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Title
DEDICATION
CERTIFICATE
DECLARATION
ACKNOWLEDGEMENT
Preface
Abbreviations
ABSTRACT
CONTENTS
List of Tables
List of Figures and Schemes
1 Introduction
Introduction
1.1 Silicon containing polymers
1.1.1 Polysilanes
1.1.2 Polycarbosilanes
Scheme 1.1. Yajimas process
1.1.3 Polysilahydrocarbons
Scheme 1.2. Synthesis of polysilahydrocarbons
1.1.4 Polysilazanes and polycarbosilazanes
1.1.5 Polysilylcarbodiimides
1.1.6 Polysiloxanes and polysilsesquioxanes
Scheme 1.4. Synthesis of polysiloxane
1.2 Boron containing polymers
1.2.1 Polymers derived from borazines
Scheme 1. 5. Synthesis of Polyborazylene
1.2.2 Decaborane (14) -based polymers
Scheme 1. 6. Formation of B10H12-L2
Scheme 1.7. Synthesis of decaborane-based polymers
1.2.3 Polymers derived from vinylpentaborane
1.2.4 Polymers derived from boric acid
1.3 Boron and silicon containing polymers
1.3.1 From functional monomers of boron with functional monomers of silicon
1.3.2 From functional monomers of boron and silicon with functional monomers of silicon
1.3.3 Chemical modification of organosilicon polymers
Scheme 1. 8. Synthesis of boron-modified silazanes
1.3.4 From single source precursors
1.4 Polyborosiloxanes
1.4.1 Borosiloxanes from boric acid
Scheme 1. 9. Synthesis of poly (borodiphenylsiloxane)
1.4.2 Polymers from borate esters
Scheme 1. 10. Preparation of polyborosiloxanes and/or SiO2-B2O3 gels
Scheme 1.11. Preparation of polyborosiloxanes from silicic acid
1.4.3 Sol-gel process
1.4.4 Organically modified SiO2-B2O3 gels
1.4.5 Applications of borosiloxanes
1.5 End uses of preceramic polymers
1.5.1 Protective coatings
1.5.2 Ceramic fibers
1.5.3 Binders for ceramics
1.5.4 Matrix resins for CMC
1.5.5 Ceramic foam
1.6 Objective and scope of the present investigation
References
2 Materials and Experimental Techniques
Materials and Experimental Techniques
2.1 Materials
2.1.1 Solvents
2.1.2 Monomers
2.1.3 Other reagents and materials
2.2 Determination of char residue of phenolic resin
2.3 Synthesis of borosiloxane oligomers from different alkoxysilanes
2.3.1 Synthesis using solvent
2.3.2 Solventless synthesis
2.4 Curing of BSiEpVi oligomer
2.5 Synthesis of borosiloxane oligomer from decaborane (14), APMDEOS and boric acid
2.6 Polysilahydrocarbons for thermal degradation kinetics
2.7 AO resistant materials
2.8 Evaluation of AO resistance
2.8.1 Polysilahydrocarbons
2.8.2 Siloxane-imide-epoxy resin
2.8.3 Phosphazene-based polymers
2.9 Preparation of polyimide film modified with borosiloxane oligomer
2.10 Ceramic conversion studies
2.11 Preparation of ceramic coatings from borosiloxane oligomer
2.12 Preparation of ceramic matrix composite
2.12.1 Preparation of precursor composite
2.12.2 Pyrolysis of precursor composite
2.12.3 Infiltration of pyrolyzed composite
2.12.4 Sintering of infiltrated composite
2.13 Characterization
2.13.1 Determination of molecular weight
2.13.2 GC analysis
2.13.3 IR spectral studies
2.13.4 NMR spectral studies
2.13.5 Chemical analysis
2.13.6 Elemental analysis
2.13.7 Thermogravimetric analysis
2.14 Mechanical properties11
2.14.1 Tensile properties
2.14.2 Flexural strength
2.14.3 Compressive strength
2.15 Evaluation of oxidation resistance
2.16 X-Ray diffraction studies
2.17 Morphological Studies
References
3 Results and Discussion
Part A Borosiloxane Oligomers
CHAPTER 3.1 Synthesis and characterization of borosiloxane oligomers from alkoxysilanes
3.1.1 Background
3.1.2 Borosiloxane oligomers from PTMOS and PTEOS
3.1.2.1 Comparison of borosiloxane oligomers from PTMOS and PTEOS
Scheme 3.1.1. Synthesis of borosiloxane oligomers from phenyltrialkoxysilane
Fig. 3.1.1. GPC curves of BSiPh-1 and BSiPh-2
Fig. 3.1.2. IR spectra of BSiPh-1 and BSiPh-2
Fig. 3.1.3. 1H-NMR spectra of BSiPh-1 and BSiPh-2
Fig. 3.1.4. 13C-NMR spectra of BSiPh-1 and BSiPh-2
Fig. 3.1.5. 29Si-NMR spectra of BSiPh-1 and BSiPh-2
Fig. 3.1.6. Possible structural units present in BSiPh-1 and BSiPh-2
Scheme 3.1.2. Possible reactions taking place in the reaction medium
Fig. 3.1.8. TG curves of BSiPh-1 and BSiPh-2
Table 3.1.2. Comparison of thermal properties of borosiloxane oligomers fromboric acid and PTMOS/PTEOS
Fig. 3.1.9. Pyrograms of BSiPh-1 and BSiPh-2
3.1.2.2. Effect of monomer feed ratio on the properties of borosiloxaneoligomers from PTEOS
Fig. 3.1.10. GPC curves of BSiPh-2, BSiPh-3 and BSiPh-4
Fig. 3.1.11. 1H-NMR spectrum of BSiPh-4
Fig. 3.1.12. 29Si-NMR spectrum of BSiPh-4
Fig. 3.1.13. TG curves of BSiPh-2, BSiPh-3 and BSiPh-4
Table 3.1.4. Comparison of thermal properties of borosiloxane oligomers
3.1.2.3 Effect of reaction time on the properties of borosiloxane oligomerfrom PTEOS
Fig. 3.1.14. GPC curves of BSiPh-2 and BSiPh-5
Fig. 3.1.15. 29Si-NMR spectrum of BSiPh-5
Fig. 3.1.16. TGA curves of BSiPh-2 and BSiPh-5
3.1.3 Synthesis of borosiloxane oligomers from VTEOS
Scheme. 3.1.3. Synthesis of borosiloxane oligomers from VTEOS
Fig. 3.1.17. IR spectrum of BSiVi-1
Fig. 3.1.18. TG curves of BSiVi-1, BSiVi-2 and BSiVi-3
Fig. 3.1.19. Pyrogram of BSiVi-1
3.1.4 Synthesis of borosiloxane oligomers from mixtures of alkoxysilanes
3.1.4.1 Borosiloxane oligomers from PTEOS and VTEOS mixture
Scheme 3.1.4. Synthesis of borosiloxane oligomer fromVTEOS and PTEOS mixture
Fig. 3.1.20. IR spectrum of BSiPhVi-1
Fig. 3.1.21. Pyrograms of BSiPhVi-1, BSiPhVi-2 and BSiPhVi-3
Fig. 3.1.22. TG curves of BSiPhVi-1, BSiPhVi-2 and BSiPhVi-3
3.1.4.2 Borosiloxane oligomers from PTMOS and VTEOS mixture
Fig. 3.1.23. GPC curve of BSiPhVi-4
Fig. 3.1.24. 1H-NMR spectrum of BSiPhVi-4
Fig. 3.1.25. 13C-NMR spectrum of BSiPhVi-4
Fig. 3.1.26. 29Si-NMR spectrum of BSiPhVi-4
Fig. 3.1.27. Pyrogram of BSiPhVi-4
Fig. 3.1.28. TG curves of BSiPhVi-4, BSiPhVi-5 and BSiPhVi-6
Fig. 3.1.29. 29Si-NMR spectrum of BSiPhVi-7
Fig. 3.1.30. TG curves of BSiPhVi-4, BSiPhVi-7 and BSiPhVi-8
3.1.5 Synthesis of borosiloxane oligomers from TEOS
3.1.5.1 Effect of mole ratio of boric acid to TEOS
Fig. 3.1.31. IR spectra of BSiT-1, BSiT-2 and BSiT-3
Fig. 3.1.32. TG curves of BSiT-1, BSiT-2 and BSiT-3
3.1.6 Synthesis of borosiloxane oligomers without using catalyst
3.1.6.1 Borosiloxane oligomers from PTMOS and PTEOS
Fig. 3.1.33. GPC curves of BSiPh-6 and BSiPh-7
Fig. 3.1.34. 29Si-NMR spectra of BSiPh-6 and BSiPh-7
Fig. 3.1.35. 29Si-NMR spectrum of BSiPh-8
Fig. 3.1.36. TG curves of BSiPh-7 and BSiPh-8
3.1.6.2 Borosiloxane oligomers from boric acid and TEOS
Fig. 3.1.37. IR spectra of BSiT-2 and BSiT-4
Fig. 3.1.38. TG curves of a) BSiT-2 and b) BSiT-4
3.1.7 Conclusions
References
CHAPTER 3.2 Synthesis of epoxy functionalized borosiloxane oligomers
3.2.1 Background
3.2.2 Epoxy-functionalized borosiloxane oligomers
3.2.2.1 Effect of solvents
Fig. 3.2.1. GC of the distillate obtained during the synthesis of BSiEp-1
Scheme 3.2.1. Synthesis of epoxy-functionalized borosiloxane oligomer
Scheme 3.2.2. Possible reaction of epoxy group with B-OH group
Fig. 3.2.2. IR spectra of crosslinked BSiEp-1 and BSiEp-2
3.2.2.2 Effect of mole ratio of boric acid to GPTMOS
Fig. 3.2.3. GPC curves of BSiEp-3A and BSiEp-3B
Fig. 3.2.4. TG curves of a) BSiEp-1, b) BSiEp-4A and c) BSiEp-4B
Fig. 3.2.5. 1H-NMR spectra BSiEp-3A and BSiEp-3B
Fig. 3.2.6. 13C-NMR spectra of BSiEp-3A and BSiEp-3B
Table 3.2.2. 1H- and 13C-NMR spectral assignments of BSiEp oligomer
Fig. 3.2.7. 29Si-NMR spectra of BSiEp-3A and BSiEp-3B
3.2.3 Epoxy and vinyl-functionalized borosiloxane oligomers
3.2.3.1 Effect of solvent on the reaction of boric acid, GPTMOS and VTEOS
Scheme 3.2.3. Synthesis of vinyl and epoxy functionalized borosiloxane oligomer
Fig. 3.2.9. GPC curve of BSiEpVi -2
Fig. 3.2.10. IR spectrum of BSiEpVi -1
Fig. 3.2.11. 1H-NMR spectrum of BSiEpVi -2
Fig. 3.2.12. 13C-NMR spectrum of BSiEpVi -2
Table 3.2.3. 1H- and 13C-NMR spectral assignments of BSiEpVi -2 oligomer
Fig. 3.2.13. 29Si-NMR spectrum of BSiEpVi -2
3.2.3.2 Effect of mole ratio on the reaction of boric acid, GPTMOS andVTEOS
Fig. 3.2.14. GPC curve of BSiEpVi-4
Fig. 3.2.15. 29Si-NMR spectrum of BSiEpVi-4
Fig. 3.2.16. TG curves of BSiEp-1and BSiEpVi-3
3.2.4 Conclusions
References
CHAPTER 3.3 Solventless synthesis of borosiloxane oligomers
3.3.1 Background
3.3.2 Solventless synthesis of borosiloxane oligomers from phenyltrialkoxysilanesin the presence of catalyst
Fig. 3.3.1. GPC curves of BSiPh-9 and BSiPh-10
Fig. 3.3.2. 1H-NMR spectra of BSiPh-9 and BSiPh-10
Fig. 3.3.3. 29Si-NMR spectra of BSiPh-9 and BSiPh-10
Fig. 3.3.4. TG curves of BSiPh-9 and BSiPh-10
3.3.3 Solventless synthesis of borosiloxane oligomers in the absence of catalyst from different alkoxysilanes
3.3.3.1 Borosiloxane oligomer from PTMOS
Fig. 3.3.5. GPC curve of BSiPh-12
Fig. 3.3.6. IR spectrum of BSiPh-12
Fig.3.3.7.1H-NMR spectrum of BSiPh-12
Fig.3.3.8. 29Si-NMR spectrum of BSiPh-12
3.3.3.2 Borosiloxane oligomer from PTEOS
Fig. 3.3.9. GPC curve of BSiPh-15
Fig. 3.3.10. 1H-NMR spectrum of BSiPh-15
Fig. 3.3.11. 13C-NMR spectrum of BSiPh-15
Fig. 3.3.12. 29Si-NMR spectrum of BSiPh-15
Scheme 3.3.1. Modification of polyimide film with borosiloxane oligomer
Fig. 3.3.13. TG curves of unmodified and borosiloxane oligomer modified polyimide films
3.3.3.3 Borosiloxane oligomer from VTEOS
Fig. 3.3.14. GPC curve of BSiVi-7
Fig. 3.3.15. 1H-NMR spectrum of BSiVi-7
Fig. 3.3.16. 13C-NMR spectrum of BSiVi-7
Fig. 3.3.17. 29Si-NMR spectrum of BSiVi-7
3.3.3.4 Borosiloxane oligomer from GPTMOS
Fig. 3.3.18. GPC curve of BSiEp-6
Fig. 3.3.19. 29Si- NMR spectrum of BSiEp-6
Fig. 3.3.20. IR spectra of BSiEp a) before b) after gelation
3.3.3.5 Borosiloxane oligomer from GPTMOS and VTEOS
Fig. 3.3.21. GPC curve of BSiEpVi-5
Fig. 3.3.22. 29 Si-NMR spectrum of BSiEpVi-5
Fig. 3.3.23. TGA curves of the cured and uncured BSiEpVi-5
3.3.4 Conclusions
References
CHAPTER 3.4 Ceramic conversion studies ofborosiloxane oligomers
3.4.1 Background
Scheme 3.4.1. Flow chart for conversion of preceramicoligomers to ceramics
3.4.2 Ceramic conversion studies of borosiloxane oligomers
3.4.3 Ceramic conversion studies of decaborane (14) -based oligomerwith high boron content
Scheme 3.4.2. Reaction scheme for the formation of crosslinkedoligomer (BSiDB-1) from decaborane (14), boric acid and APMDEOS
Fig. 3.4.11. IR spectrum of BSiDB-1
Fig. 3.4.12. TGA curve of BSiDB-1
3.4.4 Conclusions
References
CHAPTER 3.5 End uses of borosiloxane oligomers
3.5.1 Background
3.5.2 Oxidation resistant coating for C-C composites
3.5.2.1 Preparation of SiC coating
Scheme 3.5.1. Curing of addition-curable phenolic resin
Scheme 3.5.2. Flow chart for the preparation of oxidation resistantSiC coating on C-C composite
3.5.2.2 Evaluation of oxidation resistance of SiC coated C-C composite
Fig. 3.5.5. SEM of a) C-C composite and b) SiC coated C-C composite beforeexposure to oxidizing environment
Fig. 3.5.6. SEM of a) C-C composite and b) SiC coated C-C after exposure tooxidizing environment
Fig. 3.5.7. SEM of SiC coated C-C composite exposedto oxidizing environment (Two views)
3.5.3 Glass coating from borosiloxane oligomers
Fig. 3.5.8. SEM of glass coating from BSiT-2
Fig. 3.5.9 SEM of glass coating fromBSiT-2 exposed to air at1000° C for 50 min
Fig. 3.5.10 SEM of unprotected graphitesurface exposed to air at1000° C for 50 min
3.5.4 Ceramic matrix composites
Scheme 3.5.3. Flow chart showing the preparation of CMC
3.5.5 Mechanical properties of CMCs prepared using rayon-basedcarbon fabric and different precursor compositions
Fig. 3.5.11. SEM of a) CMC-5 and b) CMC-6 after mechanical al testing
Fig. 3.5.12. SEM of fractured surface of CMC-10 test coupon
3.5.6 Conclusions
References
Part B Polysilahydrocarbons
CHAPTER 3.6Thermal degradation kinetics ofpolysilahydrocarbons
3.6.1 Background
3.6.2 Kinetic Equations
3.6.2.1 Isothermal kinetics
3.6.2.2 Non-isothermal kinetics
3.6.2.3 Comparison of isothermal and non-isothermal methods
3.6.2.4 Different methods for the determination of kinetic parameters usingnon-isothermal kinetic methods
3.6.3 Poly (dimethylsilylene-co-styrene) and Poly (methylphenylsilyleneco-styrene)
3.6.3.1 Composition of the copolymers
3.6.3.2 Thermal properties
Fig. 3.6.1. TG curves of PDMSS copolymers
Table 3.6.3. Comparison of thermal properties and ceramic residuefor PDMSS copolymers
Fig. 3.6.2. TG curves of PMPSS copolymers
Table 3.6.4. Comparison of thermal properties and ceramic residueof PMPSS copolymers
3.6.3.3 Thermal degradation kinetics
Fig. 3.6.3. Coats-Redfern kinetic plot for differentvalues of n for PDMSS-II
3.6.4 Poly (methylvinylsilylene-co-styrene)
3.6.4.1 Thermal properties
Fig. 3.6.4. TG curves of PMVS (homopolymer) and copolymersPMVSS-I to PMVSS-V
Fig. 3.6.5. DTG curves of PMVS, PMVSS-I and PMVSS-II
3.6.4.2 Thermal degradation kinetics
Table 3.6.12. Kinetic parameters for the thermal degradation ofPMVS and copolymers
3.6.5 Polycarbosilanes from polysilahydrocarbons
3.6.5.1 Thermal properties of polycarbosilanes obtained by heat treatmentof PSH-I and PSH-II
Fig. 3.6.6. TG curves of PSH-I and the polycarbosilanes obtained by heat treatment
Fig. 3.6.7. TG curves of PSH-II and the polycarbosilanesobtained by heat treatment
3.6.5.2 Thermal degradation kinetics
3.6.6 Conclusions
References
Table 3.6.1. Composition and GPC data of the PDMSS copolymers
Table 3.6.2. Composition and GPC data of the PMPSS copolymers
CHAPTER 3.7Polysilahydrocarbons asatomic oxygen resistant coatings
3.7.1 Background
Fig. 3.7.1. Atmospheric composition as a function of altitude
3.7.2 Poly (tetramethyldisilylene-co-styrene) (PTMDSS) as AO resistantcoating
3.7.2.1 Synthesis of PTMDSS
Fig. 3.7.2. 29Si-NMR spectrum of PTMDSS
Fig. 3.7.3. 13C-NMR spectrum of PTMDSS
3.7.2.2 AO exposure studies
Fig. 3.7.6. SEM of (a) uncoated aluminized Kapton® film and (b) PTMDSS-coated aluminized Kapton® film exposed to AO (a) (b)
Fig. 3.7.8. SEM of (a) uncoated C-polyimide composite (b) PTMDSS-coated C-polyimide composite exposed to AO (a) (b)
Fig. 3.7.9. SEM of a defect site of PTMDSS-coated C-polyimidecomposite exposed to AO
Fig. 3.7.11. SEM of a) uncoated and b) PTMDSS-coatedglass-polyimide composite exposed to AO
3.7.3 Poly (methylphenylsilylene-co-styrene) (PMPSS) as AO resistantcoating
3.7.3.1 Synthesis of PMPSS
Fig. 3.7.12. 29Si-NMR spectrum of PMPSS
3.7.3.2 AO exposure studies
Fig. 3.7.14. SEM of PMPSS-coatedaluminized Kapton® film exposed to AO
Fig. 3.7.15. SEM of PMPSS-coated C-polyimide composite exposed to AO
Fig. 3.7.16. SEM images of PMPSS-coated glass-polyimide compositeexposed to AO
3.7.4 Poly (dimethylsilylene-co-methylphenylsilylene-co-styrene) (PSH-TER) as AO resistant coating
3.7.4.1 Synthesis of PSH-TER
3.7.4.2 AO exposure studies
Fig. 3.7.17. Comparison of mass loss of different polysilahydrocarbons on exposure to AO
Fig. 3.7.18. Comparison of mass loss of substrates coated with different polysilahydrocarbons on exposure to AO
3.7.5 Comparison of AO resistance of PSH-TER with other AO resistant materials
Fig. 3.7.19. Structure of siloxane-imide-epoxy resin (SIE)
Fig. 3.7.20. Structure of phosphazene based polymer (PZ-BMM)
Fig. 3.7.21. Structure of phosphazene-triazine based polymers (PZ-TZ-BMM)
Fig. 3.7.22. Structure of vinylic phosphazene based polymer (VCP-1)
3.7.6 Conclusions
References
4 Summary and Conclusions
Summary and Conclusions
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