Liquid Silicone Rubber (LSR) - Material Properties and Processing

Product Specifications

Technical details and manufacturing context for Liquid Silicone Rubber

Definition

Liquid Silicone Rubber (LSR) is a high-purity, two-component silicone elastomer system consisting of a base polymer and a curing agent. It undergoes addition-cure vulcanization via platinum catalysis when heated, transforming from a liquid state into a solid, flexible rubber with excellent thermal stability, chemical resistance, and biocompatibility. It is processed using specialized liquid injection molding (LIM) equipment. LSR is supplied as two liquid components (Part A and Part B) that are precisely metered, mixed, and injected into a heated mold cavity. The heat activates the platinum catalyst, initiating a hydrosilylation addition reaction that cross-links the silicone polymer chains, curing the material without by-products. The cured rubber exhibits a hardness range of 20–70 Shore A (ISO 7619-1), mixed viscosity of 1000–100000 Pa·s (ISO 3219), tensile strength of 5–12 MPa (ISO 37), elongation at break of 300–700% (ISO 37), tear strength of 20–50 kN/m (ISO 34-1), and specific gravity of 1.10–1.20 g/cm³ (ISO 1183-1). Cure temperature typically ranges from 120–180°C with cure times of 1–10 seconds. The material operates continuously from -50°C to 200°C, with short peaks up to 250°C. Electrical properties include dielectric strength of 15–25 kV/mm (IEC 60243-1) and volume resistivity of 1e14–1e16 Ω·cm (IEC 60093). Linear shrinkage is 1.5–3.0% (ISO 294-4), and compression set is 10–30% (ISO 815-1). Available colors range from transparent to black, with custom colors on request. These values are typical ranges; verify model-specific data with the manufacturer.

Working Principle

LSR is supplied as two liquid components (Part A and Part B). These components are precisely metered, mixed, and injected into a heated mold cavity. The heat activates the platinum catalyst within the compound, initiating a hydrosilylation addition reaction. This cross-links the silicone polymer chains, causing the material to cure (vulcanize) from a liquid into a solid elastomer without producing by-products, resulting in a dimensionally stable, high-integrity rubber part.

Common Materials

Polydimethylsiloxane (PDMS) Base Polymer, Cross-linker (typically containing Si-H groups), Platinum Catalyst, Filler (e.g., fumed silica)

Technical Parameters

Parameter	Typical range	Notes & selection driver
HardnessRequired	20–70 Shore A	Durometer measurement of the cured material's firmness.ISO 7619-1
Viscosity (Mixed)Required	1000–100000 Pa·s (or cP)	The flow resistance of the mixed, uncured material, critical for injection molding.ISO 3219
Tensile StrengthRequired	5–12 MPa	Maximum stress the cured material can withstand while being stretched before breaking.ISO 37
Elongation at BreakRequired	300–700 %	The percentage increase in length a cured sample achieves before rupture under tension.ISO 37
Tear StrengthRequired	20–50 kN/m	Resistance to the growth of a cut or nick in the cured material.ISO 34-1
Cure TemperatureRequired	120–180 °C	The mold temperature required to initiate and complete the vulcanization (curing) process.
Cure TimeRequired	1–10 seconds	The duration the material must remain in the heated mold to achieve full cure.
Specific Gravity	1.10–1.20 g/cm³	The density of the cured material relative to water.ISO 1183-1
Operating Temperature Range	-50–200 °C	Continuous service; short peaks up to 250°C
Dielectric Strength	15–25 kV/mm	For electrical insulation applicationsIEC 60243-1
Volume Resistivity	1e14–1e16 Ω·cm	High resistivity for electrical insulationIEC 60093
Linear Shrinkage	1.5–3.0 %	Affects mold design and dimensional accuracyISO 294-4
Compression Set	10–30 %	Lower is better for sealing performanceISO 815-1
Color	Transparent–Black	Custom colors available on request

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Base Polymer (Part A) Part
Contains the primary vinyl-functionalized polydimethylsiloxane (PDMS) polymer and the platinum catalyst.

Material: Polydimethylsiloxane, Platinum Catalyst Complex, Fillers, Pigments
Cross-linker (Part B) Part
Contains the cross-linking agent (typically with Si-H groups) and an inhibitor to control cure onset.

Material: Polymethylhydrosiloxane, Inhibitor, Fillers
Filler Part
Reinforces the polymer matrix, improving mechanical properties like tear strength and modulus.

Material: Fumed Silica, Precipitated Silica
Pigment / Colorant Part
Imparts color to the final cured product. Must be thermally stable and non-inhibiting.

Material: Inorganic Pigments (e.g., iron oxides), Certified Organic Pigments
Additives Package Part
May include heat stabilizers, flame retardants, or other property modifiers specific to the grade.

Material: Various specialty chemical compounds (e.g., platinum catalyst stabilizers, process aids)

Application & selection

Application Fit & Sizing Matrix

Operational Limits

pressure:	Up to 10 MPa (100 bar) depending on hardness and geometry
flow rate:	Viscosity-dependent: 10,000-100,000 mPa·s at 25°C (varies by grade)
temperature:	-60°C to 230°C continuous, up to 250°C intermittent

Media Compatibility

✓ Medical/biological fluids ✓ Food-grade applications ✓ Automotive fluids (coolants, oils)

Unsuitable: Concentrated acids/bases or solvents (ketones, aromatics)

Sizing Data Required

Required hardness (Shore A scale)
Cure temperature/time constraints
Part geometry complexity (mold flow considerations)

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause

Thermal degradation

Cause: Exposure to temperatures exceeding the material's continuous use rating, leading to loss of elasticity, hardening, or cracking.

Chemical incompatibility

Cause: Contact with incompatible fluids (e.g., strong acids, bases, solvents, or certain oils) causing swelling, softening, or structural breakdown.

Maintenance Indicators

Visible surface cracking or crazing, especially at stress points or bends
Audible squeaking or grinding noise during operation, indicating loss of lubrication or internal friction

Engineering Tips

Implement strict temperature monitoring and control systems to prevent operation outside the specified thermal range (typically -60°C to 200°C for most LSR grades).
Establish a chemical compatibility verification protocol before introducing any new fluids or cleaning agents into the system, and use protective coatings or barriers where exposure is unavoidable.

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards

ISO 10993-1: Biological evaluation of medical devices ASTM D2000: Standard Classification System for Rubber Products CE EN 455: Medical gloves for single use

Quoted from the published standard.

Manufacturing Precision

Dimensional tolerance: +/-0.05mm for critical features
Hardness tolerance: +/-5 Shore A

Quality Inspection

Tensile strength and elongation test
Biocompatibility testing (cytotoxicity, sensitization, irritation)

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

Compare the published product scope and source details, then include your specifications and quantity in an enquiry.

Manufacturers of Liquid Silicone Rubber

12 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Hangzhou Bright Rubber Plastic Product Co., Ltd.

Hangzhou, Zhejiang, CN

ISO 9001:2015 IATF 16949

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