14
Analysis of Rubber and Rubber-like Polymers
Analysis of Rubber and Rubber-like Polymers
Analysis of Rubber and Rubber-like Polymers
Fourth Edition
M.J.R. Loadman
~.
" SPRINGER SCIENCE+BUSINESS MEDIA, BV.
Library of Congress Cataloging-in-Publication Data
ISBN 978-94-010-5905-3 ISBN 978-94-011-4435-3 (eBook) DOI 10.1007/978-94-011-4435-3
Printed on acid-free paper
AU Rights Reserved © 1998 Springer Science+Business Media Dordrecht OriginaUy published by Kluwer Academic Publishers in 1998· Softcover reprint ofthe hardcover 4th edition 1998 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.
Contents
Preface Acknowledgements
Chapter 1 Introduction The nature of materials The historical perspective
Natural rubber The synthetic rubbers
Scope of the book The analytical problem Compositional categories
Polymers Plasticizers and oils Solid fillers Ancillary chemicals and their residues Adventitious materials
References
Chapter 2 Sampling and sample preparation
Analysis of average composition Thin calendered sheets or proofings Dipped goods Small moulded articles Large manufactured articles Rubberized fabrics
Homogenization of sample Analysis of localized composition
Vulcanization state of thick articles Analysis of blooms Bond failure problems
xii xiv
1 1 4 4
10 14 16 19 19 20 20 21 21 22
25
25 26 26 26 26 26 27 28 28 28 28
vi Contents
Inhomogeneity and poor dispersion 28 Phase morphology within a blend 29
Size of test portion 29 Sample preparation 29
Chapter 3 Extraction 31
Preliminary remarks 31 Nature of the extraction process 32 Standard apparatus for determination of extract level 37 Choice of solvent 38 Time of extraction 40 Rapid extraction 41 Microwave extraction 42 Micro scale extraction 43 Multiple extractions 44 Specific extractions 45 Supercritical fluid extraction 46 ~~ ~
Thermal extraction 48 Adsorption/ extraction 49 References 52
Chapter 4 Analysis of extracts 54
Identifications with no separation 55 Plasticizers 55 Factice 56 Tests for some specific additives 57 Analysis for antioxidants 58 Analysis for accelerators 59 Natural rubber extracts 59 Analysis for other extractants 62 Ultraviolet spectroscopy (UV) 63 Infrared spectroscopy (IR) 64 Atomic absorption spectroscopy (AAS)/inductively coupled plasma-atomic emission spectroscopy (ICP-AES) 64
Identification with separation 65 Column/paper chromatography 65 Thin layer chromatography (TLC) 66 High performance liquid chromatography (HPLC) 72 Ion chromatography (IC) 75 Gas chromatography (GC) 75 Flame ionization detector (FlO) 76
Contents vii
Mass selective detector (MSD), also known as the mass spectrometer Nitrogen phosphorus detector (NPD) Thermal energy analyser (TEA)
Identification after separation References
Chapter 5 Solution methods
Theoretical considerations Theta temperature Guidelines to solubility
Practical considerations Preparation of a solution Removal of solvent Selective solution Selective precipitation
References
Chapter 6 Quantitative elemental analysis
Carbon and hydrogen Nitrogen Oxygen Chlorine and bromine
Instrumental methods of analysis Conversion of 'organic' chlorine to chloride Determination of chloride and bromide
Fluorine Silicon Phosphorus
Phosphorus determination in rubber Sulphur
Determination of total (or combined) sulphur Intrinsic (inactive) sulphur in carbon black Determination of free (elemental) sulphur Determination of sulphide sulphur
Ion chromatography (IC) References
Chapter 7 Instrumental polymer analysis
Introduction Infrared spectroscopy (IR)
Sample preparation and presentation
76 77 77 77 79
81
82 87 88 88 89 89 92 93 93
95
95 96 98
100 100 101 103 103 105 106 108 109 109 115 115 120 123 126
129
129 129 132
viii Contents
Running the spectrum 137 Interpretation of spectral data 138 Raman spectroscopy 141
Nuclear magnetic resonance spectroscopy (NMR) 143 Pyrolysis-gas chromatography (PGq 148 Derivative thermogravimetry (DTG) 154
Heating rate and calibration 156 Polymer identification 159 Polymer blend quantification 160
Differential scanning calorimetry (DSq 163 Glass transition temperatures 164 Crystallization and melting 165 High temperature events 167
Scanning electron microscopy (SEM) 168 Visual aspects of polymer analysis 170 Elemental analysis 170
References 171
Chapter 8 Polymer characterization 174
Molar Mass 174 End group analysis (Mn) 175 Measuremen~f col!!gative property (Mn) 176 Viscometry (Mn or Mw) 179 Light scattering (Mw) 180 Gel permeation chromatography (Mn, Mw, Mz) 183 Thermal field flow fractionation 189 Differential scanning calorimetry / differential thermal analysis (Mn) 192 Ultracentrifugation (Mw) 192 Sedimentation effects (Mw or Mz) 192
Microstructure 193 Monomer type 194 Monomer distribution 197
Metathesis 201 Latex particle sizing 202
Sample pretreatment for transmission electron microscopy 202 Transmission electron microscopy 204 Particle sizing by photon correlation spectroscopy (PCS) 204
References 205
Chapter 9 Blend morphological analysis 208
Light microscopy (LM) 208 Scanning electron microscopy (SEM) 209
Contents ix
Transmission electron microscopy (TEM) 211 SEM based scanning transmission electron microscopy (S(T)EM) 212 TEM based scanning transmission electron microscopy (STEM) 214 Microtomy and associated techniques 215
Microtomy using a base-sledge microtome 215 Ultramicrotomy using a cryo-ultramicrotome 215 Common problems with sectioning 223
Freeze fracture 226 Chemical staining 226
Osmium tetroxide 226 Ruthenium tetroxide 227 Uranyl acetate 228
Chemical etching 229 Case study 231 Swollen vulcanized elastomer network observation 238 References 242
Chapter 10 Inorganic fillers and trace metal analysis 243
Ashing 243 Temperature of ashing 244 Changes in mineral constituents during ashing 244 Loss of trace elements during ashing 245 Thermogravimetry 246 Acid ashing 246 Wet ashing 247 Digestion in pressure vessels 249
Bulk filler analysis 251 Trace metals 252 Analysis of prepared solutions 252
Atomic spectroscopy 252 Total sample elemental analysis 256
Destructive elemental analysis 256 Non-destructive elemental analysis 259 Quantitation of energy-dispersive X-ray analytical data 262
References 263
Chapter 11 Carbon black 265
Obtaining free carbon black from the rubber matrix 265 Destruction and filtration methods 266 Removal of polymer by distillation 267
Types of carbon black 267 Analysis of carbon black particles and aggregates 270 Analysis of carbon black type 270
x Contents
Spectrophotometric methods Surface area measurements
Total surface area External surface area
Black type by thermogravimetry Carbon black dispersion in vulcanizates
The Cabot dispersion test The cut-surface and tom-surface methods Transmission electron microscopy
Other techniques used to examine carbon black Inverse gas chromatography (ICC) Neutron scattering Raman spectroscopy and X-ray scattering Surface compositional analysis Models of carbon black using fractal dimensions
References
Chapter 12 Formulation derivation and calculation
Polymer content Copolymers Latex
Formulation derivation Extract Polymer Black Ash Sulphur
Formulation calculation References
Chapter 13 Blooms and visually similar phenomena
True blooms Modified blooms Pseudo blooms Surface contamination Hazing of transparent rubbers Staining/ discoloration Pre-analytical check-list
Colour changes Analytical methods
Spot tests Multiple internal reflectance
270 274 274 278 279 284 284 284 285 285 285 286 286 286 287 287
290
290 303 303 303 305 306 307 307 307 309 310
312
312 314 314 315 315 315 317 318 319 319 319
Contents xi
Scanning electron microscopy 320 Removal of bloom prior to analysis 320 References 323
Chapter 14 Validity of results 325
Introduction 325 Precision, accuracy, bias and error 325
Meaningful information from imprecise data 328 Confidence limits 330 Uncertainty 330 Coefficient of variation 331 Significance tests 331 Analysis of variance 335 Outliers 336 Graphical data presentation 340
Traceability 341 Validation of analytical methods 343
Validation steps 343 Limits of detection (LaD) and quantitation (LOQ) 345
References 346
Appendix A Table of Official National and International Standards 347
Appendix B Elastomers: nomenclature, description and properties
Appendix C Intercorrelation of analytical techniques
Subject index Author index
352
359
361 369
Preface
The first edition of this book (1958) described an analytical situation which had existed for a number of years for maintaining quality control on vulcanizates of natural rubber although the situation had recently been disturbed by the introduction of a range of synthetic rubbers which required identification and quantitative estimation.
For the former purpose 'wet' chemistry, based on various imperfectly understood organic reactions, was pressed into service. Alongside this was the first introduction of instrumental analysis, using the infrared spectra of either the polymers or, more usually, their pyrolytic products to 'fingerprint' the material. The identification of a range of organic accelerators, antioxidants and their derivatives which had been introduced during the 1920s and 30s was, in the first edition, dealt with by a combination of column chromatography and infrared spectroscopy or by paper chromatography.
Quantitative procedures were, however, still classical in the tradition of gravimetric or volumetric assays with an initially weighed sample yielding, after chemical manipulation, a carefully precipitated, dried and weighed end product, or a solution of known composition whose weight or titre, as a percentage of the initial sample, quantified the function being determined.
The second edition of this work (1968) consolidated the newer techniques which had been introduced in the first without adding to them although, in other applications of analytical chemistry, instrumental analysis had already brought about a transformation in laboratory practice.
In 1983 the third edition was published and gave full credit to modem instrumentation in all spheres of the analysis of rubber and rubber-like polymers, describing techniques and illustrating applications where equipment still at the 'research stage' could add to the strength of the analysts' armoury of the future. Nevertheless, the financial stric-
Preface xiii
tures confronting modem 'instrumental' laboratories were appreciated so, within each area of analysis, there was a variety of techniques presented, from the 'bum test', costing essentially nothing, to those using instrumentation costing many tens of thousands of pounds.
In this, the fourth edition, the structure of the previous edition has been maintained and expanded in that each chapter provides a complete package of information on a particular topic as viewed by an enquirer or analyst rather than discussing the range of uses of a particular instrument or technique. After covering a range of topics, the book continues by showing how specific primary analytical data can be intercorrelated and how this can then be expressed in the technological language of compound or product 'formulation'. Finally, the validity of any conclusions drawn from the analytical data is discussed in terms of its statistical Significance so that a reasoned interpretation may be made of the final information package.
The impact of 'health and safety' oriented legislation has taken its toll of many of the older chemical methods of analysis. Not only are the chemicals used now considered potentially hazardous, but it is also important to note that many of the older methods present in the literature of the last century have not been fully validated against the thousands of new substances which may, today, be found in a commercial rubber product and which may interfere with a colorimetric or spot test which would have been perfectly satisfactory in earlier times. Many new or extended instrumental techniques have, however, replaced those which have been eliminated, and, at the same time, the opportunity has been taken to invite my colleagues in the Materials Characterization Group of the Tun Abdul Razak Research Centre to comment on, rewrite, or expand any areas which they believed to be deficient. Because these experts operate under areas of instrumental expertise and the book is structured under topics of interest to the rubber analyst or technologist, individual contributions are scattered throughout the text and I can only claim to have attempted to produce a coherent whole!
To my staff, in alphabetical order, I give my thanks: Bob Crafts (elemental analysis and statistics), Paul Cudby (microscopical techniques), Jim Gleeson (GC and TLC), Colin Hull (NMR, thermal methods and carbon black), Kevin Jackson (spectroscopic and thermal methods), Chris Lewan (LC and GPC), and Sue Stephens (GC and TLC). To others of my staff whose contributions were indirect in that they freed those listed above to make their direct contributions I also offer my thanks.
Acknowledgement is also due to the Board of the Tun Abdul Razak Research Centre (T ARRC) for permission to undertake this project and for the facilities made available to my staff and me.
MJRL (1998)
Acknowledgements
In a book of this nature it is inevitable that a wide range of publications be consulted to afford as balanced a picture as possible of the current position in the analysis of rubber and rubber-like polymers. From these publications many tables and figures have been culled to illustrate relevant points throughout the text and it is with much gratitude that I and the publisher thank the copyright holders for permission to use their data. The very number of these necessitates only the briefest of comments but this brevity in no way reduces the sincerity of our appreciation to:
The British Standards Institution for Figure 6.3, taken from BS 7164: Part 24: 1966 and the American Society for Testing and Materials, together with A. Krishen (1974) for Figures 7.10, 7.11 and 7.12. Full copies of these documents may be obtained from 389 Chiswick High Road, London W4 4AL and 100 Barr Harbour Drive, West Conshohocken, PA19428, USA respectively. The National Institute of Standards and Technology, Technology Administration, US Department of Commerce, for permission to reprint Table 11.7.
John Wiley & Sons, Inc. with Evans, Higgins, Lee and Watson (1960) J. Appl. Polym. Sci. for Figure 5.2; with Gelling, Loadman and Sidek (1979) J. Polym. Sci. Polym. Chern. Edn. for Figures 7.16,7.17 and 7.18; with Kim and Mendelkern (1972) J. Polym. Sci. Part A2 for Figure 7.20; with Lee and Singleton (1979) J. Appl. Polym. Sci. for Figure 7.21 and with Billmeyer (1971) Textbook of Polymer Science, 2nd Edn for Figure 8.2
The Managing Editor of Rubber Chemistry and Technology with Swarin and Wims (1974) for Figures 12.2, 12.3 and 12.4 as well as Tables 12.6 and 12.7; Sircar and Lamond (1978) for Figure 12.5; Brazier and Nickel (1975) for Table 12.5 and Pautrat et al. (1976) for Figure 11.4.
Acknowledgements xv
The Editor of The European Journal for the following tables which appeared in Rubber J.: White (1967) for Table 4.2 and Lamond and Gillingham (1970) for Tables 11.5 and 11.6.
The American Chemical Society with Carman (1973) Macromolecules for Figure 8.14 and Krishen (1972) Anal. Chem. for Figure 7.9.
The Editor of Materials World with Davies and Kam (1967) J. IRI for Table 11.3, Ney and Heath (1968) J. IRI for Figures 7.7 and 7.8, McSweeney (1970) J. IRI for Figure 3.4, Davey et al. (1978) Plast. and Rubb. Mat. and Applic. for Figure 6.4 and Charsley and Dunn (1981) Plast. and Rubber Process Applic. for Figure 11.5.
MCM Publishing for allowing Figures 11.2 and 11.3 to be taken from Maurer (1970a), Rubber Age, Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam for allowing Figure 7.23 to be reprinted from Thermochim. Acta (1980), 39, 593 (Goh) and Addison Wesley Longman Ltd for permission to reproduce Davies and Goldsmith's table of '%age of Student's t distribution' from 'Statistical Methods in Research and Production (0-852-45087-X) as Figure 14.1.
Figure 10.2 was supplied by the Parr Instrument Company and is published with its permission, Figures 6.5 and 6.6 are published with the permission of Dionex (UK) Ltd whilst Figure 7.13 was provided by, and is published with the permission of, the Perkin Elmer Corporation.
Finally I thank the Director of the Rubber Research Institute of Malaysia for permission to use the data shown in Tables 6.2 (Davey (1989) J. Nat Rubber Res.) and 14.2 and the Board of the Tun Abdul Razak Research Centre (TARRC), through the Director of Research, for permission to refer to unpublished work carried out within the Research Centre over many years and for Figure 7.2 taken from the house publication, NR Technol. (G.M.C. Higgins and M.J.R. Loadman, 1970). Work carried out under the earlier name of the Research Centre - the Malaysian Rubber Producers' Research Association (MRPRA) - is credited to that name.
