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

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Results and Discussion 152 Figure 3.40: Comparison of stress-strain curves of samples conventionally and microwave cured. drawing a tangent to the steepest initial straight-line portion of the load-deflection curve using the following equation: E B = L3 m 4bd 3 (3.36) where E B [MPa] is the modulus of elasticity in bending, L [mm] the support span, b [mm] and d [mm] respectively the width and depth of the beam tested and m [N/mm] the slope of the tangent to the initial straight-line portion of the loaddeflection curve. In Table 3.28 the average flexural modulus of elasticity for samples thermally and microwave cured are reported. The modulus of elasticity is higher for specimens microwave cured. This is in agreement with the results, obtained by Singer et al. [35] in a comparison of the mechanical properties of epoxy resin microwave and thermal cured. The more elevated modulus could be due to molecular arrangement in the electric field, because alignment may produce higher molecular packing with lower free volume resulting in an enhanced modulus. Also Yarlagadda et al. [34] have noticed an 152
Results and Discussion 153 Flexural Modulus Conventional Microwave Modulus [MPa] 1475,78 2515,87 Table 3.28: Flexural elastic modulus for specimens conventionally and microwave cured. improvement of the flexural strength of the samples microwave cured compared to that thermally polymerized. 3.7 Spectroscopic Characterization A spectroscopic analysis in infrared and near infrared region has been performed for measuring the residual concentration of the functional groups after polymerization process. In particular the possible presence of epoxy group and primary amino group has been studied. The tests have been carried out using the Fourier transform technique. For EC 57 epoxy prepolymer and K 21 hardener agent, that are liquid at room temperature, small droplets have been spread on a potassium bromide (KBr) pastille. While epoxy samples microwave and thermally cured, that are solid at room temperature, have been crushed in a agate mortar with a pestle and then a small amount of powder has been mixed with a potassium bromide pastille. 3.7.1 FT-IR Spectra In Figure 3.41 the spectrum of EC 57 epoxy prepolymer is shown and the peak at 916-918 cm −1 , corresponding to epoxy group has been highlighted. While in Figure 3.42 the region of infrared spectrum between 750 and 1000 153
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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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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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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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Kinetic Analysis and Characterization of Epoxy Resins ... - FedOA

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