7 Things to Know Before Buying Silicone Rubber
Buying borracha de silicone is not as simple as choosing a Shore A hardness and asking for the lowest price. Two silicone compounds can look similar, carry the same hardness and still behave very differently during extrusion, molding, heat aging, electrical service or long-term sealing.
The correct silicone rubber should match both the manufacturing process and the finished application. A cable compound needs stable extrusion and dielectric performance. A composite-insulator material needs hydrophobicity and tracking resistance. A food-contact grade requires different documentation from an industrial sealing compound. An EV component may need heat aging, electrical insulation and tear resistance at the same time.
Before sending a purchase order, buyers should define the critical technical requirements clearly. The following seven points help reduce material mismatch, production problems and unnecessary supplier changes later.
1. Know Which Type of Silicone Rubber You Actually Need
The first question is not hardness. It is material type and processing method.
Silicone rubber is available in several major forms, and each one is designed around a different production route. HTV/HCR silicone is a high-consistency, gum-like material used for extrusion, compression molding and transfer molding. LSR is a flowable two-component system commonly used for automated injection molding. RTV silicone is typically used for sealing, potting or mold-making applications.
| Tipo de silicone | Processamento típico | Aplicações comuns |
|---|---|---|
| Silicone HTV / HCR | Extrusion, compression molding, transfer molding, calendering | Cable, seals, insulators, profiles, industrial molded parts |
| LSR | Moldagem por injeção de líquido | Precision molded components, medical, food-contact and high-volume parts |
| Silicone RTV | Pouring, sealing, potting, room-temperature curing | Mold making, sealing, encapsulation and repair |
If the material type does not match the production equipment, even a technically good silicone rubber can become the wrong purchase.
2. Do Not Choose Silicone Rubber by Hardness Alone
Shore A hardness is useful, but it describes only how soft or firm the cured rubber feels. It does not tell you how the uncured material will process or how well it will perform mechanically.
Two 60 Shore A silicone rubber grades can differ significantly in tensile strength, elongation, tear strength, plasticity, viscosity, die swell, cure behavior and heat-aging performance.
| Propriedade | Why Buyers Should Check It |
|---|---|
| Dureza | Controls firmness and deformation behavior |
| Resistência à tração | Shows resistance to pulling force |
| Alongamento | Indicates how far the material can stretch before breaking |
| Resistência ao rasgo | Important for thin sections, demolding and repeated flexing |
| Deformação residual por compressão | Critical for seals and gaskets |
| Plasticity / Rheology | Influences milling, extrusion and mold flow |
3. Match the Silicone Rubber to the Production Process
A silicone compound should be selected around the equipment that will process it. Production problems often occur when buyers approve a material only from a datasheet without testing how it behaves on the actual line.
Extrusion, compression molding and transfer molding all require different uncured behavior.
Extrusão
Needs stable feeding, controlled die swell, smooth surface and consistent pressure.
Moldagem por compressão
Needs suitable mold flow, flash control, cure response and demolding behavior.
Moldagem por transferência
Needs controlled flow through runners with enough scorch safety.
Calandragem
Needs consistent plasticity and stable sheet thickness.
If a new silicone rubber grade has the same hardness but different rheology, the production line may need changes to roll temperature, mill gap, extruder speed, die dimensions, molding pressure or cure time.
4. Define the Real Operating Temperature
Temperature is one of the most common reasons buyers choose silicone rubber, but it is also one of the most misunderstood specifications.
A maximum temperature number does not tell the full story. Continuous service temperature, short-term peak temperature and thermal cycling should be considered separately.
For many applications, heat-aging retention is more useful than the highest advertised temperature. Buyers should review changes in hardness, tensile strength, elongation and compression behavior after thermal exposure.
5. Check the Application-Specific Requirements
General-purpose silicone rubber is not automatically suitable for electrical, food-contact, flame-retardant or high-temperature applications.
Specialized applications usually require additional formulation priorities.
Electrical & High Voltage
May require dielectric strength, volume resistivity, hydrophobicity, tracking resistance and erosion resistance.
Fios e cabos
May require extrusion stability, electrical insulation, heat aging and flame performance.
EV Components
May require electrical insulation, temperature cycling, tear strength and long-term sealing.
Vedações industriais
May prioritize compression set, heat resistance and chemical compatibility.
Food-Contact Products
Need the appropriate formulation controls and supporting documentation for the intended market.
Flame-Retardant Parts
Need performance against the required flammability test rather than simply high-temperature resistance.
Electrical Silicone Rubber Needs More Than High Dielectric Strength
For electrical applications, buyers often focus on dielectric strength alone. But outdoor and high-voltage components may fail through surface processes rather than bulk electrical breakdown.
Composite insulators and cable accessories can experience moisture, contamination, leakage current, dry-band arcing and localized heating. This makes surface hydrophobicity, tracking resistance and erosion resistance important.
| Electrical Property | Por que isso é importante |
|---|---|
| Rigidez dielétrica | Resistance to electrical breakdown under defined conditions |
| Resistividade volumétrica | Resistance to current passing through the bulk material |
| Acompanhamento da resistência | Helps resist conductive path formation on the surface |
| Resistência à erosão | Helps resist surface material loss under electrical discharge |
| Hidrofobicidade | Helps reduce continuous water-film formation outdoors |
Food-Contact Silicone Rubber Requires Documentation
If the finished part will contact food, buyers should not rely only on the words “food grade silicone.”
The material should be evaluated according to the intended market, contact conditions, temperature and finished-product requirements. Depending on the project, buyers may ask for documentation supporting applicable FDA 21 CFR, LFGB, BfR or other requirements.
Flame Resistance and Heat Resistance Are Not the Same
A silicone compound can perform well under continuous high temperature without meeting a specific flame classification.
If the application requires UL 94 or another fire-performance test, the exact compound, specimen thickness and test documentation should be checked separately.
Do not assume that a high-temperature silicone rubber is automatically flame retardant.
6. Ask About the Cure System
The curing system affects both processing and finished performance.
HTV/HCR silicone commonly uses peroxide curing, while selected high-consistency compounds can also use platinum-catalyzed addition curing. LSR typically uses platinum addition cure.
| Cure System | What Buyers Should Consider |
|---|---|
| Peroxide Cure | Widely used in conventional HCR extrusion and molding; cure conditions and post-curing may matter depending on the application. |
| Platinum Cure | Used where addition-cure chemistry, low by-products or specific process requirements are important. |
The cure system can influence scorch safety, cure speed, odor, post-curing requirements and compatibility with pigments or other additives.
7. Evaluate Supplier Consistency, Not Just the First Sample
A silicone rubber supplier should be evaluated on more than whether the first sample passes testing.
Industrial production depends on repeatability. Changes in polymer, silica dispersion, heat treatment, mixing quality or cure ingredients can influence processing and finished properties from batch to batch.
Why Batch Consistency Matters in Extrusion
Extrusion lines are especially sensitive to changes in silicone rubber rheology.
If one batch has higher plasticity or different elastic recovery, extrusion pressure, line speed, surface quality and die swell may change.
A supplier that controls uncured behavior consistently can reduce the amount of line adjustment required between batches.
Why Batch Consistency Matters in Molding
Molding operations can also be affected by material variation. A change in flow or cure response may alter flash, cavity filling, cycle time and demolding.
If the same mold suddenly requires different pressure or time, the issue may be related to compound behavior rather than tooling alone.
This is why process consistency should be considered part of silicone rubber quality.
Do Not Compare Silicone Rubber Suppliers by Price per Kilogram Alone
The cheapest silicone rubber is not always the lowest-cost material in production.
A lower material price can be offset by slower line speed, more flash, higher scrap, difficult demolding, unstable extrusion or shorter component life.
A better comparison is total production cost and application reliability, not simply raw-material price.
Ask for the Right Technical Data
A useful silicone rubber technical datasheet should provide more than hardness.
The exact data needed depends on the application, but industrial buyers may want to review mechanical, thermal, electrical and processing information.
| Data Category | Useful Information |
|---|---|
| Mechanical | Hardness, tensile strength, elongation, tear strength |
| Physical | Density and uncured plasticity where relevant |
| Thermal | Heat-aging results and recommended service conditions |
| Electrical | Dielectric strength, resistivity, tracking or erosion data where applicable |
| Processamento | Cure system, recommended processing conditions and material form |
| Conformidade | Applicable declarations or test reports required by the project |
Run a Production Trial Before Full Approval
Datasheets help narrow the options, but production equipment provides the final answer.
Whenever possible, buyers should run the silicone rubber under real process conditions before approving a full supplier switch or large production order.
What Should Be Included in a Silicone Rubber RFQ?
A detailed RFQ gives the supplier enough information to recommend a material that fits production instead of simply matching one property.
Buying Silicone Rubber from Yakows
Yakows supplies HTV/HCR silicone rubber compounds for electrical insulation, composite insulators, wire and cable, EV systems, high-temperature components, food-contact products and general industrial molding.
Material selection can be based on processing method, Shore A hardness, mechanical properties, heat aging, electrical performance, curing system and end-use requirements rather than hardness alone.
For customers replacing an existing material, information about current processing performance can also be useful. Problems such as excessive die swell, roll tack, unstable extrusion, difficult demolding or insufficient tear strength can help identify which formulation characteristics need to change.
Perguntas frequentes
What should I know before buying silicone rubber?
Define the silicone type, processing method, hardness, mechanical properties, operating temperature, application-specific requirements, cure system and supplier consistency before approving a material.
Is all silicone rubber the same?
No. Silicone compounds can differ significantly in polymer structure, filler system, curing chemistry, processing behavior and final properties.
Can two silicone rubber grades with the same hardness perform differently?
Yes. Hardness measures only cured firmness. Processing, tear strength, heat aging and electrical performance may be very different.
What is the difference between HCR and LSR silicone?
HCR is a high-consistency gum-like silicone typically used for extrusion and compression molding, while LSR is a two-component liquid commonly processed by injection molding.
Should I choose silicone rubber based on maximum temperature?
No. Continuous temperature, short-term peaks, thermal cycling and heat-aging property retention should all be considered.
Is high-temperature silicone automatically flame retardant?
No. Heat resistance and flame resistance are different properties and should be tested separately.
How do I compare two silicone rubber suppliers?
Compare not only price and datasheet properties, but also processing consistency, batch variation, technical support, documentation and performance on your production equipment.
Should I run a production trial before buying a large quantity?
Yes. A production trial helps verify extrusion, molding, cure behavior and finished-part properties under real manufacturing conditions.