The Thermal Decomposition of Some Poly(methylphenylsiloxanes)

Francey, Kenneth F (1978) The Thermal Decomposition of Some Poly(methylphenylsiloxanes). PhD thesis, University of Glasgow.

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The demand for materials with high thermal and oxidative stability increases with the technological advances made by industry. Silicones have found extensive use as thermally stable oils, rubbers and resins since their introduction in the early forties. In recent years, research has been carried out to relate fundamental knowledge of polymeric reactions to their physical behaviour under working conditions in order to improve their properties. This work is aimed at increasing the understanding of the thermal breakdown of some linear polysiloxanes with methyl and phenyl side groups. A comprehensive review of the literature relating to the degradation of polysiloxanes is given in Chapter 1 along with brief notes on their history, uses and nomenclature. A list of the chemicals used and polymerisation techniques is given in Chapter 2 along with details of the apparatus and experimental techniques employed in this study. Notes on thermal analysis techniques and techniques for qualitative and quantitative analyses of products are also given in this Chapter. The preparation and thermal degradation of poly(methylphenylsiloxane) is discussed in Chapter 3. The main products are cyclic trimer, tetramer and pentamer isomers. Benzene is also formed. In Chapter the preparation and thermal properties of a series of poly(dimethyl/methylphenylsiloxane) copolymers is described. Twenty six different cyclic compounds, from trimer to hexamer, have been identified in the degradation products along with small amounts of benzene. A series of poly(dimethyldiphenylsiloxane) copolymers has been prepared and their thermal degradation under vacuum has been studied. Over twenty different cyclic siloxanes have been separated from the degradation products and the results are described in Chapter 5. Benzene is again a product. The results from Chapters 3, 4 and 5 are summarised in Chapter 6 and the stability of the three systems is compared. In Chapter 7, preliminary studies on block copolymers of poly(siloxane-urethane) are described. There is evidence that these copolymers depolymerise by a similar mechanism to organic polyurethanes with the formation of urea and carbodiimide structures. Carbon dioxide and benzene are present in the volatile products of degradation.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Polymer chemistry, Thermodynamics
Date of Award: 1978
Depositing User: Enlighten Team
Unique ID: glathesis:1978-78781
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:55
Last Modified: 30 Jan 2020 14:55

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