🧪 PEEK

PEEK Machining in Burlington, NC: Unfilled, Glass-Filled, and Carbon-Filled Grades

PEEK — polyetheretherketone — sits at the top of the performance polymer hierarchy, combining a continuous-use temperature of 250 degrees Celsius, chemical resistance to most industrial solvents and hydraulic fluids, and mechanical properties that make it a credible replacement for aluminum and mild steel in bearing, bushing, seal, and structural insulator applications. For Burlington's manufacturing community, PEEK opens design options that reduce part weight, eliminate galvanic corrosion between dissimilar metals, and extend maintenance intervals in heavy-equipment systems exposed to contaminated fluids and elevated temperatures. The three primary grades — unfilled, glass-filled, and carbon-filled — address different performance trade-offs, and choosing correctly matters enormously for application success.

ISO 9001AS9100ISO 13485
Unfilled PEEK in its natural (tan/beige) or extruded rod and plate form is the starting point for evaluating PEEK as a material choice. It offers tensile strength of approximately 14,000 psi, flexural modulus of 550,000 psi, and a continuous service temperature of 480 degrees Fahrenheit in air — properties that comfortably exceed those of most engineering plastics at a fraction of the weight of aluminum. The absence of reinforcing fillers means unfilled PEEK provides the best chemical resistance of the three grades, as there are no glass or carbon fiber interfaces that could act as pathways for fluid infiltration. This makes unfilled PEEK the default choice for seals, valve components, chemical-process pump housings, and any application where contact with aggressive hydraulic fluids, fuels, or cleaning agents is a design requirement. Burlington shops machining unfilled PEEK for automotive and heavy-equipment customers report that it machines similarly to 6061 aluminum in terms of cutting forces and cycle time — sharp carbide or HSS tooling at high speeds and moderate feeds produces clean chips and good surface finish. The critical machining variables are thermal management and fixturing. PEEK has a relatively high coefficient of thermal expansion — roughly 25 to 50 percent higher than aluminum — so aggressive chip loads that generate heat in the workpiece introduce dimensional errors on tight-tolerance features. Conventional flood coolant is acceptable on most grades of PEEK, but misting or air blast is often preferred to prevent moisture absorption in components that will be used in dry-sliding or bearing applications where dimensional stability is critical. For procurement teams specifying unfilled PEEK parts, the grade designation should reference a recognized material standard. Victrex 450G is a widely known commercial designation for unfilled extruded PEEK, but equivalent materials from other suppliers (Solvay KetaSpire, Evonik VESTAKEEP) are interchangeable in most structural applications. If biocompatibility is required — as in medical device or food-contact applications — specify the applicable FDA or USP Class VI compliance requirement explicitly, because not all unfilled PEEK rod and plate stock carries these certifications even when chemically identical.

Glass-Filled PEEK: Enhanced Stiffness and Creep Resistance for Structural Components

Adding 30 percent short glass fiber to PEEK more than doubles its flexural modulus to approximately 1,200,000 psi and substantially improves its creep resistance under sustained compressive loading — a critical property for structural brackets, bearing housings, and load-bearing insulator components in Burlington's heavy-equipment supply chain. Glass-filled PEEK also improves dimensional stability with temperature change, reducing the thermal expansion coefficient to roughly half that of unfilled grades. For applications where a PEEK component must maintain dimensional consistency across temperature swings of 100 to 150 degrees Celsius, glass-filled grades provide meaningfully better performance. The trade-off is reduced chemical resistance at fiber-matrix interfaces and significantly increased abrasiveness to cutting tools. Burlington shops machining glass-filled PEEK require carbide tooling throughout — HSS tools wear rapidly against the glass fibers — and feed rates are typically reduced 20 to 30 percent relative to unfilled PEEK to manage edge wear and surface quality. Machining glass-filled PEEK also generates fine glass-particle dust in the cutting zone, requiring proper dust collection or coolant application to prevent inhalation hazard and to protect machine-spindle bearing surfaces from abrasive contamination. In Burlington's automotive supply chain, glass-filled PEEK is specified for electrical connector housings, throttle body insulator brackets, and under-hood structural clips where the 250-degree-Celsius continuous rating, dimensional stability, and chemical resistance to engine oil and brake fluid are all simultaneously required. At roughly 1.49 g/cc density versus 2.70 g/cc for aluminum, a glass-filled PEEK connector housing weighing one pound replaces an aluminum part that would weigh 1.8 pounds — a meaningful contribution to vehicle lightweighting goals.

Carbon-Filled PEEK: Bearing, Wear, and Static-Dissipative Applications

Carbon-filled PEEK — typically 30 percent short carbon fiber — pushes the composite's stiffness to the highest level among the standard PEEK grades, reaching flexural modulus values of 2,000,000 to 2,400,000 psi, comparable to some aluminum alloys on a per-density basis. More importantly, the carbon fiber reinforcement dramatically improves wear and friction performance relative to unfilled or glass-filled grades. The coefficient of friction of carbon-filled PEEK against steel in dry-sliding conditions drops to 0.1 to 0.2 — comparable to PTFE-lubricated surfaces — making it the preferred bearing and bushing material for applications where oil or grease lubrication is undesirable or impractical. Burlington heavy-equipment applications for carbon-filled PEEK include hydraulic cylinder bushings running in contaminated environments where conventional bronze bushings seize when debris enters the running clearance, conveyor guide rails operating in wet or chemically aggressive wash-down areas, and rotary-seal rings in pneumatic and hydraulic valves where PTFE seals lack the structural integrity to survive side-load conditions. The specific PEEK 30CF grade from Victrex and equivalent designations from other suppliers combine the bearing performance of filled PTFE with 10 to 20 times the compressive strength, allowing thinner wall sections and more compact designs. An additional benefit of carbon-filled PEEK is its electrical conductivity relative to insulating unfilled grades. While not conductive in the sense of copper or aluminum, carbon-filled PEEK is antistatic — surface resistivity of 10 to the 4th to 10 to the 6th ohms per square — which prevents electrostatic charge accumulation in semiconductor handling equipment, fuel-system components, and electronic assembly fixtures. Burlington shops serving electronics manufacturing and precision-equipment OEMs in the broader Triad and Research Triangle Park corridor specify carbon-filled PEEK specifically for this static-dissipative property combined with its dimensional stability and chemical inertness. Machining carbon-filled PEEK requires fully carbide tooling, and the carbon fiber generates conductive dust particles that should not be allowed to enter machine controls or sensitive equipment.

Frequently Asked Questions

All three standard PEEK grades — unfilled, glass-filled, and carbon-filled — share the same continuous-use temperature limit of approximately 250 degrees Celsius (480 degrees Fahrenheit) in air, which is the polymer matrix's thermal ceiling regardless of filler content. For short-term excursions, PEEK can withstand temperatures up to 300 degrees Celsius without permanent degradation, though mechanical properties decline above 200 degrees Celsius. In Burlington automotive applications, this means PEEK is rated for most under-hood environments where aluminum (660 degrees Celsius melting point, 150 to 175 degrees Celsius typical peak service temp) is also used, but it cannot replace steel in locations adjacent to exhaust manifolds where surface temperatures exceed 400 degrees Celsius. For applications in that temperature range, PTFE, ceramic, or metal alternatives are required. The practical advantage of PEEK's 250-degree rating is that it comfortably covers hydraulic fluid temperatures, coolant-circuit temperatures, and transmission-fluid environments without requiring heat shielding.
Managing thermal expansion is the central challenge in tight-tolerance PEEK machining, and Burlington shops with PEEK experience use several complementary strategies. First, tooling is kept sharp and geometry is optimized for free-cutting — high positive rake angles reduce cutting forces and heat generation compared to tooling set up for metal work. Second, air blast or light misting is used rather than heavy flood coolant, which can cause dimensional shifts in PEEK as moisture is absorbed during machining and then released during post-machining stabilization. Third, parts are staged at room temperature for a minimum of four hours after roughing before finish machining, allowing any machining-induced thermal gradients to equalize. Under these conditions, tolerances of plus or minus 0.001 inch on milled and turned features are routine, and plus or minus 0.0005 inch is achievable on ground surfaces with diamond or CBN wheels. For bearing-bore applications requiring diametral tolerances of H7 or tighter, honing after initial bore machining is the preferred approach.
Carbon-filled PEEK is the correct choice for sliding-contact bearing and bushing applications in the vast majority of heavy-equipment scenarios. The carbon fiber reinforcement reduces the coefficient of friction to 0.1 to 0.2 in dry sliding against steel, compared to 0.3 to 0.4 for glass-filled PEEK in equivalent conditions. This lower friction translates directly to less heat generation, lower wear rate, and longer bushing life in applications like hydraulic cylinder pivot bushings, suspension articulation points, and loader-arm pin bushings that see high contact pressure with limited lubrication. Glass-filled PEEK is the better choice when the application demands maximum stiffness in a structural component that sees primarily compressive or bending load rather than sliding contact — connector housings, load-spreading pads, and insulator brackets are examples. In short: if the part slides against metal, specify carbon-filled PEEK. If the part is a structural element that doesn't slide, glass-filled PEEK provides better stiffness-to-weight performance for the price premium over unfilled grades.
For automotive applications, ISO 9001 is the minimum acceptable certification for a PEEK machining supplier in Burlington; IATF 16949 is preferred if the parts will be submitted through PPAP and supplied to a Tier 1 customer with automotive-quality-system requirements. For aerospace-adjacent or defense applications, AS9100 certification adds the configuration management, traceability, and risk management disciplines expected by those customers. For medical-device or food-contact applications, ISO 13485 is the relevant quality management standard, and the PEEK material itself must carry FDA or USP Class VI compliance documentation — a statement that the machining shop is ISO 13485 certified does not automatically mean the specific PEEK stock they are using meets those biocompatibility standards. Always request the material certification confirming biocompatibility compliance for the specific lot being machined, not just the shop's quality certificate.
Lead times for machined PEEK parts from Burlington-area suppliers range from 5 to 10 business days for simple geometries in standard grades when material is in stock, to 3 to 5 weeks for complex multi-feature parts requiring staged machining with stress-relief holds between operations. Material availability is the most common schedule driver: unfilled PEEK rod and plate in standard sizes (0.25 inch to 4 inch diameter rod, 0.25 to 2 inch thick plate) is typically available from Triad-area plastics distributors within 2 to 3 business days. Glass-filled and carbon-filled grades in non-standard sizes can require 2 to 4 weeks of material lead time from specialty distribution. For production programs with repeat orders, blanket purchase orders with quarterly releases allow Burlington shops to stage raw-material inventory and compress delivery to 5 to 7 business days per release. Prototype orders sent with complete drawings and clear grade specifications can typically be quoted and scheduled within 24 to 48 hours on ManufacturingBase.

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Last updated: July 2026

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