What Is the Difference Between Peroxide-Cured and Platinum-Cured Silicone?

Two silicone parts can look identical, yet the wrong curing system can cause odor, cure failure, compliance gaps, surface defects, or unnecessary cost.

Peroxide-cured silicone uses free-radical crosslinking and suits economical industrial processing. Platinum-cured silicone uses addition curing, creates no peroxide decomposition products, and often suits clear, low-odor, medical, food-contact, and precision parts. Neither system is always better.

I never select silicone from the curing-system name alone. The exact compound, part geometry, processing method, post-curing, contamination risk, service environment, compliance documents, and finished-part tests must support the decision.

What Do Peroxide-Cured and Platinum-Cured Silicone Mean?

The word “silicone” does not define one finished material. Two silicone compounds with the same hardness can use different polymers, fillers, additives, and curing systems.

Peroxide-cured silicone uses organic peroxide to generate free radicals and crosslink silicone polymer chains. Platinum-cured silicone uses a platinum catalyst to support an addition reaction between vinyl-functional polymers and silicon-hydride crosslinkers. Both systems convert uncured silicone into an elastic network.

What Is Peroxide-Cured Silicone?

Peroxide curing is widely used with high-consistency rubber¹, which is also called HCR, HTV, or solid silicone rubber. The uncured material normally has a firm, gum-like consistency.

A controlled quantity of organic peroxide is mixed into the silicone compound. Heat decomposes the peroxide and produces reactive free radicals. These radicals help create chemical links between the polymer chains.

Peroxide-cured silicone is commonly used for:

• Compression-molded seals and gaskets
• Transfer-molded components
• HCR injection-molded parts²
• Extruded tubing and profiles³
• Calendered silicone sheets
• Die-cut silicone gaskets
• Wire and cable insulation
• Silicone sponge sheets and profiles⁴
• General industrial silicone parts

Peroxide curing is not one fixed formula. Different peroxide types support different production processes. A peroxide suitable for pressureless hot-air extrusion may not be the best choice for compression molding.

The selected peroxide can affect⁵:

• Cure temperature⁶
• Cure speed
• Scorch safety
• Surface condition
• Odor
• Blooming
• Color stability
• Post-curing requirements
• Compression set
• Finished-part cleanliness

What Is Platinum-Cured Silicone?

Platinum-cured silicone is also called addition-cured silicone. The system normally contains vinyl-functional silicone polymer, a silicon-hydride crosslinker, a platinum catalyst, fillers, processing additives, and cure-control agents.

The platinum catalyst supports a hydrosilylation reaction. The silicon-hydride groups react with the vinyl groups and form a crosslinked network.

Platinum curing can be used with:

• Liquid silicone rubber
• Addition-cured HCR silicone
• Precision molded seals⁷
• Transparent tubing
• Medical components
• Food-contact products⁸
• Baby-care parts
• Electrical components
• Low-odor industrial parts⁹
• Self-bonding silicone systems

Platinum-cured silicone is not automatically LSR. Addition-cured HCR compounds also exist. They can be molded, extruded, and processed through other HCR production methods.

Basic Comparison

Factor	Peroxide-Cured Silicone	Platinum-Cured Silicone
Crosslinking mechanism	Free-radical reaction	Platinum-catalyzed addition reaction
Main curing components	Organic peroxide	Platinum catalyst and Si-H crosslinker
Common material form	Mainly HCR, solid silicone, and sponge	HCR and LSR
Cure-related by-products	Peroxide decomposition products can form	No peroxide decomposition products form
Common position	Economical industrial molding and extrusion	Clean, precise, low-odor, or automated production
Post-curing	Often important	Application and compound dependent
Cure inhibition	Generally less sensitive to platinum poisons	Sensitive to sulfur, amines, tin, and other contaminants
Typical entry cost	Often lower	Often higher
Regulatory compliance	Must be demonstrated	Must be demonstrated

⚠️ Platinum is a catalyst. The word “platinum” does not prove that a finished part is food-safe, medical-grade, chemically pure, or suitable for every sensitive application.

How Do the Two Silicone Curing Reactions Differ?

Cure chemistry changes more than production speed. It affects reaction products, mixing control, surface quality, post-curing, contamination sensitivity, and process stability.

Peroxide curing begins when heat breaks the peroxide into free radicals. Platinum curing joins vinyl-functional polymers with silicon-hydride crosslinkers through addition curing. Peroxide reactions form decomposition products, while the platinum addition reaction does not create peroxide by-products.

How Peroxide Crosslinking Works

The organic peroxide first decomposes when the compound reaches its activation temperature. The resulting free radicals react with the silicone polymer and help create crosslinks between the chains.

The final cure state depends on¹⁰:

• Peroxide chemistry
• Peroxide dosage
• Polymer structure
• Vinyl content
• Mixing uniformity
• Heating rate
• Cure temperature
• Cure time
• Part thickness
• Mold pressure
• Oxygen exposure
• Pigments and additives
• Post-curing conditions¹¹

The decomposition products depend on the peroxide used. Some can cause odor. Some can migrate to the surface and produce white deposits or blooming. Others may affect color, taste, or cleanliness if the part is not cured and post-cured correctly.

Selected peroxide systems are also affected by oxygen. An exposed surface may remain tacky or undercured when the peroxide, heating method, and production environment are not compatible.

How Platinum Addition Curing Works

The platinum catalyst helps silicon-hydride groups add across the carbon-carbon double bonds in vinyl-functional silicone polymers.

The reaction forms crosslinks without generating peroxide decomposition products. This can provide several practical benefits:

• ✅ Low cure-related odor
• ✅ No peroxide-related blooming
• ✅ Good transparency with a suitable compound
• ✅ Fast heat-activated curing
• ✅ Dry cured surfaces
• ✅ Short molding cycles
• ✅ Strong automation potential
• ✅ Consistent processing with controlled metering
• ✅ Reduced need to remove peroxide residues

However, this system introduces another risk. Small quantities of incompatible substances can poison the platinum catalyst. The silicone may cure slowly, remain sticky, develop soft areas, or fail to cure.

Reaction Comparison

Reaction Issue	Peroxide System	Platinum System
Main activation	Heat decomposes the peroxide	Heat accelerates the addition reaction
Crosslinking action	Free radicals create crosslinks	Si-H groups react with vinyl groups
Peroxide decomposition products	Present	Not present
Cure-related odor	Possible	Normally lower
Peroxide-related blooming	Possible	Not applicable
Cure speed	Compound and process dependent	Often faster under controlled heating
Oxygen-related surface problems	Possible with selected peroxides	Not the main inhibition mechanism
Catalyst poisoning	Not a platinum-catalyst issue	A major production concern
Dosage control	Peroxide dosage and dispersion	A/B ratio, crosslinker, catalyst, and inhibitor
Premature curing	Scorch control is important	Temperature and pot-life control are important

Cure Density Still Controls Performance

The curing-system name does not show the final crosslink density. An undercured platinum silicone can perform worse than a correctly cured peroxide silicone.

Crosslink density affects:

• Hardness
• Modulus
• Elongation
• Tear behavior
• Elastic recovery
• Compression set
• Stress relaxation
• Heat-aging performance
• Swelling
• Demolding strength

I therefore review rheometer data, cured test sheets, production parameters, and finished-part tests. I do not assume that selecting platinum or peroxide automatically creates the required material network.

How Do Purity, Odor, Clarity, and Post-Curing Compare?

“High-purity silicone” is often used as a general sales phrase. Real cleanliness depends on the entire formulation, production environment, post-curing, handling, and packaging.

Platinum-cured silicone normally offers lower cure-related odor, better clarity, and fewer cure residues because addition curing produces no peroxide decomposition products. Peroxide-cured silicone often needs post-curing to remove odor and volatiles. Platinum-cured parts may still need post-curing for sensitive applications.

Purity Is a Complete-System Property

A platinum-cured compound can still contain or collect:

• Low-molecular-weight siloxanes
• Residual crosslinking ingredients
• Fillers
• Pigments
• Processing additives
• Mold-release contamination
• Dust
• Equipment oil
• Cleaning-agent residues
• Packaging contamination

A peroxide-cured compound can also achieve controlled cleanliness when its formulation, post-curing, handling, testing, and packaging are properly managed.¹²

I separate four statements that are often confused:

Statement	What It Actually Means
No peroxide by-products	The material uses addition curing
Low volatile content	The finished part meets a defined volatile limit
Low extractables	The part passes an application-specific extraction test
Food or medical suitability	The formulation and finished part meet identified requirements

These ideas are related, but they are not interchangeable.

Odor and Taste

Peroxide decomposition products can create a noticeable smell. The actual odor depends on the peroxide type, dosage, primary cure, part thickness, oven loading, and post-curing cycle.

Odor can be critical for:

• Food-processing seals
• Beverage tubing
• Bottle closures
• Kitchenware
• Respiratory components
• Personal-care products
• Consumer products used near the face
• Enclosed electrical equipment

Platinum-cured silicone normally has a cleaner odor profile because the addition reaction does not generate peroxide decomposition products. However, “odorless” should still be verified on the finished part.

Odor may also come from pigments, packaging, cleaning agents, contaminated ovens, storage conditions, or other materials used in the assembly.

Clarity and Color Stability

Platinum-cured silicone is often preferred for highly transparent products. It avoids peroxide-related deposits and cure by-products that can affect odor or appearance.

Common transparent applications include:

• Clear silicone tubing
• Medical connectors
• Flow-viewing components
• Transparent protective sleeves
• Food-contact tubes
• Baby-care products
• Inspection components

Peroxide-cured silicone can also be translucent or transparent. Its final appearance still depends on the filler, peroxide, wall thickness, cure cycle, post-curing, and heat exposure.

Color should be approved after every required thermal process. A translucent part can yellow during post-curing. The same pigment can also look different in a thin wall and a thick molded section.

Why Peroxide-Cured Silicone Is Post-Cured

Post-curing heats the finished silicone again in a controlled circulating-air oven.¹³

For peroxide-cured silicone, post-curing may:

• Remove peroxide decomposition products
• Reduce odor
• Reduce surface blooming
• Lower volatile content
• Stabilize finished properties
• Improve selected compression-set results
• Support extraction requirements
• Reduce later property changes

The post-curing cycle should define:

• Oven temperature
• Holding time
• Fresh-air supply
• Part spacing
• Maximum oven load
• Heating and cooling method
• Part support
• Contamination controls
• Dimensional inspection after post-curing

A thick molded component may need a different cycle from thin tubing¹⁴. Overloading the oven can also reduce airflow and slow volatile removal.

Why Platinum-Cured Silicone May Still Need Post-Curing

Platinum curing does not create peroxide by-products¹⁵. However, the compound can still contain low-molecular-weight siloxanes and other volatile or extractable substances.

Post-curing may still be needed when the application has¹⁶:

• Strict volatile limits
• Extractables and leachables requirements
• Sensitive food contact
• Medical contact
• Pharmaceutical contact
• Low-fogging requirements
• Odor limits
• Sterilization requirements
• Tight compression-set targets
• Special dimensional-stability requirements

⚠️ “No peroxide decomposition products” does not mean “no post-curing required.” The decision must follow the exact compound data and finished-part acceptance requirements.

Which System Provides Better Mechanical and Sealing Performance?

Platinum-cured silicone is sometimes described as mechanically superior.¹⁷ That statement is too broad because the cure system is only one part of the compound design.

Neither curing system always delivers better tensile strength, tear resistance, compression set, recovery, or sealing life. Both systems can provide strong performance. The actual compound, crosslink density, post-curing, geometry, temperature, media, compression, and manufacturing consistency control the result.

Compound Design Matters More Than the Cure Label

Two 60 Shore A silicone compounds can have very different:

• Tensile strength¹⁸
• Elongation
• Tear strength
• Modulus
• Rebound
• Compression set¹⁹
• Stress relaxation
• Heat-aging retention
• Surface friction
• Fatigue resistance

Hardness only measures indentation resistance. It does not directly show sealing force, recovery, leakage resistance, or service life.

The finished properties also depend on:

• Polymer structure
• Filler type and loading
• Vinyl content
• Crosslink density
• Heat stabilizers
• Processing additives
• Primary cure
• Post-curing
• Pigments
• Manufacturing conditions

Mechanical Property Comparison

Property	Peroxide-Cured Silicone	Platinum-Cured Silicone	Correct Validation
Tensile strength	Can be high with the correct compound	Can be high with the correct compound	Test the complete cured formulation
Elongation	Grade dependent	Grade dependent	Use an agreed test method
Tear strength	Standard and high-tear grades exist	Standard and high-tear grades exist	Test the required tear direction
Compression set	Can be improved by formulation and post-curing	Low-compression-set grades are available	Test at actual time and temperature
Stress relaxation	Compound and aging dependent	Compound and aging dependent	Test sealing-force retention
Resilience	Formulation dependent	Formulation dependent	Test under dynamic conditions
Heat resistance20	Grade dependent	Grade dependent	Heat-age and retest
Fluid resistance	Not defined by cure system	Not defined by cure system	Immerse in the actual fluid
Fatigue life21	Geometry and compound dependent	Geometry and compound dependent	Conduct cycle testing
Abrasion resistance22	Often limited for standard silicone	Often limited for standard silicone	Test the finished contact condition

Compression Set Does Not Equal Sealing Life

Compression set measures the deformation that remains after a compressed specimen is released. It is useful, but it does not describe the complete sealing system.

A gasket can pass compression-set testing and still leak because of:

• Insufficient initial compression
• Poor flange flatness
• Excessive surface roughness
• Bolt relaxation
• Thermal movement
• Pressure cycling
• Incorrect groove fill
• Poor gasket geometry
• Stress relaxation
• Surface damage
• Assembly contamination

I also review compression-deflection and stress relaxation. Compression-deflection²³ shows the force needed to compress the gasket. Stress relaxation shows how much sealing force is lost while the part remains installed.

Geometry Can Reverse a Material Comparison

A soft silicone compound is not always easier to seal with. A wide solid gasket can require high clamping force even at low hardness. A hollow profile made from harder silicone may compress more easily.

The sealing design should define:

• Original gasket thickness
• Installed gap
• Compression percentage
• Compression force
• Groove dimensions
• Internal pressure
• Extrusion gap
• Flange condition
• Thermal movement
• Allowable leakage
• Required service life

Chemical Resistance Is Not Automatically Better

Platinum curing does not automatically improve resistance to:

• Mineral oil
• Fuel
• Refrigerants
• Compressor oil
• Steam
• Strong acids
• Strong alkalis
• Hydrocarbon solvents
• Food oils and fats

The exact compound must be tested with the actual medium, concentration, temperature, pressure, and exposure time.

In some conditions, FVMQ, FKM, EPDM, HNBR, or another elastomer may be more suitable than standard VMQ silicone.

🛠️ I compare curing systems only after the material family, media, temperature, pressure, geometry, movement, and expected failure mode are defined.

How Do Molding, Extrusion, LSR Processing, and Cure Inhibition Differ?

The cure system affects equipment, tooling, material handling, mixing, automation, contamination control, and production risk.

Peroxide-cured HCR is widely processed through compression molding, transfer molding, HCR injection molding, extrusion, calendering, and foaming. Platinum-cured HCR can use several of the same methods. Platinum-cured LSR normally uses metered two-component injection molding and requires strict contamination control.

Compression and Transfer Molding

Peroxide-cured HCR is a common material for compression molding. The compound is mixed, formed into preforms, placed in a heated mold, and cured under pressure.

This method is suitable for:

• Gaskets
• Grommets
• Boots
• Bellows
• Stoppers
• Bushings
• Protective caps
• Silicone-to-metal parts
• Large molded components
• Low and medium production volumes

Transfer molding can improve material delivery into small cavities. HCR injection molding can provide more automation and more controlled material flow.

Addition-cured HCR can also use these processes. The production area must still prevent substances that can inhibit platinum curing.

Extrusion and Calendering

Peroxide-cured HCR is widely used for:

• Silicone tubing
• Solid cord
• Hollow profiles
• Oven seals
• Door gaskets
• Flat strips
• Cable insulation
• Calendered sheets
• Die-cut gaskets
• Fabric-coated materials
• Sponge profiles

The curing agent must match the heating process. Pressureless hot-air extrusion requires a system that can cure the exposed surface correctly.

Platinum-cured HCR can also be extruded. It can offer low odor, a dry surface, and no peroxide-related blooming. However, it requires accurate material control and clean processing equipment.

How LSR Processing Differs

Liquid silicone rubber is normally supplied as a two-component platinum-cured system. Components A and B remain separate until the injection system meters and mixes them.

A typical LSR process includes:

1. Supplying components A and B
2. Controlling the mixing ratio
3. Adding approved pigment when required
4. Mixing the components
5. Injecting the cool material into a heated mold
6. Curing the part
7. Demolding
8. Post-curing when required
9. Inspecting dimensions and function

LSR processing can offer:

• Fast molding cycles
• High-cavity production
• Fine detail reproduction
• Thin-wall molding
• Low material waste
• Automated demolding
• Low-flash production
• Consistent mixing
• Overmolding onto qualified substrates

However, LSR tooling and equipment usually need greater initial investment. A cold-runner system, accurate venting, thermal control, balanced cavities, metering equipment, and automated handling may be required.

Cure Inhibition in Platinum Systems

Very small quantities of incompatible substances can delay or prevent platinum-catalyzed curing.

Possible inhibitors include:

• Sulfur and sulfur-containing compounds
• Amines
• Organotin compounds
• Condensation-cured silicone residues
• Natural and selected synthetic rubber compounds
• Some polyurethane systems
• Amine-cured epoxy
• Certain adhesives
• Certain primers
• Some masking tapes
• Contaminated gloves
• Contaminated mixers, molds, ovens, or tools

Possible symptoms include:

• Sticky surfaces
• Soft areas
• Slow curing
• Partial curing
• Uncured material around inserts
• Variable hardness
• Poor bonding
• Demolding damage
• Complete cure failure

Cleaning should be validated. A tool may still carry enough contamination to cause inhibition even after visible residue has been removed.

Production Separation

A factory that processes organic rubber and platinum-cured silicone may need:

• Dedicated mixing equipment
• Dedicated tools
• Controlled molds
• Separate material storage
• Approved gloves
• Validated cleaning procedures
• Controlled ovens
• Traceable handling records
• Cure-inhibition tests
• Separate processing zones

Peroxide-cured HCR is generally less sensitive to the catalyst poisons that affect platinum curing. It still requires control of peroxide dispersion, temperature, scorch, oxygen exposure, moisture, and general contamination.

Process Risk Comparison

Production Risk	Peroxide-Cured HCR	Platinum-Cured HCR or LSR
Uneven curing-agent dispersion	Important	Important
Premature curing	Scorch risk	Temperature and pot-life risk
Peroxide odor or blooming	Possible	Not applicable
Catalyst inhibition	Not a platinum issue	Major concern
Mixing-ratio error	Peroxide dosage error	A/B or additive ratio error
Cross-contamination	General quality risk	Can cause cure failure
Automation potential	Moderate to high	Very high with LSR
Flash removal	Often required	Can be low with precision LSR
Post-curing	Common	Application dependent
Production separation24	Normal compound control	Strict control may be required

Which System Fits Food, Medical, Pharmaceutical, and Industrial Parts?

The curing system can support an application, but it cannot approve the finished product. Suitability depends on the complete formulation, exposure, production controls, and test results.

Platinum-cured silicone is often preferred for clear, low-odor, food-contact, medical, and pharmaceutical components. Peroxide-cured silicone remains suitable for many industrial and selected regulated applications when the formulation, post-curing, documentation, and finished part are properly validated.

Food-Contact Parts

Both curing systems can support selected food-contact products. Platinum curing is often preferred when low odor, low taste transfer, transparency, or reduced cure residues are important.

Possible applications include:

• Food-processing gaskets
• Beverage tubing
• Bottle stoppers
• Dispensing valves
• Oven seals
• Kitchenware
• Canning lids
• Repeated-use silicone articles

A food-contact specification should identify:

• Destination market
• Applicable regulation
• Food type
• Aqueous or fatty contact
• Contact temperature
• Contact time
• Repeated-use cycle
• Cleaning method
• Color
• Extraction requirements
• Finished-part testing

FDA 21 CFR 177.2600 covers rubber articles intended for repeated food-contact use under specified composition, use, and extraction conditions. A material declaration does not replace finished-article verification.

For European and German supply chains, BfR Recommendation XV may also be requested for silicone. BfR recommendations provide technical guidance but are not binding legal standards.

I avoid using “FDA approved silicone” as a general claim. A more accurate statement identifies the exact regulation, compound, intended use, and available test evidence.

Medical Components

Platinum-cured silicone is widely selected for medical components because it supports precision LSR molding, controlled formulations, low cure-related odor, and clean production.

Possible products include:

• Respiratory seals
• Medical tubing
• Valve components
• Device gaskets
• Medical connectors
• Protective caps
• Pump components
• Syringe seals
• Instrument handles

“Medical-grade silicone” should refer to a controlled material, production system, and validation plan. It should not mean only that the silicone uses platinum curing.

A medical evaluation may need:

• Exact material identity
• Supplier change control
• Manufacturing cleanliness
• Biological safety evaluation
• Chemical characterization
• Extractables and leachables
• Sterilization compatibility
• Particulate control
• Packaging validation
• Finished-device risk assessment

ISO 10993-1 uses a risk-based approach to the biological safety of medical devices. The complete device, intended contact, contact duration, processing history, and chemical exposure must be considered.

Passing one selected biological test does not make a silicone compound suitable for every medical application.

Pharmaceutical Components

Pharmaceutical contact requires more than clean appearance and low odor. The component may contact a drug for a long period and can affect stability, delivery, or container-closure integrity.

Possible silicone components include:

• Processing tubing
• Transfer hoses
• Pump diaphragms
• Filling-system gaskets
• Valve parts
• Sealing components
• Device interfaces
• Selected closures

Qualification may include:

• Extractables and leachables
• Drug compatibility
• Adsorption or absorption
• Particle release
• Sterilization resistance
• Container-closure integrity
• Functional testing
• Dimensional compatibility
• Traceability
• Change control

USP chapters <381> and <382> may apply to elastomeric components and the functional suitability of parenteral packaging or delivery systems. Their use depends on the exact component and packaging system.

Platinum curing can reduce peroxide-related residues, but it cannot replace pharmaceutical compatibility and system testing.

Industrial Components

Peroxide-cured silicone is often practical for:

• Industrial seals
• HVAC gaskets
• Extruded profiles
• Oven seals
• Electrical insulation
• Cable components
• Machinery covers
• General silicone tubing
• Sponge gaskets
• Protective boots
• Vibration pads
• Calendered sheets

Platinum-cured silicone becomes attractive when the industrial component requires:

• Low odor
• High transparency
• Fast automated molding
• Thin precision sections
• Low-flash production
• Controlled volatiles
• Clean surfaces
• Overmolding onto a qualified substrate

However, LSR tooling and equipment usually need greater initial investment. A cold-runner system, accurate venting, thermal control, balanced cavities, metering equipment, and automated handling may be required.

Cure Inhibition in Platinum Systems

Very small quantities of incompatible substances can delay or prevent platinum-catalyzed curing.

Possible inhibitors include:

• Sulfur and sulfur-containing compounds
• Amines
• Organotin compounds
• Condensation-cured silicone residues
• Natural and selected synthetic rubber compounds
• Some polyurethane systems
• Amine-cured epoxy
• Certain adhesives
• Certain primers
• Some masking tapes
• Contaminated gloves
• Contaminated mixers, molds, ovens, or tools

Possible symptoms include:

• Sticky surfaces
• Soft areas
• Slow curing
• Partial curing
• Uncured material around inserts
• Variable hardness
• Poor bonding
• Demolding damage
• Complete cure failure

Cleaning should be validated. A tool may still carry enough contamination to cause inhibition even after visible residue has been removed.

Production Separation

A factory that processes organic rubber and platinum-cured silicone may need:

• Dedicated mixing equipment
• Dedicated tools
• Controlled molds
• Separate material storage
• Approved gloves
• Validated cleaning procedures
• Controlled ovens
• Traceable handling records
• Cure-inhibition tests
• Separate processing zones

Peroxide-cured HCR is generally less sensitive to the catalyst poisons that affect platinum curing. It still requires control of peroxide dispersion, temperature, scorch, oxygen exposure, moisture, and general contamination.

Process Risk Comparison

Production Risk	Peroxide-Cured HCR	Platinum-Cured HCR or LSR
Uneven curing-agent dispersion	Important	Important
Premature curing	Scorch risk	Temperature and pot-life risk
Peroxide odor or blooming	Possible	Not applicable
Catalyst inhibition	Not a platinum issue	Major concern
Mixing-ratio error	Peroxide dosage error	A/B or additive ratio error
Cross-contamination	General quality risk	Can cause cure failure
Automation potential	Moderate to high	Very high with LSR
Flash removal	Often required	Can be low with precision LSR
Post-curing	Common	Application dependent
Production separation	Normal compound control	Strict control may be required

Which System Fits Food, Medical, Pharmaceutical, and Industrial Parts?

The curing system can support an application, but it cannot approve the finished product. Suitability depends on the complete formulation, exposure, production controls, and test results.

Platinum-cured silicone is often preferred for clear, low-odor, food-contact, medical, and pharmaceutical components. Peroxide-cured silicone remains suitable for many industrial and selected regulated applications when the formulation, post-curing, documentation, and finished part are properly validated.

Food-Contact Parts

Both curing systems can support selected food-contact products. Platinum curing is often preferred when low odor, low taste transfer, transparency, or reduced cure residues are important.

Possible applications include:

• Food-processing gaskets
• Beverage tubing
• Bottle stoppers
• Dispensing valves
• Oven seals
• Kitchenware
• Canning lids
• Repeated-use silicone articles

A food-contact specification should identify:

• Destination market
• Applicable regulation
• Food type
• Aqueous or fatty contact
• Contact temperature
• Contact time
• Repeated-use cycle
• Cleaning method
• Color
• Extraction requirements
• Finished-part testing

FDA 21 CFR 177.2600 covers rubber articles intended for repeated food-contact use under specified composition, use, and extraction conditions. A material declaration does not replace finished-article verification.

For European and German supply chains, BfR Recommendation XV may also be requested for silicone. BfR recommendations provide technical guidance but are not binding legal standards.

I avoid using “FDA approved silicone” as a general claim. A more accurate statement identifies the exact regulation, compound, intended use, and available test evidence.

Medical Components

Platinum-cured silicone is widely selected for medical components because it supports precision LSR molding, controlled formulations, low cure-related odor, and clean production.

Possible products include:

• Respiratory seals
• Medical tubing
• Valve components
• Device gaskets
• Medical connectors
• Protective caps
• Pump components
• Syringe seals
• Instrument handles

“Medical-grade silicone” should refer to a controlled material, production system, and validation plan. It should not mean only that the silicone uses platinum curing.

A medical evaluation may need:

• Exact material identity
• Supplier change control
• Manufacturing cleanliness
• Biological safety evaluation
• Chemical characterization
• Extractables and leachables
• Sterilization compatibility
• Particulate control
• Packaging validation
• Finished-device risk assessment

ISO 10993-1 uses a risk-based approach to the biological safety of medical devices. The complete device, intended contact, contact duration, processing history, and chemical exposure must be considered.

Passing one selected biological test does not make a silicone compound suitable for every medical application.

Pharmaceutical Components

Pharmaceutical contact requires more than clean appearance and low odor. The component may contact a drug for a long period and can affect stability, delivery, or container-closure integrity.

Possible silicone components include:

• Processing tubing
• Transfer hoses
• Pump diaphragms
• Filling-system gaskets
• Valve parts
• Sealing components
• Device interfaces
• Selected closures

Qualification may include:

• Extractables and leachables
• Drug compatibility
• Adsorption or absorption
• Particle release
• Sterilization resistance
• Container-closure integrity
• Functional testing
• Dimensional compatibility
• Traceability
• Change control

USP chapters <381> and <382> may apply to elastomeric components and the functional suitability of parenteral packaging or delivery systems. Their use depends on the exact component and packaging system.

Platinum curing can reduce peroxide-related residues, but it cannot replace pharmaceutical compatibility and system testing.

Industrial Components

Peroxide-cured silicone is often practical for:

• Industrial seals
• HVAC gaskets
• Extruded profiles
• Oven seals
• Electrical insulation
• Cable components
• Machinery covers
• General silicone tubing
• Sponge gaskets
• Protective boots
• Vibration pads
• Calendered sheets

Platinum-cured silicone becomes attractive when the industrial component requires:

• Low odor
• High transparency
• Fast automated molding
• Thin precision sections
• Low-flash production
• Controlled volatiles
• Clean surfaces
• Overmolding onto a qualified substrate

Application Selection Matrix

Application	Preferred Starting Direction	Main Reason	Required Validation
General molded industrial gasket	Peroxide-cured HCR	Economical and widely processable	Compression, aging, and leakage
Industrial extruded profile	Peroxide-cured HCR	Practical extrusion process	Dimensions, cure, and recovery
Silicone sponge seal	Peroxide-cured HCR	Established foaming process	Density, cells, absorption, and compression
Clear beverage tubing	Platinum-cured silicone	Transparency and low odor	Food contact, extraction, and pressure
Precision LSR valve	Platinum-cured LSR	Thin geometry and automated molding	Leakage, opening pressure, and cycle life
Medical connector	Qualified platinum HCR or LSR	Controlled formulation and precision	Biological and functional evaluation
Pharmaceutical contact part	Application-specific qualified material	Controlled extractables and supply	Chemical, system, and functional testing
Low-volume molded component	Peroxide-cured HCR	Lower entry cost	Material and finished-part tests
High-volume precision part	Platinum-cured LSR	Fast automated production	Tooling and process capability

How Should Cost, Tooling, MOQ, and Production Risk Be Compared?

Raw-material price does not show the real production cost. Labor, cycle time, deflashing, post-curing, inspection, contamination control, and scrap can change the final result.

Peroxide-cured HCR often has lower material, tooling, and equipment entry costs. Platinum-cured HCR and LSR may cost more to implement, but faster curing, automation, low flash, and reduced secondary work can lower unit costs at suitable production volumes.

Compare Total Production Cost

I compare cost through the complete manufacturing route:

1. Silicone compound
2. Curing agent or catalyst
3. Pigment and additives
4. Mixing and preparation
5. Tooling
6. Machine setup
7. Molding or extrusion cycle
8. Labor
9. Scrap
10. Deflashing
11. Post-curing
12. Cleaning
13. Inspection
14. Testing
15. Packaging
16. Compliance documentation
17. Production risk

A platinum catalyst is expensive, but its price alone does not determine the finished-part cost. A stable LSR process may reduce cycle time, manual loading, flash removal, and material waste.

A lower-priced peroxide compound can become more expensive if the part needs long post-curing, heavy deflashing, repeated cleaning, or extra odor inspection.

Tooling Differences

Peroxide-cured HCR compression molds are often practical for prototypes, low-volume projects, large components, thick sections, and parts that may still require design changes.

Possible benefits include:

• Lower initial tooling investment
• Easier sample production
• Practical design modification
• Flexible production quantity
• Suitability for large molded parts

However, compression molding may require more labor, preform preparation, flash removal, and manual inspection.

Precision LSR molds may require:

• Cold-runner technology
• Balanced cavity design
• Accurate venting
• Needle shut-off systems
• Vacuum control
• Stable thermal control
• Automated demolding
• Tight tooling tolerances
• Insert-handling equipment

This investment can be justified for stable designs and high annual quantities. It may not be economical for an uncertain or low-volume project.

Platinum-cured HCR does not always need LSR tooling. It can use conventional HCR processing when the compound and part design support it.

What Determines MOQ?

MOQ can be affected by:

• Minimum raw-material package
• Custom compound batch size
• Custom color requirements
• Peroxide or catalyst preparation
• LSR A/B package size
• Extrusion line setup
• Mold setup
• Post-curing oven loading
• Controlled-area preparation
• Inspection cost
• Packaging quantity
• Compliance testing
• Sterilization batch
• Traceability requirements

A standard translucent peroxide-cured compound may support a lower MOQ than a custom-colored platinum-cured medical compound.

I do not assign one general MOQ to either curing system. The compound, color, geometry, process, first order, annual volume, and testing requirements must be reviewed.

Production Risk Comparison

Cost or Risk Area	Peroxide-Cured HCR	Platinum-Cured HCR	Platinum-Cured LSR
Raw compound cost	Often lower	Often higher	Often higher
Basic tooling entry	Often lower	Moderate	Usually higher
Equipment investment	Standard HCR equipment	Controlled HCR equipment	Metering and LSR injection equipment
Cycle time	Process dependent	Often shorter	Suited to fast automation
Manual labor	Often higher	Moderate	Can be low
Flash removal	Often required	Process dependent	Can be very low
Post-curing	Common	Application dependent	Application dependent
Cure-inhibition risk	Lower	High	High
Cross-contamination control	Standard control	Strict control	Strict control
Low-volume suitability	Strong	Possible	Often limited by tooling cost
High-volume suitability	Strong with automation	Strong	Very strong for suitable parts
Design-change cost	Often moderate	Moderate	Can be high after precision tooling
Compliance cost	Application dependent	Application dependent	Application dependent

A Practical Selection Checklist

Part and Process

• Is the component molded, extruded, calendered, or foamed?
• Is HCR or LSR better for its geometry?
• Is the wall thin, thick, hollow, or highly detailed?
• Does the part contain metal, plastic, fabric, or adhesive?
• Can the insert or substrate inhibit platinum curing?
• Is low flash essential?
• Can the part be demolded automatically?

Performance

• What hardness is required?
• What tensile and tear properties are needed?
• What compression set is acceptable?
• How much sealing force must remain?
• Is the component static or dynamic?
• What temperature cycle applies?
• Which exact fluids contact the silicone?
• What service life is required?

Appearance and Cleanliness

• Must the part be transparent?
• Is there an odor limit?
• Are surface deposits unacceptable?
• Is low volatile content required?
• Is the color critical?
• Is controlled packaging required?

Compliance

• Is the component for food, medical, or pharmaceutical use?
• Which destination market applies?
• Which regulations or standards are required?
• Is finished-part extraction testing needed?
• Is a biological safety evaluation required?
• Which sterilization method will be used?
• What traceability and change-control documents are required?

Commercial Information

• What is the prototype quantity?
• What is the first production quantity?
• What is the estimated annual demand?
• Is the design stable?
• What tooling budget is available?
• What delivery schedule is required?

Final Decision Matrix

Main Requirement	Recommended Starting Direction
Economical general industrial molding	Peroxide-cured HCR
Low-volume custom molded component	Peroxide-cured HCR
Standard extrusion or sponge production	Peroxide-cured HCR
Transparent and low-odor component	Platinum-cured silicone
High-volume precision injection molding	Platinum-cured LSR
Thin or complex molded geometry	Platinum-cured LSR
Food-contact application	Qualified platinum system often preferred, but validation is required
Medical application	Qualified medical silicone, often platinum-cured
Pharmaceutical contact	Application-specific material with complete testing
High tear or low compression set	Compare actual compounds, not cure names
Oil, fuel, steam, or chemical exposure	Select by media compatibility before curing system
High contamination risk	Review platinum-inhibition controls before selection

At Julong Rubber, I review the silicone grade, curing system, geometry, tooling, processing method, post-curing, service conditions, and validation plan together. You can send your drawing and application requirements for a custom silicone part review.

Conclusion

Peroxide curing supports economical industrial production, while platinum curing supports clean and precise applications. The final choice still depends on the compound, process, cost, risks, and validation.

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