Silicon

Submitted by,
Menon Lakshmi Suresh
Roll No : 11
CPBST

 Introduction
 Manufacturing
 How silicone materials work
 Properties
 Applications

 Silicones are a family of materials that
include siloxanes & silanes.
 Silicones derive ultimately from silicon, as
contained in sand & other minerals. It is the
second most common element in the Earth’s
crust.
 Silicones are sophisticated products that are
extremely versatile & can be manufactured in
more than 2,000 different forms, withinthe
general categories of silanes, fluids,
elastomers & resins.

 Silicones have important chemical & physical
qualities derived from their molecular
structure.
 Depending on requirement these include
longevity, thermo stability, chemical,
electrical & ultraviolet resistance, enduring
elasticity, tensile strength ,inertness
& microbial resistance.
 They can be formulated either to resist or
absorb water. They are much valued
for their purity, especially for
advanced electrical devices,&
for their cleanliness

 Silicones are durable, reliable & often
employed to enhance or to confer specific
performance properties.
 They promote sustainable development by
making other materials last longer-reducing
society’s consumption of basic raw
materials to ensure their availability for
future generations.

 Silicones, or polysiloxanes, are inorganic-
organic polymers with the chemical formula
[R2SiO]n, where R = organic groups such as
methyl, ethyl, and phenyl.
 These materials consist of an inorganic
silicon-oxygen backbone (...-Si-O-Si-O-Si-O-
...) with organic side groups attached to the
silicon atoms, which are four-coordinate.

 Silicon does not exist on its own in nature. Most of it is
bound with oxygen in materials like sand and quartzite and
granite rock.
 The silicon-oxygen bond in quartz is so stable it can only
be broken by white heat!
 Silicon producers reduce high-grade quartz sand to
elemental silicon via a carbo-thermic smelting process:
SiO2 + 2C Si + 2CO
Sand(silica ) carbon Silicon carbon monoxide
 This reaction occurs in an electric furnace at <1,400°C
(<2,600°F).
 The carbon monoxide gas (g) leaves the furnace so the
silicon cannot react with the carbon to form silicon
dioxide.

 The molten elemental silicon, which is about
99 percent pure, is then cooled and broken
into lumps.
 When used in silicone production, the silicon
is ground into a fine powder to increase the
surface area available for reactions

Silicones Value Chain
 Silicones are a vital ingredient in a large &
diverse number of final applications.
 Silicones may be supplied directly to
producers of final products but more often
they pass through several stages of what is
known as the ‘value chain’.
 This means that their routes to end markets
may be complex, involving several
interdependent stages.

 The diagram below shows the way the value chain works. This is a
highly simplified representation of a system which, in real life, is
sophisticated, complex & covers many more products than the examples
shown.
Raw
materials
Silicone producers
Transform
silicon
metal
made from
sand into
basic
silicones
Basic
silicones
Formulators
Silicone fluid
Silicone elastomer
Silicone resin
Silicon metal
Convert basic
silicones into
products

 Silicones’ chemical structure allows them to be
produced in a number of variations.
 By using siloxane units with different valences,
products can be made with oily, polymeric, resinous
or cross linked properties.
 At the same time, the organic groups bound to the
silicon pave the way for a diverse range of
modifications.
 It is this variability that makes possible the
impressive variety of silicone products: greases,
release agents, antifoam agents, paint additives,
paper coatings, hydrophobizing agents, high or
room-temperature vulcanizing silicone rubbers, and
many, many more.

 Silicone is usually tetravalent but can assume hexavalant
characteristics
 Silicon is more electropositive than carbon and hence silicon-
carbon bonds are polar
Moulded silicones are characterised by the following points :
 Good dimensional stability at high temperature
 Good electrical and dielectric properties over wide frequent
& temperature ranges
 Low water absorption
 Good flow properties
 Long curing time in comparison with other moulding
compounds
 Limited shelf life
 Average level of mechanical properties
 High cost

 Resistance to Chemicals : Dilute mineral acid & alkaline
solutions, sea water, methanol, glycol & formic acid
but not resistant to aromatic hydrocarbons, numerous solvents
& concentrated acids & alkalis
 Weathering resistance : The weathering resistance of silicone
resin mouldings is same as other thermo set compounds such
as epoxy, phenol formaldehyde & unsaturated polyester-
styrene mouldings
 Flammability : Silicone exhibits a higher temperature than
other plastics. It burns so long as an ignition source is
present, developing a characteristic silica smoke.
 Toxicological Assessment: Silicone resins not usually used for
utensils which come in contacts with food, although the
silicones are basically physiological inert

 Compounded rubbers are suitable for normal
processing techniques employed in rubber
technology
e.g Extrusion, calendaring and compression
moulding
Availability
 Silicone polymers are available in various
forms such as oils, resins ,pastes and
elastomeric moulding compounds.

 Silicones work two ways – mechanically and
chemically – to improve performance and
enable innovation.
 Their flexible backbone and unique surface
activity, silicones can do many things very
well.
 Common types of silicone products adhere,
manage foam, add gloss and shine, lubricate,
release, soften and condition, emulsify, and
waterproof substrates.

 Silicone fluids principally consist of chains of
alternating silicon and oxygen atoms with the
free valences of the silicon occupied with
organic radicals (“R,” usually methyl groups,
though in special cases they may also be phenyl,
vinyl or amino groups).
 Silicone fluids are transparent, tasteless and
odourless liquids with no known harmful effects.
 Their viscosities lie between 0.65 and 1,000,000
mm2/s depending on the type. They have
excellent thermal resistance from -60 to +300°C.

 Silicone fluids are also characterized by very
low volatility, excellent shearing resistance,
low surface tension and very good water
repellence
 Another important feature, of course, is
their remarkable electrical properties over a
wide temperature range.

 Silicone fluids are ideal for use as hydraulic or
transformer oils, damping liquids, diffusion pump
fluids, thermally resistant lubricants, dielectrics,
defoamers and release agents for photocopiers
and laser printers.
 Used for hydrophobic treatment of glass and
mineral wool.
 Special silicone fluids can be processed into
impregnating agents for textiles and leathers.
 They are also used in very small amounts as
paint additives. Other important applications are
to be found in cosmetics, pharmaceuticals and
medicine.

How silicone release agents work
 One of the key properties of silicone is its
low surface tension – in particular, its low
critical surface tension of wetting (or low
surface energy). This combines with the low
cohesive strength conferred by its methyl
groups to give silicone excellent release
characteristics.
 Unlike more rigid carbon-carbon backbones,
silicone polymers can easily expose their
low-interacting/surface-active methyl groups
to provide low adhesion, or easy release.

Silicone benefits for release
 Excellent spreading on many different
substrates, including metal mould surfaces
 Thermal stability
 Formulations with the ability to cure to form
thin films that do not transfer or interfere
with the bulk properties of the substrate
 Lower surface tension than typical acrylic
and SBR adhesives, facilitating release in
pressure-sensitive label applications

Typical silicone release agent applications
 Release liners for pressure-sensitive adhesive
labels
 Rubber tire release
 Metal mould release
 Food release

 Silicone resins are prepared batchwise by
hydrolysis of a blend of cholorosilanes.
 Highly branched polymer structures, they are
networks of irregular, mainly tri- or
tetrafunctional structural units. Because they
can be combined with many organic
polymers, it is possible to tailor the
numerous properties of silicone resins
e.g. their curing behaviour, flexibility,
adhesion properties or weathering resistance.
 The outstanding heat resistance of silicone
resins is particularly striking.

 They can sustain high temperatures of 200 to
250 °C in continuous service, and even up to
600 °C for brief periods.
 Their dielectric behaviour is ideal.
 Moreover, silicone resins’ excellent oxidation
resistance and superb mechanical properties
make them particularly durable and
economic materials.

 Silicone resins as pure products, solvent-based and
solvent-free systems, emulsions, but also powders.
 With their excellent thermal resistance, silicone
resins are first class binders for all heat-resistant
coatings.
 Silicone resins with reactive groups are principally
used for modifying alkyd, epoxy and acrylic
coatings. Such modified coatings offer excellent
weathering resistance and elasticity (e.g. for coil
coating).
 In the plastics industry, silicone resins are also used
as heat-resistant moulding compounds and release
coatings.

 Silicone resins’ excellent heat resistance and
outstanding range of properties are also very
much in demand for electrical applications,
such as binders for fiberglass laminates and
cements for incandescent lamp base.
 In addition, they are useful as water
repellents in masonry protection or as
binders in silicone resin facade paints.

 Silicone rubber compounds consist of long-
chain polysiloxanes and various fillers, such
as pyrogenic silica. They can be cured to
form silicone elastomers.
 They are classified according to the curing
method, the viscosity of the base polymer,
and whether they cure at high or room
temperature.

• heat stability 180 °C , 300 °C peak temperature)
• down to -50 °C, special grades -110 °C
• color
• flame retardance
• low compression set
• sun, weathering, UV resistance

Only contain : siloxanes, silica, cross linker/catalyst
• No organic stabilizers, organic impurities, preservatives, animal-derived products
and genetically-modified organisms
• No plasticizers or softeners like phthalates
 medical and pharmaceutical articles

Silicone Elastomer
Room temperature curing
One component
RTV-1
moisture curing
Tin-catalyzed
High temperature
curing
Solid Silicone Rubber
HCR
Peroxide curing Platinum curing
Liquid Silicone Rubber
LSR
Two components
RTV-2
Platinum curing
Addition curing
Platinum-catalyzed
Condens. curing
Tin-catalyzed
SILICONE ELASTOMERS –
CLASSIFICATION BY CHEMISTRY

 High-Consistency Silicone Rubber (HCR) Solid silicone
rubbers are cured at elevated temperature, either by
means of organic peroxides or platinum catalysts.
 The cured rubber is compounded with reinforcing
fillers to give it its mechanical strength.
 No known physical or physiological harmful effects,
and excellent aging resistance.
 Applications in the automotive industry, in the
electrical transmission and distribution sector,
electrical applications, food and personal hygiene,
machinery and plant construction and in the
construction industry.

 High-temperature-vulcanizing rubbers also
include liquid silicone rubbers. Their consistency
and curing mechanism give them outstanding
processing advantages.
 Liquid silicone rubbers are characterized by a
low viscosity compared to solid silicone rubbers
and other elastomers. Liquid silicone rubbers are
free-flowing, pumpable two-component
compounds that are supplied ready to process..
 Used in the automotive industry, transmission
and distribution, electrical, food and personal
care, through the machinery, plant engineering
and construction sectors to medical
applications.

advantages
- short cycle time
- fully automated injection molding process
- molds with up to 128 cavities
- complex part geometries possible
- 2-compentent injection molding possible
HCRLSR
advantages
- better mechanical properties,
- various processing techniques
- compression molding
- extrusion
- calendering

Two-Component Silicone Rubber (RTV-2)
 RTV-2 silicone rubbers are two-component
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:
condensation curing is performed with an
organotin catalyst, generating alcohol as
byproduct. On the other hand, uses a platinum
catalyst and does not produce byproducts.

 RTV-2 silicone rubber products allows cured
rubbers to be produced with extremely
versatile, highly specialized properties.
 Therefore, they offer solutions to problems
in diverse industrial sectors, including
moldmaking, electronics and
optoelectronics, household appliances,
machinery and industrial plant engineering,
medical applications.

One-Component Silicone Rubber (RTV-1)
 RTV-1 silicone rubbers are one-component
systems.
 They consist of polydimethylsiloxane, curing
agent, fillers and additives. After application,
they are cross-linked by contact with atmospheric
moisture releasing by-products in the process.
 Crosslinking starts with the formation of a skin on
the surface of the applied silicone rubber and
gradually works its way into the compound.
 RTV-1 silicone rubbers solve numerous problems
in sealing bonding and coating. Their outstanding
weathering and aging resistance is the result of
their special chemical properties

 Silicones can take many forms – from liquids to solids –
that allow engineers, scientists, inventors and
companies to use them as a vital component in
thousands of consumer and industrial applications.
 Whether as fluids, rubber, gels, resins or mixtures, it is
their versatility that makes silicones a key ingredient in
products that make our lives better every day.
 From baking moulds and cars to computers and
precision engineered spacecraft, silicones can be found
in a myriad of applications.
Put simply, silicones make things work better.

SILICONES &
CONSTRUCTION
Silicone materials have revolutionized
construction since they were first introduced on
the market in the 1960s.

 Silicones bond with most materials, from concrete,
glass, granite and marble to aluminium, steel and
plastics.
 They are extremely durable and can resist decay caused
to other materials by rough weather conditions,
moisture or sunlight.
 Silicone sealants can prevent humidity and hot or cold
air from coming through joints and cracks, thereby
making buildings more energy efficient. Their flexibility
can also reduce damage from small to medium-scale
earthquakes.
 These unique properties silicones are essential not only
in residential and office buildings, but also in bridges,
oil rigs, industrial plants and pipelines

 As modern means of transport become faster, more reliable
and more efficient, demands on materials to perform become
tougher. As such, smaller parts must resist exposure to
extreme heat, moisture, salt and fuels. Most materials
deteriorate in these conditions, but not silicones.
 Silicones retain their properties and – most important –
ensure that cars, ships, airplanes and trains operate safely
for the long haul.
SILICONES &
TRANSPORT

Cars and vans
 Silicones are used in almost all aspects of car
assembly, from the tires to the engine, windows
and sun-roof.
 They insulate electronic parts, reduce tire rolling
resistance, bond lightweight materials together,
and seal windows and doors.
 The same can be said about silicones’ uses in
airplanes, trains, and even space vessels.

Ships and boats
 Silicone-based paints and coatings are safer alternatives
to traditional marine coatings and paints.
 By applying these silicone products to hulls of ships and
boats, the build-up of dirt and film is dramatically
reduced, thereby improving fuel efficiency enormously.
 For large cargo ships, this improvement is particularly
important because ships’ fuel consumption is quite
significant. This fact makes the benefit of silicones in
this application all the more impressive – fuel savings
outweigh CO2 emissions from production of the silicone
product 182 times!

Reducing the environmental impact
 Silicones make an impressive contribution to
minimising fuel consumption of cars and ships, thus
reducing significantly the CO2 footprint of the
transport sector.

SILICONES &
HEALTH
When it comes to health care, we want the best for ourselves and our families.
We want the reassurance that the tools used by health care professionals are
safe, clean and dependable. Health care professionals want that too and more.

 Silicones are well tolerated by the human skin and body.
 They can facilitate healing, improve the appearance of
existing scars, and reduce discomfort. This makes silicones
an integral part of innovative medical treatments and
care.
 Medical applications and infant care products with silicone
can satisfy the highest quality standards demanded by
health care professionals and their patients.
 Resistant to bacteria, silicones are easy to sterilize and
are excellent for sensitive applications, such as respiratory
tubing and topical medications.

 Silicones do not react with other materials and do
not irritate the body.
 They are also hypoallergenic so can be used safely
for skin contact use as well as intravenously. Of
course silicones used in medical applications are
subject to thorough testing and regulations to
ensure their safety

Silicon

More Related Content

What's hot

Viewers also liked

Similar to Silicon

More from Arjun K Gopi

Recently uploaded

Silicon

Editor's Notes