There are dozens of engineering plastics, and prices between them differ several-fold. Pick the wrong one and you don't just overpay — the part can fail early, stop a production line, and cost far more than the material ever did. This guide covers the five questions our technicians actually ask customers before recommending any material.
What is an engineering plastic, and how is it different from ordinary plastic?
Engineering plastics are the family of polymers designed to carry real mechanical loads and run continuously at temperatures above roughly 90°C — unlike commodity plastics (PS, PE-LD, packaging materials). They are strong, wear-resistant, and dimensionally stable enough to replace metal in machine components. Compared with metal they are about 4–7× lighter, never rust, run without lubrication, run quietly, and don't conduct electricity — which is why they dominate bushes, gears, rollers, wear pads, and food-line parts where metal can't go. The top tier is called Advanced or High-Performance Plastic (PTFE, PEEK, PEI), rated beyond 150–260°C at a clearly higher price.
Question 1 — What kind of load does the part carry?
- Sliding / abrasion (bushes, gears, rollers) — Nylon (PA6, PA66, MC Nylon): tough, abrasion-resistant, long service life
- Heavy impact (bumper pads, slide rails) — HDPE / UHMW-PE: outstanding impact resistance and very low friction
- High dimensional precision (small gears, mechanisms) — POM (Acetal): stiff, springy, dimensionally stable
Question 2 — What is the maximum service temperature?
- Ambient to ~80°C — Nylon, POM, HDPE all work comfortably
- Up to ~150°C — move up to higher-temperature grades
- 200°C and beyond — PTFE (Teflon) or PEEK, the advanced tier
Question 3 — Does it touch chemicals or food?
- Food contact — use certified food grades: HDPE PE500/PE1000 or PET (Ertalyte)
- Acids and alkalis — PVC offers good chemical resistance at excellent value; for aggressive or hot chemistry, PTFE
- Plating lines, concentrated chemicals — PTFE is the industry standard
Question 4 — What environment does the part live in?
Moisture is the variable people miss. Nylon absorbs up to 2–3% moisture in humid air, and its dimensions swell accordingly. If the part must stay precise in wet or humid conditions, use POM or PET instead — see our full comparison in Nylon vs POM. For outdoor parts in sunlight, choose a UV-stabilised grade, or acrylic for clear applications.
Question 5 — What is the budget and quantity?
The rule is simple: never pay for spec the job doesn't need. PEEK is the best material on paper and several times the price of Nylon. If the job isn't hot or chemically aggressive, Nylon or POM is more than enough. A good technician's value is finding that balance point for you.
Key reference numbers for popular materials
Typical values for standard grades (each manufacturer's datasheet governs the batch you order — use this to compare ranking, not as certified spec):
| Material | Tensile Strength (MPa) | Continuous Service Temp | Moisture Absorption (24h) | Headline Trait |
|---|---|---|---|---|
| PA6 (Nylon) | ~70–85 | ~80–100°C | High, ~1.5–3% | Tough, abrasion-resistant, good value |
| POM-C (Acetal) | ~60–70 | ~90–100°C | Low, <0.8% | Dimensionally stable, machines beautifully |
| PET (Ertalyte) | ~80–90 | ~100–110°C | Very low, ~0.1% | Precise, food-contact safe |
| UHMW-PE (PE1000) | ~20–40 | ~80°C | ~0% | Slipperiest, best impact resistance |
| PC | ~60–70 | ~100–120°C | Low, ~0.15% | Clear with very high impact strength |
| PTFE (Teflon) | ~20–35 | −200 to +260°C | ~0% | Chemical/heat proof, lowest friction |
| PEEK | ~90–100 | ~250°C | Low, ~0.1% | Strongest of the high-heat tier |
| PEI (Ultem) | ~85–105 | ~170°C | Low, ~0.25% | Excellent electrical insulator |
Common selection scenarios
Conveyor roller in a food packing line: must be food-safe, frequently washed, and slippery — Nylon is out because it swells with moisture. The right answers are food-grade UHMW-PE (PE1000), or PET when higher dimensional precision matters.
Shaft bush on machinery with impact loads: POM holds size but is more brittle under repeated impact — MC Nylon is tougher, absorbs shock better, and casts economically in large sizes, making it the standard answer for big bushes.
Flange gasket on a hot chemical line: aggressive chemistry above 150°C eliminates every general-purpose material. PTFE is the only sensibly-priced answer (PEEK also survives but costs far more — worth it only when high mechanical load is added).
Summary
Answer five questions before ordering: what load, how hot, chemical/food contact, what environment, and what budget. Still unsure? Ask our technicians for free at +66 92-949-0376. We stock all 9 core material groups with cut-to-size service, and can deliver finished machined parts in one stop.