I= SYNTHESIS AND DEGRADATION OF FLUOROCARBON POLYMERS
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Title of Thesis
SYNTHESIS AND DEGRADATION OF FLUOROCARBON POLYMERS

Author(s)
Syed Masroor –al-Hassan Rizvi
Institute/University/Department Details
Department of Chemistry/ Quaid-i-Azam University, Islamabad
Session
1993
Subject
Chemistry
Number of Pages
172
Keywords (Extracted from title, table of contents and abstract of thesis)
fluorocarbon polymers, copolymerization, chlorotrofluoro ethylene, vinyledene fluoride, methylmethacrylate, styrene, thermal degradation, homopolymers, copolymers

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.

Download Full Thesis
899.11 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
47.72 KB
2 1 General Introduction 1
137.34 KB
  1.1 Thermal Analysis 1
  1.2 Thermal Degradation 5
  1.3 Thermal Degradation Reactions 6
  1.4 Degradation Techniques 13
  1.5 Preview Of Chlorofluoro Polymerization 21
  1.6 Aim Of Work 23
3 2 Characterization Techniques 25
87.62 KB
  2.1 Thermogravimetry 26
  2.2 Thermal Volatilization Analysis 26
  2.3 Differential Condensation Tva 29
  2.4 Sub-Ambient Thermal Volatilization Analysis 32
  2.5 Infr-Red Spectroscopy 35
  2.6 Gel Permeation Chromatography 35
  2.7 Elemental Analysis 36
  2.8 Neutron Activation Analysis 36
  2.9 Mass Spectrometry 37
  2.10 Pyrolysis Gas Chromatography 37
4 3 Experimental 39
160.56 KB
  3.1 Materials 40
  3.2 Synthesis Of Chlorotrifluoroethylene 43
  3.3 Synthesis Of Vinyledenefluoride 47
  3.4 Methyl Methacrylate 49
  3.5 Styrene 49
  3.6 Polymerization Procedure 49
  3.7 Preparation Of Phenyl Kel-F 54
  3.8 Purification Of Polymers 54
  3.9 Characterization Of Polymers 55
5 4 Thermal Degradation Studies Of Pcte , Pvdf And A Series Of Poly ( Ctfe-Co-Vdf ) 62
144.36 KB
  4.1 Introduction 63
  4.2 Results And Discussion 64
  4.3 Mechanism Of Degradation 82
6 5 Thermal Degradation Studies Of Homopolymers And Copolymers Of Ctfe Mma 85
125.68 KB
  5.1 Introduction 86
  5.2 Results And Discussion 88
  5.3 Mechanism Of Degradation 102
7 6 Thermal Degradation Studies Of Polystyrene And Poly ( Ctfe -Co-Styrene) 105
94.81 KB
  6.1 Introduction 106
  6.2 Results And Discussion 107
  6.3 Mechanism Of Degradation 118
8 7 Pyrolysis Gas Chromatography Of Polymers Of Ctfe , Vdf , Mma And Styrene 121
149.14 KB
  7.1 Introduction 122
  7.2 Results And Discussion 124
9 8 Thermal Degradation Of Phenyl Modified Chlorofluoro Polymers 146
65.69 KB
  8.1 Introduction 147
  8.2 Results And Discussion 148
  8.3 Mechanism Of Degradation 155
10 9 Comparative Thermal Degradation Studies Of Phenyl Modified Kel-F 158
48.52 KB
  9.1 Introduction 158
  9.2 Results And Discussion 158
11 10 Conclusion 165
10.81 KB
12 11 References 166
50.06 KB
  11.1 List Of Publications 172
13 0 Contents
47.72 KB
14 1 General Introduction 1
137.34 KB
  1.1 Thermal Analysis 1
  1.2 Thermal Degradation 5
  1.3 Thermal Degradation Reactions 6
  1.4 Degradation Techniques 13
  1.5 Preview Of Chlorofluoro Polymerization 21
  1.6 Aim Of Work 23
15 2 Characterization Techniques 25
87.62 KB
  2.1 Thermogravimetry 26
  2.2 Thermal Volatilization Analysis 26
  2.3 Differential Condensation Tva 29
  2.4 Sub-Ambient Thermal Volatilization Analysis 32
  2.5 Infr-Red Spectroscopy 35
  2.6 Gel Permeation Chromatography 35
  2.7 Elemental Analysis 36
  2.8 Neutron Activation Analysis 36
  2.9 Mass Spectrometry 37
  2.10 Pyrolysis Gas Chromatography 37
16 3 Experimental 39
160.56 KB
  3.1 Materials 40
  3.2 Synthesis Of Chlorotrifluoroethylene 43
  3.3 Synthesis Of Vinyledenefluoride 47
  3.4 Methyl Methacrylate 49
  3.5 Styrene 49
  3.6 Polymerization Procedure 49
  3.7 Preparation Of Phenyl Kel-F 54
  3.8 Purification Of Polymers 54
  3.9 Characterization Of Polymers 55
17 4 Thermal Degradation Studies Of Pcte , Pvdf And A Series Of Poly ( Ctfe-Co-Vdf ) 62
144.36 KB
  4.1 Introduction 63
  4.2 Results And Discussion 64
  4.3 Mechanism Of Degradation 82
18 5 Thermal Degradation Studies Of Homopolymers And Copolymers Of Ctfe Mma 85
125.68 KB
  5.1 Introduction 86
  5.2 Results And Discussion 88
  5.3 Mechanism Of Degradation 102
19 6 Thermal Degradation Studies Of Polystyrene And Poly ( Ctfe -Co-Styrene) 105
94.81 KB
  6.1 Introduction 106
  6.2 Results And Discussion 107
  6.3 Mechanism Of Degradation 118
20 7 Pyrolysis Gas Chromatography Of Polymers Of Ctfe , Vdf , Mma And Styrene 121
149.14 KB
  7.1 Introduction 122
  7.2 Results And Discussion 124
21 8 Thermal Degradation Of Phenyl Modified Chlorofluoro Polymers 146
65.69 KB
  8.1 Introduction 147
  8.2 Results And Discussion 148
  8.3 Mechanism Of Degradation 155
22 9 Comparative Thermal Degradation Studies Of Phenyl Modified Kel-F 158
48.52 KB
  9.1 Introduction 158
  9.2 Results And Discussion 158
23 10 Conclusion 165
10.81 KB
24 11 References 166
50.06 KB
  11.1 List Of Publications 172