PPS Injection Molding: Properties, Process, Applications & Design Guide

Table of Contents

1. Introduction

2. What is PPS (Polyphenylene Sulfide)?

3. Properties of PPS for Injection Molding

4. PPS Injection Molding Process

5. Design Considerations for PPS Injection Molded Parts

6. Applications of PPS Injection Molding

7. PPS vs Other Engineering Plastics

8. How to Choose a PPS Injection Mold Manufacturer

9. Conclusion

1. Introduction

PPS injection molding is one of the most reliable solutions for producing high-performance plastic parts that must withstand extreme heat, chemicals, and mechanical stress. Polyphenylene Sulfide (PPS) stands out for its excellent dimensional stability, natural flame retardancy, and outstanding electrical insulation.

Because of these properties, PPS is widely used in automotive, electronics, industrial, and aerospace applications where standard plastics like ABS, PA66, or PBT cannot meet performance demands. Offering a balance between cost and performance, PPS has become the go-to choice for engineers looking for durable, precision-molded parts.

2. What is PPS (Polyphenylene Sulfide)?

PPS (Polyphenylene Sulfide) is a crystalline, high-performance engineering plastic known for its exceptional thermal stability, inherent flame retardancy, and resistance to aggressive chemicals.

Key Characteristics:

High Heat Resistance: PPS maintains mechanical strength at continuous-use temperatures of 200–240°C.

Chemical Resistance: Resistant to fuels, oils, acids, and bases, even at elevated temperatures.

Dimensional Stability: Extremely low moisture absorption and high stiffness, ensuring precision in molded parts.

Electrical Properties: Excellent insulation and dielectric strength, making it ideal for electrical connectors.

Self-Flame Retardant: Naturally UL94 V-0 rated without the need for additional flame retardants.

Limitations:

Brittleness: PPS is stiffer and more brittle than some engineering plastics, requiring careful part design.

Cost: More expensive than PA66 or PBT, though cheaper than PEEK.

Processing Requirements: High processing temperatures and precise mold design are necessary.

3. Properties of PPS for Injection Molding

The performance of PPS molded parts depends heavily on its material characteristics.

Mechanical Properties

• Tensile strength: 80–120 MPa

• Flexural modulus: 8–12 GPa

• Impact strength: Moderate, often enhanced with glass fiber reinforcement

Thermal Properties

• Melting point: ~280°C

• Heat deflection temperature: Above 260°C (reinforced grades)

• Continuous use temperature: 200–240°C

Electrical Properties

• High dielectric strength

• Excellent tracking resistance

• Stable insulating performance even in humid or hot environments

Chemical Resistance

• Resistant to hydrocarbons, fuels, acids, alkalis, and solvents

• Not affected by automotive fluids or corrosive gases

• These properties make PPS one of the most stable thermoplastics available for precision injection molding.

4. PPS Injection Molding Process

PPS requires strict control of processing conditions to achieve high-quality parts.

4.1 Material Preparation

PPS has very low moisture absorption but should still be dried at 120–150°C for 3–4 hours before molding to prevent voids or surface defects.

4.2 Molding Parameters

Barrel temperature: 300–330°C

Mold temperature: 120–150°C

Injection speed: Medium to fast, to ensure proper filling of thin-walled parts

Injection pressure: 80–150 MPa, depending on part geometry

Holding pressure & cooling: Proper balance to reduce shrinkage and warpage

4.3 Common Molding Defects & Troubleshooting

Brittleness: Can occur if processing temperature is too low or parts are too thin.

Flash: Due to high fluidity, mold clamping force must be sufficient.

Voids & bubbles: Inadequate drying or poor venting.

Warping: Uneven cooling or poor mold design.

5. Design Considerations for PPS Injection Molded Parts

Design plays a crucial role in achieving the best performance from PPS.

5.1 Wall Thickness

• Uniform wall thickness between 1.0–3.0 mm recommended.

• Avoid sudden thickness changes to reduce stress concentration.

5.2 Draft Angles

• Minimum 0.5°–1° draft for easy demolding.

5.3 Ribs and Bosses

• Ribs should be 50–70% of wall thickness.

• Bosses should include fillets to avoid stress cracking.

5.4 Gate Design

• PPS requires balanced gate placement due to its high fluidity.

• Submarine gates or pin gates are commonly used for small precision parts.

5.5 Shrinkage & Tolerance Control

• Shrinkage rate: 0.1–0.4% (very low, ideal for precision parts).

• Tight tolerances possible with proper mold design.

6. Applications of PPS Injection Molding

PPS is widely used in industries that demand long-term reliability under harsh conditions.

Automotive

• Fuel system components

• Coolant pumps & impellers

• Under-the-hood connectors and housings

Electronics & Electrical

• High-voltage connectors

• Switch housings

• Circuit breaker components

Industrial

• Valves, seals, and pump parts

• Chemical-resistant housings

• High-temperature mechanical components

Aerospace & Medical

• Lightweight structural parts

• Precision electrical insulation

• Medical devices requiring sterilization resistance

7. PPS vs Other Engineering Plastics

Property	PPS	PEEK	PA66	PBT
Heat resistance (°C)	200–240	250–300	120–150	110–140
Chemical resistance	Excellent	Excellent	Moderate	Moderate
Cost	Medium-High	Very High	Low	Low
Dimensional stability	Excellent	Excellent	Moderate	Good
Electrical insulation	Excellent	Excellent	Good	Good

Conclusion: PPS injection molding offers a cost-effective alternative to PEEK while outperforming PA66 and PBT in high-temperature and chemically aggressive environments.

8. How to Choose a PPS Injection Mold Manufacturer

When sourcing PPS injection mold manufacturers, consider the following:

Experience with high-performance polymers: PPS requires special expertise in mold design and process control.

Knowledge of international standards: HASCO, DME, and LKM standards ensure global compatibility.

One-stop service: DFM reports, mold flow analysis, precision mold manufacturing, and molding production under one roof.

Proven track record: Look for case studies or references in automotive and electronics projects.

Partnering with an experienced PPS injection molding supplier ensures consistent quality, reduced lead times, and cost optimization.

9. Conclusion

PPS injection molding has established itself as a leading solution for industries requiring durability, dimensional precision, and resistance to extreme environments. With its outstanding thermal stability, chemical resistance, and electrical properties, PPS is an ideal choice for automotive, electronics, aerospace, and industrial applications.

By understanding the material properties, processing parameters, and design considerations, engineers and manufacturers can unlock the full potential of PPS. Choosing a reliable PPS injection mold manufacturer is the final key step to achieving long-term success in product development.

At Alpine Mold, we specialize in precision mold manufacturing and high-performance plastic injection molding, helping global clients transform complex designs into reality with PPS and other engineering plastics.