Properties of ebonite
– Sulfur percentage, temperature, and duration of vulcanizing determine the properties of hard rubber polysulfide elastomer.
– Addition of sulfur at double bonds forms intramolecular ring structures.
– Sulfur content affects swelling resistance, dielectric loss, mechanical properties, heat resistance, and impact strength.
– Van der Waals forces between sulfur atoms contribute to the rigidity of hard rubber.
– Hard rubber has a thermoplastic transition temperature of 70 to 80°C.
Ultraviolet and daylight exposure effects on ebonite
– Ultraviolet exposure causes oxidation of hard rubber.
– Moisture bonds with free sulfur on the surface, creating sulfates and sulfuric acid.
– Sulfates condense water from the air, forming a hydrophilic film on the surface.
– Aging processes cause discoloration and deterioration of electric surface resistivity.
Contamination of ebonite
– Contaminated ebonite used for electronics had traces of metal left behind during manufacturing.
– Metal particles were removed by grinding the surface.
Applications of ebonite
– Hard rubber was used in early 20th-century bowling balls.
– It was used in electric plugs, tobacco pipe mouthpieces, fishing reels, hockey pucks, and fountain pen bodies.
– Hard rubber is commonly used in casters and physics classrooms for static electricity demonstrations.
– It was used in automobile battery cases and hair combs.
– Ebonite is used as an anticorrosive lining for vessels containing hydrochloric acid.
References
– Hartgummi (Ebonite) (in German)
– EboDUST Ebonite/Hard-rubber dust.
– Merriam-Webster defines vulcanite.
– History of Polymeric Composites by Raymond Benedict Seymour and Rudolph D. Deaning.
– Minutes of the Proceedings of the Institution of Civil Engineers, Volume 189, 1912. Source: https://en.wikipedia.org/wiki/Ebonite
Ebonite is a brand name for a material generically known as hard rubber, obtained via vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as an artificial substitute for ebony wood. The material has also been called vulcanite, although that name formally refers to the mineral vulcanite.
Charles Goodyear's brother, Nelson Goodyear, experimented with the chemistry of ebonite composites. In 1851, he used zinc oxide as a filler. Hugh Silver was responsible for giving it its name.
