1、BRITISH STANDARD BS6716:1986 Guide to Properties and types of rubber UDC678.4+678.7:678.01BS6716:1986 This British Standard, having been prepared under the directionof the Rubber StandardsCommittee, was published under the authority ofthe Board of BSI and comes intoeffect on 31 July 1986 BSI 04-1999
2、 The following BSI references relate to the work on this standard: Committee reference RUM/15 Draft for comment84/35977 DC ISBN 0 580 15208 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Rubber Standards Committee (RUM/-) to Technical
3、 Committee RUM/15 upon which the following bodies were represented: British Rubber Manufacturers Association Malaysian Rubber Producers Research Association Ministry of Defence RAPRA Technology Ltd. Society of Motor Manufacturers and Traders Limited Amendments issued since publication Amd. No. Date
4、of issue CommentsBS6716:1986 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Rubbers commercially available 1 3 Properties of vulcanized rubbers 1 4 Types of rubber 13 5 Cellular materials 19 6 Ebonite 20 7 Latex 20 8 Designing a rubber component 20 Appe
5、ndix A British Standards for rubber and rubber products 23 Appendix B Index 23 Figure 1 Scheme for selection of type of rubber 22 Table 1 Rubbers in general use 2 Table 2 Less common rubbers 3 Table 3 Relationship between hardness and medium strain shear modulus 3 Table 4 Heat resistance of rubbers
6、8 Table 5 Low temperature resistance of rubbers 10 Publications referred to 26BS6716:1986 ii BSI 04-1999 Foreword This British Standard has been prepared under the direction of the Rubber Standards Committee. It originated from a draft Defence Standard prepared by the Rubbers, Plastics and Adhesives
7、 subcommittee of the Defence Engineering and Equipment Standardization Committee. The guide provides users and designers with basic information on the properties of rubber and how these may be best utilized in finished products. Rubber is a generic term for a group of polymeric materials whose main
8、characteristic is a unique ability to undergo large elastic deformations, in tension, compression, shear or torsion, without rupture and to recover almost completely after such deformation. This characteristic is exploited in a wide variety of end-uses ranging from disposable household goods and veh
9、icle tyres (the main use of rubber) to large mountings and bearings required to last the life-span of the building or bridge they support. Other uses include adhesives, electrical insulation and chemical plant linings. In a document of this length such a range of applications cannot be considered in
10、 any detail, and for this reason some emphasis has been placed on the properties of rubber as an engineering material, although the information given is of wider interest. In engineering, rubber is mainly used as a seal or as a spring; it is also used in hoses and belting of various descriptions. It
11、 should be noted that British Standards are available for several of these and other applications of rubber. A comprehensive list, comprising test methods, specifications, and other related standards, is given in a classified format in BSI Sectional List SL12 “Leather, plastics, rubber”. NOTEFurther
12、 details about SL12 are provided in Appendix A. The material is usually in the form of vulcanized rubber. Vulcanization is the insertion of chemical crosslinks at intervals along adjacent rubber molecular chains. The type and density of the crosslinking depend upon the time and temperature of the pr
13、ocess as well as the amount and type of vulcanization ingredients used in the formulation. The properties of the vulcanized rubber are affected by the type and density of crosslinking. Thermoplastic rubbers rely on crystalline or glassy domains for their strength and thermoplasticity. Initially the
14、only rubber polymer available was that produced from tree latex, i.e.natural rubber, but since the1930s there has been tremendous activity in the field of polymerization with the development of a large number of synthetic rubber polymers. This vast increase in the number of rubber polymers available
15、 has greatly increased the complexity of choice of a suitable material. The inherent properties of vulcanizable rubber polymers can be varied over a wide range by differences in compounding. Compounding involves the addition of powder and liquid ingredients to the rubber polymer. The ingredients add
16、ed fall into two classes, those essential to the production of a vulcanizate having the desired properties, and those used to minimize the cost of the end product. Key ingredients in the rubber compound include the vulcanization system, fillers that impart specific properties, and antidegradants. Al
17、l rubber vulcanizates are liable to degradation during storage and service although the rate of deterioration of some rubbers can be considered to be extremely slow. When made to appropriate specifications, and when properly packaged and stored, most rubbers will remain in a serviceable condition fo
18、r many years. A controlled system of storage is necessary to ensure rubbers are issued for use in a serviceable state (see BS3574). The life in service is dependent on the service conditions and advice should be sought at an early stage of the design study. Factors affecting the life of vulcanized r
19、ubber are discussed in3.5. Throughout this standard the term “rubber” is intended to cover both natural and synthetic rubbers in dry and latex form. This and other terms are used in accordance with definitions given in BS3558. An index to the principal clauses in this standard is included as Appendi
20、x B.BS6716:1986 BSI 04-1999 iii WARNING NOTE. The guide refers to the use of substances and/or test procedures that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and in no way absolves either the supplier or the user from statutory obligati
21、ons necessary to meet the requirements of the Health and Safety at Work, etc.Act1974, relating to health and safety at any stage of manufacture or use. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corr
22、ect application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1to26, an inside back cover and a back cover. This standard has been updated (see copyright
23、date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.iv blankBS6716:1986 BSI 04-1999 1 1 Scope This British Standard gives designers and users of rubber products guidance on the properties and types of rubber, associated test methods
24、and terms used in the rubber industry. It draws attention to relevant British Standards in this field. Guidance is also included on designing a rubber component for a particular end-use. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Rubbers co
25、mmercially available The chemical names of rubbers in general use are given in Table 1, together with their abbreviations as given in BS3502-3 and, where appropriate, their common names. Applications of rubbers involve contact with environments where their resistance to heat, oil and atmospheric con
26、ditions have to be considered. The rubbers available provide a range of performance under these conditions. However, a compromise is usually necessary and expert advice should be sought early in the design study. Generally it is advantageous to carry out an initial trial under service conditions bef
27、ore finalizing the formulation. An outline guide to the selection of basic rubber is given in8.3. Trade names should not normally be used on drawings or in specifications. Only the generic name should be used except in instances where a particular type/grade has to be specified for technological rea
28、sons. In addition to the rubbers listed in Table 1, BS3502-3 also contains the names of rubbers that are much less common, and in some instances there is no current production of the type mentioned. The names of these rubbers are listed in Table 2. Attention is also drawn to the increasing availabil
29、ity of thermoplastic rubbers (see4.20). 3 Properties of vulcanized rubbers 3.1 General Rubbers are viscoelastic materials of low rigidity exhibiting large strain elasticity. The deformations imposed on rubber components (typically20% to50% strain in compression or shear) are far larger than those en
30、countered for most other materials, and the stress-strain relationships are correspondingly more complex. In general, it is not possible to characterize rubbers by a unique combination of moduli, such as shear and bulk moduli, as the shear moduli of rubbers vary with strain. It is often possible, ho
31、wever, to predict the performance of a component from the shear modulus at a known strain. The ability of a rubber to store elastic energy depends largely on the type of polymer used. In general, polymers having relatively high glass transition temperatures exhibit the highest energy losses during d
32、eformation. These energy losses are exploited in components intended to damp motion, but generally the higher the damping obtained the more sensitive are the modulus and damping to frequency and temperature. The tensile strength of a rubber is low compared with other materials but the energy storage
33、 capacity at break can be greater than that of an equivalent mass of steel. Failure of rubber components rarely occurs by simple tensile failure; tearing or fatigue crack growth is more likely. A major factor determining the strength of rubber is an ability to crystallize under the influence of an a
34、pplied strain. Rubbers possessing this ability (e.g.NR and CR) are intrinsically strong while those that do not crystallize rely on the incorporation of reinforcing fillers to impart adequate strength. A limitation on the use of rubbers in some applications is the effect of certain fluids. The exten
35、t of swelling or property change in a given fluid is critically dependent on both the rubber and the fluid. Selection of a rubber for a given application should take into account its resistance to any fluids it is likely to be in contact with in service. A similar consideration applies to the effect
36、s of temperature and the climate in which a product is to be used. 3.2 Stress-strain properties 3.2.1 Introduction. Rubbers exhibit non-linear stress-strain behaviour, and as a measure of stiffness, Youngs modulus only applies to strains of the order of a few percent. Thereafter “modulus” will vary
37、with the magnitude of the strain, and it is also influenced by the mode of deformation and, as will be described later, by the conditions of any cycling. Relationships between low strain and high strain measurements can sometimes be established for individual rubber types, but a general correlation
38、suitable for design purposes should not be assumed. Common measurements of stiffness used by the rubber industry are hardness and stress at a given elongation.BS6716:1986 2 BSI 04-1999 Table 1 Rubbers in general use Abbreviation Chemical name (based on BS3502-3) Common name ACM Copolymers of ethylac
39、rylate or other acrylates and a small amount of a monomer which facilitates vulcanization Polyacrylic AU Polyester urethane (see note1) BR Butadiene rubbers Polybutadiene BIIR Bromo-isobutene-isoprene Bromobutyl CIIR Chloro-isobutene-isoprene Chlorobutyl CO Polychloromethyloxiran Epichlorohydrin CR
40、Chloroprene rubbers Neoprene CSM Chlorosulphonylpolyethylene Chlorosulphonated polyethylene ECO Ethylene oxide and chloromethyloxiran copolymers Epichlorohydrin EPDM Terpolymers of ethylene, propylene and a diene with the residual unsaturated portion of the diene in the side chain EPDM EPM Ethylene-
41、propylene copolymers Ethylene-propylene EU Polyether urethane (see note1) FPM Rubbers having fluoro and fluoroalkyl or fluoroalkoxy substituent groups on the polymer chain Fluorocarbon GPO Copolymers of propylene oxide and allyl glycidyl ether Polypropylene oxide IIR Isobutene-isoprene rubbers Butyl
42、 IR Isoprene rubber, synthetic Polyisoprene NBR Acrylonitrile-butadiene rubbers Nitrile NR Isoprene rubber, natural Natural rubber OT (EOT) Polysulphide rubbers a Polysulphide rubbers Q group Silicone rubbers b Silicone rubbers SBR Styrene-butadiene rubbers SBR XNBR Carboxylic-acrylonitrile-butadien
43、e rubbers Carboxylated nitrile XSBR Carboxylic-styrene-butadiene rubbers Carboxylated SBR NOTE 1AU and EU are generally polyurethane rubbers. NOTE 2Common and widely used trade names are Neoprene (CR), Hypalon (CSM), Viton (FPM), Thiokol OT (EOT). a This is not defined in BS3502-3. b FEMQSilicone ru
44、bbers having both methyl and fluorine substituent groups on the polymer chain. FVMQSilicone rubbers having methyl, vinyl and fluorine substituent groups on the polymer chain. MQSilicone rubbers having only methyl substituent groups on the polymer chain, such as dimethyl polysiloxane. PMQ Silicone ru
45、bbers having both methyl and phenyl substituent groups on the polymer chain. PVMQSilicone rubbers having methyl, vinyl and phenyl substituent groups on the polymer chain. VMQSilicone rubbers having both methyl and vinyl substituent groups on the polymer chain.BS6716:1986 BSI 04-1999 3 Table 2 Less c
46、ommon rubbers 3.2.2 Hardness 3.2.2.1 General. Hardness, as measured by an indentation test, is a semi-empirical measure of modulus (see BS903-A26). The strains involved in a hardness measurement are complex and not well defined, but an approximate relationship between hardness and a medium strain sh
47、ear modulus (10% to25% shear strain) exists as given in Table 3. The measurement is widely used because of its simplicity and applicability to the surfaces of components. As rubber is a poor conductor of heat the effect vulcanization has on properties may vary throughout the thickness of a component
48、, and this should be taken into account when using hardness tests as a means of quality control of thick products. Rubber components made from the same material may vary in hardness due to their shape and size. Table 3 Relationship between hardness and medium strain shear modulus 3.2.2.2 Internation
49、al Rubber Hardness Degrees. Hardness is internationally quoted in International Rubber Hardness Degrees (IRHD), the scale being so chosen that zero represents a material of infinite softness (modulus of elasticity of zero) not practically achievable, and100 a material of infinite hardness (modulus of elasticity of infinity). For most applications, the operative range is from30IRHD to90IRHD and it is usual in specifications for rubbers to quote a hardness tolerance to allow for slight differences in the materials and manufacturing techniques used. Elastic
