The Thermal Degradation of Some Bromine Containing Copolymers

Johnston, Alexander (1979) The Thermal Degradation of Some Bromine Containing Copolymers. PhD thesis, University of Glasgow.

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Abstract

The recent increasing commercial interest in the flammability properties of polymeric materials brought about by relevant legislation has stimulated renewed research into the nature and quantity of volatiles produced during polymer pyrolysis. By influencing the degradation behaviour of a polymer in either a physical or chemical manner, its burning properties can be drastically altered. The non-flammability properties of halogenated species has stimulated interest in their thermal stability both in the form of chemical additives and as an integral part of the polymer molecules. This work is aimed at increasing our understanding of the mechanisms involved in the thermal degradation of a brominated methacrylate monomer in a number of different copolymer and polymer blend environments. A brief description of the various ways in which a fire-retardant may affect a burning polymer is presented in Chapter 1. This introductory chapter also reviews briefly the relationship between chemical structure and the thermal stability of vinyl polymers. A list of the chemicals used and polymerisation conditions are given in Chapter 2 along with details of the apparatus and experimental techniques employed. Two methods for obtaining compositions of copolymers of 2-bromoethyl methacrylate and methyl acrylate are described and evaluated in Chapter 3. Reactivity ratios for the monomer pair were calculated using a Nuclear Magnetic Resonance spectroscopy method. In Chapter 4 the thermal properties of poly(2-bromo-ethyl methacrylate) homopolymer are found to be consistent with a depropagation mechanism giving monomer in yields greater than 90%, Trace amounts of ester decomposition products are formed at higher temperatures. This chapter also includes a detailed review of the thermal degradation mechanism of poly(methyl acrylate). Chapter 5 presents a qualitative and quantitative study of the various degradation fractions from copolymers of 2-bromoethyl methacrylate and methyl acrylate covering the entire composition range. The presence of compounds such as methyl bromide, 1,2 dibromoethane and acetaldehyde provides evidence for interactions occurring between the two degrading monomer units. A qualitative study on the thermal behaviour of 1:1 (by weight) blends of poly(2-bromoethyl methacrylate) and poly(raethyl acrylate) is given in Chapter 6. This study provides evidence for an intermolecular reaction between the two polymers. The results from Chapters 4, 5 and 6 are discussed in Chapter 7 in terms of possible mechanisms of formation of the various products of degradation in the 2-bromoethyl methacrylate - methyl acrylate copolymer system. Qualitative studies on the thermal degradation of an approximately 1:1 copolymer of 2-bromoethyl methacrylate and styrene are presented in Chapter 8. The nature of the volatile products suggest that depropagation reactions predominate to give the respective monomers but that transfer processes involving hydrogen and bromine atoms on the ester group of a 2-bromoethyl methacrylate unit can also occur. Chapter 9 describes the qualitative aspects of the thermal decomposition of an approximately 1:1 copolymer of 2-bromoethyl methacrylate and acrylonitrile. The methacrylate unit participates in the nitrile oligomerisation reaction with concomitant release of fragments from the ester group giving volatiles such as acetaldehyde and 1,2 dibromoethane. At higher temperatures these cyclic structures break down to give a number of volatile gases. The results from all the copolymer systems are summarised in Chapter 10 which also includes suggestions for future work.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Polymer chemistry
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-78718
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:59
Last Modified: 30 Jan 2020 14:59
URI: http://theses.gla.ac.uk/id/eprint/78718

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