PEEK (Polyether Ether Ketone) Material Overview

Introduction
PEEK (Polyether Ether Ketone) is a linear aromatic high-performance polymer with repeating units of –O–Ph–O–C(=O)–Ph– in its molecular backbone. It is a semi-crystalline thermoplastic and a high-performance specialty engineering plastic with numerous advantages over other specialty plastics.

PEEK has a melting point of 334 °C, a softening point of 168 °C, and a tensile strength of 132–148 MPa. It exhibits excellent mechanical properties, high-temperature resistance up to 260 °C, good self-lubrication, chemical resistance, flame retardancy, peel resistance, wear resistance, and radiation resistance. It can be used in high-end mechanical, nuclear, and aerospace applications. It can also serve as a high-temperature structural material and electrical insulation material, or be compounded with glass fiber or carbon fiber to produce reinforced materials. PEEK is synthesized through a condensation reaction of 4,4′-difluorobenzophenone and hydroquinone in the presence of an alkali metal carbonate, using diphenyl sulfone as a solvent.

Properties of PEEK Resin

PEEK plastic raw materials are aromatic, crystalline thermoplastic polymers with a melting point of 334 °C. They exhibit high mechanical strength, high-temperature resistance, impact resistance, flame retardancy, acid and alkali resistance, hydrolysis resistance, wear resistance, fatigue resistance, radiation resistance, and excellent electrical properties.

High-Temperature Resistance

PEEK resin features a high melting point (334 °C) and a glass transition temperature of 143 °C, with a continuous use temperature of 260 °C. Grades reinforced with 30% glass fiber or carbon fiber have a heat deflection temperature as high as 316 °C.

Mechanical Properties

PEEK resin offers excellent toughness and rigidity. Its fatigue resistance under alternating stress is comparable to that of metal alloys.

Flame Retardancy

Flammability is measured according to UL94 standards, which involves igniting a vertically mounted sample and recording the time taken for it to self-extinguish. PEEK achieves UL94 V-0, the highest flame-retardant rating.

Dimensional Stability

PEEK exhibits outstanding dimensional stability under changing environmental conditions such as temperature and humidity, making it suitable for applications requiring high precision.

PEEK has low injection molding shrinkage, enabling tighter dimensional tolerances than general plastics.
Its low thermal expansion coefficient ensures minimal dimensional changes due to temperature fluctuations.
PEEK maintains stable dimensions under usage and storage, as polymer chain movement is minimal.
Its hydrolysis resistance prevents dimensional changes caused by moisture absorption, unlike common plastics like nylon.

Electrical Insulation

PEEK exhibits excellent electrical insulation properties over a wide temperature range, with low dielectric loss even at high frequencies.

Radiation and Peel Resistance

PEEK resin has good radiation and peel resistance, making it suitable for specialized electrical wires. It can be used in sterilizers and wireless verification systems, providing performance comparable to stainless steel.

Exceptional Performance

• Outstanding high-temperature performance: continuous use up to 250–260 °C, short-term exposure up to 300 °C.
• Very high stiffness, tensile and compressive strength, and impact resistance.
• Excellent flame retardancy: inherent flame retardancy, low smoke and low toxicity.
• Resistant to almost all organic and inorganic chemicals (except highly corrosive agents like fuming sulfuric acid, nitric acid, or dichloromethane).
• High dielectric strength and excellent insulation properties.
• Superior wear resistance and low friction coefficient.

Applications

As a high-performance semi-crystalline aromatic engineering plastic, PEEK can replace metals and ceramics in many demanding applications. Its high temperature resistance, chemical stability, mechanical properties, dimensional stability, low thermal expansion, wear resistance, and self-lubricating properties make it ideal for aerospace, mechanical, petroleum, chemical, nuclear power, and railway industries. Even under 200 °C steam, its tensile strength, mass, and appearance remain stable. It has excellent fatigue resistance under high alternating stress, long-term load-bearing capability, flame retardancy, self-extinguishing property, and environmentally friendly combustion (halogen-free, UL94 V-0, oxygen index 24–35).

PEEK is only soluble in concentrated sulfuric acid and nitric acid; otherwise, it is chemically stable, though insufficiently crystallized PEEK may develop cracks in certain solvents like chlorinated hydrocarbons.

Processing

PEEK can be processed via injection molding, extrusion, blow molding, or compression molding. For small-batch or prototype PEEK components, machining from rods or sheets is preferred. Machining should use carbide or diamond tools due to PEEK's wear resistance. Pre-annealing the material can relieve residual stresses, and post-machining stress-relief treatment is recommended to prevent local stress buildup during processing.

Current Uses

PEEK is widely used in electrical insulation (wires, flexible PCBs), mechanical components, chemical equipment, nuclear engineering, oilfield connectors, valves, heat-resistant or corrosion-resistant coatings, and in sterilizers and wireless verification systems, sometimes serving as a stainless steel alternative. Its exceptional combination of properties continues to make it a high-demand material across multiple advanced industries, including aerospace, automotive, electronics, medical, and food processing.