- Email: [email protected]
Penn's PVC technology
Book Reviews Penn's PVC technology Edited by W. V. Titow and B. J. Lanham Applied Science Publishers, Barking, 3rd Edn, 1971, 545 pp. £12.50
Engineering principles of plasticating extrusion Z. Tadmor and I. Klein Van Nostrand, New York, 1970, 500 pp. £9.35
The late W. S. Penn's well established reference book 'PVC Technology' has been revised extensively and up-dated by Titow and Lanham. They have maintained the essential character of the earlier editions which have been valuable to the technologist in providing an easy reference source for commercial polymers, compounds, plasticizers, stabilizers, fillers and other compounding ingredients. Not only is the chemical identity of these products indicated but commercial names, grades and sources are given. The manifold processes for converting PVC to products are described lucidly. A substantial rewriting of many chapters had added to the technological content. The pattern of presentation is such that there is an excellent balance between the discussion of the principles of technology and commercial details. Because of this the book well achieves the aims of the authors to present a reference source which can be read and utilized at several levels. The non-specialist has a useful guide to PVC technology whilst the student will have a well presented and readable textbook. For those who wish to read the subject in more detail there are ample references to original papers in each chapter. The final chapter of the book reviews applications of PVC and is followed, appropriately, by an appendix which lists BS, ASTM, D I N and ISO standards relevant to PVC and its products. A second appendix includes units, conversions and definitions. The index, although not comprehensive is adequate. The book is well produced and is strongly recommended to all who have an interest in PVC, its processing and its uses. Finally one might comment that this publication is a fitting testimony to the valuable contributions which the late W. S. Penn made to education and plastics technology.
This is probably the first book to attempt to represent mathematically the performance of each section of the single-screw extruder--solid feed, melting, and melt pumping. It draws largely on previously published work by the authors and others, which should permit a lucid treatment of the overall behaviour of the complete machine. However, the sheer weight of mathematics seems to magnify trivial details and obscure the major effects, many of which have previously been represented, at least qualitatively, by simpler approximations. The chapter on 'Basic flow concepts' reproduces the fundamental equations of continuity, motion, and energy (unfortunately with several errors*) followed by a brief discussion including the effects of shear rate, temperature, and pressure. There is little adaptation to practical situations or indication of how the equations may be handled, since in most cases many factors are unknown. Equation 2.4 assumes constant density, which implies isothermal conditions, though this is not stated, nor is it clear whether thermal expansion has been ignored subsequently. Appendix C provides little viscometric data additional to that published in 1959 in 'Processing of thermoplastic materials' by Bernhardt. The chapter on 'Screw geometry' is an example of undue attention to detail, some of it inapplicable to screws as manufactured. The feed section is treated by the method of Darnell and Mol, with some additional work by the authors covering the effects of flight width and pressure rise and of different coefficients of friction on the screw and barrel. The latter suggests that the temperature difference between screw and barrel in this section will have a profound influence on the rate of feeding, although no experimental data are presented on the variation of friction coefficient with temperature for commercial polymers. In practice the temperature conditions are rarely critical, providing cooling is applied to the feed section. Pressure rise is shown to be exponential and hence critically dependent on the initial pressure. However, factors influencing flow in the feed hopper and the filling of the screw, e.g. particle size distribution, degree of hopper filling, air entrainment, and geometry of the hopper and feed opening are not considered. The melt pumping section is treated in a very long chapter (nearly 150 pages) similarly to a number of other computer analyses, where the equations are progressively developed from the Newtonian isothermal case to non-Newtonian non-isothermal with shear heating and channel curvature. The first 40 pages or so present the work of previous authors on the isothermal Newtonian case, but in what appears to be an unnecessarily obscure manner. In 'Polymer processing' McKelvey shows curves of output versus helix angle which clearly explain why the apparent optimum angle of 30 ° is not often used, yet these are not reproduced; the conditions for maximum pressure gradient (p 222) could be much more clearly described in terms of the dimensionless factor Q~Wbh or the pressure flow/drag flow ratio; there is much discussion of velocity profiles yet only one rough pressure profile (p 237), although these are used later in Section 8.3 as basis for comparison of theory and experiment. A section of seven pages of mathematics on the effect of flight clearance leads to the well-known correction (1 - 8/H) to the drag flow, yet the much more significant effect on power input is not really tackled. Although given in great detail, the treatment is not critical as in 'Extruder screw design' by Fenner, and Fig. 6.43 is the only attempt to justify the additional computing time required for the more sophisticated solutions. The key section of the book deals with the process of melting the solid polymer in the screw; this is based on work done by the authors and colleagues in the Western Electric laboratories. They are to be congratulated on deriving expressions with a minimum number of factors to be determined experimentally. However, some of the assumptions are surprising, e.g. that the molten film above the solid bed is of uniform thickness in the cross-channel
K. A. Scott
Multicomponent Polymer Systems Advances in Chemistry Series 99 American Chemical Society, Washington, 1971, 588 pp. $16.50 The above-mentioned book represents another in the well known
Advances in Chemistry Series published by the American Chemical Society. It contains the series of thirty-seven papers given at a recent national ACS meeting. The subject of the symposium, namely 'Multicomponent polymer systems', is one of the most topical subjects in polymer chemistry at this time. Essentially, it is the use of two or more polymeric components to produce a different species having certain improved properties over those of the original material. This area of research is truly 'applied' in that the goals are usually distinct, namely the improvement of properties using existing products. This area of research becomes even more important if we assume that few, if any, new major polymers will appear on the market in the foreseeable future. Instead, new polymeric species will be prepared by modification of polymerization conditions using existing monomers or by the modification of existing polymers. This last area is the one with which this series of papers is concerned. The subjects covered in the symposium are extremely divergent and include topics such as simple polyblends, random block and graft copolymers, reinforced plastics and elastomers and fringe areas, such as surface coatings. It is within these confines that the polymer engineer, polymer physicist and polymer chemist find that their own particular disciplines merge into what could be loosely termed materials science. With regard to the book itself, it is printed in a style which suits the reviewer. The diagrams and photographs are very clear and at $16.50 for 588 pages it represents exceedingly good value for money. It can be thoroughly recommended to anyone with an interest in polymer science.
J. M . Locke
* E.g. p 12, Table 2.2A: minus sign omitted before penultimate term and third denominator given as 0x in place of ~z. p 18, Table 2.6A: first denominator given as 0x in place of 0t~
POLYMER, 1972, Vol 13, October 507
Engineering principles of plasticating extrusion Z. Tadmor and I. Klein Van Nostrand, New York, 1970, 500 pp. £9.35
The late W. S. Penn's well established reference book 'PVC Technology' has been revised extensively and up-dated by Titow and Lanham. They have maintained the essential character of the earlier editions which have been valuable to the technologist in providing an easy reference source for commercial polymers, compounds, plasticizers, stabilizers, fillers and other compounding ingredients. Not only is the chemical identity of these products indicated but commercial names, grades and sources are given. The manifold processes for converting PVC to products are described lucidly. A substantial rewriting of many chapters had added to the technological content. The pattern of presentation is such that there is an excellent balance between the discussion of the principles of technology and commercial details. Because of this the book well achieves the aims of the authors to present a reference source which can be read and utilized at several levels. The non-specialist has a useful guide to PVC technology whilst the student will have a well presented and readable textbook. For those who wish to read the subject in more detail there are ample references to original papers in each chapter. The final chapter of the book reviews applications of PVC and is followed, appropriately, by an appendix which lists BS, ASTM, D I N and ISO standards relevant to PVC and its products. A second appendix includes units, conversions and definitions. The index, although not comprehensive is adequate. The book is well produced and is strongly recommended to all who have an interest in PVC, its processing and its uses. Finally one might comment that this publication is a fitting testimony to the valuable contributions which the late W. S. Penn made to education and plastics technology.
This is probably the first book to attempt to represent mathematically the performance of each section of the single-screw extruder--solid feed, melting, and melt pumping. It draws largely on previously published work by the authors and others, which should permit a lucid treatment of the overall behaviour of the complete machine. However, the sheer weight of mathematics seems to magnify trivial details and obscure the major effects, many of which have previously been represented, at least qualitatively, by simpler approximations. The chapter on 'Basic flow concepts' reproduces the fundamental equations of continuity, motion, and energy (unfortunately with several errors*) followed by a brief discussion including the effects of shear rate, temperature, and pressure. There is little adaptation to practical situations or indication of how the equations may be handled, since in most cases many factors are unknown. Equation 2.4 assumes constant density, which implies isothermal conditions, though this is not stated, nor is it clear whether thermal expansion has been ignored subsequently. Appendix C provides little viscometric data additional to that published in 1959 in 'Processing of thermoplastic materials' by Bernhardt. The chapter on 'Screw geometry' is an example of undue attention to detail, some of it inapplicable to screws as manufactured. The feed section is treated by the method of Darnell and Mol, with some additional work by the authors covering the effects of flight width and pressure rise and of different coefficients of friction on the screw and barrel. The latter suggests that the temperature difference between screw and barrel in this section will have a profound influence on the rate of feeding, although no experimental data are presented on the variation of friction coefficient with temperature for commercial polymers. In practice the temperature conditions are rarely critical, providing cooling is applied to the feed section. Pressure rise is shown to be exponential and hence critically dependent on the initial pressure. However, factors influencing flow in the feed hopper and the filling of the screw, e.g. particle size distribution, degree of hopper filling, air entrainment, and geometry of the hopper and feed opening are not considered. The melt pumping section is treated in a very long chapter (nearly 150 pages) similarly to a number of other computer analyses, where the equations are progressively developed from the Newtonian isothermal case to non-Newtonian non-isothermal with shear heating and channel curvature. The first 40 pages or so present the work of previous authors on the isothermal Newtonian case, but in what appears to be an unnecessarily obscure manner. In 'Polymer processing' McKelvey shows curves of output versus helix angle which clearly explain why the apparent optimum angle of 30 ° is not often used, yet these are not reproduced; the conditions for maximum pressure gradient (p 222) could be much more clearly described in terms of the dimensionless factor Q~Wbh or the pressure flow/drag flow ratio; there is much discussion of velocity profiles yet only one rough pressure profile (p 237), although these are used later in Section 8.3 as basis for comparison of theory and experiment. A section of seven pages of mathematics on the effect of flight clearance leads to the well-known correction (1 - 8/H) to the drag flow, yet the much more significant effect on power input is not really tackled. Although given in great detail, the treatment is not critical as in 'Extruder screw design' by Fenner, and Fig. 6.43 is the only attempt to justify the additional computing time required for the more sophisticated solutions. The key section of the book deals with the process of melting the solid polymer in the screw; this is based on work done by the authors and colleagues in the Western Electric laboratories. They are to be congratulated on deriving expressions with a minimum number of factors to be determined experimentally. However, some of the assumptions are surprising, e.g. that the molten film above the solid bed is of uniform thickness in the cross-channel
K. A. Scott
Multicomponent Polymer Systems Advances in Chemistry Series 99 American Chemical Society, Washington, 1971, 588 pp. $16.50 The above-mentioned book represents another in the well known
Advances in Chemistry Series published by the American Chemical Society. It contains the series of thirty-seven papers given at a recent national ACS meeting. The subject of the symposium, namely 'Multicomponent polymer systems', is one of the most topical subjects in polymer chemistry at this time. Essentially, it is the use of two or more polymeric components to produce a different species having certain improved properties over those of the original material. This area of research is truly 'applied' in that the goals are usually distinct, namely the improvement of properties using existing products. This area of research becomes even more important if we assume that few, if any, new major polymers will appear on the market in the foreseeable future. Instead, new polymeric species will be prepared by modification of polymerization conditions using existing monomers or by the modification of existing polymers. This last area is the one with which this series of papers is concerned. The subjects covered in the symposium are extremely divergent and include topics such as simple polyblends, random block and graft copolymers, reinforced plastics and elastomers and fringe areas, such as surface coatings. It is within these confines that the polymer engineer, polymer physicist and polymer chemist find that their own particular disciplines merge into what could be loosely termed materials science. With regard to the book itself, it is printed in a style which suits the reviewer. The diagrams and photographs are very clear and at $16.50 for 588 pages it represents exceedingly good value for money. It can be thoroughly recommended to anyone with an interest in polymer science.
J. M . Locke
* E.g. p 12, Table 2.2A: minus sign omitted before penultimate term and third denominator given as 0x in place of ~z. p 18, Table 2.6A: first denominator given as 0x in place of 0t~
POLYMER, 1972, Vol 13, October 507