SILICONE MATERIAL SELECTION RESOURCE
Silicone Materials Library for OEM Engineers & Product Designers
A practical reference guide covering LSR and HCR silicone grades, Shore A hardness selection, temperature performance, and compliance documentation — organized by application requirement, not catalog number.
Wacker · Dow · Shin-Etsu · Elkem · Material TDS available under NDA
Why Material Selection Determines Product Performance
Silicone is not a single material. The wrong grade selection causes compliance failures, mechanical degradation, and costly late-stage engineering changes.
Shore A tolerance must be specified as a CTQ dimension on every drawing
Grade compliance must be confirmed before tooling investment begins
Continuous vs peak temperature must both be specified
Material grade selection errors identified during DFM review cost nothing to fix. The same errors identified after tooling completion cost 10–100x more.
LSR vs HCR: Understanding the Difference
Both are silicone. Both are flexible. Both are heat resistant. But they are processed differently, behave differently, and are right for different applications.
Choose LSR when:
Choose HCR when:
LSR Material Grades by Supplier
We source LSR from four globally certified suppliers. Each brand has specific strengths for different application environments.
WACKER ELASTOSIL®
Medical & General Purpose
Wacker Elastosil series covers the broadest range of LSR applications — from general industrial grades to platinum-cured medical-grade compounds meeting USP Class VI and ISO 10993.
✅ USP Class VI ✅ ISO 10993 ✅ FDA 21 CFR ✅ LFGB
DOW SILASTIC®
High-Purity Medical Grade
Dow SILASTIC grades are among the most widely specified medical-grade LSR materials globally. Particularly strong in implantable and drug-contact applications where biological inertness and extractable/leachable profiles are critical.
✅ USP Class VI ✅ ISO 10993-1 ✅ FDA 21 CFR ✅ EU MDR compatible
SHIN-ETSU KE SERIES
Precision & Electronics
Shin-Etsu KE series offers excellent batch-to-batch consistency and is widely used in precision electronic components, optical applications, and medical devices where dimensional repeatability across high-volume production runs is critical.
✅ USP Class VI ✅ ISO 10993 ✅ FDA 21 CFR ✅ REACH / RoHS
ELKEM BLUESIL™
Industrial & Specialty
Elkem Bluesil offers strong performance in industrial and specialty applications, including self-adhesive grades for overmolding, high-tear-strength compounds for dynamic sealing, and specialty formulations for extreme environment applications.
✅ ISO 10993 ✅ FDA 21 CFR ✅ LFGB ✅ REACH
HCR compression molding is the preferred process for silicone components exceeding 150mm in any dimension, where LSR tooling costs become prohibitive for the required annual production volume.
Shore A Hardness Selection Guide
Shore A hardness is the single most important material parameter to specify correctly. Here is a practical reference for the most common application categories.
| Shore A Range | Tactile Feel | Typical Applications | Key Consideration |
|---|---|---|---|
| 5 – 15 | Gel-like, very soft | Dynamic seals, soft-touch medical interfaces | High tear risk — requires careful demolding design |
| 15-30 | Soft, highly flexible | Baby feeding components, skin-contact seals | Low compression set critical for repeated use |
| 30-50 | Medium-soft | Respiratory mask seals, wearable device interfaces | Most common medical and consumer range |
| 50-70 | Medium-firm | Industrial gaskets, button keypads, valve diaphragms | Good balance of sealing force and durability |
| 70-80 | Firm | Structural seals, high-pressure applications | Flash control becomes more critical at higher hardness |
| 80 – 90 (HCR) | Semi-rigid | Enclosure gaskets, vibration isolation pads | LSR typically not recommended above Shore A 80 |
Important: Shore A hardness must be specified with a tolerance range (e.g., Shore A 40 ± 5) and marked as a CTQ (Critical to Quality) dimension on your technical drawing. Hardness variation beyond ±5 Shore A from specification can cause functional failures in sealing and assembly applications.
Material Recommendations by Application
Matching the right silicone grade to your application environment from the start prevents the most common causes of product development delays.
Peroxide-cured grades are not suitable for medical applications due to residual byproduct migration risk.
EU and US food-contact compliance require different certification pathways — specify your target market early.
Micro-bubble entrapment is the primary production risk for optical LSR — requires vacuum-assisted injection and venting strategy review at DFM stage.
Specify compression set requirements as a percentage under defined test conditions (temperature, time, compression) — not just as a general requirement.
Flame retardant additives are generally not compatible with LSR injection systems — HCR compression molding is the standard process for FR-grade silicone components.
Conductive filler type (carbon vs silver) significantly affects conductivity, cost, and mechanical properties — specify your target resistance range early.
Compliance Quick Reference
The most commonly required silicone material compliance standards — organized by application area and target market.
| Standard | What It Covers | Applicable Application |
|---|---|---|
| FDA 21 CFR 177.2600 | US food-contact silicone rubber | Food contact, medical, maternal care |
| ISO 10993-1 | Biological evaluation of medical devices | Medical devices, implantable components |
| USP Class VI | Pharmaceutical-grade biological reactivity | Medical devices, drug-contact applications |
| LFGB §30/31 | EU food-contact materials | EU food contact, baby products |
| EU Regulation 10/2011 | EU food-contact plastics and elastomers | EU food contact products |
| REACH SVHC | Restriction of hazardous substances | EU market products |
| RoHS | Restriction of hazardous substances in electronics | Electronic components |
| UL94-V0 | Flame retardancy rating | Electrical enclosures, industrial equipment |
| ISO 3302-1 | Dimensional tolerances for rubber | All precision silicone components |
Compliance documentation requirements vary by end product, target market, and regulatory pathway. We provide material COA and compliance documentation for all production batches.
Material Data & Compliance Support
Technical data sheets and compliance documents are provided based on confirmed project requirements, material grade, and application conditions.
Material data sheets are typically provided after project requirements, application conditions, and sample or trial order scope are confirmed. This helps ensure that the recommended silicone grade matches your actual production and compliance needs.
Frequently Asked Questions for Silicone Metarial
A1: Platinum-cured silicone uses a platinum catalyst that leaves no residual byproducts after vulcanization. It is the standard for medical, food-contact, and optical applications where chemical cleanliness is critical. Peroxide-cured silicone leaves volatile organic residues that require extensive post-curing to remove, and even then may not meet medical-grade purity requirements. For any skin-contact, food-contact, or medical application, always specify platinum-cured silicone.
A2: Shore A hardness should be specified as a target value with a tolerance range, marked as a CTQ (Critical to Quality) dimension. For example: Shore A 40 ± 5, tested per ASTM D2240 or ISO 48-4. Specify the test method to ensure consistent measurement across suppliers. Hardness without a tolerance range and test method reference is not a manufacturable specification.
A3: In many cases, yes. Platinum-cured LSR grades meeting USP Class VI and ISO 10993 are typically also compliant with FDA 21 CFR 177.2600 for food contact. However, EU food-contact compliance (LFGB, EU 10/2011) requires separate testing and documentation that is not automatically covered by US medical certifications. If you are targeting both EU and US markets, both compliance pathways need to be confirmed with your material supplier.
A4: Every production batch ships with a material Certificate of Analysis (COA) from the original silicone supplier, including lot number, physical property test results, and compliance confirmation. For medical programs, we additionally provide batch-level production records linking the material lot to specific production dates, machine parameters, and inspection results — enabling full traceability back to the raw material supplier.
A5: The decision depends on three factors: part geometry, annual volume, and performance requirements. Choose LSR when your part requires tight tolerances below ±0.1mm, cleanroom production, weights below 50g, or volumes above 50,000 pieces annually. Choose HCR when your part exceeds 150mm in any dimension, requires flame retardant or conductive compound grades, or when annual volume is below 50,000 pieces and lower tooling cost is the primary constraint. Our engineering team provides material selection recommendations as part of the DFM review process.