Unfilled PEEK, GF30 or CF30: Which grade should you specify?

PEEK identifies the polymer family, not a complete machining-stock specification. Unfilled, glass-fibre-reinforced and carbon-fibre-reinforced grades can behave differently in stiffness, deformation under load, electrical properties and contact surfaces. This guide starts after the PEEK family has been selected; it does not repeat the broader POM-versus-PEEK comparison. In purchasing language, “virgin” may describe non-recycled resin rather than the absence of fillers. Specify unfilled explicitly when that is the design requirement.

Reinforcement can improve stiffness and sustained-load performance, but it does not improve every requirement simultaneously. Use this table to ask design questions, not as guaranteed material data. Compare test method, temperature, direction and duration of loading. A room-temperature tensile value alone can miss the condition that governs the component.

A static support and a sliding bush may need different grades despite identical dimensions. Fibres exposed by machining can affect the mating part. Consider its material and finish together with load, sliding speed and lubrication. Ensinger warns that GF30 may abrade mating surfaces, while its CF30 grade has different friction and heat-transfer advantages. Such guidance does not replace evaluation of the actual contact pair.

Fibres and manufacturing history can make properties direction-dependent. If a critical fit lies in a different direction from the datasheet test specimen, consult the stock supplier instead of applying one expansion coefficient to every axis. Define stock orientation, datums and measurement condition before machining. For close fits, distinguish dimensions during inspection from dimensions under operating temperature and load. Typical properties support initial assessment; they do not guarantee a tolerance for every shape or stock lot.

Reinforcement changes the interaction with the cutting edge and tool wear. Assess tooling, chip evacuation, clamping and edge condition for the actual grade rather than reusing an unfilled-PEEK program unchanged. Look for protruding fibres, chipped edges and rubbing, and inspect dimensions after unclamping and stabilization. If particle shedding or cleanliness matters, define acceptance criteria in advance. A glossy surface alone does not prove functional suitability.

Provide the approved manufacturer and grade, datasheet, stock form, colour requirements if applicable, substitution permissions and lot-traceability documents. State important tolerances, finish, sliding or insulating zones and inspection conditions. Describe temperature, media, load and intended life for design review. VietTech uses this information to assess CNC machining and inspection within its confirmed scope. Availability, special tests and suitability of each grade must be established before order acceptance; no universal stock availability is implied.

Reviewed on 18 October 2026 against Victrex PEEK documentation and Ensinger’s GF30, CF30 and machining guidance. Published material benefits are not performance guarantees for a VietTech component. A grade or stock-source change needs approval from the design authority and a decision on revalidation. Start from function, review the correct product documentation, then confirm the part: colour, price and fibre percentage alone are insufficient selection criteria.