🧪 PEEK
PEEK Components for Chemical Processing and Heavy-Equipment Applications in Terre Haute, IN
Polyether ether ketone (PEEK) earns its premium price in applications where the service environment destroys conventional engineering plastics. Continuous use temperature of 480°F, resistance to virtually all industrial solvents and acids except concentrated sulfuric acid, and inherent flame retardance (UL 94 V-0) make PEEK the right call for Terre Haute specialty chemical plant components, high-load equipment bearings, and structural elements that must maintain dimensional stability through wide temperature swings. The three commercially significant grades — unfilled, glass-filled, and carbon-filled — each address a different performance priority, and selecting the wrong grade wastes cost without gaining service life.
ISO 9001ISO 13485ISO 14001
Unfilled PEEK for Chemical Resistance and Electrical Isolation
Unfilled PEEK (natural, semi-crystalline) is the baseline grade specified when chemical resistance, purity, and electrical insulation properties are the primary requirements. In Terre Haute's specialty chemical manufacturing facilities, unfilled PEEK appears in pump internals (impellers, wear rings, and valve seats exposed to concentrated acid streams), fluid handling manifolds for aggressive solvent systems, and electrical insulator bushings in high-voltage chemical processing equipment. Its resistance profile is exceptional: it survives continuous exposure to sulfuric acid up to 30%, phosphoric acid, acetone, toluene, methylene chloride, and most organic process solvents at temperatures up to 250°C without measurable swelling or degradation.
Mechanically, unfilled PEEK has tensile strength of approximately 14,000 PSI, flexural modulus of 525,000 PSI, and a heat deflection temperature of 320°F at 264 PSI load — sufficient for structural components in many chemical equipment applications. The material is fully machinable to tight tolerances: bore dimensions to ±0.001 inch and surface finishes of 32 Ra are achievable with sharp carbide tooling, light cuts, and appropriate fixturing. PEEK machines similarly to aluminum — feed rates and speeds are moderate, chips evacuate cleanly, and internal stress-relieving by annealing extruded rod stock before machining prevents dimensional drift in precision components.
For Terre Haute procurement, unfilled PEEK rod and plate stock in standard sizes (0.25–6.0 inch diameter rod, 0.25–3.0 inch plate) is available with 1–3 week lead times from plastics distributors serving the Midwest. FDA-compliant grades of unfilled PEEK are stocked separately for food contact and medical applications and carry specific lot certifications — buyers should specify FDA-compliant explicitly when required, as standard grades may not carry the same documentation.
Glass-Filled PEEK for Improved Stiffness and Dimensional Stability
Glass-filled PEEK — typically 30% glass fiber by weight (GF30) — significantly upgrades the unfilled grade's stiffness and creep resistance without substantially compromising chemical resistance. Flexural modulus increases from 525,000 PSI to approximately 1,400,000 PSI, and heat deflection temperature at 264 PSI rises from 320°F to 500°F. Coefficient of thermal expansion drops from 2.7×10⁻⁵ /°F to approximately 1.3×10⁻⁵ /°F — a critical property for precision components in Terre Haute equipment that must maintain dimensional tolerances through operating temperature cycles.
For heavy-equipment applications in western Indiana — bearing housings, structural inserts, wear-resistant guide components, and hard-stop blocks in hydraulic systems — GF30 PEEK delivers the stiffness needed to prevent deflection under load without the corrosion and weight issues of steel alternatives. A PEEK GF30 guide rail or wear plate in a packaging conveyor system weighs roughly one-eighth of the steel equivalent and will not corrode in washdown environments typical of food-grade packaging lines.
Machinability of GF30 PEEK is more abrasive than unfilled PEEK — the glass fibers are essentially cutting tool abrasives. Carbide tooling is required (HSS wears quickly), cutting speeds should be reduced 20–30% versus unfilled PEEK, and dust extraction is important because the glass fiber-laden chips are a respirable hazard. Dimensional tolerance achievement is similar to unfilled PEEK when proper tooling and speed selection are applied. For Terre Haute CNC shops machining GF30 PEEK, fresh inserts at the start of each setup and conservative depth-of-cut strategies protect both tool life and surface finish quality.
Carbon-Filled PEEK for Bearing and Wear Applications Under High Load
Carbon-filled PEEK — typically 30% carbon fiber (CF30) — is the grade specified when the primary performance requirement is load-bearing, wear resistance, and dimensional stability under compression. The carbon fiber reinforcement raises flexural modulus to approximately 2,100,000 PSI — nearly three times unfilled PEEK — and dramatically reduces the coefficient of thermal expansion (to roughly 0.7×10⁻⁵ /°F in the fill direction). In bearing and wear pad applications, carbon fiber also provides inherent lubricity, reducing the friction coefficient versus steel from approximately 0.35 (unfilled PEEK on steel) to 0.12–0.15 (CF30 PEEK on steel).
For Terre Haute heavy-equipment manufacturers, CF30 PEEK bushings and plain bearings are a compelling replacement for bronze or filled-nylon alternatives in high-load, high-temperature, or chemically exposed bearing locations. A CF30 PEEK bushing in an excavator pin joint exposed to grit and intermittent chemical wash runs cooler, lasts longer, and tolerates misalignment better than standard bronze in many applications. Compressive strength of CF30 PEEK exceeds 25,000 PSI — substantially higher than standard engineering plastics — which allows bearing wall thickness to be reduced compared to lower-strength polymers, fitting the bearing into tighter OD envelopes.
One important limitation: CF30 PEEK has reduced chemical resistance versus unfilled grades in certain environments. The carbon fiber itself is inert, but the fiber-matrix interface can degrade in prolonged exposure to steam above 300°F or concentrated oxidizing acids. For Terre Haute chemical plant applications, verify the specific chemical exposure against CF30 PEEK resistance data before substituting for unfilled PEEK in aggressive environments.
Machining PEEK to Specification in Terre Haute: Process Notes
PEEK is semi-crystalline, which means it holds dimension well post-machining compared to amorphous plastics — but pre-machining annealing of rod and plate stock is still best practice for tight-tolerance components. Extruded PEEK rod carries residual stress from the extrusion process; annealing at 250°C for one hour per inch of cross-section before machining relaxes this stress and prevents dimensional shift after final machining.
For CNC turning, unfilled PEEK runs well at 600–900 SFM with carbide tooling, light depth of cut (0.010–0.040 inch), and high feedrate to produce chips rather than heat. Flood coolant is preferred over mist or dry cutting — PEEK conducts heat poorly, and elevated cutting zone temperature degrades surface finish and can cause dimensional expansion that affects tolerance achievement. Glass and carbon filled grades use similar parameters but at 20–30% lower speed to manage abrasion. Boring to ±0.0005 inch is achievable with a finishing boring bar and fresh carbide insert.
For Terre Haute buyers specifying PEEK machined parts on drawings, calling out material grade explicitly (PEEK Unfilled, PEEK GF30, or PEEK CF30), annealing requirement, and surface finish is important — a plastics shop receiving only 'PEEK' on a drawing may substitute grades based on stock availability. Request a material certification with density confirmation (unfilled PEEK: 1.30–1.32 g/cm³; GF30: 1.49–1.51 g/cm³; CF30: 1.40–1.42 g/cm³) as a quick check that the correct grade was used.
Frequently Asked Questions
Unfilled PEEK is one of the best-performing engineering polymers for continuous chemical service at elevated temperature. It maintains structural integrity in continuous immersion in concentrated phosphoric acid, 30% sulfuric acid, acetone, methanol, toluene, and most organic solvents up to 200°C with minimal dimensional change or property degradation. The material's semi-crystalline structure resists solvent absorption that swells and weakens amorphous polymers like PETG or polycarbonate. The primary chemical vulnerability is concentrated sulfuric acid above 30% concentration, which degrades the aromatic ether linkages in the PEEK backbone at elevated temperature. Hydrofluoric acid and strong oxidizing agents at high concentrations can also attack PEEK. For Terre Haute specialty chemical plants, running an immersion coupon test in the actual process fluid at operating temperature for 500 hours before finalizing the PEEK specification is recommended for new applications — actual plant chemistry is often more complex than pure reagent data, and confirming performance in the real mixture adds confidence before committing to a production part.
Standard PEEK rod and plate stock (unfilled, GF30, CF30) in common sizes is stocked by Midwest plastics distributors with typical lead times of 1–2 weeks for standard diameters (0.5–4.0 inch rod) and plate (0.25–2.0 inch thick). Larger cross-sections and non-standard sizes may require 3–6 week lead times from resin molders. Cost-wise, PEEK runs approximately 20–30× the cost of nylon 6/6, 10–15× the cost of Delrin, and 4–6× the cost of PPS — significant premiums that are justified only when the service environment genuinely demands PEEK's performance envelope. For applications where operating temperature stays below 200°F, chemical exposure is mild, and load is modest, materials like Delrin or nylon are more economical and technically sufficient. The business case for PEEK comes when temperature exceeds 250°F continuously, chemical resistance to aggressive solvents is required, or a combination of high load and temperature would degrade lower-cost polymers within the target service life.
PEEK can be joined by hot-gas welding, ultrasonic welding, and adhesive bonding, but each method has important limitations. Hot-gas welding with a PEEK welding rod at 380–420°C produces joints with 70–85% of the base material tensile strength — acceptable for non-critical structural assemblies but not for pressure-containing applications. Ultrasonic welding works for thin sections and produces clean, repeatable joints in production volumes. Adhesive bonding requires surface activation — chemical etching with sulfuric acid or plasma treatment — because PEEK's low surface energy resists most adhesives in untreated condition. Epoxy adhesives on properly prepared PEEK surfaces can achieve 2,000–3,000 PSI lap shear strength. For Terre Haute industrial applications involving chemical exposure, bonded or welded PEEK joints need to be evaluated for chemical resistance at the joint interface — adhesive degradation in process chemicals is a failure mode that base material data does not predict. Mechanical fastening with PEEK or titanium fasteners is the most reliable approach for chemical service assemblies requiring disassembly for maintenance.
Carbon-filled PEEK (CF30) is the preferred grade for wear pads and plain bushings in heavy-equipment applications where load, wear rate, and heat generation are the primary concerns. Its flexural modulus of 2,100,000 PSI resists deformation under compressive bearing loads, its inherent lubricity (friction coefficient 0.12–0.15 on steel) reduces heat generation and wear rate versus unfilled grades, and its CF30 composition handles the combination of abrasion, moderate chemical exposure (grease, hydraulic fluid, road grime), and temperature cycling typical of heavy equipment pin joints and slide bearings. For lighter-load applications where chemical resistance to wash-down fluids or mild acids is the primary requirement, GF30 PEEK provides better chemical resistance than CF30 while still delivering stiffness and dimensional stability well above unfilled PEEK. In high-load construction equipment pivot applications with access to continuous lubrication, CF30 PEEK bushings can achieve 3–5× the service life of standard bronze bushings in grit-contaminated environments.
With proper pre-machining annealing, sharp carbide tooling, and flood coolant, PEEK machined components routinely achieve bore tolerances of ±0.0005 inch, outside diameter tolerances of ±0.001 inch, and flatness of 0.002 inch per foot. Surface finish of 32–63 Ra is standard; 16 Ra is achievable on critical sealing or bearing surfaces with a light finishing pass at high surface speed and minimal feed. The key variables that affect tolerance achievement are: stock annealing (skip it and residual stress will cause the part to move after machining), tooling sharpness (dull carbide generates heat and smears the surface rather than cutting), and clamping force (excessive chuck pressure on thin-wall PEEK parts causes elastic deformation that springs back after unclamping). Thread machining in PEEK is reliable for coarse threads (1/4-20 and coarser); fine threads in high-modulus filled grades can be brittle — consider thread inserts for frequently assembled joints. CF30 PEEK is more abrasive in machining and typically achieves 15–20% wider tolerance bands than unfilled at equivalent process capability.
Last updated: July 2026
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