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

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Results and Discussion 124 DSC can be carried out. However this degree of cure is not completely attributable to the microwave process, because, as explained above, during the delay time τ 11 the sample continues to react, following the conventional kinetic. The non linear regression of degree of cure versus reaction time data 12 has been performed with the growth-sigmoidal function, described by the equation 3.22: y= a 1+be −kx SLogistic 3 (3.22) where, in this case, y is the simulated degree of conversion, x the reaction time, and a, b and k are numerical parameters computed by the software. In this way a simulated α versus t profile has been determined, the comparison of experimental and fitting data of degree of cure against reaction time is illustrated in Figure 3.21. Figure 3.21: Comparison of experimental and fitting data of degree of conversion against reaction time for a MW cure process at 1500 W. The agreement between experimental and fitting data is acceptable. Then the 11 Estimated equal to 10 s. 12 Elaborated with OriginPro 7.0, using the Levenberg-Marquardt algorithm. 124
Results and Discussion 125 simulated reaction rate α ′ i can be numerically calculated as incremental ratio of degree of cure: α i ′ = dα i dt ≈ α i+1 − α i (3.23) t i+1 − t i Knowing the profiles of α, α ′ and T in function of time, the increment of degree of cure during the delay time τ can be estimated. In fact the variation of degree of conversion α i+1 − α i is correlated to the corresponding variation of time t i+1 − t i , through the following numerical equation: t i+1 − t i = α i+1 − α i α ′ i+1 ⇒ α i+1 = α i + α ′ i+1 (t i+1 − t i ) (3.24) Therefore approximating α ′ i+1 with α′ i and considering a conversion of 50% the increase of degree of cure during the delay time τ is equal to: α 0,5+τ = α 0,5 + α ′ 0,5 · τ (3.25) The reaction rate α ′ 0,5 can be calculated, using the autocatalytic model and the conventional kinetic parameters, reported in Tables 3.8 and 3.7, and the temperature, recorded by the datalogger during the microwave cure at 1500 W at the time corresponding to the 50% of conversion. Table 3.14 presents the values used for the evaluation of the increment of degree of cure for the microwave cure at 1500 W. The degree of conversion α 0,5+τ is equal to 0,52, therefore the influence of τ on the degree of conversion is almost negligible. The same analysis has been performed for the microwave cure process at a radiation power of 2000 W and analogous results have been achieved. In Table 3.15 the degree of cure versus reaction time, obtained under microwave radiation at 2000 W, calculated using equation 3.21 and the residual enthalpy, reported in Table 3.12 has been presented. The same data are also plotted in Figure 3.22. 125
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UNIVERSITA’ DEGLI STUDI DI NAPOLI
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3 I thank all the lecturers of PhD
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5 Microwaves are electromagnetic ra
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CONTENTS 7 1.8.1 DielectricProperti
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CONTENTS 9 4 Conclusions and Outloo
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LIST OF TABLES 11 3.2 Average value
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List of Figures 1.1 Diglycidylether
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LIST OF FIGURES 15 2.23 Onset tempe
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LIST OF FIGURES 17 3.38 Comparison
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Introduction 19 cannot be melted an
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Introduction 21 • bismaleimides;
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Introduction 23 cold solders, casti
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Introduction 25 Average Properties
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Introduction 27 In Figure 1.4 n can
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Introduction 29 ducts and it genera
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Introduction 31 tween current-carry
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Introduction 33 that describe the p
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Introduction 35 1.3.5 Lorentz Force
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Introduction 37 Figure 1.11: Electr
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Introduction 39 Even microwaves can
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Introduction 41 production requirem
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Introduction 43 fect of the electro
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Introduction 45 following different
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Introduction 47 Debye equations bas
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Introduction 49 Although these mode
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Introduction 51 materials that have
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Chapter 2 Experimental In this chap
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Experimental 55 Characteristic Note
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Experimental 57 If the oven is used
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Experimental 59 In monomodal applic
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Experimental 61 Figure 2.5: Right s
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Experimental 63 Figure 2.8: Front v
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Experimental 65 regardless of the a
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Experimental 67 • The number of t
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Experimental 69 Figure 2.11: Surfac
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Experimental 71 Figure 2.12: Repeti
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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
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Page 109 and 110: Results and Discussion 109 Kinetic
Page 111 and 112: Results and Discussion 111 Figure 3
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Page 115 and 116: Results and Discussion 115 pedestal
Page 117 and 118: Results and Discussion 117 Tables 3
Page 123: Results and Discussion 123 t MW [s]
Page 129 and 130: Results and Discussion 129 t DSC [s
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Page 145 and 146: Results and Discussion 145 ditions.
Page 147 and 148: Results and Discussion 147 3.23 and
Page 149 and 150: Results and Discussion 149 The T g
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Page 153 and 154: Results and Discussion 153 Flexural
Page 155 and 156: Results and Discussion 155 3.7.2 FT
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Page 161 and 162: Results and Discussion 161 Also in
Page 163 and 164: Conclusions and Outlook 163 degree
Page 165 and 166: Appendix A A Brief History of Micro
Page 167 and 168: A Brief History of Microwave Oven 1
Page 169 and 170: Bibliography [1] W. Callister, “M
Page 171 and 172: BIBLIOGRAPHY 171 [19] P. I. Karkana
Page 173: BIBLIOGRAPHY 173 [34] K. D. V. Pras
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