Engineering Plastics

Plastics are chosen for what metals do badly: they are one-sixth the density of steel, they insulate, they do not corrode, they can be transparent, flexible or self-lubricating, and in volume an injection-molded part costs cents. The family runs from commodity polyethylene at a few dollars a kilogram to PEEK and polyimide at a hundred times that, with a matching span in temperature (60 °C to 300 °C continuous) and strength (a fraction of aluminum to, with carbon fiber, nearly matching it). The choice is rarely about strength alone; it is about temperature, chemicals, wear, clarity, and how the part will be made.

CAD render of a 3D-printed PA12 nylon intake manifold with four runner flanges, in the natural gray of Multi Jet Fusion.

Plastics by performance tier

Commodity thermoplasticsPE, PP, PVC, ABS, PS, PLA · to ~80 °C665 – 95Enclosures, tanks, packaging, cutting boards, chemical piping, prototypes — cheapest per kilogram, easy to mold and thermoform; ABS is the standard housing plastic, HDPE and PP the standard chemical-resistant ones.

Engineering thermoplasticsPA (nylon), POM, PC, PBT, PET, PMMA, ASA, UHMW · 80–150 °C8218 – 145Gears, bushings, snap-fits, lenses, structural housings, wear strips — the workhorse tier for machined and molded functional parts. POM (Delrin) for precision, PA for toughness, PC for impact and clarity.

High-performance & fluoropolymersPEEK, PEI, PPS, PSU, PAI, PI, PTFE, PVDF · 150–300 °C7111 – 185Semiconductor, aerospace, medical and oil-gas parts that run hot, wet or in aggressive chemistry — the strength of engineering plastics at twice the temperature; PTFE and PVDF for the lowest friction and best chemical resistance.

ElastomersTPU, TPE, silicone, NBR, EPDM, FKM, cast PU373 – 20Seals, gaskets, grips, bumpers, tubing, wheels and overmolds — rubber-like stretch and recovery; the choice is by chemical and temperature exposure (NBR for oil, EPDM for weather, FKM for fuel and heat, silicone for food and medical).

ThermosetsEpoxy, phenolic, melamine, polyester, vinyl ester, BMI, cyanate ester17—Cast and potted electrical parts, tooling boards, insulators, brake and clutch friction plates, laminate matrices — cross-linked once cured so they do not soften with heat; machined from sheet or cast to shape rather than molded from pellets.

Photopolymer resinsSLA / DLP / PolyJet resins · Standard, Tough, Clear, High Temp534 – 75Fine-detail prototypes, dental and jewelry patterns, clear display models, snap-fit checks — cured by light, so surfaces are smooth but properties are more brittle and less stable than molded thermoplastics.

FoamsPU, EVA, EPP, Poron600 – 43Padding, packaging inserts, gaskets, vibration isolation, tooling boards — density and cell structure matter more than the base polymer.

Other polymersVarious1—Blends, specialty compounds and trade-name grades outside the groups above.

PUR/PIR Board

Choose a plastic for

Housings, covers, guards and enclosures; gears, bushings, rollers and wear pads that run dry; fluid-handling parts in acids, solvents or chlorine; electrical insulators and connectors; lenses, windows and light guides; seals, grips and dampers; and any prototype or low-volume part where CNC-machined or 3D-printed plastic is cheaper and faster than a metal equivalent.

Look elsewhere when

The part carries high sustained load (plastics creep — a bolted joint loosens, a shelf sags), stiffness matters (even filled plastics are 5–20 × less stiff than aluminum), tolerances tighter than ±0.05 mm must hold across temperature and humidity (nylon absorbs water and grows), service temperature exceeds ~150 °C for anything but the high-performance tier, or the part must survive UV, flame or impact without an additive package. Most plastics also scratch easily and cannot be repaired by welding once machined.

Tensile strength against max service temp, every polymer grade

No materials in view have both of these properties.

Loading the library…

Polymer by application

General housings and covers: ABS for cost and paintability; PC when it must survive a drop; PC-ABS as the molded compromise; PETG for machined and printed prototypes with some clarity.
Gears, bushings and precision wear parts: POM (Delrin / acetal) holds the tightest tolerances and machines like brass; nylon for tougher, noisier gears; UHMW for sliding wear and impact; PET for dimensional stability in moisture.
Heat, chemicals and cleanroom: PEEK to 250 °C in steam and solvents; PEI (Ultem) for autoclavable clear-amber parts; PPS for chemical resistance at lower cost; PAI (Torlon) and PI (Vespel) for the hottest bearings and insulators.
Acids, solvents and chlorine: PP and HDPE for most tanks and fittings; PVC / CPVC for piping and machined manifolds; PVDF for purity and strength; PTFE, PFA and FEP when nothing else survives.
Clear windows and lenses: PMMA (acrylic) for optical clarity and scratch resistance; PC for impact and safety glazing; PETG for formed guards; clear resin for printed light guides (polish after).
Impact, UV and outdoor exposure: ASA is UV-stable ABS for outdoor housings; PC for impact; UHMW for abuse; EPDM for seals that see sun and ozone.
Seals, grips and flexible parts: TPU for printed and molded flexible parts; NBR for oil seals; FKM for fuel and heat; silicone for food, medical and –60 to 200 °C; Poron and EVA for cushioning.
Medical, food and cryogenic: PEEK and PPSU (Radel) survive hundreds of autoclave cycles; medical silicone for soft contact parts; PCTFE seals and valve seats to –250 °C.
High strength and stiffness: Glass- or carbon-filled nylons and PPA replace aluminum brackets and housings at a third of the weight; expect 2–3× the stiffness of the unfilled resin and anisotropy in printed parts.

FabAgentAI

AI suggestions — verify with an engineer before ordering. Estimates are indicative; the quote page prices your exact geometry.

Manufacturing notes

CNC machining

Feed per tooth mm/tooth

Ø6 mm · 3-flute carbide end mill

Distance the cutter advances between successive teeth (chip load). Published per material; independent of tool diameter.

Polycarbonate has the highest feed per tooth (0.0762 mm/tooth); 6061-T6 the lowest (0.0508 mm/tooth).

n = 1,000 v_c / (πD)v_f = f_z × z × nD = 6 mm · z = 3 flutes · diagram not to scale

POM, PET, PEEK, PC and PMMA machine cleanly to ±0.05 mm; nylon and UHMW are tougher and less stable; PTFE and soft PE smear and need very sharp tools. Plastics move with heat and moisture — we rough, rest, and finish thin or precision parts, and machine from stress-relieved stock. Sharp internal corners crack PC and PMMA; specify radii.

3D printing: SLS nylon (PA12, PA11, glass- or carbon-filled) for functional parts without support marks; MJF PA12 for volume; FDM in ABS, ASA, PC, PETG, PEEK and Ultem for large or high-temperature parts; SLA / DLP resins for fine detail and clear parts; PolyJet for multi-material and rubber-like overmolds. Printed properties are 60–90 % of molded and direction-dependent.
Injection molding and casting: Every thermoplastic here molds; the resin choice decides tool steel, cycle time and shrinkage (POM and PA shrink 2 %, ABS and PC under 0.7 %). Urethane casting in silicone molds bridges 10–200 parts with ABS-, PC- or rubber-like resins before a steel tool is justified.
Sheet, thermoforming and welding: ABS, PETG, PMMA, PC and HDPE sheet thermoform and bend; PVC, PP, PE and PVDF weld with hot gas or extrusion for tanks and ducts. POM, PA and PEEK are not practical to weld or form after machining — design them as one machined or molded piece.
Finishing: Bead blast or vapor smoothing on printed parts; paint, EMI shielding and pad printing on ABS / PC housings; polishing and anti-scratch coating on PMMA / PC optics; annealing on machined POM, PEEK and PC to relieve stress before tight-tolerance measurement. Most plastics cannot be plated or anodized; some ABS and PC-ABS take electroless nickel with an etch.

Most-quoted polymer grades

Grade	Performance tier	Yield, MPa	Tensile, MPa	Density, g/cm³	Machinability	Weldability	Best for
ABS	Commodity thermoplastics	42	43	1.04	Very good	Very good	Housings, prototypes, painted parts
PC	Engineering thermoplastics	63	68	1.2	Good	Very good	Impact-resistant clear or opaque parts
POM-C	Engineering thermoplastics	63	65	1.41	Excellent	Fair	Precision gears, bushings, machined parts
PA6	Engineering thermoplastics	75	80	1.14	Good	Good	Tough machined and molded parts
PMMA	Engineering thermoplastics	68	70	1.19	Very good	Good	Optical windows and covers
HDPE	Commodity thermoplastics	26	28	0.96	Very good	Excellent	Chemical tanks, cutting boards
PEEK	High-performance & fluoropolymers	100	100	1.3	Very good	Fair	Hot, wet, chemically aggressive service
PTFE	High-performance & fluoropolymers	12	30	2.17	Very good	Not recommended	Lowest friction, any chemistry
TPU	Elastomers	10	40	1.18	Poor	Excellent	Flexible grips, seals, printed rubber-like parts
PA66	Engineering thermoplastics	80	82	1.14	Good	Very good	Harder wear-resistant nylon

Finishes for polymer

All 111 finishes

59 of our 111 surface finishes take polymer: 25 recommended outright, 11 with process care, 23 in limited cases. Each finish opens to its datasheet — thickness, hardness, salt-spray hours, spec codes and the polymer-specific notes — and the configurator prices it on the grade you pick.

Finish	Group	On polymer	Thickness, µm	Hardness, HV	Salt spray, h	Cost
Chrome Plating on Plastic	Plating & metallizing	Yes	20–50	700–1,000	—	$$$$
Electroless Plating on Plastic	Plating & metallizing	Yes	5–15	80–150	—	$$$$
Vacuum Metallization	Plating & metallizing	Yes	0.05–1	—	—	$$$$
Conductive Coating	Paint, powder & polymer coatings	Yes	15–50	—	—	$$$
EMI Shielding Coating	Paint, powder & polymer coatings	Yes	15–30	—	—	$$$$
Hydrophobic Nano-Coating	Paint, powder & polymer coatings	Yes	—	—	—	$$
Deburring	Mechanical finishing & post-processing	Yes	0	—	—	$
Degating	Mechanical finishing & post-processing	Yes	0	—	—	$
Support Removal	Mechanical finishing & post-processing	Yes	0	—	—	$$
Embossing and Debossing	Marking, decoration & colour	Yes	200–1,000	—	—	$$$
Hot Stamping	Marking, decoration & colour	Yes	10–20	—	—	$$
In-Mold Decoration (IMD)	Marking, decoration & colour	Yes	100–300	—	—	$$$$

47 more finishes accept polymer — see the full material × finish matrix →

Polymer — frequently asked

Which plastic is best for machined parts?

POM (acetal / Delrin) for most: it is dimensionally stable, low-friction, does not absorb water and machines to ±0.05 mm with a clean finish. PET for even better stability, nylon (PA6 / PA66) when toughness matters more than precision, PC or PMMA for clear parts, PEEK when the part runs hot or in chemicals. Avoid PTFE and soft PE for tight tolerances.

How hot can plastics go?

Continuous-use limits: commodity ABS, PP, PVC ~70–90 °C; engineering POM, PA, PC ~100–130 °C; PPS, PEI, PSU ~170–200 °C; PEEK ~250 °C; PAI and PI ~260–300 °C; PTFE 260 °C with low strength. Glass fill raises the load-bearing temperature of a resin by 20–50 °C. Above 300 °C there is no plastic — use a ceramic or metal.

Nylon or acetal (Delrin)?

Acetal (POM) when the part must hold size and run smoothly: gears, bearings, valve bodies, precision housings. Nylon (PA6 / PA66) when it must survive impact and abrasion and a little dimensional change is acceptable: rollers, wear pads, sprockets, rope sheaves. Nylon absorbs up to 3 % water and grows with it; acetal absorbs almost none.

Is 3D-printed plastic as strong as molded or machined?

Not quite. SLS and MJF nylon reach 80–95 % of molded strength and are nearly isotropic; FDM parts are 60–80 % in-plane and weaker across layers; SLA resins are stiff but more brittle and creep under load. For a functional prototype the difference rarely matters; for a production part that carries load, machine it from stock or mold it.

Which plastics resist chemicals?

Fluoropolymers (PTFE, PFA, FEP, PVDF) resist nearly everything. PP and HDPE handle most acids, bases and alcohols; PVC and CPVC most acids and chlorine but not solvents; PPS and PEEK cover hot solvents and steam. Weak spots: PC and PMMA craze in solvents and alkalis, nylon swells in water and dissolves in strong acids, ABS softens in ketones and esters.