Rubber Technology

Frontmatter

1. Rubber Compounding: Introduction, Definitions, and Available Resources

Abstract

Rubber compounding is the art and science of selecting various compounding ingredients and their quantities to mix and produce a useful rubber formulation that is processable, meets or exceeds the customer’s final product requirements, and can be competitively priced.

John S. Dick

2. Compound Processing Characteristics and Testing

Abstract

The processing of a rubber formulation is a very important aspect of rubber compounding. Also, it is important to understand the rubber properties needed for good processability and the tests performed to measure these properties.

John S. Dick

3. Vulcanizate Physical Properties, Performance Characteristics, and Testing

Abstract

The physical properties of cured rubber compounds are major determinants of product performance. The following physical properties are discussed as follows in this chapter:

• ■ Density (in Section 3.2)
• ■ Hardness (in Section 3.3)
• ■ Stress–Strain Properties Under Tension (in Section 3.4)
• ■ Stress–Strain Properties Under Compression (in Section 3.5)

John S. Dick

4. Rubber Compound Economics

Abstract

Compound cost is not just the simple calculation of the cost per pound or kilogram of material; it must also take into account whether the application is volume-based or weight-based. The case of volume-based applications includes the concept of cost-volume relationships and calculations.

There is always the temptation to use the lowest cost compound. But one must be constantly vigilant that product quality is not compromised by less expensive ingredients. By the same token, over-design wastes money and can make products non-competitive. Often alternative materials can be used; however, careful evaluation, including appropriate cost calculations, is essential.

John M. Long

5. The Technical Project Approach to Experimental Design and Compound Development

Abstract

Rubber technology has two sources of complexity:

1

New materials and new processing methods continually appear on the technical horizon.

 

2

Properties of rubber compounds depend in a complex way on the materials in the compound in addition to the processing operations.

 

Alan G. Veith

6. Elastomer Selection

Abstract

The selection of a particular rubber or elastomer depends on the intended job for the end product. Once a series of elastomers is selected for a project, the compounder then choose a polymer based on its properties, costs, or perhaps a combination of the two.

Rudy School

7. General Purpose Elastomers and Blends

Abstract

General purpose elastomers are the work horses of the tire and mechanical rubber goods industry. Natural rubber (NR), polyisoprene (IR), polybutadiene (BR), and styrene-butadiene rubber (SBR) are always included in this classification; sometimes nitrilebutadiene (NBR) and ethylene propylene rubber (EPR and EPDM) are included as well. This chapter covers only natural rubber, polyisoprene, polybutadiene, and styrene-butadiene rubber. These rubbers have good physical properties, processability, and compatibility and are generally very economical. They are the largest volume rubbers in the industry.

Gary Day

8. Specialty Elastomers

Abstract

Specialty elastomers are very important to the rubber industry. They impart unique properties to a rubber compound, which cannot be matched by a general purpose elastomer. The specialty elastomers being discussed in this chapter are:

John S. Dick

9. Polyurethane Elastomers

Abstract

Otto Bayer and his colleagues laid the foundation of present-day polyurethane chemistry and technology in the laboratories of I. G. Farbenindustrie in Germany in the late 1930s. Since that time, all types of polyurethanes, including high performance polyurethane elastomers, have continued to grow in many divergent areas to become the materials of choice in demanding applications.

Ronald W. Fuest

10. Thermoplastic Elastomers

Abstract

A thermoplastic elastomer (TPE) is officially defined [1] as a member of “a diverse family of rubberlike materials that, unlike conventional vulcanized rubbers, can be processed and recycled like thermoplastic materials.” All TPEs are rubbery, but not necessarily a “rubber” as defined by ASTM [1] and ISO [2]. Most softer TPEs (less than 90 Shore A hardness [3]) are true rubbers; the harder ones (greater than 90 Shore A or 38 Shore D) are generally not, but are somewhat similar to soft, impact-modified thermoplastics.

Charles P. Rader

11. Recycled Rubber

Abstract

The focus of this chapter on recycled rubber is to provide practical information on how to use this material in many new rubber products to help achieve the targeted application requirements. Although a brief history and preparation methods of recycled rubber will be provided, a more detailed history and production details can be found elsewhere in the references. The history provided will be for the reader to obtain an understanding of the challenges faced by the industry to make the recycled rubber for use back in new rubber products and to understand the differences among the various recycled rubber types. Information on use of recycled rubber in non-rubber applications, such as plastics, polyurethanes, asphalt, and other applications, is best obtained from specific industry organizations.

Frank P. Papp

12. Compounding with Carbon Black and Oil

Abstract

Carbon black comprises about 30% of most rubber compounds. The addition of carbon black can affect virtually all phases of a rubber factory’s operation, as well as all the performance characteristics of the end product, whether it is a tire component or an industrial rubber product (IRP).

Steve Laube, Steve Monthey, Meng-Jiao Wang

13. Precipitated Silica and Non-Black Fillers

Abstract

Fillers are relatively inexpensive, solid substances that are added in large volumes to elastomers for adjusting volume, weight, cost, surface, color, processing behavior, mechanical strength, and other properties. Fillers are one of the most important components in the manufacture of rubber products, with their consumption second only to the elastomer itself. In most industrial applications, elastomers are compounded with fillers to improve their performance properties (stiffness, toughness, tensile properties), to enhance the durability of rubber compounds, and to reduce the cost of the final product.

Chenchy Jeffrey Lin, W. Michael York

14. Ester Plasticizers and Processing Additives

Abstract

Synthetic ester plasticizers and processing additives are used extensively in the rubber industry to impart specific cured physical properties to a rubber compound and/or to achieve certain processing characteristics during the manufacturing process. In the first portion of this chapter, synthetic ester plasticizers are reviewed followed by processing additives in the second portion.

John S. Dick

15. Sulfur Cure Systems

Abstract

Vulcanization (or curing) is a chemical process designed to reduce the effects of heat, cold, or solvents on the properties of a rubber compound and to create useful mechanical properties. This is most often accomplished by heating with vulcanizing agents, such as elemental sulfur, organic peroxides, organic resins, metal oxides, or urethanes. This process converts a viscous entanglement of long chain molecules into a three dimensional elastic network, as shown in Figure 15.1.

Byron H. To

16. Cures for Specialty Elastomers

Abstract

Vulcanization systems for specialty elastomers such as ethylene-propylene-diene terpolymer (EPDM), nitrile rubber (NBR), polychloroprene (CR), and isobutylene-isoprene (butyl) elastomer (IIR) are generally different from those for natural rubber (NR), styrene butadiene rubber (SBR), and polybutadiene rubber (BR) and their blends. This difference results from the higher saturations in the polymer backbones in the specialty polymers, which means higher ratios of accelerator to sulfur are required. This chapter deals with selected cure systems for vulcanizing these four specialty polymers.

Byron H. To

17. Peroxide Cure Systems

Abstract

Guidelines, thought processes, and examples of selecting and using organic peroxides in crosslinking are reviewed in this chapter. There are several different classes of organic peroxides used in crosslinking and polymer modification. Peroxide half-life and the specific types of free radicals produced beyond simple homolytic cleavage can play an important role in this selection. Other considerations, such as the type of elastomer chosen, effect of various additives, and the use of coagents can influence crosslinking efficiency. A comparison between peroxide and sulfur vulcanization is also provided here.

Leonard H. Palys

18. Tackifying, Curing, and Reinforcing Resins

Abstract

Resins are used in the rubber industry as tackifiers, cure agents, and reinforcing agents. Tackifying resins are probably the largest and most diversified group. Phenolformaldehyde, thermoreactive, resol-curing resins generally are used to cure polymers such as butyl rubber for high temperature resistance. Reinforcing resins include phenol-formaldehyde, novolak resins, and styrene resins. Table 18.1 lists the three major functional groups of resins. Chemically, there are many types of resins and variations, but because of limited space, they are not all discussed in this chapter. Phenol-formaldehyde based resins are by far the largest group of resins used in the rubber industry, so this chapter focuses on them.

Bonnie Stuck

19. Antidegradants

Abstract

The term “antidegradants” is a relatively recent descriptive term covering materials that protect rubber products against degradation by a variety of forces. The major need for antidegradants is in the unsaturated elastomers such as NR, SBR, BR, nitrile rubber, and neoprene. While the saturated or mostly saturated elastomers and plastics such as PP, EP, IIR, and EPDM also require protection, the unsaturated elastomers containing unsaturated bonds with allylic or tertiary benzylic hydrogen atoms are somewhat reactive and more prone to degradation. Most prominent degradants are oxygen, ozone, dynamic fatigue (or flexing), heat, and light (UV) [1]. The degradative results of these forces fall into one of the following categories:

Fred Ignatz-Hoover

20. Compounding for Brass Wire Adhesion

Abstract

Steel-cord reinforced ply compounds in tire, hose, and belting products have performance characteristics dependent on the quality and durability of the rubber compound, wire reinforcement, and adhesive interface connecting these materials. The basic concepts for bonding wire to rubber are similar to those for other bonding applications. The rubber compound should have sufficient scorch delay and viscosity for satisfactory wetting and contact with the wire surface prior to vulcanization. The rubber compound should then develop robust wire-to-rubber adhesion through primary and secondary bond formation, diffusion, and physical anchoring during vulcanization.

Alex Peterson

21. Chemical Blowing Agents

Abstract

Chemical blowing agents for rubber and plastics are available in a wide range of formulations depending on the polymer involved, processing temperature, and end use. For simplicity, this discussion is limited to those commercially available blowing agents commonly employed for producing cellular rubber products. This chapter summarizes their characteristics, uses, and processing.

Ralph A. Annicelli

22. Flame Retardants

Abstract

Hydrocarbon elastomers, like all other organic substances, are highly flammable. As a result, in some applications, special attention must be paid to fire resistance. This chapter covers the practical aspects of preparing flame retardant elastomeric compounds. Major applications of flame retardant elastomers, common fire tests, the flame retardants used, and most importantly, the effects of flame retardant additives on elastomer processing and physical properties are reviewed.

Kelvin K. Shen, David R. Schultz

23. Rubber Mixing

Abstract

The mixing operation is one of the most important stages through which raw materials must pass in manufacturing elastomers. The processing stages subsequent to the mixing depend on the dispersion and the homogeneity of the mixed compound. Also, the economical manufacturing of quality elastomer products is directly affected by mixing.

W. J. Hacker

Backmatter