ebonite
Ebonite is a particularly hard rubber made from natural rubber and sulfur , which can be easily machined. In 1851 Charles Goodyear applied for a patent for ebonite . The name of the almost black material absorbs Ebony ( English ebony ) reference.
use
Ebonite is mainly used for mouthpieces on woodwind instruments (clarinets, saxophones) and tobacco pipes , for piano keys , but also for jewelry and combs . Mouthpieces of good wind instruments and pipes are often made of high-quality ebonite, as these have a more pleasant (softer) "bite" compared to the otherwise used acrylic . Occasionally, guitar picks were also made from ebonite, as it was considered a reference material in terms of sound.
The hard rubber rod for generating static electricity with a cloth is also made of ebonite.
In the decades that followed, ebonite was used in the manufacture of writing implements and ink feeds (of fountain pens). Since it can become brittle over time, it has been largely superseded by thermoplastics since the 1960s , which are cheaper and easier to process.
properties
Compared to phenolic resins ( phenoplast , Bakelite ), ebonite is somewhat softer and offers very high impact strength . It is considered to be very long-term stable and extremely resistant to many chemicals . It only changes color over time when exposed to ultraviolet radiation (e.g. sunlight).
Manufacturing
Only highly unsaturated rubbers (with many C = C double bonds) can be used to produce ebonite in order to be able to achieve the high degree of crosslinking required for strength .
A mixture of natural rubber and sulfur is melted in the furnace. The molten rubber is then poured into a metal mold and heated to 100 to 200 ° C for 15 minutes to vulcanize . After that, the form is removed and the contents are reheated in the oven for about a day and a half. The long reaction time leads to a complete reaction of the mixture and thus to the greatest possible crosslinking of the available double bonds of the rubber chains with sulfur bridges. In this way, the natural rubber and the sulfur can completely react with one another. This process gives the ebonite its high density and durability.
The amounts of sulfur for the production of ebonite are between 25 and 80%, mostly 30 to 40 parts by weight of sulfur per 100 parts of rubber.
Web links
Individual evidence
- ↑ Hans-Georg Elias: Applications of polymers (= macromolecules . Volume 4 ). 6th, completely revised edition. John Wiley-VCH, Weinheim 2009, ISBN 978-3-527-62654-0 , pp. 295 ( preview in Google Book Search [accessed November 12, 2014]).
- ^ Dietrich Braun: Brief history of plastics . Carl Hanser Verlag, Munich 2013, ISBN 978-3-446-43686-2 , pp. 109 ( Preview in Google Book Search [accessed November 12, 2014]).
- ^ Bryan G. Crowther: Handbook of Rubber Bonding . Revised ed. ISmithers Rapra Publishing, Shawbury, U. K. 2003, ISBN 1-85957-394-0 , pp. 59 (English, preview in Google Book Search [accessed November 12, 2014]).