Ebonite

Use

Use is mainly for ebonite mouthpieces for musical instruments and tobacco pipes, for piano keys, but also for jewelery and combs. Mouthpieces good instruments and pipes are often made ​​of high quality ebonite, as these a more comfortable ( softer ) "bite" have compared to the acrylic otherwise used. Chance also guitar picks from ebonite were made ​​because it was considered as reference material by the sound of her. Historically documented is the scientific use of ebonite by Alessandro Volta, who used it as a dielectric for the Elektrophor, developed by him early form of capacitor. In the following centuries ebonite for the manufacture of pens and ink conductors ( of fountain pens ) was used. Since it can become brittle over time, it is largely replaced by thermoplastics since the 1960s, which are cheaper and easier to process.

Properties

Although it is softer than phenolic resins ( phenolic, bakelite ), Ebonite is extremely resistant to chemical attack and generally very stable due to its very dense structure. Under sunlight but it changes color with time.

Production

For the production of highly unsaturated rubbers may ebonite only (with many C = C double bonds ) is used in order to achieve the high degree of crosslinking required for the strength can.

A natural rubber - sulfur mixture is melted in the oven. The molten rubber is poured into a metallic mold and heated to 100 to 200 degrees to the vulcanization for 15 minutes. Thereafter, the mold is removed and the contents are heated for about one and a half days in the oven again. The long reaction time results in a complete reaction of the mixture and therefore to a maximum cross-linking of the available double bonds of the rubber chains having sulfur bridges. So the natural rubber and the sulfur can react with each other completely. Through this process, the ebonite obtains its high density and resistance.

The amounts of sulfur for the production of ebonite are between 25 and 80, usually 30 to 40 parts by weight sulfur per 100 parts of rubber.

• Thermoset