Kinetic Analysis and Characterization of Epoxy Resins ... - FedOA

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Chapter 1 Introduction In this chapter a brief description of epoxy resins and electromagnetic waves will be presented. The first section is dedicated to a short introduction of thermosetting resins, their properties and applications. The second section is focused on epoxy resins as particular class of thermosetting polymers. The third section illustrates the basic principles and the main properties of electromagnetic radiations with particular emphasis on microwaves and their interactions with materials. 1.1 Thermosetting Resins Thermosetting resins are an important class of polymers. They become permanently and irreversibly hard when heat is applied and do not soften upon subsequent heating [1]. During the initial heat treatment, covalent crosslinks are formed between the adjacent molecular chains. These bonds anchor the chains together 1 to resist the vibrational and rotational chain motions at high temperatures. Only heating to excessive temperatures will cause break of these crosslink bonds and polymer degradation. Therefore a thermoset material 1 At chemically active sites, as for example unsaturated or epoxy groups. 18
Introduction 19 cannot be melted and re-shaped after it is cured. This implies that thermosets cannot be recycled, except as filler material. Thermosetting polymers are generally harder and stronger than thermoplastics and have better dimensional stability 2 and are also better suited to high-temperature applications up to the decomposition temperature of the material. They are usually liquid or malleable prior to curing and designed to be molded into their final form, or used as adhesives. Thermosetting resins are generally composed by two components. The first is the prepolymer and the second is the hardener or curing agent 3 . This is used for starting chemical reactions with the prepolymer forming a three-dimensional network with a larger molecular weight, resulting in a material with high melting point. In this final structure the main chain of the prepolymer are joined together through crosslinks realized by the hardener agent. Curing process may be done through heat 4 , chemical reactions or irradiation. It can happen only if there is a chemical affinity between the functional groups of prepolymer and hardener agent. For example in epoxy resins the prepolymer possesses an ossiranic or epoxy ring, that is a strong functional group and the typical hardener agent is an aliphatic or aromatic diamine. Some examples of thermosets polymerization mechanisms are: • Step-growth polymerization, through elimination reaction, between phenol and formaldehyde forming phenolic resins; • Reaction between isocyanate groups and diols forming polyurethanes; • Transesterification of dimethyl terephthalate and ethylene glycol forming polyester resins. 2 Due to their 3-D network. 3 In some systems catalysts, fillers, pigments, plasticizers and other additives can be present. 4 Generally above 200 ◦ C. 19
Page 1 and 2: UNIVERSITA’ DEGLI STUDI DI NAPOLI
Page 3 and 4: 3 I thank all the lecturers of PhD
Page 5 and 6: 5 Microwaves are electromagnetic ra
Page 7 and 8: CONTENTS 7 1.8.1 DielectricProperti
Page 9 and 10: CONTENTS 9 4 Conclusions and Outloo
Page 11 and 12: LIST OF TABLES 11 3.2 Average value
Page 13 and 14: List of Figures 1.1 Diglycidylether
Page 15 and 16: LIST OF FIGURES 15 2.23 Onset tempe
Page 17: LIST OF FIGURES 17 3.38 Comparison
Page 21 and 22: Introduction 21 • bismaleimides;
Page 23 and 24: Introduction 23 cold solders, casti
Page 25 and 26: Introduction 25 Average Properties
Page 27 and 28: Introduction 27 In Figure 1.4 n can
Page 29 and 30: Introduction 29 ducts and it genera
Page 31 and 32: Introduction 31 tween current-carry
Page 33 and 34: Introduction 33 that describe the p
Page 35 and 36: Introduction 35 1.3.5 Lorentz Force
Page 37 and 38: Introduction 37 Figure 1.11: Electr
Page 39 and 40: Introduction 39 Even microwaves can
Page 41 and 42: Introduction 41 production requirem
Page 43 and 44: Introduction 43 fect of the electro
Page 45 and 46: Introduction 45 following different
Page 47 and 48: Introduction 47 Debye equations bas
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Page 51 and 52: Introduction 51 materials that have
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Page 55 and 56: Experimental 55 Characteristic Note
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Experimental 69 Figure 2.11: Surfac
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Experimental 71 Figure 2.12: Repeti
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Experimental 73 From the Figure 2.1
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Experimental 75 in the centre of th
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Experimental 77 not read the water
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Experimental 79 Test number 1 2 3 4
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Experimental 81 Figure 2.19: Plot o
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Experimental 83 2.5 Datalogger This
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Experimental 85 same reason a wood
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Experimental 87 Material Behaviour
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Experimental 89 in function of the
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Experimental 91 2.6.3 Influence of
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Chapter 3 Results and Discussion Th
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Results and Discussion 95 There is
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Results and Discussion 97 Figure 3.
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Results and Discussion 99 Parameter
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Results and Discussion 101 After pr
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Results and Discussion 103 of insta
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Results and Discussion 105 1. Mecha
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Results and Discussion 107 where k
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Results and Discussion 109 Kinetic
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Results and Discussion 111 Figure 3
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Results and Discussion 113 3.3 Comp
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Results and Discussion 115 pedestal
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Results and Discussion 117 Tables 3
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Results and Discussion 123 t MW [s]
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Results and Discussion 125 simulate
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Results and Discussion 129 t DSC [s
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Results and Discussion 133 Using th
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Results and Discussion 135 forward
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Results and Discussion 141 than the
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Results and Discussion 143 Since ev
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Results and Discussion 145 ditions.
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Results and Discussion 147 3.23 and
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Results and Discussion 149 The T g
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Results and Discussion 151 3.6.1 St
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Results and Discussion 153 Flexural
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Results and Discussion 155 3.7.2 FT
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Results and Discussion 157 identifi
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Results and Discussion 159 This eff
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Results and Discussion 161 Also in
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Conclusions and Outlook 163 degree
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Appendix A A Brief History of Micro
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A Brief History of Microwave Oven 1
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Bibliography [1] W. Callister, “M
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BIBLIOGRAPHY 171 [19] P. I. Karkana
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BIBLIOGRAPHY 173 [34] K. D. V. Pras
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