Guide to Mold Steel Selection for PPSU Materials

PPSU (Polyphenylsulfone) is a high-performance engineering plastic with excellent heat resistance, chemical resistance, impact strength and biocompatibility, widely used in medical, baby products, automotive and electronic fields. However, PPSU requires harsh processing conditions: melting temperature 340–400°C, mold temperature 160–200°C. It releases corrosive gas at high temperatures and becomes highly abrasive when glass fiber reinforced. Improper mold steel selection leads to corrosion, wear, short service life and poor product appearance. Therefore, mold steel must be selected based on material characteristics, product requirements and production volume.

Mold Steel for Unfilled PPSU (Cost-Effective Choice)

For standard non-reinforced PPSU products, premium hot-work tool steels are preferred.8407 / SKD61 / H13 (1.2344) are the most widely used. After heat treatment, hardness reaches HRC48–52, with excellent thermal stability and fatigue resistance. Deep nitriding (0.1–0.2mm) is required to resist corrosion. Service life reaches 500,000–1,000,000 cycles, suitable for mass production.

Mold Steel for Glass Fiber Reinforced PPSU (High-Wear Applications)

Glass fiber reinforced PPSU causes severe abrasive wear. High-hardness, high-wear-resistant steels are required.VIKING / 1.2379 (D2) with hardness HRC58–62 provides outstanding wear resistance. For high-volume production, ASP23 powder metallurgy high-speed steel (HRC60–64) is recommended, with service life over 2,000,000 cycles. TD coating or PVD coating is highly recommended.

Mold Steel for High-Precision PPSU (Medical & Food Grade)

Medical, food-contact and baby products require high cleanliness, corrosion resistance and mirror finish.S136 / S136H / STAVAX stainless steel is the best choice. High chromium content provides excellent corrosion resistance; it can be polished to mirror level (Ra ≤ 0.015μm). Hardness HRC48–54 ensures stability at high temperatures. It is the first choice for high-end transparent and medical PPSU products.

Key Selection Guidelines

Hardness: Maintain HRC48–54 for all PPSU molds.

Surface treatment: Nitriding for general molds; TD/PVD for fiber-reinforced grades.

Material matching: 8407/SKD61 for standard parts; D2/ASP23 for high glass fiber; S136 for medical and mirror applications.

Avoid low-grade steels such as P20 and 45# steel, which cannot withstand high-temperature PPSU molding.

Conclusion

PPSU’s high-temperature, corrosive and abrasive characteristics require mold steels with excellent heat resistance, corrosion resistance and wear resistance. Correct steel selection and proper surface treatment ensure product precision, extend mold life, reduce maintenance costs and support stable, high-volume production.