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

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Introduction 40 and engineering industries for drying, promoting chemical or physical change, and many other purposes [6]. Yet it remains one of the most difficult techniques to control, being slow and imprecise when practiced in the usual way of heating the surface of the workpiece by radiation, convection or conduction or, commonly, a poorly controlled mixture of all three, and even if perfection were achieved in surface heating, the process time is limited by the rate of heat flow into the body of the workpiece from the surface, which is determined entirely by the physical properties of the workpiece: its specific heat, thermal conductivity and density. These last three are combined into one parameter, the thermal diffusivity, which uniquely determines the temperature rise within a material as a function of time and depth from the surface, subject to a given set of conditions at the surface. Nothing can be done in the application of surface heating to accelerate heating once the surface has reached a specified maximum temperature. Internal temperature distribution is then limited by the thermal diffusivity of the material. Because, in conventional heating, all the heat energy required in the workpiece must pass through its surface, and the rate of heat flow to within is limited by temperature and the thermal diffusivity, the larger the workpiece, the longer the heating takes. Everyone’s experience is that surface heating is especially slow in a thick material. It is not only slow but nonuniform, with the surfaces, and in particular edges and corners, being much hotter than the inside. Consequently, the quality of the treated workload is variable and frequently inferior to what is desired. Imperfect heating resulting from these difficulties is a frequent cause of product reject and energy waste. Above all the extended process time results in large production areas devoted to ovens. Large ovens are slow to respond to impressed temperature changes, take a long time to warm up and have high heat capacities. Their sluggish performance results in a failure to respond to sudden changes in 40
Introduction 41 production requirements: management control becomes difficult, subjective and expensive. 1.6 Electrical Volumetric Heating By electrical means, volumetric heating is possible wherein all the infinitesimal elements constituting the volume of a workload are each heated individually, ideally at substantially the same rate. The heat energy injected into the material is transferred through the surface electromagnetically, and does not flow as a heat flux, as in conventional heating. The rate of heating is no longer limited by thermal diffusivity and surface temperature, and the uniformity of heat distribution is greatly improved. Heating times can often be reduced to less than 1% of that required using conventional techniques, with effective energy variation within the workload less than 10%. Any material can be heated directly by electrical volumetric heating provided that it is neither a perfect electrical conductor nor a perfect insulator, implying that the range extends from metals to dielectric materials which could be considered quite good insulators. 1.7 Volumetric and Conventional Heating: a Comparison That a fixed continuous power dissipation into a dry, passive workload causes its average temperature to rise linearly with time is of fundamental importance, distinguishing it from conventional heating, in which the average temperature of the workload asymptotically reaches the oven temperature, and cannot rise above it. 41
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 and 18: LIST OF FIGURES 17 3.38 Comparison
Page 19 and 20: Introduction 19 cannot be melted an
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: Introduction 39 Even microwaves can
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
Page 49 and 50: Introduction 49 Although these mode
Page 51 and 52: Introduction 51 materials that have
Page 53 and 54: Chapter 2 Experimental In this chap
Page 55 and 56: Experimental 55 Characteristic Note
Page 57 and 58: Experimental 57 If the oven is used
Page 59 and 60: Experimental 59 In monomodal applic
Page 61 and 62: Experimental 61 Figure 2.5: Right s
Page 63 and 64: Experimental 63 Figure 2.8: Front v
Page 65 and 66: Experimental 65 regardless of the a
Page 67 and 68: Experimental 67 • The number of t
Page 69 and 70: Experimental 69 Figure 2.11: Surfac
Page 71 and 72: Experimental 71 Figure 2.12: Repeti
Page 73 and 74: Experimental 73 From the Figure 2.1
Page 75 and 76: Experimental 75 in the centre of th
Page 77 and 78: Experimental 77 not read the water
Page 79 and 80: Experimental 79 Test number 1 2 3 4
Page 81 and 82: Experimental 81 Figure 2.19: Plot o
Page 83 and 84: Experimental 83 2.5 Datalogger This
Page 85 and 86: Experimental 85 same reason a wood
Page 87 and 88: Experimental 87 Material Behaviour
Page 89 and 90: 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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Kinetic Analysis and Characterization of Epoxy Resins ... - FedOA

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