Marcel Dekker, Inc. New York • Basel Rubber Compounding Chemistry and Applications edited by Brendan Rodgers The Goodyear Tire & Rubber Company Akron, Ohio DK1284_FM 6/21/04 1:44 PM Page i Although great care has been taken to provide accurate and current information, neither the author(s) nor the publisher, nor anyone else associated with this publica- tion, shall be liable for any loss, damage, or liability directly or indirectly caused or alleged to be caused by this book. The material contained herein is not intended to provide specific advice or recommendations for any specific situation. Trademark notice: Product or corporate names may be trademarks or registered trade- marks and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress. ISBN: 0-8247-4871-9 This book is printed on acid-free paper. 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Current printing (last digit): 10987654321 PRINTED IN THE UNITED STATES OF AMERICA 4871-9_Rodgers_Prelims_R2_052404 MD: RODGERS, JOB: 03286, PAGE: ii Copyright © 2004 by Taylor & Francis Preface Rubber compounding includes the science of elastomer chemistry and the modification of elastomers and elastomer blends by addition of other materials to meet a set of required mechanical properties. It is therefore among the most complex disciplines in that the materials scientist requires a thorough understanding of materials physics, organic and polymer chemistry, inorganic chemistry, thermodynamics, and reaction kinetics. The rubber industry has changed over the last few years. For example, tires have evolved from bias to tubeless radial constructions, and now ultralow-profile products are emerging. Service lives of tires and of industrial products such as automobile engine hoses have dramatically improved. None of these innovations would have been possible without an emphasis on the understanding of the chemistry of raw materials and compounds. Examples of advances in materials technologies over recent years include 1. Commercialization of functionalized and coupled, solution-poly- merized polymers 2. Thermoplastic elastomers 3. Development of silica tread compound for high-performance tires 4. Hybrid filler systems and nanocomposite technologies 5. Reversion-resistant vulcanization systems 6. Halobutyl polymers, which were the foundation for the develop- ment of the tubeless radial tire 7. A new emphasis on recycling and renewable sources for raw materials 4871-9_Rodgers_Preface_R2_052404 MD: RODGERS, JOB: 03286, PAGE: iii Copyright © 2004 by Taylor & Francis To elaborate on the philosophy behind this book, we want to emphasize the chemistry of the materials used in building a compound formulation for a tire or engineered product. Although subjects are not presented at an introductory level, this is not an advanced treatise. Rather, it is intended as a tool for the industrial compounder, teacher, or other academic scientist, to provide basic information on materials used in the rubber industry. It also addresses a gap in the body of literature available to the chemist in industry and academia. One chapter describes the application of materials technolo- gies in products such as hoses, conveyor belts, and tires. As Fred Barlow said in his book, Rubber Compounding, Second Edition (Dekker, 1993), no comprehensive review of a subject such as this could be written by one individual. The compilation of this work thus depended on many contributors, and I want to express my thanks to the authors who participated in the project. All are recognized authorities in their field, and this is reflected in the quality of their contributions. I also wish to express many thanks to both Joseph Gingo, Senior Vice President, and Carl Payntor at The Goodyear Tire & Rubber Company for their support, to the staff at Marcel Dekker, Inc., Rita Lazazzaro and Lila Harris for their patience, and most important to my wife, Elizabeth, for her encouragement. Brendan Rodgers 4871-9_Rodgers_Preface_R2_052404 MD: RODGERS, JOB: 03286, PAGE: iv Copyright © 2004 by Taylor & Francis Contents Preface Contributors 1.NaturalRubberandRecycledMaterials William Klingensmith and Brendan Rodgers 2.General-PurposeElastomers Howard Colvin 3.Special-PurposeElastomers Sudhin Datta 4.ButylRubbers Walter H. Waddell and Andy H. Tsou 5.ThermoplasticElastomers:FundamentalsandApplications Tonson Abraham and Colleen McMahan 6.CarbonBlack Wesley A. Wampler, Thomas F. Carlson, and William R. Jones 4871-9_Rodgers_Contents_R2_052104 MD: RODGERS, JOB: 03286, PAGE: v Copyright © 2004 by Taylor & Francis 7.SilicaandSilanes Walter Meon, Anke Blume, Hans-Detlef Luginsland, and Stefan Uhrlandt 8.GeneralCompounding Harry G. Moneypenny, Karl-Hans Menting, and F. Michael Gragg 9.Resins James E. Duddey 10.AntioxidantsandOtherProtectantSystems Sung W. Hong 11.Vulcanization Frederick Ignatz-Hoover and Byron H. To 12.CompoundDevelopmentandApplications George Burrowes and Brendan Rodgers 4871-9_Rodgers_Contents_R2_052104 MD: RODGERS, JOB: 03286, PAGE: vi Copyright © 2004 by Taylor & Francis Contributors Tonson Abraham Advanced Elastomer Systems, L.P., Akron, Ohio, U.S.A. Anke Blume Degussa AG, Cologne, Germany George Burrowes The Goodyear Tire & Rubber Company, Lincoln, Nebraska, U.S.A. Thomas F. Carlson Sid Richardson Carbon Company, Fort Worth, Texas, U.S.A. Howard Colvin Riba-Fairfield, Decatur, Illinois, U.S.A. Sudhin Datta ExxonMobil Chemical Company, Baytown, Texas, U.S.A. James E. Duddy Akron, Ohio, U.S.A. F. Michael Gragg ExxonMobil Lubricants & Petroleum Specialties Company, Fairfax, Virginia, U.S.A. Sung W. Hong Crompton Corporation, Uniroyal Chemical, Naugatuck, Connecticut, U.S.A. Frederick Ignatz-Hoover Flexsys America LP, Akron, Ohio, U.S.A. 4871-9_Rodgers_Contributors_R2_052104 MD: RODGERS, JOB: 03286, PAGE: vii Copyright © 2004 by Taylor & Francis William R. Jones Sid Richardson Carbon Company, Fort Worth, Texas, U.S.A. William Klingensmith Akron Consulting Company, Akron, Ohio, U.S.A. Hans-Detlef Luginsland Degussa AG, Cologne, Germany Colleen McMahon Advanced Elastomer Systems, L.P., Akron, Ohio, U.S.A. Karl-Hans Menting Schill & Seilacher ‘‘ Struktol’’ Aktiengesellschaft, Hamburg, Germany Harry G. Moneypenny Moneypenny Tire & Rubber Consultants, Den Haag, The Netherlands Walter Meon Degussa Corporation, Parsippany, New Jersey, U.S.A. Brendan Rodgers The Goodyear Tire & Rubber Company, Akron, Ohio, U.S.A. Byron H. To Flexsys America LP, Akron, Ohio, U.S.A. Andy H. Tsou ExxonMobil Chemical Company, Baytown, Texas, U.S.A. Stefan Uhrlandt Degussa Corporation, Piscataway, New Jersey, U.S.A. Walter H. Waddell ExxonMobil Chemical Company, Baytown, Texas, U.S.A. Wesley A. Wampler Sid Richardson Carbon Company, Fort Worth, Texas, U.S.A. 4871-9_Rodgers_Contributors_R2_052104 MD: RODGERS, JOB: 03286, PAGE: viii Copyright © 2004 by Taylor & Francis 1 Natural Rubber and Recycled Materials William Klingensmith Akron Consulting Company, Akron, Ohio, U.S.A. Brendan Rodgers The Goodyear Tire & Rubber Company, Akron, Ohio, U.S.A. I. INTRODUCTION The nature of the tire and rubber industry has changed over the last 30 to 40 years in that, like all other industries, it has come to recognize the value of using renewable sources of raw materials, recycling materials whenever possible, and examining the potential of reclaiming used materials for fresh applications. Renewable raw materials range from natural rubber, more of which is used than any other elastomer, naturally occurring process aids such as pine tars and resins, and novel biological materials such as silica derived from the ash of burned rice husks. Naturally occurring materials include inorganic fillers such as calcium carbonate, which is distinct from naturally occurring organic material, whose total supply may be restricted. Consider- able work is underway today to develop markets and applications where rubber products can be recycled into existing new products and new appli- cations developed for discarded rubber products such as tires. Given the desire to maximize the content of renewable, recycled, and reclaimed materi- als in rubber compounds, this review merges these topics under one title and treats each in turn. 4871-9_Rodgers_Ch01_R2_052704 MD: RODGERS, JOB: 03286, PAGE: 1 Copyright © 2004 by Taylor & Francis II. NATURAL RUBBER Of the range of elastomers available to technologists, natural rubber (NR) is among the most important, because it is the building block of most rubber compounds used in products today. In the previous edition of this text (1) Barlow presented a good introductory discussion of this strategic raw ma- terial. Roberts (2) edited a very thorough review of natural rubber covering topics ranging from basic chemistry and physics to production and applica- tions. Natural rubber, which is a truly renewable resource, comes primarily from Indonesia, Malaysia, India, and the Philippines, though many more additional sources of good quality rubber are becoming available. It is a material that is capable of rapid deformation and recovery, and it is insoluble in a range of solvents, though it will swell when immersed in organic solvents at elevated temperatures. Its many attributes include abrasion resistance, good hysteretic properties, high tear strength, high tensile strength, and high green strength. However, it may also display poor fatigue resistance. It is difficult to process in factories, and it can show poor tire performance in areas such as traction or wet skid compared to selected synthetic elastomers. Given the importance of this material, this section discusses 1. The biosynthesis and chemical composition of natural rubber 2. Industry classification, descriptions, and specifications 3. Typical applications of natural rubber A. Chemistry of Natural Rubber Natural rubber is a polymer of isoprene (methylbuta-1,3-diene). It is a polyterpene synthesized in vivo via enzymatic polymerization of isopentenyl pyrophosphate. Isopentenyl pyrophosphate undergoes repeated condensa- tion to yield cis-polyisoprene via the enzyme rubber transferase. Though bound to the rubber particle, this enzyme is also found in the latex serum. Structurally, cis-polyisoprene is a highly stereoregular polymer with an UOH group at the alpha terminal and three to four trans units at the omega end of the molecule (Fig. 1). Molecular weight distribution of Hevea brasiliensis rubber shows considerable variation from clone to clone, ranging from 100,000 to over 1,000,000. Natural rubber has a broad bimodal molecular weight distribution. The polydispersity or ratio of weight-average molecular weight to number-average molecular weight, M w /M n , can be as high 9.0 for some variety of natural rubber (3,4). This tends to be of considerable significance in that the lower molecular weight fraction will facilitate ease of processing in end product manufacturing, while the higher molecular 4871-9_Rodgers_Ch01_R2_052704 MD: RODGERS, JOB: 03286, PAGE: 2 Copyright © 2004 by Taylor & Francis [...]... rubber particles NSR Nigerian standard rubber SIR Standard Indonesian rubber SLR Standard Lanka rubber SMR Standard Malaysian rubber SRP Serum rubber particles SSR Standard Singapore rubber TSR Technically specified rubber TTR Thai tested rubber Copyright © 2004 by Taylor & Francis 2 3 Cup-lump is produced when the latex is left uncollected and allowed to coagulate, due to bacterial action, on the side of... wrapping, and bale weights and dimensions, with the objectives of improving rubber quality, uniformity, and consistency and developing additional uses for contaminated material (11,12) The three sources leading to crumb rubber (i.e., unsmoked sheet rubber, aged sheet rubber, and field cup-lump) typically provide different grades of technically specified rubbers For example, one grade of technically specified rubber. .. the production of natural rubber 1 Sheet Rubber Natural rubber in sheet form is the oldest and most popular type Being the simplest and easiest to produce on a small scale, smallholders’ rubber in most countries is processed and marketed as sheet rubber From the end user’s perspective, two types of sheet rubbers are produced for the commercial market: ribbed smoked sheets (RSS) and air-dried sheets (ADS)... sheets, and lower grades such as TSR 10 and 20 are produced from field coagulum A simplified schematic of the production process is presented in Figure 4 C Natural Rubber Products and Grades Natural rubber is available in six basic forms: 1 2 3 Sheets Crepes Sheet rubber, technically specified Copyright © 2004 by Taylor & Francis Figure 4 4 5 6 Schematic of the natural rubber production process Block rubber, ... Tetramethylthiuram disulfide (TMTD) and zinc oxide are also used as preservatives because of their greater effectiveness as bactericides Most latex concentrates are produced to meet the International Standard Organization’s ISO 2004 (8) This standard defines the minimum content for total solids, dry rubber content, nonrubber solids, and alkalinity (as NH3) B Production of Natural Rubber Total global rubber consumption... removed, and the material is sheeted with a rough surface to facilitate drying Sheets are then suspended on poles for drying in a smokehouse for 2–4 days Only deliberately coagulated rubber latex processed into rubber sheets, properly dried and smoked, can be used in making RSS A number of prohibitions are also applicable to the RSS grades Wet, bleached, undercured, and original rubber and rubber that... Francis (SIR) In Thailand, the TSRs are called Standard Thai Rubber (STR; sometimes denoted as TTR) In India, the TSRs are designated as Indian Standard Natural Rubber (ISNR) Grading is based on the dirt content measured as a weight percent Dirt is considered to be the residue remaining when the rubber is dissolved in a solvent, washed through a 45 Am sieve, and dried Technically specified rubber (TSR) accounts... HNS and PHZ block the reaction of the aldehyde groups with UNH2 by reacting with the UC(CH3) = O group to form RVUCðCH3 Þ ¼ N À NHUCOUR RVUCðCH3 ÞUCH ¼ NUCOUR and In compounded rubber, the term ‘‘bound rubber ’ has frequently been used to describe this cross-linking condition in both natural rubber and polymers such as polybutadiene Bound rubber can be found in all synthetic unsaturated elastomers and. .. protein and other nonrubber material into water-soluble residues The residues are then washed out of the rubber to leave a polymer with low sensitivity to water Typically, natural rubber contains around 0.4% nitrogen as protein; deproteinized rubber contains typically 0.07% Deproteinized natural rubber has found application in medical gloves to protect workers from allergic reactions and in automotive applications, ... seals, and bushings The polymer displays low creep, exhibits strain relaxation, and enables greater control of product uniformity and consistency (26) Epoxidized natural rubber Compared with natural rubber, epoxidized NR shows better oil resistance and damping and low gas permeability However, its tear strength is low, which has prevented its use in pneumatic tires Two grades are available, ENR 25 and . Large rubber particles. NSR Nigerian standard rubber. SIR Standard Indonesian rubber. SLR Standard Lanka rubber. SMR Standard Malaysian rubber. SRP Serum rubber particles. SSR Standard Singapore rubber. TSR. biosynthesis and chemical composition of natural rubber 2. Industry classification, descriptions, and specifications 3. Typical applications of natural rubber A. Chemistry of Natural Rubber Natural rubber. Taylor & Francis 7.SilicaandSilanes Walter Meon, Anke Blume, Hans-Detlef Luginsland, and Stefan Uhrlandt 8.GeneralCompounding Harry G. Moneypenny, Karl-Hans Menting, and F. Michael Gragg 9.Resins