Solid state structure of some polyenes

Vile, Jacqueline (1984) Solid state structure of some polyenes. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The role of disordered phases intermediate between meltand final product in defining the properties of partially crystalline isotactic polypropylene were investigated. Molten isotactic polypropylene films (varying thickness) were either quenched into liquid nitrogen or cooled slowly to room temperature from three melt temperatures. The quenched films were examined by X-ray diffraction and vibrational spectroscopy at liquid nitrogen and temperatures up to room temperature. Density and infrared measurements were made on samples warmed to higher temperatures. It was concluded that the morphology of quenched isotactic polypropylene depended on the morphology of the melt prior to quenching and the rate of quenching. On warming the films to temperatures >Tg(-20 C)<80 C, the temperature of the environment now controlled the morphology, whereas the structure of melt-crystallized polypropylene did not alter with increasing temperature i.e. >25 C<80 C.The nature and location of the short chain branching was investigated for three branched polyethylenes and ~ur ethylene copolymers, by combining high resolution C NMR spectroscopy with nitric acid digestion. Crystallinity by X-ray, density.DSC and Raman spectroscopy and the melting temperature were also calculated. It was concluded that the morphology of branched polyethylene contained three phases with isolated >C branches located on the edges of the crystalline cores, isolated butyl and longer branches situated in the transition zones and branched and bunched ethyl and longer branches positioned in the amorphous layers. Finally the structure and properties of linear polyethylene produced by rapid quenching of a flowing melt was studied. Extruded molten polymer was quenched inside a capillary die from different flow rates, pressure and die head temperatures. The quenched rods were examined using optical microscopy, Raman spectroscopy, density, DSC and a mechanical test. It was concluded that the physical properties of the moulded rods depended on flow rate, shear at the die wall, die head temperature, viscosity and pressure of the molten polymer and the design of the die.

This record has no associated files available for download.