into fibers by the industrial melt spinning process. The study also includes the standard quality properties commonly used by industry. Two important features of this thesis is the application of the Cogswell analysis for the transient and steady-state elongational viscosity using a double bore capillary rheometer and the development of a non-isothermal melt-spinning mathematical model that, using laboratory (rheological) data, can help to understand and establish the processability of new polymers at industrial conditions. The rheological tests included double bore capillary rheometry, frequency sweeps, stress under constant shear rate, and creep and recovery compliance. The transient elongational viscosity technique using the double bore capillary rheometer (Rosand) was developed using the original Cogswell's analysis.. The standard industrial quality properties tested were Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetry (DSC), Permeation Chromatography (GPC), melt flow index (MFI), and percentage of solubles (PS). The melt spinning model was developed from mass, momentum and energy balances coupled to the multi-mode Phan-Thien and Tanner constitutive equation. The model uses the resins' rheological data and helps to establish their melt spinning processability. The stress under elongational deformation is important in the breakage of the fibers. iii