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SYNTHESIS AND DEGRADATION OF FLUOROCARBON POLYMERS

Syed, Masroor-al-Hassan Rizvi (1993) SYNTHESIS AND DEGRADATION OF FLUOROCARBON POLYMERS. PhD thesis, Quaid-i-Azam University, Islamabad.

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Abstract

The exceptional physical and chemical characteristics of fluoropolymers under hostile service conditions inspired us to work on the copolymerization of chlorotrofluoro ethylene with vinyledene fluoride, methylmethacrylate and styrene. The modification of fluorocarbon polymers was also done. All polymers are degraded thermally and the effects of heat on chemical structure are observed. The history of degradation, brief notes on the general concepts of polymer degradation and techniques of degradation are described in chapter 1. A review of Chlorofluoro Polymerization and aim of present work are also presented Chapter 2 includes a description of the apparatus and experimental techniques of thermal degradation employed in the present study. Techniques used for characterization of polymers and for the identification of pyrolyzed products are also given in this chapter. In chapter 3 synthesis of chlorotrifluoro ethylene (CTFE) and vinyledene fluoride (VDF) monomers are given. The emulsion polymerization procedures using K2S2O8 as initiator, for homopolymers of CTFE, VDF, methylmethacrylate (MMA) styrene and copolymerization of CTFE with VDF, MMA and styrene are described. Modification of fluoropolymer with phenyl lithium is also given. Analytical details of polymer compositions are tabulated in the end of this chapter followed by IR spectra of polymers. The thermal degradation of homopolymers of CTFE and VDF and a series of their copolymers is discussed in chapter 4. The copolymers are more stable then that of homopolymers. The homopolymer of CTFE (PCTFE) on thermal degradation gives CTFE monomer in major amount along with carbon dioxide (CO2)' 1,2 dichloro-1,2 difluoro ethylene (C2F2C12)3-chloroperfluoropropene (C3F5Cl3), and 1,1,2 trichloro-1,2,2 trifluoroethene(C2F3C13). While homopolymer of VDF degrades to VDF monomer, silicon tetrafluoride (SiF4) formed by the reaction of hydrogen fluoride (HF) with glass and C4F3H3 All series of copolymers are showing similar types of degradation pattern which varies with composition. The structural changes just below the degradation temperature of polymers show unsaturation. The mechanism of degradation reaction are based on the initial homolysis of C-Cl bond. This initiates chain unzipping and at higher temperature depolymerization takes place. The products other than monomer are formed by the molecular elimination of hydrogen halides and by the attack or abstraction of chlorine atom. In chapter 5 the thermal degradation of homopolymer of MMA (PMMA) and a series of copolymers of CTFE-MMA are described. PMMA formed by emulsion polymerization shows that emulsifier units are incorporated in the chain. These are interfering in depolymerization as well as stabilizing at least part of the polymer. The copolymers gives products formed from the degradation of PCTFE alongwith MMA monomer and CO2. The lactonization gives rise to the small amount of methyl chloride (CH3Cl). Degradation of polystyrene (PS) is well known of giving styrene monomer, ethylene (C2H4), acetylene (C2H2), toluene (C7H8) and α-methylstyrene (C9H10). The degradation products for the copolymers are mainly CTFE and styrene monomers alongwith other degradation products of homopolymers. A small amount of chloroethylene (C2H3Cl) is also detected. These degradation studies constitutes the chapter 6. In chapter 7 pyrolysis gas chromatographic studies of all homopolymers and copolymers are described. The identification of products is done by IR. All these results are supporting the results of thermal volatilization analysis. The degradation of phenyl modified polymers is discussed in chapter 8. It is observed that assistance of phenyl group leads to early depolymerization. Above 400oC extensive crosslinking due to the presence of aromatic ring stabilised the polymers. The products of degradation are same as for PCTFE and copolymers of CTFE-VDF alongwith small amounts of phenyl chloride (C6HSC1). The chapter 9 comprise of comparative degradation studies of phenyl modified copolymer. Effects of heating time on structure, molecular weight and extent of crosslinking are described. The exceptional physical and chemical characteristics of fluoropolymers under hostile service conditions inspired us to work on the copolymerization of chlorotrofluoro ethylene with vinyledene fluoride, methylmethacrylate and styrene. The modification of fluorocarbon polymers was also done. All polymers are degraded thermally and the effects of heat on chemical structure are observed. The history of degradation, brief notes on the general concepts of polymer degradation and techniques of degradation are described in chapter 1. A review of Chlorofluoro Polymerization and aim of present work are also presented Chapter 2 includes a description of the apparatus and experimental techniques of thermal degradation employed in the present study. Techniques used for characterization of polymers and for the identification of pyrolyzed products are also given in this chapter. In chapter 3 synthesis of chlorotrifluoro ethylene (CTFE) and vinyledene fluoride (VDF) monomers are given. The emulsion polymerization procedures using K2S2O8 as initiator, for homopolymers of CTFE, VDF, methylmethacrylate (MMA) styrene and copolymerization of CTFE with VDF, MMA and styrene are described. Modification of fluoropolymer with phenyl lithium is also given. Analytical details of polymer compositions are tabulated in the end of this chapter followed by IR spectra of polymers. The thermal degradation of homopolymers of CTFE and VDF and a series of their copolymers is discussed in chapter 4. The copolymers are more stable then that of homopolymers. The homopolymer of CTFE (PCTFE) on thermal degradation gives CTFE monomer in major amount along with carbon dioxide (CO2)' 1,2 dichloro-1,2 difluoro ethylene (C2F2C12)3-chloroperfluoropropene (C3F5Cl3), and 1,1,2 trichloro-1,2,2 trifluoroethene(C2F3C13). While homopolymer of VDF degrades to VDF monomer, silicon tetrafluoride (SiF4) formed by the reaction of hydrogen fluoride (HF) with glass and C4F3H3 All series of copolymers are showing similar types of degradation pattern which varies with composition. The structural changes just below the degradation temperature of polymers show unsaturation. The mechanism of degradation reaction are based on the initial homolysis of C-Cl bond. This initiates chain unzipping and at higher temperature depolymerization takes place. The products other than monomer are formed by the molecular elimination of hydrogen halides and by the attack or abstraction of chlorine atom. In chapter 5 the thermal degradation of homopolymer of MMA (PMMA) and a series of copolymers of CTFE-MMA are described. PMMA formed by emulsion polymerization shows that emulsifier units are incorporated in the chain. These are interfering in depolymerization as well as stabilizing at least part of the polymer. The copolymers gives products formed from the degradation of PCTFE alongwith MMA monomer and CO2. The lactonization gives rise to the small amount of methyl chloride (CH3Cl). Degradation of polystyrene (PS) is well known of giving styrene monomer, ethylene (C2H4), acetylene (C2H2), toluene (C7H8) and α-methylstyrene (C9H10). The degradation products for the copolymers are mainly CTFE and styrene monomers alongwith other degradation products of homopolymers. A small amount of chloroethylene (C2H3Cl) is also detected. These degradation studies constitutes the chapter 6. In chapter 7 pyrolysis gas chromatographic studies of all homopolymers and copolymers are described. The identification of products is done by IR. All these results are supporting the results of thermal volatilization analysis. The degradation of phenyl modified polymers is discussed in chapter 8. It is observed that assistance of phenyl group leads to early depolymerization. Above 400oC extensive crosslinking due to the presence of aromatic ring stabilised the polymers. The products of degradation are same as for PCTFE and copolymers of CTFE-VDF alongwith small amounts of phenyl chloride (C6HSC1). The chapter 9 comprise of comparative degradation studies of phenyl modified copolymer. Effects of heating time on structure, molecular weight and extent of crosslinking are described.

Item Type:Thesis (PhD)
Uncontrolled Keywords:fluorocarbon polymers, copolymerization, chlorotrofluoro ethylene, vinyledene fluoride, methylmethacrylate, styrene, thermal degradation, homopolymers, copolymers
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:1411
Deposited By:Mr. Muhammad Asif
Deposited On:26 Feb 2007
Last Modified:04 Oct 2007 21:06

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