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Last Updated on August 20, 2026

Platinum cured silicone offers a high-purity curing method for silicone rubber used in demanding food, healthcare and industrial applications. The inherent physical properties of silicone rubber, including its resistance to water and heat, make it suitable for a wide range of products. While peroxide curing has been an industry standard for many years, platinum curing provides a high-purity alternative that can produce stronger, clearer and more aesthetically pleasing silicone products.

Unlike peroxide curing, platinum curing does not produce residuals or volatile byproducts during the addition-curing reaction. This can improve product purity, reduce mold contamination and support applications where transparency, cleanliness and mechanical performance are important.

What Is Peroxide-Cured Silicone?

Platinum cured silicone is silicone rubber that uses a platinum catalyst to initiate an addition-curing reaction. The catalyst initiates a reaction between the Si-H groups of crosslinkers and the vinyl groups of polymers, creating a three-dimensional structure.

Platinum curing is one of the primary methods used to vulcanize, or cure, silicone rubber. The other common method is peroxide crosslinking. Because the curing agents work differently, platinum-cured and peroxide-cured silicone can have different processing characteristics and final properties.

Uses of Silicone Rubber

Silicone rubber is a synthetic elastomer with a range of physical properties that distinguish it from other elastomers. It is known for its excellent mechanical properties, high resistance to heat and flame, ability to repel water and high transparency. These qualities make it a strong choice for applications such as:

• Gaskets and seals for the automotive industry
• Seals, tubes and valves for healthcare instruments and equipment
• Molded and extruded articles that require good transparency

Many industrial applications require silicone in solid form for injection molding, extrusion, compression molding and other processes. High consistency rubber (HCR), a solid form of silicone rubber, contains high-molecular-weight polymers with long polymer chains and must be vulcanized before use.

There are different methods for vulcanizing, or curing, silicone rubber, but two commonly used methods are peroxide crosslinking and platinum-catalyzed addition curing. Because these curing mechanisms differ chemically, they can produce silicone products with different properties and processing characteristics.

What is Peroxide-Cured Silicone?

Peroxide curing is a well-established free-radical curing process that uses organic peroxide at elevated temperatures to cure silicone rubber. It works by chemically crosslinking different polymer chains to form a resilient, three-dimensional lattice.

This method is straightforward and offers processing benefits. The uncured material has an extended shelf life and is not susceptible to catalyst poisons. Peroxide-cured silicone rubber can be processed using standard methods such as:

• Extrusion
• Compression molding
• Transfer molding
• Calendering
• Injection molding

Because of its strength and durability, peroxide-cured silicone rubber is well suited to mechanical rubber goods. However, peroxide curing has limitations. The process can leave residuals and generate byproducts, which can limit its suitability for certain food-grade and medical applications.

Grades of Peroxide-Cured Silicone Rubber

Peroxide-cured silicone rubber is available in different grades with characteristics designed to address specific application requirements, including:

• High strength
• High heat resistance
• Low-temperature resistance
• Electrical conductivity or insulation
• Tear resistance

WACKER offers a range of peroxide-cured HCR grades marketed as ELASTOSIL® R.

The ELASTOSIL® R 401 series consists of general-purpose silicone grades featuring good flexibility, high transparency and good mechanical properties. They are typically used to produce molded, extruded or calendered articles such as seals, gaskets, sheets, tubing and profiles, as well as automotive parts, ignition and battery cables**,** and cables for household appliances.

The ELASTOSIL® R 420 and R 427 series build on the characteristics of the R 401 series with high tear resistance and high transparency. Applications include molded parts, profiles and vibration-damping components.

Other grades offer low compression set, high rebound resilience and high heat resistance. For example, ELASTOSIL® R 770/75 is a peroxide-cured HCR silicone intended for manufacturing flame-retardant products.

What are the Benefits of Platinum Cured Silicone

Platinum curing, also known as addition curing, offers several advantages when purity, transparency and mechanical performance are important.

High Purity and No Curing Byproducts

One of the biggest advantages of platinum cured silicone is the purity of the curing process. Unlike peroxide curing, platinum-catalyzed addition curing does not produce residuals or byproducts. This can help prevent mold contamination and improve manufacturing productivity. The curing process is also fast, with the cure rate controlled by temperature.

Suitable for Food and Healthcare Applications

Platinum-catalyzed addition reactions do not produce odor- or flavor-impairing byproducts, an important consideration for food and beverage applications.

Because platinum cured silicone does not release volatile curing byproducts, it is often preferred for certain healthcare and food-contact applications, including pharmaceutical and medical-technology tubing, as well as seals, valves, filters and membranes for respiratory equipment. Suitability and regulatory compliance depend on the specific silicone grade, processing conditions and application requirements.

Greater Transparency

Platinum cured silicone rubber is highly transparent and resists discoloration after curing. In comparison, peroxide-cured HCR can have a slightly hazy appearance, which may interfere with visual inspection of applications such as tubing.

High Mechanical Strength

Products manufactured from platinum cured silicone rubber can provide higher tensile and tear strength than comparable peroxide-cured materials, making platinum curing useful when mechanical performance is an important consideration.

Platinum Cured Silicone vs. Peroxide-Cured Silicone

The primary differences between platinum cured silicone and peroxide-cured silicone involve the curing mechanism, byproducts, purity, transparency and processing characteristics.

The best curing system depends on the application’s performance requirements, manufacturing process and applicable regulatory requirements.

What Grades of Platinum Cured Silicone Are Available?

WACKER offers a range of platinum cured silicone grades marketed as ELASTOSIL® R plus 4305. These are addition-curing, two-component high consistency silicone rubbers used to manufacture molded or extruded parts.

Cured parts offer excellent transparency and good mechanical properties. Applications include baby care, dairy and food products, profiles, tubing and sanitary products. When properly post-cured, these vulcanizates comply with applicable BfR and FDA food-contact requirements identified for these grades.

How Are Platinum Catalysts Selected?

The platinum catalyst is added later in the mixing process. Depending on the processing method, the formulator can select either the AUX PT 1 or AUX PT 2 catalyst.

• AUX PT 1: A faster-curing catalyst typically used for extrusion, where line speed and dimensional stability are important. The approximate dosage is 1.5 phr.
• AUX PT 2: A slower-curing catalyst used for molded applications. The slower cure allows uncured rubber to flow and fill the mold cavity before curing. AUX PT 2 is also added at approximately 1.5 phr.

Selecting the appropriate catalyst allows manufacturers to match the curing behavior of platinum cured silicone to the requirements of extrusion or molding processes.

How Do You Choose Between Platinum and Peroxide Curing?

Choosing between platinum cured silicone and peroxide-cured silicone depends on the finished product and manufacturing requirements. Platinum curing may be preferred when an application requires high purity, excellent transparency, minimal curing byproducts or high tensile and tear strength. It is also well suited to appropriate food, beverage and healthcare applications.

Peroxide curing remains a practical option for many mechanical rubber goods and provides advantages such as good uncured shelf life and resistance to catalyst poisoning.

Manufacturers should evaluate the required physical properties, processing method, regulatory requirements and end-use environment before selecting a silicone grade and curing system.

Read more about the solid silicone rubber offered by WACKER at   or  to discuss your application and to find the right HCR to meet your specifications.

Find the Right Platinum Cured Silicone for Your Application

The right silicone curing system depends on your processing requirements, desired physical properties and end-use application. H.M. Royal supplies Solid silicone rubber (HTV) – Wacker Chemie AG , including platinum cured silicone grades for demanding molded and extruded applications. Contact H.M. Royal at (800) 826-8175

Frequently Asked Questions About Platinum Cured Silicone

What is platinum cured silicone?

Platinum cured silicone is silicone rubber cured through a platinum-catalyzed addition reaction. The platinum catalyst initiates crosslinking between the silicone polymer and crosslinker to create the cured three-dimensional structure.

What are the advantages of platinum cured silicone?

Platinum cured silicone offers high purity, excellent transparency and strong mechanical properties. The curing reaction does not generate residual or volatile byproducts, which can reduce mold contamination and make appropriate grades suitable for demanding food, beverage and healthcare applications.

What is the difference between platinum cured and peroxide-cured silicone?

The primary difference is the curing mechanism. Platinum cured silicone uses a platinum-catalyzed addition reaction, while peroxide-cured silicone uses organic peroxide and free-radical crosslinking. Platinum curing does not generate curing byproducts, while peroxide curing can leave residuals. Platinum-cured silicone can also provide greater transparency and higher tensile and tear strength.

Is platinum cured silicone food safe?

Certain platinum cured silicone grades are designed for food-contact applications. For example, properly post-cured ELASTOSIL® R plus 4305 vulcanizates can comply with applicable BfR and FDA food-contact requirements. Always verify that the specific silicone grade and processing conditions meet the requirements of the intended application.

Why is platinum cured silicone used for medical applications?

Platinum cured silicone does not release volatile curing byproducts and can provide excellent transparency and mechanical properties. These characteristics make appropriate grades useful for applications such as pharmaceutical and medical-technology tubing, seals, valves, filters and respiratory-equipment membranes.

Can platinum cured silicone be extruded or molded?

Yes. Platinum cured HCR can be used to manufacture extruded and molded parts. Catalyst selection can be matched to the process: faster-curing AUX PT 1 is typically used for extrusion, while slower-curing AUX PT 2 allows material to flow and fill a mold before curing.