This thesis presents a detailed study of the simultaneous biaxial stretching of isotactic polypropylene (iPP) films in the partly molten state. Four commercial grades of isotactic PP (PP1--PP4) were investigated. The first three resins differed principally in isotacticity levels, which were 94.8%, 98.6%, and 99.5%, and the fourth resin had molecular weight and isotacticity levels similar to those of PP2, but differed in crystallization behavior. The four iPP resins were extruded and cast under similar conditions. The severity of the cooling was varied for PP4. The cast films were stretched on the laboratory film stretcher, that simulates closely the stretching conditions encountered in the industrial tenter-frame stretching process. The morphology of the cast films and the final stretched films was characterized by differential scanning calorimetry and wide-angle X-ray diffraction. The reflection technique was used for the X-ray measurements. Finally, the mechanical and optical properties of the films were determined, and the results were correlated with the film morphology and orientation. The effects of drawing temperature, stretching ratio, strain rate, initial morphology, and chain tacticity on deformation behavior, stretched film morphology, and end-film properties were studied, and correlations were sought. / Simultaneous equibiaxial stretching was found to be homogeneous for sufficiently high deformation rates ( 3&d2;H > 0.1 s-1). The stiffness and the thermal stability of the crystallites played an important role in deformation behavior. In fact, the biaxial yield stress showed linear dependence on the crystallite size. Upon simultaneous equibiaxial deformation, crystallinity and especially orientation increased, while crystallite size decreased. The isotacticity content was found to influence greatly the thermal stability of the initial morphology. Increasing isotacticity leads to an increase in DSC melting peak temperature of the initial morphology, overall stress of deformation, and in the final crystallinity, orientation, elastic modulus, and tensile strength of the end film. Finally, it was concluded that the crystalline phase, that melts during preheating prior to stretching forms a "structured melt" phase. The amount of structured melt is related to the tensile strength at break of the end film. Finally, it was showed that an optimal gloss is obtained, if the cast film is stretched about 15°C below its melting point.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.82839 |
| Date | January 2003 |
| Creators | Capt, Ludovic |
| Contributors | Kamal, M. R. (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 | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001983029, proquestno: AAINQ88433, Theses scanned by UMI/ProQuest. |
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