Experiments were carried out to measure the surface energy of boron nitride (BN)
powders. A reliable procedure has been developed for measurement of surface energy of
powders using the capillary rise technique based on Washburn's equation. It is measured
by finding the contact angle from liquid penetration experiments with polar and non-polar
liquids. Both the dispersive and non-dispersive components of surface energy are
determined. The results of the surface energy of BN powders has been found to correlate
well with the critical shear rate for the onset of melt fracture, indicating the importance of
surface energy in the procedure of selecting an effective processing aid.
In addition, experiments were carried out in both an Instron capillary rheometer equipped
with a special annular die (Nokia Maillefer wire coating cross-head) and a parallel-plate
rheometer to investigate the effect of a new processing additive (boron nitride powder in
combination with a fluoroelastomer) on the rheology and processability of molten
polymers. Metallocene polyethylenes with and without boron nitride (BN) and
fluoroelastomer are tested in extrusion. First, it is demonstrated that BN is a superior
processing aid compared to conventional fluoropolymer ones. Secondly, it is found that
the combination of BN powders with a small amount of a fluoroelastomer improves even
further the processability of molten polymers. They can essentially be processed at higher
shear rates without exhibiting gross melt fracture. DSC and TGA experiments using
polymer specimens with and without BN were also carried out to investigate the
mechanism by which gross melt fracture is being eliminated in the presence of boron
nitride. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/37979 |
| Date | January 2011 |
| Creators | Seth, Manish |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
Page generated in 0.0026 seconds