All About Liquid Silicone Rubber For Moulding: Specifications, Performance, and Common Uses

Types of Liquid Silicone Rubber for Moulding

With the rising trend of using advanced moulding processes, the variety of Liquid Silicone Rubber (LSR) formulations has expanded significantly. This diversity ensures that manufacturers can select materials tailored to specific performance requirements, regulatory standards, and production efficiency goals. LSR is prized for its thermal stability, flexibility, biocompatibility, and resistance to UV and environmental degradation, making it ideal for high-performance applications across industries such as medical devices, automotive, consumer electronics, and food processing.

The curing method, chemical composition, and additives used in LSR formulations directly impact their mechanical properties, processing behavior, and end-use suitability. Below is a comprehensive overview of the most commonly used types of liquid silicone rubber in modern injection and compression moulding.

Platinum-Cured Silicone Rubber

Also known as addition-cure or hydrosilylation-cured silicone, this high-purity LSR uses a platinum catalyst to initiate curing. It does not produce byproducts during vulcanization, resulting in excellent dimensional stability and clean, precise moulded parts.

Advantages

• Exceptional thermal stability (-60°C to 200°C+)
• High biocompatibility and FDA-compliant for food/medical use
• No harmful byproducts during curing
• Excellent tensile strength and elongation
• Resistant to UV, ozone, and chemical exposure

Limitations

• Sensitive to contamination (e.g., sulfur, amines)
• Higher material cost compared to peroxide-cured options
• Requires precise mixing and metering equipment

Best for: Medical implants, baby care products, food-grade seals, and precision electronic components

Heat-Cured (Peroxide-Cured) Silicone Rubber

Also referred to as free-radical cured silicone, this type uses organic peroxides as initiators and requires heat (typically 100–180°C) to complete the cross-linking process. It may produce minor byproducts, which must be vented during curing.

Advantages

• Lower material and processing costs
• Good mechanical properties and tear resistance
• Less sensitive to contaminants than platinum-cured LSR
• Suitable for thick-section parts

Limitations

• Byproducts (e.g., odorous volatiles) require post-curing
• Not suitable for direct food or medical implant applications
• Slightly lower temperature resistance over time

Best for: Automotive gaskets, industrial seals, technical components, and non-critical consumer goods

Two-Part Liquid Silicone Rubber

A versatile formulation consisting of two components (Part A: base polymer with catalyst; Part B: cross-linker) that are mixed before curing. The reaction begins immediately upon mixing, allowing for room-temperature vulcanization (RTV) or accelerated heat curing.

Advantages

• Room-temperature or low-heat curing options
• Excellent flow and mold-filling capabilities
• Customizable pot life and cure speed
• Ideal for complex geometries and encapsulation
• Widely used in prototyping and small-batch production

Limitations

• Precise mixing ratio required (typically 1:1)
• Limited working time after mixing (pot life)
• May require degassing to remove air bubbles

Best for: Prototyping, electronics encapsulation, dental impressions, and custom mould making

Self-Releasing Silicone Rubber

Engineered with internal mold-release additives (e.g., waxes or low-surface-energy compounds), this LSR reduces adhesion between the cured part and the mould surface, enabling faster demolding without external sprays.

Advantages

• Significantly reduced cycle times
• Eliminates need for external release agents
• Improves production consistency and part finish
• Reduces maintenance and cleaning of moulds
• Enhances automation compatibility

Limitations

• Potential for additive migration over time
• Higher material cost than standard LSR
• May affect surface energy for secondary bonding or painting

Best for: High-volume manufacturing, automotive components, consumer appliances, and intricate parts prone to sticking

Expert Tip: When working with platinum-cured silicones, ensure all tools and moulds are free from contaminants like sulfur-based rubbers or amine-containing materials, as these can poison the catalyst and lead to incomplete curing.

Production Insight: Self-releasing LSRs can improve production efficiency by up to 20% in high-cycle operations by reducing demolding time and eliminating the need for manual spray applications of release agents.

Important Features of Liquid Silicone Rubber for Moulding

Liquid Silicone Rubber (LSR) is a premium elastomer widely favored in precision manufacturing due to its exceptional physical, thermal, and chemical properties. Its two-part, platinum-cured formulation enables high consistency, excellent flow characteristics, and reliable curing—making it ideal for injection molding complex, high-performance components across critical industries such as medical, automotive, electronics, and food processing.

Key Properties and Industrial Advantages

High-Temperature Resistance

LSR demonstrates outstanding thermal stability, capable of withstanding continuous exposure to temperatures up to 250°C and short-term peaks exceeding 300°C without degradation. Unlike many conventional rubbers, LSR does not harden, crack, or lose elasticity under extreme heat.

This resilience makes it ideal for high-heat environments such as engine compartments, exhaust systems, and kitchen appliances like baking mats and oven seals. Its ability to maintain structural integrity under thermal cycling also ensures long-term reliability in demanding applications.

Chemical Stability

LSR is highly inert and exhibits excellent resistance to a broad range of chemicals, including aliphatic and aromatic hydrocarbons, weak acids, bases, and oxidizing agents. It remains unaffected by prolonged exposure to oils, greases, detergents, and many industrial solvents.

This chemical inertness is crucial for seals, gaskets, and diaphragms used in automotive fuel systems, chemical processing equipment, and pharmaceutical machinery, where material breakdown could lead to contamination or system failure. Additionally, LSR does not support microbial growth, enhancing its suitability in sterile environments.

Flexibility and Durability

One of LSR’s most valued traits is its ability to maintain flexibility across an extremely wide temperature range—from as low as -50°C to over 200°C. It can undergo repeated compression, stretching, and flexing without permanent deformation or fatigue.

This makes it perfect for dynamic mechanical components such as seals, bellows, vibration dampeners, and wearable device interfaces. Its high tear strength and low compression set ensure long service life even under continuous stress, reducing maintenance and replacement costs in industrial and consumer applications.

Electrical Insulation

LSR is an excellent electrical insulator with high dielectric strength and low conductivity. It maintains consistent insulation performance even at elevated temperatures and in humid conditions, where other materials may fail.

This property is vital in electronics and automotive sectors—used in connectors, sensor housings, ignition components, and circuit protection devices. Its flame resistance (self-extinguishing when tested per UL94 standards) further enhances safety in high-voltage or high-temperature electrical systems.

Biosafety and Regulatory Compliance

Platinum-cured LSR is biocompatible, non-toxic, and odorless, making it safe for direct contact with food, skin, and mucous membranes. It meets stringent regulatory standards including FDA 21 CFR, USP Class VI, ISO 10993, and REACH/ROHS compliance.

These certifications allow its use in medical devices (e.g., catheters, implants, respirator masks), baby care products (e.g., bottle nipples), and food-grade kitchenware (e.g., molds, seals). The absence of plasticizers and sulfur compounds eliminates leaching risks, ensuring long-term safety and product purity.

Precision Molding Capabilities

Due to its low viscosity in the uncured state, LSR flows easily into intricate mold cavities, enabling the production of thin-walled, complex geometries with tight tolerances. It replicates fine surface details with high accuracy, making it ideal for micro-molded parts in medical and electronics fields.

The material cures rapidly under heat and pressure, supporting high-volume automated production. With minimal shrinkage and excellent demolding characteristics, LSR reduces defects and increases yield rates—key advantages in cost-sensitive, high-precision manufacturing environments.

Why Choose LSR for Your Molding Needs?

Note: While LSR offers exceptional performance, proper mold design, processing parameters (temperature, pressure, curing time), and material handling are essential to achieving optimal results. Always consult with material suppliers and mold engineers to ensure compatibility with your application requirements and manufacturing setup.

Commercial Uses of Liquid Silicone Rubber for Moulding

Liquid Silicone Rubber (LSR) has become a cornerstone material in modern manufacturing due to its exceptional combination of flexibility, durability, thermal stability, and biocompatibility. Its unique properties make it ideal for high-precision injection moulding processes across a wide range of industries. As demand for reliable, safe, and long-lasting components grows, LSR continues to replace traditional materials in both everyday and highly specialized applications.

Medical and Healthcare Products

LSR is a preferred material in the medical device industry due to its platinum-cure formulation, which ensures high purity and biocompatibility—critical for products that contact human tissue or fluids. It meets stringent regulatory standards such as ISO 10993 and USP Class VI, making it safe for implantable and disposable devices.

• Used in life-saving implants like pacemaker seals, breast implants, and drug delivery systems due to its inertness and resistance to bodily fluids
• Manufactures catheters, respiratory masks, and endotracheal tubes that require soft touch, flexibility, and repeated sterilization (autoclaving, gamma radiation, or ethylene oxide)
• Ideal for baby care products such as bottle nipples, teethers, and feeding spoons because it resists bacterial growth and can withstand boiling and dishwasher cleaning
• Enables production of ergonomic surgical tools with non-slip grips that maintain performance under prolonged heat exposure

Key advantage: Maintains structural integrity and comfort over extended use, even when exposed to body heat and moisture

Consumer Goods

Thanks to its food-grade safety, heat resistance, and aesthetic versatility, LSR is widely used in household and personal care items. Its ability to be colored, textured, and moulded into intricate shapes makes it perfect for consumer-facing products.

• Kitchenware such as non-stick baking mats, oven mitts, spatulas, and ice cube trays that can endure temperatures from -50°C to over 200°C
• Personal hygiene products including electric toothbrush seals, facial cleansing brushes, and massage devices requiring waterproofing and skin-safe materials
• Baby products like soothers, bath toys, and bottle valves that must be free from BPA, phthalates, and other harmful chemicals
• High-end accessories such as watch bands, phone cases, and kitchen appliance handles that combine comfort, durability, and design flair

Design benefit: Excellent demoulding properties allow complex geometries and fine details without damaging parts during ejection

Automotive Industry

In automotive engineering, LSR plays a vital role in both engine compartment components and interior features, where reliability under extreme conditions is non-negotiable.

• Produces durable seals, gaskets, and O-rings for engines, transmissions, and HVAC systems that resist degradation from oil, coolant, and road salts
• Used in under-the-hood sensors and connectors requiring long-term stability at temperatures exceeding 150°C
• Manufactures soft-touch interior elements like dashboard buttons, key fobs, gear shift knobs, and steering wheel grips for enhanced user experience
• Supports electric vehicle (EV) innovation with battery pack seals and charging port components that ensure safety and weather resistance

Performance edge: Retains elasticity and sealing capability across wide temperature swings—from Arctic winters to desert summers

Industrial Applications

LSR’s resilience in harsh environments makes it indispensable in industrial machinery and processing equipment, where downtime and maintenance costs must be minimized.

• Seals and diaphragms in pneumatic and hydraulic systems that resist abrasion, ozone, and chemical exposure
• Gaskets for pumps, valves, and reactors in chemical plants handling aggressive solvents and acids
• Components in food and beverage processing equipment that meet FDA and EHEDG hygiene standards
• Vibration dampeners and insulation parts in heavy machinery operating under constant stress

Cost-saving benefit: Extended service life reduces replacement frequency and unplanned shutdowns

Electronics and Electrical Components

As electronic devices become smaller, more powerful, and increasingly exposed to environmental hazards, LSR provides critical protection and functionality.

• Serves as an encapsulant for sensitive circuitry, protecting against moisture, dust, thermal shock, and mechanical impact
• Used in membrane switches, keypads, and tactile buttons for appliances, medical devices, and industrial controls due to its excellent rebound and conductivity control
• Enables miniaturization through precision micro-moulding—capable of producing features down to 0.1 mm with tight tolerances
• Provides electrical insulation in high-voltage applications while maintaining flexibility and flame resistance (UL 94 V-0 rated formulations available)
• Used in wearable tech and IoT devices where comfort, durability, and water resistance are essential

Innovation driver: Facilitates the development of next-generation compact, rugged electronics for smart devices and connected systems

Additional Benefits of LSR Moulding

Beyond industry-specific applications, LSR offers universal advantages that enhance manufacturing efficiency and product quality.

• Rapid Curing: LSR cures quickly during injection moulding, enabling high-volume production with cycle times as low as 30 seconds
• Dimensional Accuracy: Low shrinkage (<0.3%) ensures consistent part dimensions and tight tolerances
• Color Stability: Pigments can be uniformly mixed into LSR without affecting performance, allowing for vibrant, fade-resistant colors
• Sustainability: LSR is recyclable, inert, and does not degrade into harmful byproducts, supporting eco-friendly manufacturing
• Automation-Friendly: Compatible with robotic handling and cleanroom environments, ideal for medical and electronics manufacturing

Future outlook: Growing adoption in 3D printing and multi-material overmoulding expands design possibilities

Professional Insight: When specifying LSR for commercial applications, consider not only the material’s physical properties but also the precision of the moulding process. Partnering with experienced LSR moulder who uses closed-loop control systems, cleanroom facilities (for medical/electronics), and rigorous quality testing ensures consistent, high-performance results. For critical applications, opt for medical-grade or high-purity LSR with full traceability and compliance documentation.

Conclusion: Why LSR Is the Material of Choice

Liquid Silicone Rubber stands out as a versatile, high-performance material that meets the evolving demands of modern manufacturing. Its ability to perform reliably in extreme conditions—whether inside the human body, under the hood of a car, or within a smartphone—makes it indispensable across sectors. With ongoing advancements in formulation and processing technology, LSR will continue to enable innovation in product design, safety, and sustainability.

For businesses investing in product development, choosing LSR means investing in durability, regulatory compliance, and customer satisfaction—making it one of the most strategic material decisions in industrial design today.

How to Choose Liquid Silicone Rubber for Moulding: A Comprehensive Buyer's Guide

The demand for high-performance liquid silicone rubber (LSR) is rapidly increasing across industries such as medical devices, automotive, consumer goods, and food-grade applications. As businesses scale production, selecting the right LSR becomes a strategic decision that directly impacts product quality, regulatory compliance, and operational efficiency. This guide outlines the key factors buyers must evaluate when sourcing LSR in bulk to ensure consistent performance and long-term supply chain reliability.

Critical Note: Never compromise on material certification or supplier reliability when working with LSR, especially for regulated industries. Using substandard or uncertified silicone can lead to product recalls, compliance violations, and safety risks.

Key Factors in Selecting the Right Liquid Silicone Rubber

• Quality Standards and Regulatory Compliance

  Ensuring that your LSR meets stringent domestic and international standards is essential, particularly for sensitive applications like medical devices, baby products, and food-contact items. Always verify that the material complies with recognized certifications such as:

  • FDA 21 CFR – Required for food-safe and medical-grade silicones in the U.S.
  • USP Class VI – Ensures biocompatibility for implants and prolonged skin contact
  • ISO 10993 – Biological evaluation of medical devices (critical for healthcare applications)
  • REACH and RoHS – Compliance with EU chemical and environmental regulations

  Ask suppliers for full material test reports (CoA – Certificate of Analysis), including mechanical properties like tensile strength, elongation at break, and tear resistance. A high tensile strength (typically 6–10 MPa or higher) indicates durability under stress, while consistent elongation ensures flexibility without cracking during demolding or use.

• Type of Silicone Rubber: Cure Chemistry Matters

  LSR is available in two primary cure systems—platinum-cured and peroxide-cured—each with distinct advantages depending on the application:

  • Platinum-Cured LSR: Offers superior purity, clarity, and biocompatibility. Ideal for medical devices, baby bottle nipples, wearable tech, and food-grade molds. It cures quickly via addition reaction, produces no byproducts, and allows for precise molding with excellent detail reproduction.
  • Peroxide-Cured LSR: More cost-effective and resistant to extreme temperatures and aggressive chemicals. Best suited for industrial applications like gaskets, seals, and under-hood automotive components. However, it may leave behind odor-causing byproducts and is not recommended for direct skin or food contact unless specially formulated.

  Choose the cure type based on your end-use requirements, regulatory needs, and customer expectations. For consumer-facing or regulated products, platinum-cured LSR is typically the safer and more future-proof choice.

• Consistency in Supply and Manufacturing Control

  Bulk buyers depend on uninterrupted supply chains. A reliable LSR supplier should demonstrate:

  • Vertical integration or tight control over raw material sourcing (e.g., siloxane base, fillers, catalysts)
  • In-house production capabilities with ISO 9001-certified manufacturing processes
  • Batch-to-batch consistency verified through standardized testing protocols
  • Adequate inventory of raw materials to prevent delays due to market shortages
  • Scalable production capacity to accommodate growing order volumes

  Request samples from multiple batches to test for uniformity in viscosity, cure time, and physical properties. Suppliers who offer technical data sheets (TDS) and batch-specific CoAs provide greater transparency and traceability—key for quality assurance and audit readiness.

• Lead Time and Logistics Management

  Even the highest-quality LSR is useless if it arrives late or degraded. Evaluate suppliers based on their logistical reliability:

  • Clear communication of lead times, including production, packaging, and shipping schedules
  • Use of temperature-controlled storage and transport to prevent premature curing or viscosity changes
  • Proper packaging (e.g., sealed drums or cartridges under inert atmosphere) to protect against moisture and contamination
  • Flexible shipping options and partnerships with trusted carriers
  • Contingency plans for disruptions (e.g., natural disasters, customs delays)

  Consider working with suppliers located regionally to reduce transit time and carbon footprint. Also, clarify whether shipping, insurance, and import duties are included (DDP terms) or if you’ll manage them (EXW/FCA). Poor logistics planning can result in material degradation, production downtime, and missed deadlines.

Expert Tip: Before committing to a large order, request a small trial batch to test in your molding process. Evaluate flow behavior, demolding ease, surface finish, and final part performance. This pilot run can uncover compatibility issues early and save significant costs down the line.

Additional Recommendations for Long-Term Success

• Maintain a relationship with at least one backup supplier to mitigate supply chain risks
• Store LSR in a cool, dry place (ideally 15–25°C) away from direct sunlight and moisture
• Monitor shelf life—most LSR has a 6–12 month window from date of manufacture
• Work closely with your supplier’s technical team for troubleshooting and process optimization
• Stay updated on regulatory changes that may affect material compliance

Selecting the right liquid silicone rubber goes beyond price and availability. It requires a strategic assessment of quality, chemistry, supply stability, and logistics. By partnering with a reputable, transparent supplier and adhering to best practices in material evaluation, businesses can ensure consistent product performance, regulatory compliance, and customer satisfaction in competitive markets.

Frequently Asked Questions About Liquid Silicone Rubber (LSR)

Processing liquid silicone rubber (LSR) can present several technical challenges that directly impact product quality, production efficiency, and consistency. Understanding these issues and their solutions is crucial for manufacturers aiming to achieve optimal performance in high-volume or precision applications.

Common Processing Issues:

• Improper Mould Temperature: If the mould is too cold, the LSR may not flow evenly, leading to incomplete filling or weak seams. If too hot, it can cause premature curing or degradation.
• Under-Curing (Incomplete Cross-Linking): Results in soft, sticky parts that lack mechanical strength and durability. This often stems from insufficient heat, incorrect catalyst levels, or moisture contamination.
• Over-Curing or Premature Curing: Occurs when the LSR cures too quickly, typically due to excessive temperature or incorrect catalyst concentration, leading to flash, tearing during demoulding, or reduced elongation.
• Void Formation or Air Trapping: Caused by poor venting or injection speed, resulting in bubbles or weak spots in the final product.

Effective Solutions:

• Optimize Mould Temperature: Maintain a consistent temperature between 140°C and 200°C (depending on the LSR grade) using precise temperature control systems.
• Select the Right LSR Grade: Choose a formulation tailored to your processing conditions—such as fast-cure, low-viscosity, or high-temperature resistant variants.
• Adjust Catalyst Levels: Fine-tune platinum catalyst concentrations to balance cure speed and working time (pot life).
• Improve Process Control: Use closed-loop monitoring systems for injection pressure, temperature, and timing to ensure repeatability.
• Enhance Venting and Degassing: Design moulds with proper venting channels and consider pre-degassing the LSR before injection.

Collaborating with experienced silicone material suppliers can provide access to technical support, custom formulations, and troubleshooting assistance to overcome these challenges efficiently.

Yes, liquid silicone rubber—particularly platinum-cured LSR—is widely regarded as safe for food contact applications and is commonly used in kitchenware, baby products, medical devices, and food processing equipment.

Why LSR is Safe for Food Contact:

• High Purity: Platinum-cured LSR contains no harmful by-products (such as peroxides or nitrosamines), making it odorless, tasteless, and non-toxic.
• Regulatory Compliance: Many LSR grades are certified by the U.S. Food and Drug Administration (FDA) under 21 CFR 177.2600 and meet EU Regulation (EC) No 1935/2004 for materials intended to come into contact with food.
• Biocompatibility: LSR is also compliant with USP Class VI and ISO 10993 standards, making it suitable for medical and pharmaceutical uses.
• Thermal and Chemical Stability: It resists extreme temperatures (from -50°C to over 200°C) and does not leach chemicals when exposed to oils, acids, or detergents.
• Hygienic Properties: Its smooth, non-porous surface inhibits bacterial growth and is easily cleaned and sterilized using steam, autoclaving, or chemical disinfectants.

When selecting LSR for food-grade applications, always verify that the specific product carries official food safety certifications and is explicitly labeled as “food-safe” or “FDA-compliant.”

Recycling liquid silicone rubber (LSR) is more complex than recycling thermoplastics due to its thermoset nature—once cured, LSR forms permanent cross-linked polymer networks that cannot be remelted or re-molded like conventional plastics.

Challenges in Recycling LSR:

• Cross-Linked Structure: The strong covalent bonds in cured silicone prevent it from being reprocessed through traditional melting methods.
• Contamination: Mixed materials (e.g., metal inserts, plastic overmolding) complicate separation and reduce recyclability.
• Limited Infrastructure: Few recycling facilities are equipped to handle silicone waste, especially post-consumer or mixed industrial scrap.

Emerging Recycling Methods:

• Pyrolysis: High-temperature decomposition in an oxygen-free environment breaks down silicone into reusable silicate compounds and oils.
• Chemical Recycling: Uses solvents or catalysts to depolymerize silicone into raw materials like siloxanes, which can be repurposed in new silicone production.
• Grinding and Repurposing: Cured silicone scraps can be ground into fine powder and used as fillers in construction materials, coatings, or lower-grade rubber products.
• Industrial Take-Back Programs: Some silicone manufacturers offer closed-loop recycling services where off-spec or production waste is returned for reprocessing.

While full circular recycling is still developing, efforts are growing to improve sustainability in the silicone industry. Buyers are encouraged to consult with suppliers or specialized recycling companies to explore responsible disposal and reuse options for silicone waste.

Selecting the appropriate LSR requires a thorough understanding of the application’s functional, environmental, and regulatory demands. The right choice ensures durability, performance, safety, and cost-effectiveness.

Key Factors to Consider:

• Operating Temperature Range: Determine the minimum and maximum temperatures the part will experience. Standard LSR performs well from -50°C to 200°C, while specialty grades can withstand up to 300°C.
• Mechanical Properties: Evaluate required tensile strength, elongation at break, tear resistance, and compression set based on usage (e.g., seals, gaskets, flexible hinges).
• Hardness (Shore A): Choose from soft (10–30 Shore A) for sealing and cushioning to firm (60–80 Shore A) for structural components.
• Transparency and Aesthetics: Opt for clear, translucent, or pigmented LSR depending on visual requirements.
• Regulatory Compliance: Ensure the LSR meets relevant standards such as FDA, USP Class VI, REACH, or RoHS, especially for medical, food, or consumer products.
• Cure Speed and Processing Method: Match the LSR’s pot life and cure time to your production cycle (e.g., high-speed injection molding vs. slow compression molding).
• Adhesion Requirements: Some applications may require LSR to bond to thermoplastics (e.g., overmolding); use adhesive-promoted or self-bonding LSR grades.

Selection Process:

1. Define Application Needs: List all performance, environmental, and compliance criteria.
2. Consult Material Datasheets: Compare technical specifications across multiple LSR suppliers.
3. Request Samples: Conduct prototyping and testing under real-world conditions.
4. Engage with Experts: Work with material engineers or silicone manufacturers to fine-tune selection and processing parameters.

By aligning material properties with application demands, buyers can ensure optimal performance, longevity, and regulatory compliance of their LSR components.