The Versatility of Silicone Rubber Extrusions

Silicone rubber bears properties that enable its use in extreme conditions, through exposure to a wide range of chemicals, and even resistance to UV light, without degrading in quality. It is a highly reliable material and can be used in rubber extrusion to produce products that help us advance technology, engineering, and innovation in many industries. Here’s everything you need to know about silicone rubber extrusion.

Introduction to Silicone Rubber Extrusions

Silicone rubber extrusion is the process of shaping silicone rubber into a specific, continuous, uniform shape determined by a cross-sectional hollow known as a profile. The process involves feeding rubber strips or pellets into a machine that gradually heats and softens the rubber and kneads it by shear force until it can be pressed through a uniquely shaped hole (the profile).

The physical process of rubber extrusion is generally the same, no matter the type of rubber. You can find out how it works in our guide, Understanding Rubber Extrusions: A Comprehensive Guide. This article focuses on silicone rubber, how its extruded form is different from raw, natural rubber, and why or when we use silicone rubber over other rubber compounds.

First, let’s examine silicone in more detail.

About Silicone Rubber

Created in 1943, silicone is now widely manufactured worldwide. It is a high-performance elastomer (a material composed of chain-like polymers that can recover its shape when stretched) made up of silicon, carbon, hydrogen, and oxygen.

Unlike natural rubber, which is derived from the latex produced by rubber trees and composed of polyisoprene, which provides high elasticity and tensile strength​, silicone rubber is a synthetic polymer based on silicon that has excellent heat and chemical-resistance properties.

Applications in Various Industries

Silicone’s specific composition and properties make it a better choice for certain products. Here’s a guide to where silicone rubber extrusions are commonly used.

Automotive Industry

Applications: Door seals, hoses, rubber gaskets, vibration-dampening components

• With excellent sealing capabilities

• Extreme temperature resistance

• Durability under harsh conditions

• Long-lasting performance

Medical and Healthcare

Applications: Medical tubing, seals, gaskets, surgical instruments, and healthcare equipment

• Biocompatibility

• Sterility (and ability to withstand repeated sterility)

• Non-toxicity

• Non-reactivity

Electronics

Applications: Insulation for cables and wires, gaskets for electronic enclosures, seals for connectors

• Electric insulation properties

• Durability

• Resistance to heat and electrical interference

Construction and Architecture

Applications: Window and door seals, expansion joints, weatherproofing solutions

• UV stability

• Weather resistance

• Flexibility

• Reliable performance in sealing

Food and Beverage Industry

Applications: Gaskets, seals, tubing for food processing and packaging equipment

• Compliance with food-grade standards

• High-temperature resistance

• Maintains integrity in contact with food

Aerospace and Defense

Applications: Aircraft door seals, window seals, gaskets, vibration-dampening components, cable harnesses

• Lightweight

• Durable

• Can withstand extreme temperatures and environmental conditions​.

HVAC (Heating, Ventilation, and Air Conditioning)

Applications: Gaskets and seals in air handling units, ductwork, HVAC enclosures, and refrigeration systems

• Sealing against air leakage

• Temperature resistance

• Flexibility

Industrial and Manufacturing

Applications: Conveyor belts, seals in food processing, pharmaceutical manufacturing, and other industrial equipment

• Temperature resistance

• Chemical resistance

• Resistance to mechanical wear

• Efficient and reliable

Energy and Power

Applications: Sealing and insulating applications in power generation equipment, transformers, switchgear, and electrical enclosures

• Sealing against environmental factors

• Electrical insulation properties

Marine and Offshore

Applications: Seals and protection for boat and shipbuilding, offshore platforms, and marine equipment

• Resistance to saltwater

• Resistance to UV radiation

• Can withstand extreme temperatures

• Reliable performance and longevity

Advantages of Silicone Rubber Extrusions

Silicone rubber bears several key advantages, making it a better choice than other materials. But it depends on what you’re looking for. Here are the benefits of silicone rubber in extrusion.

The most prominent advantage of silicone rubber is its temperature resistance. Thanks to its molecular structure, it remains stable and flexible, which means it can withstand temperatures as low as -60°C up to +230°C without degrading. The same is not the case with natural rubber, which becomes brittle and breaks down. Silicone rubber is a great choice for household objects like oven mitts and specialist items like medical devices that need to be autoclaved. The fact that silicone rubber remains flexible even at very low temperatures means it can be used to create products that need to be malleable in extremely low-temperature conditions.

Strong molecular bonds in silicone rubber's structure make it a highly durable material. Silicone rubber's high durability stems from its silicon-oxygen backbone, which forms strong, stable bonds that resist heat, UV light, and chemicals. In contrast, natural rubber's carbon-based structure is more susceptible to degradation, making silicone rubber superior for more demanding applications and environments.

Silicones are generally chemically inert and are only attacked by some materials, including concentrated sulfuric acid, hydrofluoric acid, and high-pressure steam over long-term exposure. Silicone can absorb materials with similar solubility parameters (a calling card of elastomers), causing slight swelling and softening. This swelling can be advantageous in some applications, like gaskets forming tighter seals when exposed to certain solvents. The changes are mainly physical; silicone rubber returns to its original properties once the solvent evaporates. Meanwhile, silicone’s chemical resistance makes it ideal for products that need to withstand chemical exposure, like medical tubing and seals.

There’s a long list of other advantages to using silicone rubber for extrusion projects.

• Due to its high dielectric strength, silicone rubber is an excellent electrical insulator, which is beneficial for applications in the electrical and electronics industries.

• Thanks to their chemically inert and stable composition, medical and food-grade silicone rubbers are biocompatible, non-toxic, and can be sterilised. This makes them suitable for medical devices, implants, and food-handling equipment.

• Due to their resilient elastomeric network, silicone rubber extrusions exhibit low compression set, meaning they can return to their original shape after compression. This is vital for sealing applications.

• Silicone rubber extrusions can be customised into various shapes, sizes, and profiles due to the material's versatile and adaptable properties, meeting specific application requirements.

• Certain silicone rubber formulations are inherently flame-retardant due to the presence of flame-retardant additives, providing an added level of safety in applications where fire resistance is crucial.

• Because of its viscoelastic properties, silicone rubber can be easily extruded into complex shapes and designs, making the manufacturing process efficient and versatile.

• Silicone rubber does not stain materials it comes into contact with and is generally non-toxic due to its inert nature, making it suitable for sensitive applications.

Differences Between Silicone and Other Rubber Extrusions

Thanks to its unique molecular composition, silicone rubber offers superior temperature resistance, chemical stability, and environmental durability over natural rubber. Because of this, it is ideal for extrusions intended for use in harsh conditions and extreme environments.

A Quick Guide to Rubber Types in Extrusion

Future Trends in Silicone Rubber Extrusions

The properties of silicone rubber combined with ever-evolving developments in the extrusion process have paved the way for innovations in design and manufacturing. Here are three examples of cutting-edge creative endeavours made possible thanks to silicone rubber extrusion.

3D Printing with Silicone Rubber

Wacker Chemie AG developed a 3D printing technology called ACEO® that allows for the additive manufacturing of silicone rubber. This innovation combines traditional extrusion methods with advanced 3D printing techniques to create complex, custom silicone parts layer by layer. Apart from enabling the realistic reproduction of human organs and biocompatible silicone rubber components, applications range from medical devices and prosthetics to automotive components and wearable technology, offering enhanced precision and design flexibility.

Silicone Rubber for Medical Wearables

Companies like MC10 develop soft, stretchable electronics using silicone rubber as a key material. Its BioStampRC® sensor is a wearable device that adheres to the skin using silicone rubber, conforming to the body's contours and providing continuous health monitoring. This innovation is crucial for medical diagnostics, sports performance tracking, and remote patient monitoring, offering comfort and biocompatibility.

A 2018 study on using the BioStampRC® sensor for detecting respiration, cardiac, and limb movement signals during sleep found that it accurately captured respiration, ECG, and leg EMG signals during sleep, comparable to gold standard PSG, with 88% of participants willing to use it at home.

Advanced Silicone Rubber Seals for Hydrogen Fuel Cells

Innovative extruded silicone rubber seals are now being used in hydrogen fuel cell technology. For instance, the seals developed for hydrogen fuel cells in next-generation eco-friendly vehicles are made from specially formulated silicone rubber that can withstand the high pressures and temperatures of hydrogen fuel storage and conversion. These extruded seals ensure the containment and efficiency of hydrogen fuel cells, contributing to the advancement of clean energy technologies.

Find out more about rubber extrusion here and why it’s responsible for many innovations in hundreds of industries. Or take a look at our services in rubber extrusion, creating rubber profiles, rubber fabrications, mouldings, and many more methods for producing bespoke products.