Polymer Solidification under Pressure and High Cooling Rates
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V. Brucato
Abstract
Polymer solidification under processing conditions is a complex phenomenon in which the kinetics of flow, high thermal gradients and high pressures determine the product morphology. The study of polymer structure formed under pressure has been mainly made using conventional techniques such as dilatometry and differential scanning calorimetry under isothermal conditions or non isothermal conditions but at cooling rates several orders of magnitude lower than those experienced in industrial processes. A new equipment has been recently developed and improved to study the crystallization of polypropylene when subjected to pressure and cooled rapidly. An experimental apparatus essentially constituted of a special injection mould has been employed. Polymer samples can be cooled at a known cooling rate and under a known pressure. Micro Hardness (MH), Wide angle x-ray diffraction (WAXD), Polarised Optical Microscopy (POM) and density measurements are then used to characterize the sample morphology. The results of rapid cooling experiments under pressure on an iPP sample display a lower density and a lower density dependence on cooling rate for increasing pressure. Micro hardness confirms the trend.
A deconvolution technique of WAXD patterns is used to evaluate the final phase content of samples and to assess a crystallization kinetics behaviour. Phase distribution results indicate that the decrease of alpha phase with pressure is balanced by an increase of the mesomorphic phase leaving unaffected the amorphous phase content. This peculiar behaviour can be easily related to a negative influence of pressure on the kinetics of the crystallization of alpha phase.
© 2000, Carl Hanser Verlag, Munich
Articles in the same Issue
- Editorial
- Sixth of a Series: Pioneer of Man-Made Fibers and Solution Spinning Louis-Marie-Hilaire Bernigaud, Comte de Chardonnet
- Screw Extrusion
- A Network Analysis of a Screw Mixing Zone
- Experimental and Numerical Study of Rhomboidal Mixing Sections
- Reactive Extrusion
- Bulk Polymerization of ∊-Caprolactone in Twin Screw Extruder
- Die Extrusion
- Computer Aided Optimisation of Profile Extrusion Dies
- Fibers and Films
- An Investigation of Venturi and Coanda Effects in Blown Film Cooling
- Blends
- Solidification Behaviour of PA6/iPP Blends at High Cooling Rates
- Polymer Blends with Fibrillar Phase Morphology Prepared by Self-Reinforcing Technique
- Molding
- Compressive Squeeze Flow of Generalized Newtonian Fluids with Apparent Wall Slip
- Comparative Study of Ziegler-Natta and Metallocene Based Polypropylenes in Injection Molding
- The Pressure-Volume-Temperature Behavior Polyethylene Melts
- Evaluation of the Thermal Behaviour of Injection Moulds
- Polymer Solidification under Pressure and High Cooling Rates
Articles in the same Issue
- Editorial
- Sixth of a Series: Pioneer of Man-Made Fibers and Solution Spinning Louis-Marie-Hilaire Bernigaud, Comte de Chardonnet
- Screw Extrusion
- A Network Analysis of a Screw Mixing Zone
- Experimental and Numerical Study of Rhomboidal Mixing Sections
- Reactive Extrusion
- Bulk Polymerization of ∊-Caprolactone in Twin Screw Extruder
- Die Extrusion
- Computer Aided Optimisation of Profile Extrusion Dies
- Fibers and Films
- An Investigation of Venturi and Coanda Effects in Blown Film Cooling
- Blends
- Solidification Behaviour of PA6/iPP Blends at High Cooling Rates
- Polymer Blends with Fibrillar Phase Morphology Prepared by Self-Reinforcing Technique
- Molding
- Compressive Squeeze Flow of Generalized Newtonian Fluids with Apparent Wall Slip
- Comparative Study of Ziegler-Natta and Metallocene Based Polypropylenes in Injection Molding
- The Pressure-Volume-Temperature Behavior Polyethylene Melts
- Evaluation of the Thermal Behaviour of Injection Moulds
- Polymer Solidification under Pressure and High Cooling Rates
