A reactive melt modification of polyethylene terephthalate

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12 polymers tend to swell more, but it is not possible to generalize when both branching and MWD are altered simultaneously. In summary, melt modification of PET by inducing long chain branching and/or widening of MWD may result in increased potential of using the material for extrusion blow molding. Thermoplastic foams are prepared by various techniques. Among them, extrusion foaming by incorporating non-reacting physical blowing agents is of current interest. In a typical extrusion foaming to low densities, continuous gas phase (physical blowing agent) is injected into a continuous polymeric melt in the extruder at a high pressure (Xanthos et a1. 2000a). As shown in Figure 1.7, a solution of a gas dissolved into polymer under pressure is extruded into a region of lower pressure, usually the atmosphere, where it becomes supersaturated (Xanthos, 1998). As the gas-laden melt emerges from the die it experiences a sudden pressure drop; this thermodynamic instability causes phase separation. The escaping gas leads to expansion within the fluid matrix in such a manner that individual bubbles merge into cells and through subsequent solidification, stable expanded structures are produced.
13 During the cell growth phase of extrusion foaming, the polymeric melt undergoes intense elongational deformations. These deformations are not sustained by the typically narrow MWD of most of the commercially available PET resins. Such PET resins are rheologically characterized by low values of melt viscosity, along with poor shear sensitivity, i.e., non-Newtonian behavior, and low melt elasticity usually expressed as melt strength and extrudate swell (Young et a1., 1999, Xanthos et a1., 2002). As a result, uncontrolled cell expansion and unstable growth of bubbles may occur resulting in poor foamability. In general, changes in melt strength and extrudate swell which are representations of changes in the melt elasticity of the polymer are required to improve foamability of PET. Changes in melt elasticity have also been correlated with changes in elongational viscosity. As discussed by Throne (Throne, 1996), melts with relatively low shear and elongational viscosity are needed during the initial foaming stage to allow rapid bubble growth. However, during the subsequent stages viscosity must increase, as for example by cooling or by strain hardening, to a level adequate for the stabilization of the growing bubbles. Strain-hardening behavior in the elongational viscosity, defined as the rapid increment of the elongational viscosity with elongational time or strain under a constant strain rate, is also required for other processes such as film processing, thermoforming, and blow molding (Yamaguchi, 2000). Most of the polymers without long chain branches, however, hardly show strain-hardening behavior in the elongational viscosity, whereas polymers with long-chain branches exhibit marked strain hardening (Meissner et a1., 1981 and Meissner et a1., 1994). Additional general polymer requirements for enhanced foamability (Throne, 1996) are: moderately high elongational viscosity to allow biaxial stretching, high melt
Page 1 and 2: Copyright Warning & Restrictions Th
Page 3 and 4: ABSTRACT REACTIVE MELT MODIFICATION
Page 5 and 6: REACTIVE MELT MODIFICATION OF POLYE
Page 7 and 8: BIOGRAPHICAL SKETCH Author: Rahul R
Page 9 and 10: Copyright © 2003 by Rahul Ramesh D
Page 11 and 12: ACKNOWLEDGEMENTS I always considere
Page 13 and 14: TABLE OF CONTENTS Chapter Page 1 IN
Page 15 and 16: TABLE OF CONTENTS (Continued) Chapt
Page 17 and 18: LIST OF FIGURES Figure Page 1.1 Mac
Page 19 and 20: LIST OF FIGURES (Continued) Figure
Page 21 and 22: LIST OF FIGURES (Continued) Figure
Page 23 and 24: Striation Thickness Time Diffusion
Page 25 and 26: tertiary amine terephthalic acid th
Page 27 and 28: CHAPTER 1 INTRODUCTION After its in
Page 29 and 30: 3 of 0.5-1.00 mm Hg (Sorenson 2001)
Page 31 and 32: where rib is the solution viscosity
Page 33 and 34: 7 are not suitable for most of the
Page 35 and 36: 9 In the case of sheet applications
Page 37: 11 operation (Dealy and Wissbrun, 1
Page 41 and 42: 15 suitability of extruders as cont
Page 43 and 44: 17 conditions and additive concentr
Page 45 and 46: 19 understand the effect of evolvin
Page 47 and 48: CHAPTER 3 LITERATURE REVIEW This ch
Page 49 and 50: 23 absence of modifiers is accompan
Page 51 and 52: 25 The primary objective while modi
Page 53 and 54: 27 Polypropylene resins with high m
Page 55 and 56: 29 initially the reaction with hydr
Page 57 and 58: 31 A diglycidyl ether, often in the
Page 59 and 60: 33 Characterizing the products of t
Page 61 and 62: 35 5. Ease of mixing in the polymer
Page 63 and 64: 37 Figure 3.4 Epoxy or 0xirane ring
Page 65 and 66: 39 carbocation stability overrides
Page 67 and 68: 41 Figure 3.9 Anhydride — epoxy r
Page 69 and 70: 43 Figure 3.12 Base catalyzed hydro
Page 71 and 72: 45 activity to enhance the PET-epox
Page 73 and 74: 47 4.1.2 Chain EDtenders The struct
Page 75 and 76: TGDDM was used in the batch mixer s
Page 77 and 78: 51 4.2 Processing and Characterizat
Page 79 and 80: 53 specimens as a function of freVu
Page 81 and 82: 55 to the parallel plates). An addi
Page 83 and 84: 57 background spectrum. It took app
Page 85 and 86: CHAPTER 5 RESULTS AND DISCUSSION Th
Page 87 and 88: 61 molecular weight of MPET as also
Page 89 and 90:
63 rate expressions analogous to th
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Figure 5.5 Possible reactions betwe
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67 taking place by the convective;
Page 95 and 96:
69 5.1.4 Comparison of Epoxides Fig
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71 5.1.5 Reactions of TGIC with HPE
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73 Figure 5.11 shows the vanation o
Page 101 and 102:
75 Figure 5.13 shows the effect of
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77 to time. In a general sense, the
Page 105 and 106:
79 5.1.7 Study on Role of Catalysts
Page 107 and 108:
81 groups adjacent to the tertiary
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83 overall less activity towards TG
Page 111 and 112:
85 5.2.1 Typical Batch MiDing Runs
Page 113 and 114:
87 It appears that the higher proce
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89 injection (Dealy and Wissbrun, 1
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91 rheological power scaling law fo
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93 In the calculations, the freVuen
Page 121 and 122:
95 whereas H(?.) of the unmodified
Page 123 and 124:
97 However, the disintegration of t
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99 the Section 4.1.3. As evident fr
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101 changes in dynamic moduli and m
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103 In the case of 270 °C, the mod
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105 accessibility of unreacted grou
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107 believed to be charactenzed by
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109 increase in the melt elasticity
Page 137 and 138:
111 In general, for crosslinked sys
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113 crosslinked gels in swelling eV
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115 formation of epoxy/PET reaction
Page 143 and 144:
117 A seVuential reactive extrusion
Page 145 and 146:
CHAPTER 6 CONCLUSIONS AND RECOMMEND
Page 147 and 148:
121 of PET by the selected tnepoxid
Page 149 and 150:
REFERENCES S. Abe and M. Yamaguchi,
Page 151 and 152:
125 L. M. Dossin and W. W. Graessle
Page 153 and 154:
127 P. Huang, Z. Zhong, S. Zheng, W
Page 155 and 156:
129 J. Meissner and J. Hostettler,
Page 157 and 158:
131 T. Shiwaku, K. Hijikata, K. Fur
Page 159 and 160:
133 M. Xanthos and S. K. Dey, "Foam
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A reactive melt modification of polyethylene terephthalate

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