How to Select Mold Steels for TPV Products

TPV (Thermoplastic Vulcanizate) has high viscosity, strong flow impact, and contains additives that may cause corrosion or abrasion. Choosing the correct mold steel is critical for service life, surface quality, and production stability. Selection should be based on production volume, appearance requirements, material composition, and cost.

Key Requirements for TPV Molding

TPV places special demands on mold steels:

High wear resistance to resist scouring from high-viscosity melt.

Corrosion resistance against additives and softening oils.

Good polishability for matte, texture, or high-gloss surfaces.

Stable thermal conductivity to reduce shrinkage and internal stress.

Thermal fatigue resistance for continuous long-cycle production.

Selection by Production Volume

Small batch (under 100,000 shots)

Use P20 or 2311 pre-hardened steel. Cost-effective, no heat treatment needed.

Medium batch (100,000–500,000 shots)

Choose 718H or 738H, with better toughness and polishability.

Mass production (over 500,000 shots)

Use H13, S136, or quenched steels for high hardness and long life.

Selection by Appearance and Structure

Matte or textured surfaces: 718H / 738H provides uniform texture adhesion.

High-gloss or mirror parts: NAK80 or S136 for excellent polishing performance.

Complex or thin-wall parts: Steels with high toughness and stability.

Selection by Material Characteristics

Standard TPV: P20 or 718H is sufficient.

Glass-filled TPV: Must use H13, S136, or nitrided steel for wear resistance.

Corrosive or medical-grade TPV: S136 or 2316 stainless steel for anti-corrosion.

Common Mold Steels for TPV

P20 / 2311: HRC 28–32, economical, for low-volume products.

718H / 738H: HRC 32–36, balanced performance, widely used.

NAK80: HRC 38–42, high polish, no heat treatment needed.

H13 / 1.2344: HRC 48–52, high wear resistance for glass-filled materials.

S136 / 1.2083: HRC 48–52, stainless, corrosion-resistant, mirror-capable.

Operation and Maintenance Suggestions

For glass-filled TPV, apply ion nitriding or PVD coating.

Clean the mold after production to avoid residual additive corrosion.

Control mold temperature evenly to reduce deformation and stress.

Regularly check for wear, especially near gates and flow fronts.

Choosing the right mold steel for TPV products balances cost, life, and quality. With proper selection and surface treatment, molds can achieve high efficiency, long service life, and stable product quality.