PEEK Injection Molding Guide

How to Successfully Injection Mold PEEK (Polyether Ether Ketone) Engineering Plastic?

If plastic materials are considered a performance pyramid, PEEK (Polyether Ether Ketone), a member of the PAEK (Polyaryletherketone) family, clearly sits at the top. As a high-performance thermoplastic, PEEK stands out with superior comprehensive properties. However, in some niche markets, its advantages can still be challenged.

Let’s explore the characteristics of PEEK and how to achieve optimal results in its injection molding process.

What is PEEK?

PEEK is a semi-crystalline, high-performance engineering thermoplastic known for:

• Exceptional mechanical strength

• Chemical resistance

• Wear resistance

• Dimensional stability

• Heat resistance up to 260°C

Originally synthesized in 1972 and commercialized in 1980, PEEK has since become a standard in aerospace, medical, and industrial sectors.

Top 10 Benefits of PEEK Engineering Plastic

1. Outstanding Heat Resistance

• Melting point: 343°C

• Continuous use: 260°C

• Short-term performance: 300°C–400°C

• Maintains strength after 3000 hours at 250°C

2. Superior Mechanical Properties

• High tensile strength (90 MPa+)

• Maintains flexural strength at 200°C–250°C

• Excellent fatigue resistance, impact strength, and stiffness

3. Exceptional Wear Resistance

• Self-lubricating properties

• Low friction coefficient

• Suitable for sliding and rolling wear

4. Excellent Chemical Resistance

• Resists most acids, bases, oils, and organic solvents

• Nearly inert, except to concentrated sulfuric acid

5. Radiation Resistance

• Can withstand up to 1100 Mrad

• Suitable for gamma and e-beam sterilization in medical use

6. Hydrolysis Resistance

• Resists hydrolysis in high-pressure steam and seawater

• Tolerates 1500+ autoclave cycles at 134°C

7. Flame Retardancy

• UL 94 V-0 rating

• LOI (Limiting Oxygen Index): 35

• Low smoke and toxicity

8. Electrical Insulation

• Stable dielectric properties across a wide temperature range

• Dielectric constant: 3.2–3.3

• Dielectric strength: 17 kV/mm

9. Biocompatibility

• FDA-approved for long-term implants

• Non-toxic and compatible with human tissue

10. Dimensional Stability

• Low coefficient of thermal expansion

• Size stability comparable to aluminum

Injection Molding Requirements for PEEK

1. Injection Parameters

• Pressure: 70–140 MPa

• Speed: Medium to High

• Back pressure: 0–1.0 MPa

2. Screw Design

• L/D ratio: 18:1 to 24:1 (minimum 16:1)

3. Injection Machine

• Must maintain melt temp at 360–400°C

• Barrel capacity: 2–5× the shot weight

4. Nozzle & Shut-off System

• Nozzle heater is essential to avoid cold slug

• Prevent drop below 343°C (melt solidifies quickly)

5. Barrel Temperature

• Unfilled grades: 360–380°C

• Filled grades: 380–400°C

• Use ceramic heaters and barrel zone cooling (70–100°C)

6. Mold Temperature

• Surface temp: 175–205°C (up to 220°C)

• Use high-temp grease and H13/8407 mold steel

• Mold insulation plate (>8mm), heated with thermal oil

7. Mold Design

• Sprue >4mm; gate ≥1mm (pure) or ≥2mm (filled)

• Use round or trapezoidal runners; high-temp self-lubricating guide pillars

8. Drying Requirements

• Dry at 150°C for 3h or 160°C for 2h

• Keep clean to avoid contamination (PEEK degrades at high temps)

9. Thermal Stability & Shutdown Handling

• ≤1h stop: hold at 360°C

• 1–3h stop: reduce to 340°C

• 3h stop: clean with PSU, PEI, or low MFI polyethylene