Category: General Manufacturing Reading time: 8 min Meta description: High-performance engineering plastics — PEEK, PPS, PAI, PTFE, and PSU. Compare temperature resistance, chemical resistance, cost, and applications. Know when standard plastics won't work. URL: /blog/engineering-plastics-guide/ Tags: engineering-plastics, PEEK, PPS, PTFE, high-temperature, performance-plastics
Standard plastics like ABS, PP, and PC handle the vast majority of applications. But when temperatures exceed 120°C, chemicals attack standard materials, or fire resistance is mandatory, you need engineering plastics.
PEEK, PPS, PAI, PTFE, and PSU are the workhorses of high-performance applications. They cost 5-50x more than commodity plastics but solve problems no standard plastic can handle.
A standard plastic is probably fine if:
You need engineering plastics if:
| Property | Value |
|---|---|
| Continuous use temperature | 250°C |
| Tensile strength | 90-100 MPa |
| Chemical resistance | Excellent (resists almost all) |
| Coefficient of friction | 0.1-0.3 (very low) |
| Flammability | V-0 (self-extinguishing) |
| Sterilization | Autoclave, gamma, EtO |
| Machinability | Good (with carbide tools) |
| Injection moldable | Yes (melt temp 360-400°C) |
| Relative cost | $$$$$ ($100-200/kg) |
Best for: Medical implants, aerospace components, oil & gas seals, semiconductor processing, high-temperature electrical connectors.
Key advantage: PEEK maintains its mechanical properties up to 250°C — a temperature that would melt most standard plastics. It also resists nearly every chemical, making it the go-to for the most demanding environments.
Common grades:
| Property | Value |
|---|---|
| Continuous use temperature | 200-220°C |
| Tensile strength | 65-85 MPa (glass-filled) |
| Chemical resistance | Excellent (resists most) |
| Dimensional stability | Excellent (low moisture absorption) |
| Flammability | V-0 |
| Machinability | Good |
| Injection moldable | Yes |
| Relative cost | $$$$ ($15-30/kg) |
Best for: Automotive under-hood components (pump housings, throttle bodies), chemical processing equipment, electronics connectors and sockets.
Key advantage: PPS offers 80% of PEEK's performance at 15-20% of the cost. For applications below 220°C, it's often the more economical choice.
| Property | Value |
|---|---|
| Continuous use temperature | 260°C |
| Compressive strength | 240 MPa (highest) |
| Wear resistance | Excellent |
| Dimensional stability | Excellent |
| Flammability | V-0 |
| Machinability | Fair (post-curing needed) |
| Injection moldable | Difficult (complex process) |
| Relative cost | $$$$$ ($100-200/kg) |
Best for: Bushings, valve seats, thrust washers, seal rings, jet engine components.
Key advantage: PAI has the highest compressive strength of any thermoplastic and maintains dimensional stability under heavy loads at high temperatures. It's more creep-resistant than PEEK under load.
| Property | Value |
|---|---|
| Continuous use temperature | 260°C |
| Chemical resistance | Inert (resists everything) |
| Coefficient of friction | 0.04-0.10 (lowest) |
| Non-stick | Excellent |
| Tensile strength | 20-35 MPa (low) |
| Creep resistance | Poor (cold flows under load) |
| Machinability | Good (buttery feel) |
| Injection moldable | No (requires compression molding or machining) |
| Relative cost | $$$ ($10-30/kg) |
Best for: Seals, gaskets, bearings, non-stick surfaces, electrical insulation, chemical-resistant linings.
Key advantage: PTFE has the lowest coefficient of friction of any solid material and is chemically inert — nothing sticks to it, and nothing reacts with it.
Key limitation: PTFE creeps (cold flows) under sustained load. It's not suitable for high-stress structural applications without fillers.
| Property | Value |
|---|---|
| Continuous use temperature | 150-170°C |
| Transparency | Excellent (transparent amber) |
| Hydrolytic stability | Excellent (steam sterilizable) |
| Chemical resistance | Fair (attacked by some solvents) |
| Impact strength | Good |
| Machinability | Good |
| Injection moldable | Yes |
| Relative cost | $$$ ($20-50/kg) |
Best for: Medical device housings, food service equipment, membrane filtration, steam-sterilizable components.
Key advantage: PSU is transparent and can withstand repeated steam sterilization — unmatched for medical and food applications requiring both visibility and sterilization capability.
| Material | Key Feature | Use Temperature | Relative Cost |
|---|---|---|---|
| PVDF | Outstanding chemical resistance, UV stable | 150°C | $$$ ($25-40/kg) |
| LCP | Very thin wall flow, RF transparent | 220-280°C | $$$$ ($30-80/kg) |
| PEI (Ultem) | Good balance of properties, V-0 naturally | 170°C | $$$ ($30-50/kg) |
| PCTFE | Lowest gas permeability of plastics | 200°C | $$$$$ ($80-150/kg) |
| Material | Temp Limit | Chemical | Wear | Friction | Stiffness | Impact | Cost |
|---|---|---|---|---|---|---|---|
| PEEK | ★★★★★ | ★★★★★ | ★★★★★ | ★★★★ | ★★★★ | ★★★★ | $$$$$ |
| PPS | ★★★★ | ★★★★★ | ★★★★ | ★★★ | ★★★★ | ★★★ | $$$$ |
| PAI | ★★★★★ | ★★★★ | ★★★★★ | ★★★★ | ★★★★★ | ★★★ | $$$$$ |
| PTFE | ★★★★★ | ★★★★★ | ★★★★ | ★★★★★ | ★ | ★★ | $$$ |
| PSU | ★★★ | ★★★ | ★★★ | ★★★ | ★★★ | ★★★★ | $$$ |
| PEI | ★★★★ | ★★★ | ★★★★ | ★★★ | ★★★★ | ★★★★ | $$$ |
| Material | Cost per kg | Cost vs Standard Plastic |
|---|---|---|
| ABS | $2-3 | 1x (baseline) |
| Polypropylene | $1-2 | 0.7x |
| Polycarbonate | $4-6 | 2x |
| PPS | $15-30 | 6-12x |
| PEI (Ultem) | $30-50 | 12-20x |
| PEEK | $100-200 | 40-80x |
| PAI (Torlon) | $100-200 | 40-80x |
| PTFE | $10-30 | 4-12x |
| Temperature | Material Options | Recommendation |
|---|---|---|
| 100-150°C continuous | PC, PEI, PSU | PEI for best balance |
| 150-200°C continuous | PPS, PEI | PPS for cost, PEI for impact |
| 200-260°C continuous | PEEK, PAI, PTFE | PEEK for all-round, PTFE for seals |
| > 260°C | PAI, ceramic alternatives | PAI for structural |
| Chemical | Recommended Material |
|---|---|
| Strong acids | PTFE, PVDF, PEEK |
| Strong bases | PTFE, PEEK, PPS |
| Solvents | PTFE (only truly universal) |
| Fuels and oils | PPS, PEEK, PA66 |
| Oxidizers | PTFE, PVDF |
| Application | Material |
|---|---|
| Low load, low speed — low friction | PTFE |
| High load, high speed — wear resistant | PAI, PEEK + carbon |
| Food grade | PEEK (FDA), PTFE (FDA) |
| Dry running bearings | PEEK + PTFE filled |
Can I machine engineering plastics the same as steel? Generally yes, but use carbide tools, sharp edges, and coolant. PEEK prefers slow speeds and aggressive feeds. PTFE machines easily but dimensionally is harder to control.
Do engineering plastics need post-processing? Some do. PAI (Torlon) requires a post-curing cycle after rough machining to achieve full properties. PEEK is typically used as-machined.
Can engineering plastics be welded? Some can. PEEK, PPS, and PEI can be ultrasonic or hot-plate welded. PTFE cannot be welded with standard methods.
Need a part in a high-performance plastic? Submit your requirements to app.moldkey.com/quote and get material recommendations and pricing from specialist manufacturers.