General-purpose elastomers

Expressed as percentages of total annual synthetic mbber consumption worldwide, EPM and EPDM have increased from 0% in 1964 to 10.6% in 1990, as shown in Table 4. Contrary to the general-purpose elastomers such as NR, SBR, and BR, EPM and EPDM still show a steady growth over the years. Part of this growth stiU comes from replacement of these commodity mbbers by virtue of thek better o2one and thermal resistance. 

Chloroprene rubber (Neoprene—trade name of DuPont) was one of the earliest synthetic rubbers, first commercialized in 1932. It has a wide range of useful properties but has not become a true general purpose synthetic rubber, probably because of its cost. It does possess properties superior to those of a number of general purpose polymers, such as oil, ozone, and heat resistance but for these properties other specialized polymers excel. Polychloroprene thus is positioned between the general purpose elastomers and the specialty rubbers. 

FIG. 29-81 Typical general-purpose elastomer coupling. (Source Rexnord Corp.)... 

The worldwide demand for elastomers was estimated to be 19.44 million metric tons for 2008, excluding NR latex materials. Of this demand, 55% are synthetic elastomers of various kinds. Depending on their use elastomers have been classified into general purpose and speciality. The major general purpose elastomers are natural rubber, SBR rubber, PB rubber, isoprene rubber, and ethylene-propylene rubber. These rubbers are used in tires, mechanical goods, and similar applications. Specialty elastomers provide unique properties such as oil resistance or extreme heat stability. Although this differentiation is rather arbitrary, it also tends to classify the polymers according to the volumes used. About 74% of the rubbers used consist of SBR, butadiene rubber (BR), and ethylene-propylene rubber. 

Ethylene-propylene rubber possesses many properties superior to those of natural rubber and conventional general-purpose elastomers. In some applications, it will perform better than other materials, whereas in other applications, it will last longer or require less maintenance and may even cost less. 

This material may be processed and vulcanized by the same techniques and with the same equipment as those used for processing other general-purpose elastomers. As with other elastomers, compoimding plays an important part in tailoring the properties of EPDM to meet the needs of a... 

Features General purpose elastomer for prods, to withstand oils, soivs., heat, abrasion, ozone, and sunlight Properties Amber chips Toxicology TSCA list ... 

Chem. Descrip. Silicone-modified EPDM elastomer Uses EPDM for automotive applies, such as radiator and heater hose, ignition cable, spark plug boots, and for appliance wire, molded elec, goods, rolls for copiers, laminating, coil coating Features General-purpose elastomer with optimum heat resistance peroxide-curable... 

Three types of EOE from the wide range offered by the manufacturer were selected (Table 8.1). The general-purpose elastomers were selected with high content of octene and a defined characteristic. 

Table 37 3. Characteristic Properties of Some Reinforced General Purpose Elastomers, NR, Natural Rubber IR, Synthetic cis l,4 poly(isoprene) BR, Poly (butadiene) (Li type) TPR, trans poly(pentenamer) SBR, Styrene j Butadiene Rubber (Emulsion Grade with 40% Styrene) EPDM, Ethylene j Propylene Diene Rubber...

Halobutyl rubber (HIIR) is used primarily in tire innerliner and white sidewalls. These elastomers are best for tire air retention owing to lower air permeability as well as aging and fatigue resistance. The chlorinated (CIIR) and brominated (BUR) versions of isobutylene isoprene rubber (HR) can be blended with other elastomers to improve adhesion between HIIR compounds and those based on general purpose elastomers, and improve vulcanization kinetics [16]. 

Most reported studies on elastomer blends focus on general purpose elastomers, with emphasis on processing and attainment of specific mechanical properties. It would therefore be appropriate to review these two factors. There are three methods by which a polymer blend may be mixed with carbon black ... 

Silicone elastomers are unaffected by oxygen and ozone on natural aging. Because of their water-repellency, silicone elastomers are not seriously affected by aqueous solutions of most chemical reagents. They are attacked by strong acids and alkalis. General purpose elastomers are swollen by aliphatic, aromatic and chlorinated hydrocarbons but much improved resistance is shown by nitrile-and fluorine-containing silicones. In general, room temperature-cured materials have lower solvent resistance. 

When first introduced there were strong grounds for believing that the ethylene-propylene rubbers, particularly the EPDMs, would achieve the status of general purpose elastomers. The principal... 

The resultant of all these factors is that the ethylene-propylene rubbers have become important special purpose elastomers in the same league as the polychloroprenes and butyl rubber but still have some potential to attain the main group of general purpose elastomers. 

General-purpose elastomers represent the work horse rubbers of the rubber industry. They are the lowest cost, most cost-effective rubber polymers available today. The vast majority of these raw elastomers are used in the tire sector however, a large amount is also used in nontire applications as well, such as single-ply roofing, hose, dynamic parts (such as bushings, isolators, and dampers), and conveyor belts. 

The following general-purpose elastomers and their approximate worldwide annual consumption are shown in Table 3.1. 

Table 3.1 General-Purpose Elastomers and Approximate Annual Consumption, 2010...

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