Processing of polypropylene by melt transformation extrusion process, study of flow birefringence, using an internally cooled die
This investigation involved measurement of flow birefringence of molten polypropylene in an internally cooled die in the Melt Transformation Extrusion Process. A single screw plasticating extruder was used in conjunction with an internally cooled die to produce the highly oriented extrudate. The die was provided with glass windows for flow visualization. A laser beam was used together with a photomultiplier tube to measure the flow birefringence of the molten polypropylene inside the die. The effects of pressure on birefringence were noted. A phase transition to a liquid crystalline form seemed to take place at around 2100 psig., and pressure did not seem to have much effect on the birefringence above 4500 psig. During the flow the phase transition occurred at a further lower pressure of 1700 psig. The elevation in melting point (obtained by PSC measurement) and the high tensile strength of the extrudate indicated that there is fair amount of orientation in the sample. Thus it can be concluded that the highly oriented polypropylene, obtained by Melt Transformation Extrusion Process, was formed through an intermediate liquid crystalline transition state.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:polypropylene flow birefringence internally cooled die
Date of Publication:01/01/1984