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Boron nitride and its combinations as processing aids in the extrusion of Ziegler-Natta polyethylenes

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Title: Boron nitride and its combinations as processing aids in the extrusion of Ziegler-Natta polyethylenes
Author: Muliawan, Edward Bud
Degree Master of Applied Science - MASc
Program Chemical and Biological Engineering
Copyright Date: 2004
Abstract: It is widely known that the rate of production in many commercial polymer processing operations is limited by the appearance of flow instabilities. Flow instabilities may manifest themselves as regular distortions on the extrudate surface (sharkskin or surface melt fracture) or in the form of irregular helix distortions (gross melt fracture) at higher shear rates. Usually, polymer processing aids are used to postpone/eliminate these melt fractures. Fluoropolymer has been found to be effective in eliminating sharkskin melt fracture, but its effect in the gross melt fracture region is rather poor. Boron nitride, on the other hand, has been found not only to be effective in eliminating sharskskin melt fracture but also postpone the onset of gross melt fracture. In addition, it has also been found that the combination of fluoropolymer and boron nitride seems to enhance their performance even further. The main objective of this work is to investigate the performance of boron nitride and its combinations as polymer processing aids in the processing of Ziegler-Natta polyethylenes. A number of different polyethylene resins were tested including a variety of processing aids at various combinations and concentrations. It was found that mixing fluoropolymer in a dry form into boron nitride-compounded resin allows the synergistic effect of fluoropolymer and boron nitride to be shown. This is because separately mixing fluoropolymer and boron nitride prevents the adsorption of fluoropolymer onto the boron nitride particles. Lastly, it was observed that a relatively new processing aid, CarboGlide™, which is a proprietary mixture of boron nitride and other processing aids, is able to perform equally well as the combination of boron nitride and fluoropolymer.
URI: http://hdl.handle.net/2429/15792
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]

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