Free volume and storage stability of one-component epoxy nanocomposites [Elektronische Ressource] / Muhammad Qasim Shaikh

Harriet B. Borton

Informations

• Publié par: christian-albrechts-universitat_zu_kiel
• Publié le: 01 janvier 2011
• Nombre de lectures: 6
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Free Volume and Storage Stability of One-component
Epoxy Nanocomposites








Dissertation



zur Erlangung des akademischen Grades
Doktor der Ingenieurwissenschaften
(Dr.-Ing.)

der Technischen Fakultät
der Christian-Albrechts-Universität zu Kiel


Muhammad Qasim Shaikh

Kiel
2010




























1. Gutachter: Prof. Dr. Klaus Rätzke
2. Prof. Dr. Wolfgang Jäger
Datum der mündlichen Prüfung: 11.11.2010









Dedicated to my parents and my wife
















Table of Contents
1. Introduction ...............................................................................................................................1
2. Positrons and Positronium Annihilation .................................................................................5
2.1 Introduction ................................................................................................................................ 5
2.2 Positrons and Positronium........................................................................................................... 5
2.2.1 Self Annihilation of Positrons and Positronium........................................................... 6
2.2.2 Pick-off Annihilation of ortho-Positronium................................................................ 6
2.2.3 Theoretical models for Positronium formation ........................................................... 7
2.3 Positrons sources for PALS......................................................................................................... 8
2.4 Positrons Annihilation Techniques (PATs).................................................................................. 9
2.4.1 Positron Annihilation Lifetime Spectroscopy (PALS)............................................... 10
2.4.1.1 Scintillator-Photomultiplier Detectors.......................................................... 11
2.4.1.2 Constant Fraction Diffraction Discriminators (CFDD)................................. 12
2.4.1.3 Time to Amplitude Converter (TAC)........................................................... 13
2.4.1.4 Multi-Channel Analyzer (MCA).................................................................. 13
2.5 Data Analysis of PALS spectrum .............................................................................................. 14
2.5.1 Analysis with LifeTime routine LT 9.0..................................................................... 14
2.5.1.1 Finite lifetime analysis ................................................................................ 15
2.5.1.2 Continuous term analysis (with distribution)................................................ 16
2.6 Tao-Eldrup Model for calculating the free volume in polymers ................................................. 18
2.7 PALS studies on epoxy precursors ............................................................................................ 20
2.8 PALS studies on cured epoxy composites ................................................................................. 21
2.9 PALS related to this thesis ........................................................................................................ 21
3. Free Volume in Polymers ........................................................................................................23
3.1 Introduction .............................................................................................................................. 23
3.2 Basic concept of the free volume............................................................................................... 23
3.3 Definitions of the free volume................................................................................................... 24
3.3.1 Empty volume ......................................................................................................... 25
3.3.2 Excess free volume.................................................................................................. 25
3.3.3 Accessible free volume............................................................................................ 26
3.4 Fractional free volume and related theories ............................................................................... 27
3.5 Experimental techniques to determine free volume.................................................................... 28
3.6 Polymer properties characterized by the free volume................................................................. 29
3.6.1 Glass-Transition temperature.................................................................................... 30
3.6.2 Physical Ageing ....................................................................................................... 31
3.7 Summary of this chapter ........................................................................................................... 31
 i
Table of Contents
4. Johnson-Mehl-Avrami-Kohlmogorov Theory ......................................................................33
4.1 Introduction .............................................................................................................................. 33
4.2 Basics of phase transformations ................................................................................................ 33
4.2.1 Nucleation and growth............................................................................................. 33
4.3 Phase transformation Kinetics................................................................................................... 36
4.4 Transformation mechanisms ..................................................................................................... 37
4.5 Johnson-Mehl-Avrami-Kohlmogorov (JMAK) theory............................................................... 38
4.5.1 Important assumptions............................................................................................. 39
4.5.2 Derivation of Avrami equation................................................................................. 39
4.5.3 Avrami exponent ‘n’................................................................................................ 43
4.6 Time-Temperature Superposition.............................................................................................. 45
4.7 Summary of this chapter ........................................................................................................... 46
5. One-component Epoxy Resin formulations...........................................................................47
5.1 Epoxy Resins: An Introduction ................................................................................................. 47
5.1.1 Industrial applications of epoxy resin formulations .................................................. 47
5.2 Current state of art and aim of this project................................................................................. 48
5.3 Basic principles of formulation ................................................................................................. 49
5.3.1 Epoxy resins............................................................................................................ 50
5.3.1.1 Diglycidyl ether of bisphenol A (DGEBA) .................................................. 51
5.3.1.2 Bisphenol F Epoxy resin ............................................................................. 52
5.3.2 Hardeners (Curing agents) ....................................................................................... 53
5.3.2.1 Amine curing .............................................................................................. 54
5.3.2.1.1 Dicyandiamide (DICY)................................................................... 55
5.3.2.2 Anhydride curing ........................................................................................ 56
5.3.2.2.1 Methyl hexahydrophthalic anhydride (MHHPA)............................. 58
5.3.3 Accelerators............................................................................................................. 58
5.3.4 Fillers...................................................................................................................... 59
5.3.5 Micro and Nano/Encapsulation of Accelerators........................................................ 59
5.4 Epoxy curing process and TTT diagram.................................................................................... 60
5.5 Characterization of epoxy curing and cured epoxy networks ..................................................... 61
5.5.1 Traditional off-line methods..................................................................................... 62
5.5.2 Modern in-situ methods ........................................................................................... 62
5.6 Summary of this chapter ........................................................................................................... 63
6. Shelf life of one-component epoxy-resin formulation..........................................................