It is becoming generally accepted that wall slip, the loss of adhesion of a polymer to a solid substrate, occurs when the shear stress exceeds a critical value. Wall slip probably plays a much more important role in plastics processing than has been previously thought. For example, the extrudate distortion called sharkskin is thought to involve slip. Recent experiments have shown that this phenomenon is highly material dependant. The surface chemistry of both the molten polymer and the bounding surface interface play important roles in both the occurrence and magnitude of wall slip. The initial objectives of the research were to study slip in further detail, concentrating on the effects of the molecular weight and molecular weight distribution of the polymer. The effects of surface properties were also to be investigated. The research was performed using a sliding plate rheometer. Erratic stress signals were observed when the shear stress exceeded a critical level, and there was strong evidence that these were related to a highly complex type of slip. Thus, a steady slip velocity, which could be simply related to the shear stress, could not be determined. It was concluded that wall slip is, in general, a chaotic process with a strong dependence on initial conditions, sample history, and boundary conditions. Further research is suggested to elucidate this phenomenon.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.26394 |
| Date | January 1994 |
| Creators | Koran, François |
| Contributors | Dealy, J. M. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Engineering (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001433693, proquestno: MM99968, Theses scanned by UMI/ProQuest. |
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