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| Silicone Elastomers |
Silicone elastomers, also known as silicone rubbers, are a class of thermoset
elastomeric materials that have unique properties making them suitable for use
in a wide variety of applications. Made from silicone polymers that contain
silicone-carbon bonds, silicone elastomers demonstrate characteristics like
stability, flexibility and resilience across a broad range of temperatures. In
this article, we will explore the composition, properties and various uses of
these versatile materials.
Composition of Silicone Elastomers
Silicone elastomers are composed of silicone polymers made by polymerizing
siloxane or silicone monomers. The basic repeating unit of all siloxane
polymers is -Si(CH3)2-O-. This repeating subunit gives the polymer its
flexibility and elastic nature.
Silicone elastomers are prepared by crosslinking siloxane polymers into
insoluble network structures. Crosslinking transforms the polymers into
thermoset materials. Common crosslinking agents used are methylhydrogen
polysiloxane, dimethylhydrogensiloxy terminated polydimethylsiloxane and
similar compounds containing silicon-bonded hydrogen atoms. Curing or
vulcanization is achieved by adding a platinum catalyst which promotes the
addition reaction of silicon-bonded hydrogen atoms across alkene groups on the
polymer backbone.
Properties
The unique molecular structure of Silicone
Elastomers endows them with exceptional mechanical and chemical
resistance properties compared to organic elastomers. Some of the key
characteristics of these materials include:
- Operational temperature range of -100°C to 300°C. They can withstand both
high and low extreme temperatures.
- Inertness to oxidation, ozone, weathering and ultraviolet light. They are
highly stable.
- Resistance to moisture, acids and bases. They do not degrade when exposed to
corrosive chemical environments.
- Low toxicity and ability to maintain properties in contact with food or
medical applications.
- Low compression set and high tensile strength. They have excellent elastic
recovery properties.
- Electrical insulation properties. They do not conduct electricity very well.
These distinct material attributes make silicone elastomers ideal for countless
specialty applications where other polymers would fail.
Common Applications
Given their one-of-a-kind balance of flexibility, resilience and resistance
properties, silicone elastomers find extensive use across a wide range of
industries. Here are some of their major applications:
Automotive and Transportation
- Seals, O-rings and hoses in engines for their high heat and fluid resistance.
- Automotive moldings, exterior trims and gaskets that need to withstand
weathering.
- Shock absorbers, mountings and dampers for their compressive strength.
- Tire seals and inner tubes because of their low air permeability.
Industrial and Manufacturing
- Gaskets, sleeves, diaphragms and seals for extreme temperature equipment.
- Insulation for wires, cables and electrical components needing dielectric
strength.
- Conveyor belts, hoses, tubing for their wear and chemical resistance.
- Sealants for construction joints, ductwork and plumbing fixtures.
Healthcare and Medicine
- Orthopedic implants, replacements and prosthetics for biocompatibility.
- Tubing, valves and gaskets in medical devices contacting tissues or fluids.
- Prophylactics, breast implants and wound dressings contacting skin.
- Insulin pumps, blood oxygenator membranes and other disposable parts.
Personal Care and Consumer Goods
- Cooking and baking applications like baking mats, bakeware and tubing.
- Baby bottle nipples, pacifiers and teethers for contact with mouths.
- Thermal interface materials in electronics needing heat dissipation.
Specialized Applications
- Spacecraft o-rings, coatings and seals for their stability in outer space.
- Aquarium and plumbing sealants requiring water contact for long periods.
- Marine deck and boat paint sealants to prevent water intake.
- Architectural sealants for glazing, joints and façade applications.
Silicone elastomers combine flexibility and elasticity with remarkable
oxidative, thermal and chemical resistance. This unique property profile has
led to their widespread adoption in countless industries for applications where
longevity, reliability and safety are critical. Advanced formulations continue
to expand the possibilities for silicone elastomers in specialty
high-performance applications.
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