Extruder Principles and OperationSpringer Science & Business Media, 1995 M10 31 - 494 pages This book is intended to fill a gap between the theoretical studies and the practical experience of the processor in the extrusion of thermoplastic polymers. The former have provided a basis for numerical design of extruders and their components, but generally give scant attention to the practical performance, especially to the conflict between production rate and product quality. In practice extruders are frequently purchased to perform a range of duties; even so, the operator may have to use a machine designed for another purpose and not necessarily suitable for the polymer, process or product in hand. The operator's experience enables him to make good product in unpromising circumstances, but a large number of variables and interactions often give apparently contradictory results. The hope is that this book will provide a logical background, based on both theory and experience, which will help the industrial processor to obtain the best performance from his equipment, to recognize its limitations, and to face new problems with confidence. Mathematics is used only to the extent that it clarifies effects which cannot easily be expressed in words; ifit is passed over, at least a qualitative understanding should remain. The approximate theory will not satisfy the purist, but this seems to the authors less important than a clear representation of the physical mechanisms on which so much of the polymer processing industry depends. M. J. STEVENS J. A. |
Contents
Introduction | 1 |
12 METHOD | 2 |
Practical extrusion processes and their requirements | 4 |
21 SHAPING PROCESSES AND THEIR REQUIREMENTS | 6 |
22 OTHER APPLICATIONS AND THEIR REQUIREMENTS | 17 |
Flow behaviour relevant to extrusion | 25 |
32 SHEAR FLOW | 31 |
33 EXTENSIONAL FLOW | 45 |
92 EFFECTS OF CONTROLLED VARIABLES | 280 |
93 POLYMER PROPERTIES | 286 |
94 SCREW DESIGN | 289 |
95 OPERATIONAL STRATEGIES | 293 |
Twinscrew extruders | 314 |
101 NONINTERMESHING SCREWS | 316 |
102 PARTIAL INTERMESHING | 318 |
COUNTERROTATION | 321 |
34 ELASTIC EFFECTS | 46 |
35 MEASUREMENT OF VISCOSITY AND ELASTICITY | 49 |
Thermal and energy properties in processing | 52 |
42 THERMAL CONDUCTION | 54 |
43 NONISOTHERMAL FLOW AND HEAT TRANSFER | 57 |
44 MIXING | 60 |
Extrusion dies | 63 |
52 FACTORS INFLUENCING THE PERFORMANCE OF AN EXTRUSION DIE | 65 |
53 EXTRUSION DIES FOR SOME PROFILES | 75 |
54 GENERAL PRINCIPLES OF DIE DESIGN | 89 |
55 SPECIFIC ASPECTS OF DIE DESIGN | 101 |
56 OPERATIONAL STRATEGIES FOR PROBLEMSOLVING | 117 |
Principles of melt flow in singlescrew extruders | 125 |
62 DERIVATION OF FLOW EQUATION | 127 |
63 LEAKAGE FLOW | 138 |
64 OUTPUT EQUATIONS AND LONGITUDINAL PRESSURE PROFILES FOR COMMON SCREW TYPES | 140 |
65 GRAPHICAL REPRESENTATION OF OUTPUT FOR SCREWDIE COMBINATIONS INCLUDING VENTING | 149 |
66 OUTPUT CORRECTIONS | 162 |
67 PSEUDOPLASTIC FLOW | 165 |
68 NONISOTHERMAL FLOW | 171 |
Solids conveying and melting in singlescrew extruders | 173 |
72 PHENOMENOLOGICAL DESCRIPTION OF SOLIDS CONVEYING AND MELTING | 177 |
73 THEORETICAL ANALYSIS | 187 |
Principles of energy balance | 223 |
NEWTONIAN ISOTHERMAL CASE | 227 |
83 PSEUDOPLASTIC ISOTHERMAL APPROXIMATION | 233 |
84 POWER IN NONISOTHERMAL FLOW | 234 |
85 EFFECT OF VARIABLES ON ENERGY BALANCE | 249 |
Operation of singlescrew extruders | 268 |
COROTATION | 328 |
105 COMPARISON OF MACHINE TYPES | 346 |
Extruder operation as part of a total process | 350 |
112 STABILITY | 357 |
113 SHEAR HISTORY | 362 |
114 CONTROL | 364 |
115 SCALEUP | 374 |
Practical extruder operation | 382 |
122 COLOUR AND GRADE CHANGING | 385 |
123 STARTUP AND SHUTDOWN | 387 |
124 DISMANTLING AND CLEANING | 390 |
125 WASTE RECOVERY | 395 |
Application to the individual machine | 397 |
Properties of polymers for heat and flow | 403 |
Derivations of flow and pressure | 411 |
B2 ESTIMATION OF LEAKAGE FLOWS | 413 |
B3 LONGITUDINAL PRESSURE PROFILES | 416 |
B4 PRESSURE GRADIENTS IN A STEPPED SCREW | 418 |
B5 FURTHER EXAMPLES OF QP DIAGRAMS | 421 |
Energy consumption and energy balance | 425 |
C2 DERIVATION OF POWER ABSORBED IN SCREW | 433 |
C3 HEAT FLOWS IN MELT PUMPING SECTION | 436 |
C4 DISTRIBUTION OF SHEAR HEATING AND TRANSVERSE CIRCULATION | 448 |
C5 TEMPERATURE VARIATION IN THE FLIGHT CLEARANCE | 456 |
Stability of melt pumping section | 465 |
List of tables | 467 |
469 | |
475 | |
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Common terms and phrases
approximately axial back pressure barrel surface barrel temperature barrel wall changes channel depth coefficient conduction constant cross-section decrease depth h diameter dimensions distribution downchannel drag flow drawdown effect energy balance enthalpy extruder Figure film flight clearance flight tip flow rate friction gear pump geometry give haul-off heat conduction heat flow heat transfer heat transfer coefficient heater power increase intermeshing LDPE longitudinal machine material maximum melt pool melt pumping section melt temperature melting section mixing Newtonian fluid non-uniform operating conditions output Q polymer power-law fluid pressure drop pressure flow pressure gradient proportional pseudoplastic Q/Wbh ratio reduced rheological screw channel screw speed shear heating shear rate shear stress single-screw extruder solid bed solids conveying specific Table Tadmor tapered temperature difference temperature gradient temperature variations thermal thermocouple thickness transverse uniform usually velocity viscosity W/turn wall shear rate width zone