Silicone Rubber: A Complete Guide for Engineers, Designers, and Enthusiasts

Silicone material, with its unique molecular structure, offers outstanding material properties, excellent resistance to high and low temperatures, chemical and weather resistance, moisture resistance, insulation, dielectric properties, biocompatibility, and breathability. Widely applied in industries such as electronics, food, pharmaceuticals, petroleum, machinery, healthcare, and construction, silicone material stands as a promising and environmentally friendly material with great development prospects.

What is Silicone Rubber?

Silicone materials have come a long way since their discovery of organic polymers in 1863, with 160 years of continuous improvement and optimization by countless scientists, making them an irreplaceable and crucial material today. The composition of silicone material primarily includes silicone gum, reinforcing fillers, crosslinking agents, catalysts, and modifying additives. 

silicone

 

What Are the Key Properties of Silicone Rubbers?

Silicone High Heat and Low Temperature

Silicone High Heat and Low Temperature

Silicone materials exhibit outstanding heat resistance and cold resistance, allowing them to endure long-term use in environments up to 180°C when exposed to air. By incorporating high-temperature additives into the material, there is significant potential to enhance its temperature resistance. Standard silicone rubber materials can achieve a lifespan of 20 years at 120°C and 5 years at 150°C.

HTV Silicone Rubber Data Table:

HTV silicone rubber Data Table

 

RTV Silicone Rubber Data Table:

RTV silicone rubber data table
Silicone Rubber vs. Rubbers: Data Comparison Reference
Silicone Vs. RubberAutomatic productionWaste-free ProductionChemical StabilityLow temperature elasticity
(<-40°C)
Thermal stability
(>200°C)
Stainability
Thermoplastic RubberExcellentExcellentGood/BadBadBadGood
Ethylene Propylene RubberGoodBadGood/BadBadBadBad
Natural RubberBadBadBadBadBadBad
Polyurethane RubberGoodGoodGoodBadBadExcellent
Silicone RubberExcellentExcellentGoodExcellentExcellentExcellent

Silicone rubber has the lowest cold brittleness point among all rubber materials. Regular silicone materials maintain normal performance even in temperatures as low as -50/60°C, while materials with special formulations can achieve a cold brittleness point as low as -100°C.

Comparison of Extreme Temperatures: Synthetic Rubber Performance

Materials typeHighest usage
temperature/°C
Minimum usage
temperature/°C
Tensile Strength/MPaElongation/%
normal temperature121°C205°Cnormal temperature121°C205°C
Silicone Rubber250-7335~15060128100~800350200
Natural Rubber116-35100~280125970050080
Styrene-Butadiene Rubber94-40100~2808412300~70025060
Butyl Rubber94-52150~2007025500~70025080
Neoprene121-40100~2801001360~700350100
Polysulfide Rubber100-4040~9050>2200~700140>25
Fluororubber200-40140~20021~5611~21400100~35050~350
Nitrile Rubber121-1540~300509400~60012020
Polyurethane Rubber80-20300~50015014400~750300140
Acrylic Rubber150-200-23150~3359016100~400400150

Silicone Electrical Insulation

Insulation

Silicone rubber boasts outstanding advantages in dielectric strength, power factor, and insulation performance, exhibiting minimal changes with temperature and frequency variations. Across a broad temperature range, dielectric strength remains essentially constant. Within a wide frequency range, the dielectric constant and dielectric loss tangent also remain nearly unchanged. Silicone rubber demonstrates excellent resistance to corona and arc discharge, with a corona resistance life approximately a thousand times that of polytetrafluoroethylene and an arc resistance life roughly 20 times that of fluoroelastomers.

Electrical properties of silicone rubber

Test itemResult
Electrical strength(1/4in electrode,
Rapid pressure extraction at 500V/s,sample thickness 1/16in,/(V/mil)
450~600
Relative dielectric constant2.9~3.6
Dielectric loss factor0.0005~0.2
Volume resistivity/.cm8×1013~2×1015
Insulation resistance/1×1012~1×1013

 

Me3 SiO (MeRSiO)nSiMe3 Effect of polarity of side group R on relative dielectric constant and volume resistivity:

Me3 SiO (MeRSiO)nSiMe3 Effect of polarity of side group R on relative dielectric constant and volume resistivity

Silicone Chemical Resistance

Chemical Resistance

Silicone rubber demonstrates excellent resistance to chemicals, solvents, and oils. Solvents primarily cause expansion and softening in silicone rubber, but once the solvent evaporates, most of the original properties of silicone rubber are restored. Silicone rubber exhibits good resistance to polar solvents such as ethanol, acetone, and edible oils, causing minimal swelling and maintaining virtually unchanged mechanical properties.

Silicone rubber also withstands the effects of low concentrations of acids, bases, and salts. For instance, when immersed in 10% sulfuric acid at room temperature for 7 days, the volume and weight changes are both less than 1%, with minimal impact on mechanical properties. However, it is not resistant to concentrated sulfuric acid, strong alkalis, and non-polar solvents such as carbon tetrachloride and toluene.

Silicone rubber excels in properties like oxygen resistance, ozone resistance, and resistance to UV radiation. Therefore, it does not experience cracking when used outdoors for extended periods. It is generally believed that silicone rubber can be used outdoors for over 20 years.

Breathability

Breathability

The helical structure of polydimethylsiloxane, along with its ample free space and excellent solubility for gases, contributes to the outstanding breathability of silicone rubber. At room temperature, its permeability to gases such as air, nitrogen, oxygen, and carbon dioxide is 30 to 50 times higher than that of natural rubber.

Oxygen Permeability of Various Polymer Films:

PolymerOxygen Permeability
Dimethyl Silicone Rubber60
Fluorosilicone Rubber11
Nitrile Silicone Rubber8.5
Natural Rubber2.4
LDPE0.8
Butyl Rubber0.14
Polystyrene0.12
HDPE0.1
PVC0.014
Nylon0.004
PET0.0019
PTFE0.0004

 

Permeability of methyl silicone rubber film containing 33% silicon:

GasAir permeabilityGasAir permeabilityGasAir permeability
H265H2O435n-C6H14940
H235NO2760n-C8H18860
NH3590SO21500n-C10H22430
H2O3600CS29000HCHO1110
CO34CH495CH3OH1390
N228C2H6250COCI21500
NO60C2H4135丙酮586
O260C2H22640吡啶1910
H2S1000C3H84101080
Ar60n-C4H10900苯酚2100
CO2325n-C5H122000甲苯913

 

Flame Retardant 

Retardant

Silicone rubber exhibits outstanding flame retardancy, with a flash point above 300°C. By simply incorporating common metal oxides, modified materials can easily achieve UL-94 flame retardant ratings. This makes it suitable not only for electrical components but also for use in flame-resistant materials.

 

Types of Silicone Rubber:

Depending on the Silicon Molecule

  • Dimethyl Silicone Rubber
  • Methyl Vinyl Silicone Rubber
  • Methyl Phenyl Silicone Rubber
  • Fluorosilicone Rubber
  • Nitrile Silicone Rubber
  • Ethyl Silicone Rubber
  • Diphenyl Silicone Rubber

Classification According to Molding Curing Method

  • High-Temperature Vulcanizing Silicone Rubber (HTV)
  • Room-Temperature Vulcanizing Silicone Rubber (RTV)

Depending On The Form of the Product

  • High-temperature Vulcanizing Mixing Silicone Rubber (HCR)
  • liquid silicone rubber (LSR) 

 

Types of Silicone Additive:

Silicone Pigments

The color options for silicone material are incredibly diverse; you can achieve any color available in the Pantone color system.

Pantone color

Heat Resistant Agent

Heat-resistant additives for silicone rubber include ferric oxide, iron hydroxide, iron oxalate, alkoxysilane iron, organosilicon ferrocene, titanium dioxide, zinc carbonate, and cerium oxide.

Heat Resistant

Flame Retardant

Compared to regular organic rubber, silicone rubber inherently possesses good flame retardant properties. Adding flame retardants can further enhance its flame resistance. Commonly used flame retardants include platinum compounds, titanium dioxide, manganese carbonate, zinc carbonate, basic zinc carbonate, aluminum hydroxide, and decabromodiphenyl ether.

Retardant

Internal Mold Release Agent

Release agents containing fatty acid salts or other surfactants are included. Adding them to silicone rubber material can improve the demolding process, making it easier to release the material from the molds during production.

Mold Release

From Industry to Everyday Life: Silicone Rubber Applications:

 

  • Kitchen Tools
  • Children’s Toys
  • Pet Supplies
  • Medical Accessories
  • Petrochemical
  • Construction Materials
  • Mechanical Manufacturing
  • Electronic Components
  • Military Industry
  • Aerospace Industry

 

TOGOHK Different Silicone Molding Method:

Compression Molding

We primarily manufacture various types of silicone rubber seals, gaskets, silicone covers, tableware, children’s toys, and cake molds.

Extrusion Molding

We specialize in extruding various shapes of silicone tubes, strips, profiles, dual-color silicone tubes, LED silicone tubes, spiral tubes, and corrugated tubes.

Injection Molding

The liquid injection molding process is primarily designed for liquid silicone products. Currently, we extensively use liquid silicone injection molding for products with encapsulation structures. Additionally, it is employed for items such as pacifiers and medical accessories. However, due to cost considerations, we typically do not recommend this process for large quantities of products as it results in high costs without significant cost-effectiveness.


FAQ:

Can You Color Silicone?

Yes, you can customize the color of silicone according to your requirements. Typically, we reference the Pantone color standard for color matching.

Can the Hardness of Silicone Rubber Be Adjusted?

Certainly! The hardness of silicone rubber can be adjusted to any level between 10 and 80 degrees according to your specific customization needs.

Is Silicone Rubber Resistant to Nuclear Radiation?

Yes, silicone rubber has good radiation resistance, making it commonly used in the nuclear industry. Its radiation resistance varies with the substituents on the silicon atom; for example, organosilicon compounds containing phenyl groups exhibit better radiation resistance compared to those containing methyl or ethyl groups. Generally, organosilicon compounds with methyl groups can withstand radiation up to 10^7 to 10^8 rad, while those with phenyl groups can withstand up to 10^10 rad.

Silicone Bonding: What Can It Adhere To?

Silicone bonding can adhere to materials such as nylon, stainless steel, and aluminum. Currently, the bonding solutions involving silicone are widely used.

Silicone Insulation: Is it a Reliable Electrical Insulator?

Yes, silicone rubber material exhibits excellent electrical insulation properties.

 

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