For design engineers weighing engineering plastic options, the decision rarely turns on a single property; it is governed by the dominant failure mode the part will see in service, and seven resins cover the practical majority of cases.
PEEK, PTFE, PPS, PAI, nylon (PA), POM/acetal, polycarbonate (PC), ABS, and polypropylene (PP) appear repeatedly in industry guides as the shortlist candidates, with selection driven by four filters: peak continuous temperature, chemical exposure, wear/impact loading, and part cost [S1][S3]. The remainder of this guide maps those filters to specific grades, flags the standards and test methods that govern the property tables, and calls out where each resin fails.
Selection Criteria: The Four Filters That Drive Resin Choice
Continuous service temperature is the first filter, and PEEK grades are routinely specified up to 250°C, which puts them in a tier with PPS, PAI, and PTFE for hot-side components [S1]. Below 150°C the field widens to nylon 6/66, POM, PC, and ABS; below 100°C, PP and standard ABS become viable.
Chemical resistance is the second filter, and PTFE plus PP dominate where acids, bases, and solvents are present, with PEEK used for the upper-temperature chemical envelope [S1]. Wear and impact form the third filter, where nylon is preferred for moving parts (gears, bushings) and PC is preferred where the part must survive impact loads and remain transparent or pigmented [S1]. Cost-per-part is the fourth filter, and ABS and PP are the workhorses when neither high heat nor aggressive chemistry is present [S1].
Resin-by-Resin Property Snapshot
PEEK is the high-temperature, high-chemical, high-mechanical benchmark, rated to 250°C continuous and used across aerospace, automotive, medical, electronics, chemical processing, and industrial sectors [S1]. Its main downside is raw-material cost and the need for dedicated processing windows, so it is reserved for parts where rework or in-service failure is expensive.
PTFE offers the widest chemical compatibility of any unfilled thermoplastic and a very low coefficient of friction, but it is soft, creeps under load, and is not a structural material; it is selected for seals, gaskets, linings, and chemical-service bearings [S1][S3]. PPS and PAI fill the gap above 200°C where PTFE is mechanically inadequate, and both appear in aerospace and chemical-processing shortlists alongside PEEK [S1].
Nylon (PA 6, PA 66, and cast nylon grades) is the default for wear applications, with operating temperatures typically capped near 80–120°C and a tendency to absorb moisture that shifts dimensions and properties; the design data in vendor guides is almost always reported at conditioned (50% RH) and dry-as-molded states [S3]. POM/acetal competes with nylon for gears and bushings but is preferred where dimensional stability in wet environments matters, since it absorbs far less water than PA 6/66 [S3].
Polycarbonate (PC) is selected for transparent or impact-loaded parts, with continuous service in the 120–135°C band and notched Izod impact values typically in the 600–850 J/m range for unmodified grades; it is sensitive to certain chemicals and to stress cracking, so PC is paired with protective coatings or used behind a housing in chemical environments [S3]. ABS and PP are the cost-driven choices, with ABS offering better impact and surface finish than PP, and PP offering better chemical resistance and lower density; both are routinely used in consumer products and as the matrix in glass-filled structural grades [S1][S3].
Industry-to-Resin Mapping and What It Actually Means
Aerospace parts draw from PEEK, PPS, PAI, and PTFE, with the selection driven by FAA flammability, smoke/toxicity (FAR 25.853), and continuous-temperature ratings that exceed what commodity plastics can hold [S1]. Automotive uses nylon, PC, ABS, and PEEK; under-hood temperature is the gate, with PA 66 and PPA dominating coolant and air-intake manifolds, PC for glazing and lighting, and PEEK reserved for the most thermally loaded bushings and seal rings [S1].
Medical relies on PEEK and PTFE for implant and instrument-contact applications, plus select PP grades for single-use devices, with biocompatibility testing (ISO 10993 series) gating the grade regardless of base resin [S1]. Electronics uses PC, PEEK, PP, and ABS where dimensional stability, dielectric strength, and flammability rating (UL 94) drive choice; consumer products default to ABS, PC, and PP for cost and finish reasons [S1].
Side-by-Side Comparison Across Decision Criteria
Lining the seven principal resins up against the four decision criteria gives a structured view an engineer can paste into a selection matrix: PEEK wins three of four criteria (heat, chemicals, mechanical retention) but loses on cost; PTFE wins on chemicals and is acceptable on heat, but is soft and creeps; nylon and POM win on wear at moderate cost, but cap out near 120°C; PC wins on impact and optical clarity, but cracks in many solvents; ABS and PP win on cost and processability, but lose on heat and chemical resistance. [S1]
Quantitative anchors from the cited guides: PEEK continuous service to 250°C; PTFE chemical compatibility across essentially all commercial acids, bases, and solvents; nylon conditioned-vs-dry property shifts that can reach double-digit percent on modulus and dimensions; PC notched Izod impact in the 600–850 J/m band for unmodified grades [S1][S3]. The Mitsubishi Chemical Advanced Materials design guide explicitly notes that more than 50 machinable stock-shape grades span the performance/price range, which is why generic "plastic vs. metal" comparisons usually miss the point: the engineering choice is between specific grades within a resin family, not between plastic and metal as categories [S3].
Limitations, Failure Modes, and Standards That Govern the Data
Every property table in a resin datasheet is anchored to a specific test standard, and the property value is only meaningful if the standard, conditioning state, and test temperature are stated. The cited design guides cover ASTM D638 tensile, ASTM D790 flexural, ASTM D256 Izod impact, ASTM D648 heat-deflection temperature (HDT), ASTM D696 coefficient of thermal expansion, and ASTM D570 water absorption, which are the working set for engineering plastic property comparison [S3].
Failure modes cluster predictably: creep and stress relaxation in PA, POM, and PTFE under sustained load; stress cracking in PC exposed to polar solvents; thermal-oxidative degradation in PEEK, PPS, and PAI above their continuous service ratings; and moisture-induced dimensional and property shift in nylon 6 and 66 at humidities above 50% RH [S3]. Where any of these modes dominates the application, the resin choice must move to a higher-tier material (e.g. PEEK instead of PA for a hot, wet, sustained-load part) or to a filled grade (glass-filled PA, carbon-filled PEEK) that shifts the trade-off.
Cross-References: Plastics, Bearings, and Mechanical Design
Engineering plastic selection overlaps directly with linear guide and crossed-roller guide bearing-system design, where the plastic slideway or cage material drives friction, wear, and lubrication interval; the Mitsubishi guide devotes dedicated sections to bearing, roller/wheel, sheave, and gear design in plastics, with explicit guidance that plastic bearings often run dry but require different load and speed calculations than steel rolling-element bearings [S3].
Design engineers comparing a metal-to-plastic conversion for a structural or moving part should also weigh plastic pallet and plastic pipe selection logic as a working pattern, because the same temperature/chemical/mechanical grid applies when the part is a pallet runner or a process pipe, and the same standards framework (ASTM, ISO) governs the test data in both cases. The plastic and rubber encyclopedia entry covers the broader elastomer side of the same trade-off, useful when the part needs rubber-like recovery in addition to plastic-like load-bearing capacity.
Trackable Signals to Watch in the Next Design Cycle
Two signals are worth tracking over the next 6 to 12 months: first, the release of manufacturer design guides with ISO-aligned property tables (ISO 527, ISO 178, ISO 180, ISO 75) that supersede the ASTM-only legacy data, which would let European and Asian design teams use a single property column without unit-conversion or method-conversion risk [S3]; second, the migration of PEEK and PPS datasheets toward digital-twin-friendly formats with temperature- and moisture-conditioned property curves, which the Mitsubishi guide hints at in its "more than 50 machinable stock-shape grades" portfolio and which the broader industry is moving toward as simulation replaces point-value lookup [S3].
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