Elkem Silicone HCRA 4520 20A (HCR) High Consistency Rubber (A-4520-HCRA)

A-4520-HCRA Silicone Gum (Heat Cure HCR, Shore A 20)

A-4520-HCRA is a platinum-cure, high consistency rubber (HCR) silicone gum offering a soft, highly flexible elastomer with excellent physical properties. With a Shore A 20 durometer, it is the softest option in the HCRA series, making it ideal for applications requiring maximum flexibility and comfort while maintaining durability.

Supplied in a gum form, this material allows technicians to sculpt, shape, and laminate directly into the silicone prior to cure. It is dimensionally stable with minimal shrinkage and bonds well to a variety of substrates, supporting a wide range of fabrication techniques.

The material provides a working time of up to 2 hours (at ~65°F), allowing time for processing and detailing. Final cure is achieved through heat, resulting in a resilient, elastic finished product.

Product Features

• Shore A 20 silicone gum for maximum flexibility

• Platinum-cure (addition cure) system

• High consistency (gum) form for sculpting and shaping

• Excellent mechanical properties

• Low to no shrinkage for dimensional stability

• Bonds well to various substrates for lamination

• Heat cure required

Processing Notes

• Supplied as a two-part system (Part A & Part B)

• Mix equal parts thoroughly prior to use

• Two-roll mill required for proper blending and pigment incorporation

Typical Applications

• Sculpted silicone components

• Laminated silicone structures

• Applications requiring soft, flexible elastomers

Physical Properties (Typical)

• Durometer (Shore A): ~20 (range 15–25)

• Tensile Strength: up to ~800 psi

• Elongation: up to ~1000%

• Tear Strength: up to ~190 lb/in

• Appearance: Clear

A soft, high-performance HCR silicone designed for applications requiring flexibility, comfort, and reliable mechanical performance.