Chemical Compatibility of Liquid Silicone Rubber

Silicone Prototyping: Chemical Compatibility of LSR

Liquid Silicone Rubber (LSR) has a unique composition that makes it compatible and non-reactive with numerous chemicals and substances. Understanding LSR’s chemical compatibility helps ensure your products are durable, safe, and reliable. From biocompatibility to durability, you can rely on LSR for components and products that must meet strict requirements.

When prototyping for products that will be used in harsh medical or chemical environments, choosing chemical-compatible LSR for your prototypes is a good first step in testing to ensure your final product will withstand the chemical substances, sterilization and other environmental conditions required.

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What Makes LSR Compatible With Many Chemicals?

LSR has a silicone-oxygen backbone that gives it a higher bond strength than that of carbon-based materials such as polyethene, polycarbonate, polyurethane and others. Its unique composition makes it highly inert to several chemicals and gives it hypoallergenic properties. LSR can resist many substances, while maintaining its structure and reliability even under diverse conditions.

These attributes make LSR an exceptional option for manufacturing resilient silicone components for products used in a variety of industries.

A Detailed Look at LSR’s Chemical Resistance Spectrum

LSR is highly chemical resistant, but its compatibility varies with each chemical. Understanding how LSR interacts with specific chemicals and how various factors can impact its compatibility is important.

Excellent Compatibility

An excellent rating (A) indicates the chemical has little to no effect on LSR. These substances have excellent compatibility with LSR:

Water and alcohols: LSR is highly resistant to ozone, water, and several alcohols, such as ethyl, diacetone, and butyl alcohol.
Bases and acids: LSR is inert to several diluted inorganic bases and can withstand substances such as ammonium hydroxide, barium hydroxide, and diluted acetic acid. It is also highly resistant to diluted inorganic acids such as boric acid, tartaric acid, arsenic acid, sulfuric acid, and acetic acid.
Salts and oils: LSR resists many salt solutions, such as ammonium phosphate, and is compatible with most industry-standard transmission and mineral oils.
Environmental agents: Environmental conditions such as weather, UV radiation, and oxidation have minimal to no impact on LSR.
Bodily fluids: LSR is ideal for medical applications because it is biocompatible and inert to bodily fluids and human tissue.
Natural gas: LSR is an excellent option for components in gas flow systems, as it is highly resistant to natural gas.

Good or Fair Compatibility

A good rating (B) means the chemical has a conditional or minor effect on LSR. Slight discoloration or swelling may occur. A chemical with a fair or limited rating (C) is moderate and not recommended for continuous use. It may lead to swelling, softening or loss of strength. The following chemicals have fair or conditional compatibility (B-C) with LSR:

Acetone: At room temperature, LSR has conditional resistance to acetone. However, continuous use is not recommended.
Concentrated acids: LSR has limited resistance to concentrated sulfuric, nitric, and hydrochloric acids, especially when they are highly concentrated.
Solvents: LSR can tolerate solvents such as toluene, methyl chloride, and methanol under certain conditions, but high temperatures can hinder resistance.

Poor to Severe Compatibility

A chemical with a severe effect rating (D) is not recommended for use. This rating indicates that the chemical will decompose, severely soften, or dissolve the LSR. The following substances have poor to severe compatibility with LSR:

Aromatic hydrocarbons and fuels: LSR is not compatible with kerosene, gasoline, benzol, or benzene. These fuels and hydrocarbons can cause swelling or failure. Fluorosilicone is a safe alternative.
Chlorinated solvents: Chlorinated hydrocarbons have severe incompatibility with LSR.
Strong solvents: Aggressive solvents can degrade LSR’s stable siloxane backbone.

Factors That Impact Compatibility

These factors can impact LSR’s compatibility with chemicals:

Temperature: Extremely high temperatures can increase a chemical’s impact on LSR, making it more prone to degradation. However, LSR generally has a high temperature stability.
Concentration: LSR is more resistant to diluted chemicals than concentrated substances. This is especially true for bases and acids.
Exposure time: Prolonged contact with a chemical can gradually reduce LSR’s resistance.
Application: Service conditions are vital for compatibility. For example, a compound may perform well for a static seal but fail in a dynamic application.

How Does LSR Compare to Other Elastomers?

Consider how LSR compares to these common elastomers:

Natural rubber: Natural rubber is less resistant to harsh chemical environments than LSR. When it comes to LSR versus natural rubber chemical resistance, LSR is less prone to degradation from greases, oils, and strong acids.
Neoprene: Neoprene is typically the preferred elastomer for applications involving greases, oils, and certain solvents. LSR is more resistant to a wide range of chemicals, such as bases and acids.
EPDM: EPDM typically offers excellent resistance to bases, polar solvents, and acids, but LSR has better resistance to several oils and brake fluids.
Polyurethane: LSR offers a higher chemical resistance than polyurethane formulations. However, the full resistance for each material depends on its exact formulation and the nature of the resisted chemical.

Applications for LSR Products

LSR’s exceptional compatibility with diluted inorganic bases and acids makes it ideal for seals, gaskets, plugs and valves in the following applications:

Medical: Healthcare and medical corporations rely on LSR for parts that meet cleanliness requirements and tight tolerances. LSR is the ideal material for medical devices such as respiratory, fluid management, drug delivery, surgical, and wearable healthcare devices.
Food and beverage: The food and beverage products industry uses food-grade LSR for gaskets, seals, and other food-contact components used in their products. It is common in baby products, valves in coffeemakers and beverage dispensing stations, seals, spouts and gaskets in reuseable beverage bottle products, as well as food preparation and storage products.
Automotive: LSR’s flexibility, temperature stability, and resistance to chemicals and other fluids make it perfect for automotive and mobility components that require protection, sealing, and vibration dampening. It is often found in sensor housings, data connectors, and wire harness seals. Electric, hybrid and gas vehicles also use LSR for driving assistance components, batteries and lighting.
Silicone prototypes: Many industries use LSR during prototyping to create low-volume, functional parts that mirror the properties of final mass-produced LSR products.
Water and irrigation systems: LSR’s compatibility with water, UV and ozone substances make it an ideal choice for seals, tubes and bellows in water or irrigation systems.

Contact SIMTEC to Begin Your Next LSR Project

Compatibility data and an LSR design review are crucial for selecting the right elastomer for your products. With an understanding of LSR’s chemical compatibility, and an experienced manufacturing partner that can offer design and prototype support, you can start producing strong, durable products that meet your needs.

With decades of experience, comprehensive project management, strategic quality planning, and a state-of-the-art, ISO-certified manufacturing facility, SIMTEC delivers exceptional results. We provide complete turnkey solutions, customized to meet your exact requirements – end to end support from early design and LSR prototyping and material guidance, to precision high volume LSR injection molding and value-added inline secondary processes.