PLA, ABS, PETG and nylon: a straight-talk guide for engineers

Every maker offers these four materials. Here is how to pick between them based on what your part actually needs to do.

PLA (Polylactic Acid)

Made from corn starch. Rigid, precise, brittle.

• Tensile strength: ~50 MPa
• Heat deflection: 55 °C (sags in a hot car)
• UV stability: poor, yellows and degrades in sunlight
• Cost: $ — cheapest filament
• Use for: prototypes, display models, indoor decor, visual parts, quick-and-dirty brackets

Avoid for: anything exposed to heat, sunlight, or mechanical impact.

ABS (Acrylonitrile Butadiene Styrene)

The plastic LEGOs are made from. Tough, heat-resistant, smelly.

• Tensile strength: ~40 MPa
• Heat deflection: 98 °C
• UV stability: moderate
• Cost: $
• Use for: enclosures, automotive-adjacent parts, anything that needs impact resistance, parts that will be drilled/tapped

Avoid for: precision prints (ABS warps), outdoor use without coating, cases where you can't get vapor-smoothing (acetone fumes are unpleasant).

PETG (Polyethylene Terephthalate Glycol)

The sweet spot between PLA and ABS.

• Tensile strength: ~50 MPa
• Heat deflection: 75 °C
• UV stability: good
• Chemical resistance: excellent — shrugs off oils, greases, most solvents
• Cost: $$
• Use for: mechanical parts, food-contact containers (check certification), outdoor parts, anything that needs to be slightly flexible without breaking

Avoid for: super fine detail (PETG strings a bit).

Nylon (PA6, PA12)

The tough engineering plastic.

• Tensile strength: 45–65 MPa
• Heat deflection: 120+ °C
• Impact resistance: high — bends rather than breaks
• Water absorption: absorbs moisture from air, needs dry storage
• Cost: $$$
• Use for: gears, living hinges, high-impact parts, low-friction surfaces, cable ties

Avoid for: dimensional-accuracy-critical parts (absorbs humidity and shifts), uncoated outdoor use.

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