Molecular Orientation in Injection-molded Polypropylene Copolymers with Ethylene
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M. Fujiyama
Abstract
Flexural test specimens were injection-molded from random and block polypropylene copolymers with various ethylene contents at cylinder temperatures of 200 to 320°C. Properties such as flexural modulus (FM), flexural strength (FS), heat distortion temperature (HDT), Izod impact strength (IIS), and mold shrinkage (MS), and degrees of molecular orientation such as thickness of skin layer (ST) and crystalline orientation functions and their distributions in the flow and thickness directions were measured. The relationships between these properties and the degrees of molecular orientation were investigated. These properties decreased with increasing cylinder temperature. FM, FS and HDT were decreased by copolymerization with ethylene, in particular, by random copolymerization. IIS was increased by copolymerization with ethylene. MS was decreased by random copolymerization and slightly increased by block copolymerization. ST and crystalline c-axis orientation function fc decreased with increasing cylinder temperature and ethylene content and on increasing distance from the gate. fc is high at the surface region and decreases toward the interior. The higher the cylinder temperature and ethylene content, the lower is fc at the surface region. There are cases at high cylinder temperatures where a shoulder or a peak of fc is observed at a middle point in the thickness direction, which is assumed to be caused by secondary flow during cooling and pressure holding process. Rectilinear relationships between the properties and ST or fc were obtained for each sample. This means that the properties cannot be unified only with degree of molecular orientation and the character of sample still remains. The character of the sample is assumed to be originated from higher-order structures beside molecular orientation, for example, crystallinity, spherulite size, and thickness of lamellae, etc.
© 1992, Carl Hanser Verlag, Munich
Articles in the same Issue
- Contents
- Contents
- Internal and Continuous Mixers
- Model Development for an Internal Mixer
- Simulation of Flow in a Farrel Continuous Mixer
- Extrusion
- Influence of Process Data on the Throughput of Large Extruders within the Range of 600 to 6 000 kg/h
- Conveying and Melting in Screw Extruders with Axial Screw Movement
- Thermo-viscous Effects in Extrusion of Planar Jets with Solidification
- Film
- Dynamics and Stability of Double Bubble Tubular Film Extrusion
- Melt Strength Behavior of Polyethylene Blends**
- Optical Properties and Orientation Development in Uniaxially Stretched Syndiotactic Polystyrene from Amorphous Precursors
- Molding
- Thermoviscoelastic Calculation of Residual Stresses and Residual Shapes of Injection Molded Parts**
- Analysis and Simulation of Structural Reaction Injection Molding (SRIM)
- Crystal Orientation in Injection Moldings of Flaky Filler-Filled Polypropylenes
- Erratum
- Molecular Orientation in Injection-molded Polypropylene Copolymers with Ethylene
Articles in the same Issue
- Contents
- Contents
- Internal and Continuous Mixers
- Model Development for an Internal Mixer
- Simulation of Flow in a Farrel Continuous Mixer
- Extrusion
- Influence of Process Data on the Throughput of Large Extruders within the Range of 600 to 6 000 kg/h
- Conveying and Melting in Screw Extruders with Axial Screw Movement
- Thermo-viscous Effects in Extrusion of Planar Jets with Solidification
- Film
- Dynamics and Stability of Double Bubble Tubular Film Extrusion
- Melt Strength Behavior of Polyethylene Blends**
- Optical Properties and Orientation Development in Uniaxially Stretched Syndiotactic Polystyrene from Amorphous Precursors
- Molding
- Thermoviscoelastic Calculation of Residual Stresses and Residual Shapes of Injection Molded Parts**
- Analysis and Simulation of Structural Reaction Injection Molding (SRIM)
- Crystal Orientation in Injection Moldings of Flaky Filler-Filled Polypropylenes
- Erratum
- Molecular Orientation in Injection-molded Polypropylene Copolymers with Ethylene
