What is Ebonite?
Ebonite is a type of resin that has a very long history. It is considered the first “synthetic
resin” to become widely used.
In 1839, ebonite was invented by Mr. Charles Goodyear in the United States.
Ebonite is blackish brown and firm, but its main raw material is rubber. By mixing and
heating rubber and sulfur, they combine and become low-elastic and very firm
vulcanized rubber with an elongation percentage of approximately 3%.
This is what ebonite is.
The name “ebonite” comes from the meaning “ebony.”
Ebonite is black-colored, elastic horn-like material, and a crack in ebonite is glossy. It is
clear brownish-red in thin-film form and brownish-red in powdered form.
Ebonite is sometimes called “hard rubber.” But we distinguish with hard rubber that is
hardened with fillers.
Ebonite is durable, scientifically stable and provides excellent electrical insulation and
machinability. Before the rise of petroleum-derived plastic, ebonite was widely used in
every aspect of life.
When the surface of ebonite is polished, it gives a beautiful, lacquer-like gloss.
Also, with a characteristic that does not disturb tones, it is used as inner pipes of
woodwind instruments.
With these characteristics, ebonite is widely used in many ways, including electrical
insulation materials, premium gold or silver lacquer fountain pens, instrument
mouthpieces, smoking supplies and fishing gear.
Our company uses 100% high grade natural rubber collected from gum trees. A gum
tree is one of the trees that has a high absorption rate of carbon dioxide. We will
continue to commit ourselves to manufacturing ebonite products utilizing natural rubber.
List of Characteristics/Properties of Ebonite
<Insulation properties>
Very high insulation properties.
All hydrocarbon polymers have insulation properties.
Especially, ebonite provides excellent insulation performance.
<High-frequency dielectric loss>
Extremely low.
Perfect for wired lines as much as wireless.
<Aging resistance>
Provides extremely high resistance especially against ultraviolet rays.
<Free sulfur>
Extremely low free sulfur. Contacting parts with metal also provide low sulfurization.
<Acid resistance, alkaline resistance>
Provides excellent resistance against chemicals, including acid and alkali, at room
temperature.
<Mechanical strength>
Has hardness and strength comparable to metal.
<Appearance and workability>
Gives dark shiny gloss when polished. Easy to conduct a precision work and forming.
<Water absorbability>
Water absorbability is extremely low compared to soft rubber.
Very high moisture resistance.
Therefore, there is no rapid reduction in insulation properties when moisture is
absorbed.
The list below shows the characteristic of ebonite.
Please use as reference values.
No.
Type
Unit
Rod
Plate
1.
Specific gravity
%
1.16
1.14
2.
Amount of water absorption
mg/100cm²
0.25-0.3
0.2-0.25
3.
Heating resistance
(appearance)
-
No change
No change
-
(dimension change)
%
No change
No change
4.
Thermal resistance
mm
2-3
2-3
5.
Tensile strength
kg/mm²
6-7
6-7
6.
Elongation
%
4-6
4-6
7.
Compressive strength
kg/mm²
8-10
8-10
8.
Bending strength
kg/mm²
10-11
10-11
9.
Ash content
%
1-3
1-3
10.
Acetone extraction
%
4.3-4.7
4.3-4.7
11.
Dielectric breakdown
strength
kV/mm
27-29
27-29
12.
Specific resistance(volume)
Ωcm
10 to the 13th
power or
more
10 to the 15th
power or
more
-
Specific resistance(surface)
Ω
10 to the 13th
power or
more
10 to the 15th
power or
more
13.
Dielectric power factor
(10Mc)x10 to
the negative
4th power
70-90
70-90
14.
Permittivity
10Mc
3-3.2
3-3.2
15.
Free sulfur
%
0.3-0.9
0.3-0.9
16.
Softening point
℃
80
80
Copyright © 2010 Nikko Ebonite Mfg. Co., Ltd. All Rights Reserved.
Raw Materials of Ebonite
3 raw materials of ebonite: natural rubber, sulfur and ebonite powder as a filler.
We only use the highest-quality natural rubber and ebonite powder.
Natural Rubber
Sulfur
Ebonite Powder
Copyright © 2010 Nikko Ebonite Mfg. Co., Ltd. All Rights Reserved.
Manufacturing Processes of Ebonite
Manufacturing Processes of
Ebonite Rods
Mix natural rubber, sulfur and ebonite powder
using a roll.
Cut the mixture into thin rectangles.
Set up and adjust the extruder to necessary
diameter.
Inject ebonite materials into the extruder to make
rods.
This is how ebonite is ejected from the extruder.
The exit hole is ignited to make the surface
smooth by heating up tube sections.
Pre-vulcanized ebonite is still soft.
Power is sprinkled to prevent sticking to other
substances.
Place in cans.
Steam ebonite in the steam boiler for several
days.
A chemical reaction combining rubber and sulfur
molecules is called “vulcanization.”
Vulcanization is accelerated by applying heat and
pressure by steam.
By the chemical reaction, elasticity and strength
improves dramatically. And soft ebonite prior to
vulcanization becomes ultra hard rubber.
Temperature control at the time of heating
requires proficient skills.
At the beginning, temperature needs to be kept
down. Then, temperature is gradually increased.
And there is further increase at the end. These
temperature controls are done depending on the
shape or size of ebonite.
Because the boiler cannot be opened in the
middle of the steaming process, experts control
heating temperature by checking the steam
pressure and exhaust intervals.
After several days, the manufacturing process of
ebonite is finally completed.
Copyright © 2010 Nikko Ebonite Mfg. Co., Ltd. All Rights Reserved.