Silicone rubber ranks among the most widely used materials for the manufacturing of various products. Many industries choose it for applications that need reliable rubber performance and long-term durability.
If you are an engineer, product designer or industrial buyer, then you should know what silicone rubber is and why it is popular. Today, we will discuss silicone rubber, its types, properties and silicone rubber uses.
What is Silicone Rubber?
Silicone rubber is a flexible and highly resistant elastomer that manufacturers use to make hoses, seals, gaskets, tubing and other parts. It is a man made material and a type of polymer that contains silicon, carbon, hydrogen and oxygen.
This material stands out from most other synthetic rubbers because of its unique chemical structure. Its special structure gives it excellent heat resistance, flexibility, weather resistance and electrical insulation. Moreover, it can stretch or compress when you apply pressure.
Fact: Do not confuse silicone (rubber) with silicon. Because they are two different materials. Silicon is a natural chemical element used in products such as computer chips and some metals. However, silicone is a man-made polymer that contains silicon along with oxygen and other elements. Manufacturers use silicone to make flexible products such as silicone hoses.
What is Silicone Rubber Made of?
Silicone rubber is mainly made from silicon and oxygen along with carbon & hydrogen. Manufacturers combine these elements to create a flexible silicone polymer. They also add materials such as fillers, pigments or curing agents to give the rubber the strength, color, hardness and performance you need. Let’s look at the main materials used to make silicone rubber in more detail.
| Component | What it does |
| PDMS (silicone polymer) | Forms main structure of silicone rubber and provides flexibility/chemical stability |
| Cross-linking agents | Join polymer chains together to create a strong rubber network |
| Reinforcing silica | Strengthens silicone rubber plus improves its thermal & mechanical performance. |
| Pigments | Add color and improve appearance of the silicone rubber |
| Stabilizers | Increase durability under harsh conditions |
| Flame retardants | Improve material’s resistance to flames and high temperatures |
How is Silicone Rubber Made?
Silicone rubber goes through several manufacturing steps that turn silica into a flexible and durable synthetic elastomer. Below is the step by step process used to produce silicone rubber.
Extract and Synthesize Silicon
The sand is used to make silicone contains quartz. Quartz consists of silicon dioxide, which means silicon atoms bond strongly with oxygen atoms. Manufacturers have to separate the silicon from the oxygen. They mix the silica-rich material with carbon and place it in a large electric arc furnace. The furnace reaches around 1800°C (3,270°F).
At this extreme temperature, carbon reacts with the oxygen. The oxygen leaves as a gas and silicon remains behind. The result is silicon with a purity close to 99%. Then they grind this silicon into a fine gray powder. Next, they heat it with methyl chloride. This reaction produces dimethyldichlorosilane (DMDCS). It is an important compound used to make silicone.
Hydrolyze and Polymerize Material
Industrial producers mix dimethyldichlorosilane (DMDCS) with water to start the hydrolysis process. This reaction creates polydimethylsiloxane (PDMS), which serves as the base polymer for silicone. The vinyl or phenyl are then added to modify the PDMS chains.
These changes are made to adjust properties such as temperature resistance and elasticity of material. The PDMS then forms longer polymer chains through polymerization. This step creates a viscous or elastomeric silicone base.
Compound and Add Additives
Next, producers mix the silicone base with different additives to improve its performance. Along with pigments and stabilizers, they also add fillers such as silica reinforcement agents. This formulation controls important properties such as chemical resistance, hardness and thermal stability of material.
Cure and Vulcanize Rubber
The next step is to cure or vulcanize the PDMS base with the use of several chemical systems. These include peroxide cure, condensation cure and platinum-catalyzed addition cure. During curing, cross-linking changes the silicone from a liquid or gel into solid silicone rubber.
It creates a three-dimensional network which gives the rubber its elasticity and durability. The silicone rubber can then go through further processing such as compression molding, injection molding or extrusion to form the final product.
Process Final Rubber
After curing, makers heat the silicone rubber again at a higher temperature. This post-curing step removes leftover volatile materials. It also improves the rubber’s thermal and mechanical stability. The finished material becomes a high-performance elastomer.
Silicone rubber comes in different forms including room temperature vulcanized (RTV) silicone, heat cured rubber (HCR) and liquid silicone rubber (LSR). They are used in many industries like automotive & aerospace to make products.
Silicone Rubber Properties
Silicone rubber gets its useful performance from its molecular structure and material specifications. Below we listed the top characteristics of silicone rubber.
- Silicone rubber can stay soft and flexible during use. It can bend, stretch or move without easily cracking or losing its shape.
- It can handle sunlight, rain, harsh weather conditions and damage from UV rays or ozone exposure.
- Silicone rubber does not easily allow electrical current to pass through it. This makes it useful where you need reliable electrical insulation.
- This rubber can resist many chemicals, oils and other substances. However, its chemical resistance depends on the specific silicone grade and the type of chemical.
- Silicone rubber can resist tearing if you stretch or pull it. This makes material able to handle repeated movement and mechanical stress.
- It generally has low toxicity and can work well in applications where material safety matters. The exact safety level can vary on the formulation and any additives used.
Silicone Rubber Physical Properties
Physical properties of silicone rubber describe characteristics that you can observe or measure without changing the material’s chemical composition. Factors such as additives can also change these specifications.
| Physical Property | Value |
| Thickness | 0.500 to 2060 mil |
| Viscosity | 0.700 – 1.30e+cP |
| Density | 0.00145 to 0.137 lb/in° |
| Molecular weight | 450000 to 850000 g/mol |
| Water absorption | 0.100-3.00 % |
| Molding and post curing shrinkages | 1% to 5% |
Silicone Rubber Mechanical Properties
In this table, you will see mechanical properties of silicone rubber which actually show how it responds to forces like pulling or compression.
| Property | Minimum To Maximum Value |
| Tensile strength | 8 to 23900 psi |
| Tensile strength/yield | 7 to 21000 psi |
| Compression set | 3 to 77.3% |
| Tensile set | 5.10 to 6.00% |
| Modulus of elasticity | 0.08-276 ksi |
| Shore hardness A | 4 to 95 (average: 50.9) |
| Shore hardness D | 15-95 (average: 53.6) |
| Shore hardness OO | 10 to 86 (average: 52.3) |
| Compressive modulus | 0.0290-0.856 ksi |
| Poisson’s ratio | 0.5 |
| Shear modulus | 0.0100 to 265 ksi |
| Shear strength | 140-878 psi |
| Tear strength | 5-713 pli |
Silicone Rubber Thermal Properties
Thermal specifications show how silicone rubber behaves if temperature changes. You can use this information to understand this material behavior against heat, cold and temperature changes during use.
| Thermal Property | Range |
| Brittleness temperature | -99 to 76°F |
| Heat capacity | 0.08-0.30 |
| Average Thermal conductivity | 0.42 to 45 |
| Thermal conductivity at 86-302°F | 1-24 |
| Thermal conductivity at 122°F | 10-33 |
| Glass transition temperature | -184 to 244°F |
| Thermal expansion | 6 to 186 |
| Thermal expansion across the flow direction | 11 to 22 |
Unit note: The thermal expansion values use µin/in-°F, specific heat values use BTU/lb-°F and thermal conductivity values use BTU-in/hr-ft²-°F.
Silicone Rubber Types
Silicone rubber is categorized in three main categories based on their processing and curing methods.
Solid Silicone Rubber (HTV)
Solid silicone rubber (also called high-temperature vulcanized) contains long polymer chains with a high molecular weight. It is available in an uncured form and uses traditional rubber processing methods. To create the final rubber, you need to vulcanize it at a temperature above 150°C with the use of organic peroxides or a platinum catalyst.
- Feature: High heat resistance up to 315°C, UV resistance & ozone stability
- Specifications: 40 to 80 Shore A hardness and up to 400% elongation at break
- Industries: Aerospace, manufacturing and automotive
- Applications: Turbocharger hoses, industrial conveyor belts plus oven seals
Liquid Silicone Rubber (LSR)
Liquid silicone rubber (LSR) has shorter polymer chains, so it can flow easily and has a low viscosity. It is a high purity material that cures with heat. LSR is able to keep its mechanical properties at temperature range -50°C to 250°C. Plus, this rubber offers excellent optical clarity and good durability in UV exposure. You can use injection molding and extrusion to process LSR.
Feature: Heat resistance, UV resistance, chemical resistance, strong adhesion & water resistance
Industries: Coatings, insulation, marine, outdoor applications
Uses: Heat-resistant coatings, insulating materials, outdoor products, chemical protection and marine products
Room Temperature Vulcanizing Silicone (RTV)
Room temperature vulcanized (RTV) silicone rubber available in either a single-component formula or a two-component mixture. It cures at room temperature and forms a soft to medium-hard rubber. Plus, it works well for producing silicone rubber molds.
Features: Room-temperature curing, flexible and easy dispensing
Industries: Automotive, electronics, construction, industrial manufacturing
Used For: Sealing, bonding, potting, encapsulation, mold making
Specifications: RTV (room-temperature vulcanizing), 1-component (RTV 1) or 2-component (RTV 2) systems
Informative: Silicone rubber that meets the required food-contact safety standards is called food-grade silicone rubber. Common standards include FDA 21 CFR 177.2600 in United States and EC 1935/2004 or LFGB in Europe. It is designed for safe use with food and should not contain harmful substances such as BPA, lead or phthalates. Mostly, LSR and HTV silicone rubber types are available in food-grade formulations.
Types of Silicone Rubber Based on Chemical Composition
You can also group silicone rubber into different types based on its chemical composition and the groups attached to its polymer chains. These changes give each type different properties and performance.
ASTM D1418 gives standard names and letter codes for different types of silicone rubber, which help you to identify silicone rubber based on its chemical structure. Under this system, silicone rubber includes the following types:
MQ Silicone Rubber: MQ silicone rubber (MQ silicone or methyl silicone) is the basic type of silicone elastomer. It consists mainly of methyl-polysiloxane units.
VMQ Silicone Rubber: Vinyl methyl silicone is a synthetic elastomer. It has a silicon-oxygen backbone instead of a carbon-carbon backbone.
PMQ Silicone Rubber: It is a specialized silicone elastomer in which some methyl groups in the polymer chain are replaced by phenyl groups. This structure gives it excellent flexibility at very low temperatures.
PVMQ Silicone Rubber: PVMQ silicone rubber (Phenyl Vinyl Methyl Silicone) is a modified VMQ silicone elastomer. Due to its structure, it can perform well in extremely cold and harsh environments.
Fluorosilicone Rubber (FVMQ): Fluorosilicone rubber (FVMQ) is a high-performance silicone elastomer. It combines the wide temperature flexibility of VMQ silicone with better fuel and oil resistance.
| Type | Based on chemical group | Main characteristic |
| MQ | Methyl | Basic silicone rubber |
| VMQ | Methyl + vinyl | Good compression properties and widely used |
| PMQ | Methyl + phenyl | Better low-temperature performance |
| PVMQ | Methyl + phenyl + vinyl | Excellent low-temperature flexibility and performance |
| FVMQ | Fluoro + vinyl + methyl | Good resistance to oil, fuel and solvents |
Silicone Rubber Application
Automotive
The automotive industry prefers silicone rubber due to its high-temperature resistance, oil resistance and flex-fatigue resistance. You will find the following automotive products that are made from this raw material.
- Automobile silicone hoses (radiator hoses & air intake hoses)
- Seals
- O-rings
- Sealants & gaskets
- Waterproof connectors
- Spark plug wires
- Heat exchangers
- Engine covers and valve covers,
Medical
The medical sector chooses silicone rubber for its biocompatibility, high-temperature resistance, non-toxic nature and chemical resistance.
- Balloon catheters
- Feeding tubing
- Drainage tubing
- Peristaltic pump tubing
- Seals
- Valves
- Masks and medical instruments
- Medical cables
- Medical textile coating
- Baby bottle nipples
- Hearing aids
Electronics
Silicone rubber is ideal material for the manufacturing of consumer electronics items due to its electrical insulation, low & high-temperature resistance and low compression set.
- Microwave oven window gaskets
- Drive belts
- Defrosters
- Wiring
- Insulating tape
- Keyboards
- Housings
Aerospace
There are various aerospace items made from silicone rubber because it can handle extreme environmental conditions very well.
- Spacesuit fabrics
- Tooling materials
- Seals and gaskets
- Aircraft manufacturing applications
- Wire and cable tubing
Construction
The construction sector uses silicone rubber because it offers good weather resistance and strong bonding to metal surfaces.
- Adhesives, sealants and coatings
- Expansion joint seals
- Weatherstripping
- Waterproofing components
Consumer Products
The consumer products industry uses silicone rubber for food-contact and cooking applications. Because it is non-toxic and food-safe. It also resists cooking fats and sterilizing fluids. Hence, it is used in these products.
- Food processing and packaging equipment
- Drink vending machines
- Baking trays & molds
- Oven door profiles
Silicone Rubber Advantages
- Silicone rubber is strong, durable and flexible, which makes it suitable for heavy duty use.
- It offers good resistance to UV light and harsh outdoor conditions so that it can perform better than many organic rubbers.
- Due to its stable silicon-oxygen structure, silicone rubber provides excellent electrical insulation.
- Highly purified silicone rubber is biocompatible, so living tissue can tolerate it well. Special coatings can further reduce the risk of infection and inflammation.
- It can resist oils and most chemicals, so it works well in harsh environments such as industrial machinery and medical equipment.
- This rubber is able to handle very low and high temperatures around -65°F to -100°F at the low end. Plus, it can stay in good condition at temperatures up to 400°F to 450°F at the high end.
Disadvantages of silicone rubber: Silicone rubber offers many useful properties, but it also has some limitations.
- High cost
- Low tear strength
- Poor abrasion resistance
- Limited resistance to some oils and fuels
- Low tensile strength
- Difficult bonding
- Limited resistance to concentrated acids and alkalis
- Higher gas permeability
- Poor adhesion without treatment
Silicone Rubber Cost
There is no fixed price for silicone rubber, because it varies based on factors such as its type, grade, hardness, formulation, quantity and manufacturing process. Standard silicone grades generally cost less, but specialized grades with added performance features can be expensive.
Price of silicone rubber per kg: $3 to $15 per kg
How much does silicone cost per pound? 2 to 6 US dollars
Final Words
So now, you are very well aware of the main types, properties and uses of silicone rubber. You can make better material choices for your projects. Keep in mind, the right silicone grade can improve product performance and service life.
Due to its excellent characteristics, RONTEIX uses silicone rubber for the manufacturing of automotive hoses. So if you need to buy silicone rubber made hoses, you can send your inquiry now.
FAQs
Is silicone rubber recyclable?
Silicone rubber is technically recyclable, but you cannot place it in a regular curbside recycling bin. The reason is, it is a thermoset material. So you cannot simply shred, melt and remold it like a plastic bottle.
Can you laser cut silicone rubber?
Yes, you can laser cut silicone rubber. However, you need the right laser equipment and settings. Silicone rubber can resist heat during cutting and leave ash or residue. So you need careful control of the cutting process.
Is silicone rubber toxic?
Silicone rubber is generally non-toxic and safe for many everyday uses. However, its safety depends on the quality, formulation and use of the material.
Is silicone rubber oil-resistant?
This rubber has limited resistance to long-term oil exposure. Still, it can handle short-term contact with oils and performs better than many other rubber types at high temperatures.
How long does silicone rubber last?
On average, silicone rubber can last for 10 to 50 years in service. Its actual lifespan can vary based on the grade and surrounding environment.
