A reactive melt modification of polyethylene terephthalate

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14 strength/elasticity to resist membrane tearing (blow-out) and promote the formation of closed-cell structures, and if crystallizable, relatively rapid rate of crystallization. Linear PET resins, in general, do not meet the above requirements and are characterized by a very narrow extrusion foaming window. Extrusion foaming to low densities is also affected by a slow rate of crystallization, and the possible interference of crystal nucleation with bubble nucleation. In addition, foaming characteristics of PET are challenged by its sensitivity towards hydrolytic, thermal and/or thermooxidative degradation which becomes particularly pronounced at the high melt temperatures (>270°C) involved during processing. 1.3 Chemical Modification of PET Virgin and recycled grade PET resins offer favorable cost/performance characteristics, which may be extended to lower density foamed structures by chemical modification. Potential applications would take advantage of the combination of good mechanical properties, dimensional stability of the semicrystalline resin at temperatures up to 200 °C, and recyclability (Odian, 1991). In addition to the food packaging industry where PET foams have already made advances, other applications would be intended for the construction/building, transportation and other industries currently utilizing rigid polyurethane, polystyrene or polyvinyl chloride foams. In a broad sense, the chemical modification of single polymers may be accomplished with various reagents in the molten state, in solution, or on the surface of plastic parts/pellets. Recent advances in the technology and economics of the modification reactions for single polymers and polymer blends have demonstrated the
15 suitability of extruders as continuous reactors, often operating in the complete absence of solvents (Xanthos, 2002). It is well known that the improvement in the mechanical and chemical properties of PET, related to an increase in molecular weight, is also correlated with a decrease in the number of carboxylic end group(s) (Inata and Matsumura, 1985). Some of the property improvements are also the result of broadening the molecular weight distribution of the linear PET (Inokuchi et a1., 1981). It is very difficult to obtain PET having a molecular weight represented by an intrinsic viscosity (I.V.) above 0.9 dL/g by the usual melt polycondensation synthesis (Aharoni, 2002). As the polycondensation proceeds, the reaction rate decreases and degradation of the terminal groups occurs leading to an increase in carboxyl content (CC). Thus, the rheological properties of PET differ from those of other common thermoplastic polymers, mainly addition polymers (Gupta and Bashir, 2002). To overcome the above macromolecular structural limitations, postpolycondensation in the solid phase may be carried out, as reported by several authors (Aharoni, 2002, Inata and Matsumura, 1985). By 'solid stating' is meant that the polymer pellets remain in the solid state, below their melting temperature, during additional chain extension (Aharoni, 2002). In the first stage of the process, PET pellets are fed into crystallizers, in which they are exposed to low temperature. During crystallization, a high level of chain motion takes place, especially in the amorphous phase of the polymer allowing chain extension and transesterification. At the end of the pellets' residence time in the crystallizers, their surfaces are highly crystalline. The pellets are transferred to a vacuum dryer and stored at 160 °C, which promotes chain extension and increase in MW.
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 and 38: 11 operation (Dealy and Wissbrun, 1
Page 39: 13 During the cell growth phase of
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
Page 91 and 92:
Figure 5.5 Possible reactions betwe
Page 93 and 94:
67 taking place by the convective;
Page 95 and 96:
69 5.1.4 Comparison of Epoxides Fig
Page 97 and 98:
71 5.1.5 Reactions of TGIC with HPE
Page 99 and 100:
73 Figure 5.11 shows the vanation o
Page 101 and 102:
75 Figure 5.13 shows the effect of
Page 103 and 104:
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
Page 109 and 110:
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
Page 115 and 116:
89 injection (Dealy and Wissbrun, 1
Page 117 and 118:
91 rheological power scaling law fo
Page 119 and 120:
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
Page 125 and 126:
99 the Section 4.1.3. As evident fr
Page 127 and 128:
101 changes in dynamic moduli and m
Page 129 and 130:
103 In the case of 270 °C, the mod
Page 131 and 132:
105 accessibility of unreacted grou
Page 133 and 134:
107 believed to be charactenzed by
Page 135 and 136:
109 increase in the melt elasticity
Page 137 and 138:
111 In general, for crosslinked sys
Page 139 and 140:
113 crosslinked gels in swelling eV
Page 141 and 142:
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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