Tag Archive for: custom silicone material

Choosing the right silicone material is one of the most important decisions in custom silicone product manufacturing. The wrong material can lead to poor sealing, tearing, deformation, odor issues, failed compliance testing, unstable dimensions, or short product life. The right material, on the other hand, can improve durability, safety, production efficiency, and long-term performance.

Silicone rubber is widely used because it offers low-temperature flexibility, high-temperature resistance, weathering resistance, hydrophobicity, good mechanical properties, electrical insulation, pigmentation flexibility, and biocompatibility depending on the formulation. WACKER describes silicone rubbers as materials with excellent low-temperature flexibility, high-temperature resistance, low compression set, chemical and environmental resistance, water-repellent surfaces, and properties that can range from electrically insulating to semiconducting.

However, “silicone” is not one single material. Liquid silicone rubber, high-consistency silicone rubber, room-temperature vulcanizing silicone, fluorosilicone, conductive silicone, thermal silicone, food-grade silicone, and medical-grade silicone are designed for different applications. A material that works well for a baby-care product may fail in an automotive fuel seal. A silicone suitable for a kitchen gasket may not be suitable for long-term skin contact or medical device use.

This guide explains how to choose the right silicone material for your custom product, using practical selection criteria, real data, and application examples.

Start With the Application, Not the Material

The first mistake many buyers make is asking for “food-grade silicone,” “medical-grade silicone,” or “60 Shore A silicone” before defining the actual working conditions. A silicone material should be selected based on the product’s function, environment, manufacturing process, and compliance requirements.

Before choosing a material, define these points:

What is the product used for? Is it a seal, gasket, keypad, tube, sleeve, valve, wearable component, kitchen product, medical part, electronic potting material, or automotive component?

What temperature will it face? Will the product be used in freezing conditions, boiling water, ovens, engines, outdoor exposure, or EV battery systems?

What will it contact? Water, food, skin, oil, fuel, cleaning agents, steam, alcohol, chemicals, air, dust, or electrical components?

What mechanical performance is needed? Flexibility, tear resistance, elongation, compression recovery, abrasion resistance, vibration damping, or dimensional stability?

What certifications or testing requirements apply? For food-contact products, medical devices, electronics, automotive, or export markets, the compliance path can affect the compound choice and post-processing process.

Liquid silicone rubber, for example, is a two-component system that can be pumped into a mold and cured into a solid. Elkem notes that LSR is biocompatible, flowable, platinum-cured, and compatible with a broad temperature range from -60°C to +250°C depending on the grade and application.

Understand the Main Types of Silicone Materials

Different silicone materials are suited to different production methods and product requirements.

WACKER states that solid silicone rubber can be processed by extrusion, calendering, compression molding, transfer molding, and injection molding, while liquid silicone rubber is commonly used in injection molding and fully automated production.

Choose the Right Hardness

Hardness is usually measured in Shore A for silicone elastomers. Softer silicone feels more flexible and compressible; harder silicone provides better shape retention and resistance to deformation.

Typical selection logic:

For soft-touch products, baby-care items, flexible sleeves, skin-contact parts, and soft seals, lower Shore A values are often used.

For gaskets, O-rings, plugs, industrial seals, and structural silicone parts, medium hardness is more common.

For parts requiring dimensional stability, higher hardness or special reinforced silicone grades may be needed.

Hardness alone is not enough. Two materials with the same Shore A hardness can have very different tear strength, elongation, compression set, transparency, surface friction, and curing behavior. For example, Dow lists a fluorinated LSR designed for solvent- and chemical-resistant membranes, gaskets, O-rings, seals, diaphragms, and electrical connectors with 60 Shore A hardness, 470% elongation, and 6.5 MPa tensile strength.

That means a 60 Shore A silicone is not automatically suitable for every 60 Shore A application. The full property profile matters.

Match the Material to Temperature Requirements

Temperature resistance is one of silicone rubber’s biggest advantages, but different grades perform differently. Standard silicone may be suitable for many general high- and low-temperature applications, while special grades are needed for extreme cold, high heat, thermal cycling, or electronics.

For example, Dow’s DOWSIL™ 3-6121 Low Temperature Elastomer is designed for PCB potting and protection applications and is described as retaining performance down to -65°C. The same product data lists 34 Shore A hardness, 0.19 W/m·K thermal conductivity, and heat-cure options such as 20 minutes at 100°C or 10 minutes at 150°C.

In EV and power electronics, thermal cycling is often more important than simple peak temperature. WACKER’s SEMICOSIL® 9649 TC, a silicone thermal gap filler for electric and hybrid vehicle power electronics, is reported to have approximately 4 W/mK thermal conductivity and to withstand thermal shocks from -40°C to +150°C while maintaining the bond between power electronics and cooling systems.

For custom silicone products, always define both continuous operating temperature and short-term peak temperature. A material that survives a short heat spike may not be suitable for continuous exposure over months or years.

Check Chemical and Fluid Compatibility

Standard silicone performs well in many environmental conditions, but it is not the best choice for every chemical environment. Oil, fuel, solvents, cleaning agents, steam, acids, or disinfectants can change the material selection.

For automotive fuel systems, aerospace seals, or oil-contact applications, fluorosilicone is often considered because it offers better resistance to hydrocarbons and aggressive media than standard silicone. WACKER specifically notes that its fluorinated liquid silicone rubber grades are designed for automotive and aerospace seals and have high stability toward aggressive media such as gasoline, engine oil, and gear oil.

Dow’s SILASTIC™ LS 63 U fluorosilicone rubber provides another data point: the cured material is listed with 60 JIS Type A hardness, 1.48 g/cm³ density, 340% elongation, 7.8 MPa tensile strength, and tear strength values of 21 N/mm and 28 N/mm depending on test method.

The practical lesson is simple: if the part contacts fuel, oil, solvent, or aggressive chemicals, do not select standard silicone only by hardness. Request chemical compatibility review and, ideally, test the molded part in the real fluid under real temperature and time conditions.

Consider Food-Contact Requirements

For food-contact silicone products, material selection must consider both formulation and finished-part compliance. In the U.S., 21 CFR 177.2600 covers rubber articles intended for repeated food-contact use. The regulation states that rubber articles may be safely used in producing, manufacturing, packing, processing, preparing, treating, packaging, transporting, or holding food, subject to the listed conditions.

The same regulation includes extractives limits. For repeated-use rubber articles in contact with aqueous food, the finished food-contact surface must not yield total extractives above 20 mg per square inch during the first 7 hours of extraction, nor above 1 mg per square inch during the following 2 hours. For fatty foods extracted with n-hexane, the limits are 175 mg per square inch during the first 7 hours and 4 mg per square inch during the following 2 hours.

For silicone manufacturers and buyers, this means “food-grade silicone” should not be treated as a vague marketing claim. The correct approach is to confirm the compound, colorant, curing system, post-curing process, and finished-product test requirements.

In many food-contact applications, platinum-cured silicone is preferred because it can offer cleaner curing chemistry and lower by-product concerns than peroxide-cured systems. However, the final choice should still depend on the product design, production process, regulatory market, and required test report.

Consider Medical and Skin-Contact Requirements

Medical silicone selection is more demanding than general consumer silicone selection. For medical devices, the question is not only whether the raw silicone is “medical grade.” The finished device, its contact duration, body contact type, sterilization method, additives, processing residues, and packaging may all affect the biological evaluation.

FDA’s 2023 guidance on ISO 10993-1 explains that the standard is used for biological evaluation of medical devices within a risk-management process and is relevant to devices that have direct or indirect body contact. The guidance also discusses risk-based approaches to determine whether biocompatibility testing is needed.

A real-world example comes from DuPont’s Liveo™ case study with Cellreturn’s CX9 portable LED mask. According to DuPont, Cellreturn had performance issues with a previous elastomer, including skin irritation, and selected DuPont™ Liveo™ medical-grade high-consistency silicone rubber to optimize the product’s performance, support device registration, and enter regulated medical device markets.

For wearable products, skin-contact comfort is not only about softness. The material may need to address irritation, surface feel, sweat exposure, long wear time, cleanability, odor, pigmentation, and adhesion to other components.

Define Mechanical Performance Requirements

For many custom silicone products, the most important mechanical properties are:

Hardness: affects feel, compression, and stiffness.

Tensile strength: measures resistance to pulling force.

Elongation: shows how far the material can stretch before breaking.

Tear strength: important for thin walls, buttons, membranes, and parts with holes or sharp corners.

Compression set: critical for seals and gaskets because it measures how well the material recovers after being compressed.

Compression set is especially important for sealing applications. If a gasket loses its ability to recover after long-term compression, sealing force drops and leakage risk increases. Stockwell Elastomerics explains that compression set testing measures a rubber material’s ability to return to original thickness after prolonged compression, and that loss of resiliency can reduce the performance of gaskets, seals, and cushioning pads.

For a custom silicone seal, do not only specify “50 Shore A silicone.” A better specification is closer to this:

50 ± 5 Shore A silicone, low compression set, suitable for continuous compression at the target temperature, compatible with the contact fluid, molded to drawing tolerance, with post-curing and test report if required.

That type of specification gives the manufacturer enough information to recommend the right compound.

Select the Right Manufacturing Process

Material choice and manufacturing process are connected. A material that is technically suitable may still be inefficient or expensive if it does not match the production method.

For high-volume precision parts, LSR injection molding is often preferred. Dow describes LSR as a two-part material that can be readily mixed and rapidly heat-cured into durable elastomers, with advantages including fast heat-cure rates, reduced cycle times, and lower production costs.

For tubes, cords, profiles, and strips, solid silicone rubber is often more suitable because it can be extruded continuously. WACKER lists tubing, profiles, cables, flat tapes, and round cords as examples of extruded solid silicone rubber products.

For electronics potting, encapsulation, and bonding, RTV or two-part dispensable silicone systems may be better than molded silicone parts. WACKER notes that silicone gels and foams are used in applications such as automotive, transmission and distribution, health and wound care, lightweight construction, damping, thermal insulation, and fire safety.

A good silicone manufacturer should not only quote the drawing. They should review whether compression molding, transfer molding, LSR injection molding, extrusion, calendering, coating, or dispensing is the right process for the part.

Practical Material Selection Guide by Application

For food-contact parts such as kitchenware, baking mats, food-processing seals, and beverage-machine gaskets, consider platinum-cured food-contact silicone, suitable pigment systems, post-curing if required, and finished-part testing according to the target market.

For medical and healthcare products, consider medical-grade LSR or HCR, full traceability, controlled processing, biocompatibility planning, sterilization compatibility, and finished-device evaluation under ISO 10993-related requirements.

For automotive seals, gaskets, O-rings, and connector seals, consider heat resistance, compression set, oil or fuel exposure, weathering, assembly method, and whether fluorosilicone is needed.

For electronics and EV components, consider dielectric strength, thermal conductivity, flame resistance, low volatiles, dispensing behavior, adhesion, thermal cycling, and vibration damping.

For consumer products such as watch bands, phone cases, protective sleeves, and buttons, consider skin feel, color consistency, surface coating, tear strength, dust attraction, odor, and long-term appearance.

For industrial parts, consider mechanical strength, compression recovery, chemical resistance, working temperature, outdoor exposure, and cost stability during mass production.

Common Mistakes When Choosing Silicone Material

One common mistake is choosing based only on price. Low-cost silicone can work for simple applications, but it may create problems in odor, tearing, color stability, compression set, or compliance testing.

Another mistake is choosing only by hardness. Hardness does not define chemical resistance, tear strength, temperature resistance, or compression recovery.

A third mistake is using “food grade” or “medical grade” as a shortcut. These terms need to be connected to actual regulations, test methods, finished-product conditions, and the customer’s market.

A fourth mistake is ignoring colorants and additives. Pigments, fillers, flame retardants, conductive fillers, and processing aids can affect curing, surface quality, mechanical properties, and compliance.

A fifth mistake is skipping real-use testing. Laboratory data is useful, but molded parts should be tested under real compression, temperature, chemicals, assembly stress, and aging conditions before mass production.

What Information Should You Give Your Silicone Manufacturer?

To get the right material recommendation, provide the following information:

Product drawing or 3D file.

Application and function.

Target hardness.

Operating temperature range.

Contact media, such as food, skin, oil, water, steam, chemicals, or electronics.

Required color and transparency.

Required certifications or test standards.

Expected production volume.

Assembly method.

Special requirements such as bonding, printing, coating, flame resistance, conductivity, thermal conductivity, or low odor.

The more complete the information, the more accurate the material recommendation and quotation will be.

Conclusion

The right silicone material is not chosen by hardness or price alone. It is selected by matching the material’s full property profile with the product’s real application: temperature, chemicals, mechanical stress, compliance, manufacturing process, surface requirements, and production volume.

For simple consumer products, a standard silicone compound may be enough. For food-contact, medical, automotive, electronics, or EV applications, the material selection process must be more rigorous. Real data, finished-part testing, and early manufacturability review can prevent costly failures during mass production.

As a custom silicone manufacturer, we help customers select suitable silicone materials for molding, extrusion, sealing, food-contact products, medical components, industrial parts, and high-performance applications. Share your drawing, sample, or application requirements with our engineering team, and we can recommend a suitable silicone material and manufacturing process for your project.