Ebonites acid resistance

This is essentially hydrated aluminium silicates derived from natural deposits. There are soft clays, hard clays, calcined clays and treated clays. This is a common filler in the manufacture of acid resistant ebonites, natural soft rubbers and in Neoprene compounding for phosphoric acid duties. 

On exposure of ebonite to light there is a rapid deterioration in surface resistivity. It is believed that this is due to the formation of sulphuric acid through... 

Ebonite has a good resistance to a range of inorganic liquids, including most non-oxidising acids. It is severely swollen by aromatic and chlorinated hydrocarbons. 

Ebonite media are manufacmred from partially vulcanized rubber, which is crushed, pressed and vulcanized. These media are resistant to acids, salt solutions and alkalies. They may be used for filtration at temperamres ranging from -10 to + 110 C. 

When compounded to form ebonites they show improved chemical resistance especially to carboxylic acids and may be used for some oxidative chemicals depending on type and operating temperatures. Ebonites can be compounded to be suitable for working temperatures up to at least 100°C, but, due to brittleness, are not normally suitable for sub-zero temperatures. 

Polychloroprene and acrylonitrile-butadiene rubber compounds have satisfactory chemical resistance but, except for phosphoric acid, are not suitable for mineral acids at higher concentrations. However, they have good resistance to oils, acrylonitrile-butadiene rubber being the better, and so are often used in oil-contaminated aqueous environments. Generally, abrasion resistance is only fair. Normal maximum working temperature is about 100°C. Acrylonitrile-butadiene rubber ebonites are sometimes used especially where solvent contamination occurs, but are normally very brittle and so should be used with care. 

Reinforcement with carbon black or mineral ingredients is not possible. These reinforcing fillers affect the mechanical strength adversely and do not improve them. However the non-reinforcing fillers such as softer blacks and graphite and ebonite dust increase the resistance of ebonites to acids in an outstanding manner. 

The choice between materials for a particular application may be determined by a combination of technical economic and aesthetic considerations. Ebonites have a great dimensional stability in moist conditions with freedom from deterioration caused by oxidation and excellent resistance to various chemicals. The temperature of use is limited where the material is under mechanical load, owing to its comparatively low softening point. This can be overcome by suitable compounding to some extent. A further weakness in appearance is the tendency of ebonite to develop an acid surface and to... 

These same types of compounds are also more resistant to many acids at high temperatures than natural rubber can handle. Neoprene should not be used in parts which are bonded to metal for hydrochloric acid service because acid migration can cause failures. For hydrochloric acid service ebonite lined mild steel equipment is the correct selection. Ebonites form rubber hydrochloride film in contact with natural rubber and this film is the protective layer against corrosion. 

The classic thermosets, such as ebonite, phenolics, ureas, melamines and polyesters as well as the epoxies, when reinforced with fiberglass or graphite fibers could also be classified as high performance thermosets. While these plastics cannot be readily extruded or injection molded, they are resistant to the effects of moderately high hostile environments. Phenolic resin mortars have been used for over a half century for the construction of chemical resistant vessels and for joining brick and tile used as linings in hot acid environments. (1.)... 

A general rule is that natural rubbers have better mechanical properties than the synthetic rubbers but the latter have better corrosion resistance. Natural rubbers are superior in certain applications such as with wet chlorine and hydrochloric acid. Natural rubber-based ebonite provides good resistance for such application at higher temperatures up to 90 °C. Corrosion resistance increases with increasing hardness, from a range of 60 on the Shore A scale to 80 on the Shore D scale. Higher proportions of sulfur increase the hardness range in the Shore D scale. 

Ebonite shows very low water absorption and has good resistance to most aqueous reagents, except nitric acid. It is swollen by aromatic and chlorinated hydrocarbons. Ebonite has good electrical insulation characteristics and the major application is for car battery cases. 

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