Shore 50A Silicone Rubber

Shore 50A Silicone Rubber: The Universal Mid-Hardness Grade

Shore 50A is the most widely specified silicone rubber hardness grade. It occupies the center of the practical durometer range, balancing mechanical strength, sealing performance, dimensional stability, and processability in a single formulation. If a silicone product drawing specifies "silicone rubber" without a hardness value, Shore 50A ±5 is the default assumption for general applications.

Shore 50A silicone provides tensile strength of 7–10 MPa and elongation at break of 200–400%, making it strong enough for structural seals while remaining flexible enough for dynamic applications. Tear strength of 18–28 kN/m exceeds the softer Shore 30A grade, and compression set performance is excellent for properly cured platinum grades.

Key Applications

O-rings and face seals: Shore 50A is the standard hardness for silicone O-rings in process equipment, food machinery, and medical devices. The combination of hardness and elasticity provides reliable sealing across a wide range of groove designs and compression percentages (typically 15–25% for static seals).

Keyboard and button membranes: HTV Shore 50A is used for membrane keypads in consumer electronics, industrial control panels, and medical devices. Carbon-loaded conductive variants at Shore 50A provide the tactile response (click force 1–3 N) preferred in most keypad designs.

Baking molds and kitchen utensils: FDA 21 CFR and LFGB-compliant Shore 50A food-grade silicone is the dominant material for flexible baking molds, spatulas, ice cube trays, and reusable food bags. The Shore 50A hardness provides enough rigidity to hold shape while remaining flexible enough for easy demolding.

Automotive HVAC seals and connectors: Shore 50A seals are used in HVAC ducting joints, coolant connector seals, and under-hood cable grommets where moderate sealing force and vibration resistance are needed within the −60 °C to +230 °C operating range.

Industrial gaskets and custom seals: Shore 50A is the default starting point for custom compression gaskets and extruded sealing profiles across process industries including food, pharmaceutical, chemical, and semiconductor manufacturing.

Color and Transparency Options

Shore 50A is available in translucent base compound (suitable for color customization), standard white (FDA-grade titanium dioxide pigmented), and a full range of solid colors using food-grade silicone color masterbatch concentrates. Fluorescent colors for safety and visibility are available. Pantone color matching is offered by most specialty compounders.

Certification Options

FDA 21 CFR 177.2600: Platinum-cured, post-cured grades for food-contact applications — the standard for kitchen products, baking molds, and food processing seals in the U.S.

LFGB §30/§31: German food-contact certification including sensory testing. Required for EU and German market exports.

RoHS Directive 2011/65/EU: Shore 50A silicone base polymer complies; pigments must be verified against the restricted substance list.

USP Class VI: Available on selected platinum-cured pharmaceutical and medical grades.

Specification Checklist

When ordering Shore 50A silicone rubber, specify: Shore hardness (50A ±3 or ±5), tensile strength minimum, elongation minimum, cure system (platinum or peroxide), color and opacity, certification requirements, and post-cure requirement if applicable. For baking mold applications, also specify LFGB status.

Contact us to verify certification documents and request Shore 50A samples for your application.