18 December 2018
VIEW WACKER SILICONES BROCHURE
Silicone rubber consists essentially of
silicone polymers and fillers.
They are crosslinked with suitable reactants
to produce three-dimensional structures
that convert the fluid or ductile rubber compound
into an elastic rubber.
Silicone rubber is flexible at low temperatures
and resistant to heat and aging (UV, ozone and radiation),
is easy to process and has good mechanical properties
that remain unchanged over a wide temperature range.
Silicone elastomers are used in areas
such as automotive and mechanical engineering,
electronics and electrics, textiles, baby articles,
toys, household appliances and sports articles,
as well as in the construction industry.
The WACKER silicone rubber portfolio
comprises around 1,000 products.
SILICONE RUBBER
Product Grades
Silicone rubbers consist of long-chain polysiloxanes and various fillers,
such as pyrogenic silica.
They can be converted into silicone elastomers by vulcanization.
They are classified according to the curing method, the viscosity of the base polymer,
and whether they cure at high or room temperature:
Solid silicone rubber (HTV) –
High-Temperature Vulcanizing Silicone Rubbers
Solid silicone rubbers are cured at elevated temperature,
either by means of organic peroxides or with platinum catalyst.
The cured rubber is compounded with reinforcing fillers to give it its mechanical strength.
The preferred fillers are pyrogenic silicas with BET surface areas >100 m2/g.
It is also possible to add precipitated silicas, inactive fillers (quartz, diatomaceous earths)
or specific carbon black grades.
Thanks to their outstanding properties, HTV silicone rubbers
have a whole host of applications. This includes
a wide range of service temperatures
(-50 to +200°C, or even -90 to +300°C for special formulations),
no known physical or physiological harmful effects, and excellent aging resistance.
High-temperature vulcanizing silicone rubbers are suitable
for a wide variety of application areas
– in the automotive industry, electrical and electronics applications,
the transmission and distribution industry, the construction sector,
mechanical and process engineering, and in the fields of food,
health care and the medical sector.
Liquid silicone rubber (LSR) –
High-temperature-vulcanizing silicone rubbers
Liquid silicone rubbers are also members of the group of high-temperature-vulcanizing rubbers.
Their consistency and curing mechanism imbue them with outstanding processing advantages.
Liquid silicone rubbers are characterized by a low viscosity compared
to solid silicone rubbers (HTV).
Liquid silicone rubbers are pumpable two-part compounds that are delivered ready to use.
They are vulcanized by addition curing.
Component A contains a Pt catalyst and
component B a SiH-functional polysiloxane as curing agent.
Compared to peroxide curing, liquid silicone rubbers do not release any curing byproducts.
Liquid silicone rubbers offer a wide range of applications,
from the automotive industry, mechanical and process engineering,
through electrical applications, the transmission and distribution industry,
through to construction, foods, health care and the medical sector.
For automotive applications, in particular, we offer fluorinated liquid silicone rubbers
that are characterized by particularly high stability towards gasoline and engine and gear oils.
2-Part Silicone Rubber (RTV-2)
RTV-2 silicone rubbers are two-part pourable, spreadable or kneadable compositions
that vulcanize when the curing agent component is added
and form highly elastic silicone rubber.
They are cured at room temperature (RTV = room-temperature vulcanizing).
There are two ways of vulcanizing them:
In condensation-curing, an organotin catalyst is usually used;
alcohol is produced as a byproduct. Addition curing, on the other hand,
uses a platinum catalyst and does not produce byproducts.
Special silicone rubber grades can be flash vulcanized using UV light.
The vulcanization time can be controlled by adjusting the UV intensity and exposure time.
Most cured RTV-2 sillcone rubbers retain their full elasticity up to 200°C.
Some products can even be briefly heated to 300°C.
At low temperatures, they retain their flexibility down to -50°C, or even to -100°C
in the case of special grades.
By choosing particularly slow-acting Pt catalysts, WACKER also offers you
a range of premixed one-part systems with a long shelf life,
which only vulcanize at elevated temperature.
Based on the polymer structure, which is analogous to addition-curing RTV-2 silicone rubber grades,
this group, too, is classified as RTV-2.
The thermal conductivity of RTV-2 silicone rubber generally allows them
to be used for insulating electrical power equipment without causing overheating.
The most useful electrical properties are the insulation resistance, breakdown resistance
and dissipation factor.
The gas permeability of RTV-2 silicone rubbers is around ten times higher than
that of natural rubber at room temperature. Another feature that is advantageous
in many applications is the excellent release property of the cured rubber surfaces
towards organic and inorganic materials.
The extensive portfolio of RTV-2 silicone rubber products allows cured rubbers
to be produced with extremely versatile, highly specialized properties.
This results in a versatile, successful solution portfolio for individual problems
in diverse industrial areas, such as moldmaking, electronics and optoelectronics,
household appliances, mechanical engineering and industrial process engineering,
health care applications and solar/photovoltaics
Silicone Rubber (RTV-1)
RTV-1 silicone rubbers are one-part, ready-to-use RTV systems.
They consist of polydimethylsiloxane, curing agent, fillers and additives.
After application, they are crosslinked by contact with atmospheric moisture
releasing byproducts in the process.
Crosslinking starts with the formation of a skin on the surface of the applied silicone rubber
and gradually progresses into the interior of the compound.
Depending on the nature of the crosslinker, a small amount of
an amine, acetic acid or a neutral compound, such as alcohol, is released during vulcanization.
Thanks to their outstanding properties,
RTV-1 silicone rubbers solve a wide variety of sealing, bonding and coating problems.
Their outstanding weathering and aging resistance
is the result of their special chemical properties.
RTV-1 silicone rubbers are ideal for almost all sealing, bonding and coating applications.
This material has a similarly wide range of applications in different industries,
such as automotive, construction, household appliances, electrical and electronics,
health care, medical and textile.
Silicone Gels
Silicone gels are a special group of RTV-2 silicone rubbers that are characterized
by particularly low crosslinking density.
They produce very soft vulcanizates below the Shore A hardness range.
Silicone gels are often used as damping materials in medical applications
or as encapsulation compound in electrical and electronic applications.
Their benefit is that, under temperature fluctuations, they exert only minimal stress
on the encapsulated components.
Silicone gels are always addition-curing silicone rubber grades.
Silicone gels are suitable for various industrial applications,
such as in the automotive field, in the transmission and distribution industry
and in health care and medicine.
For the automotive industry, in particular,
we offer low-temperature gels and fluorinated materials.
DETAILS
WACKER is increasing its global production capacities
for silicone rubber.
With expansion measures at several sites,
WACKER plans to gradually raise its capacities
by a total of 40,000 metric tons per year by 2021.
Approximately €100 million has been earmarked
for this capacity expansion. With these measures,
WACKER is responding to the high demand
for silicone rubber in key sectors such as
the automotive, electronics and medical industries.
These investments are part of the
WACKER SILICONES division’s strategy
of further expanding its portfolio of specialties.
With capacity expansions in the midstream production steps
and downstream production, WACKER will significantly
improve the silicone-rubber availability
and related service for its customers in the near future.
Standard delivery form of solid silicone rubber
All solid silicone rubber product groups
will benefit from these expansion measures.
In April of this year, WACKER already brought
a new production site for silicone sealants
and thermally conductive silicone compounds
on stream in Jincheon, South Korea.
The production of
room-temperature-vulcanizing silicone elastomers
and liquid silicone rubbers has also started
in Amtala, India, where WACKER manufactures
silicones in a joint venture with Metroark.
For 2019, the chemical group is planning
further capacity enhance-ments
for liquid silicone rubber,
high- and room-temperature-vulcanizing silicones
and thermally conductive silicone compounds
at its production sites in
* Burghausen (Germany),
* Adrian (Michigan, USA) and
* Zhangjiagang (China).
WACKER is currently also evaluating
the option of building a plant
for solid silicone rubber at its US-based site
in Charleston, Tennessee.
WACKER has been producing polysilicon there since 2016.
A plant for manufacturing pyrogenic silica,
an important filler
for high consistency silicone rubber (HCR),
will come on stream at this site next year.
Silicone rubber is among the most sought-after elastomers
in the industry.
Robert Gnann,
Head of the WACKER SILICONES business division
“Silicones are high-performance materials.
They are essential for novel product solutions
and belong to the innovation drivers
in key industry sectors such as
automotive, medical, and electronics,”
"Above-average growth is being driven by the trends
toward hybrid cars, electromobility and digitalization,
as well as decentralized alternative electricity generation
using wind and solar power.
So, we are making a major contribution
to increased sustainability while pursuing our strategy
of clearly focusing on boosting specialties in our portfolio."
Contact
Wacker Chemie AG
Media Relations & Information
Florian Degenhart
Tel. +49 89 6279-1601
Email florian.degenhart@wacker.com
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