Material choice is the most common question we get. Every project starts with “what should this be made from?” and the answer depends entirely on where your part lives and what it has to survive.
Here’s a straightforward comparison of three engineering thermoplastics we print with daily: Nylon (PA6/PA12), PETG, and ASA.
The Comparison
| Property | Nylon (PA12) | PETG | ASA |
|---|---|---|---|
| Tensile Strength | 50-85 MPa | 50-55 MPa | 40-55 MPa |
| Flexural Modulus | 1,200-1,800 MPa | 2,000-2,200 MPa | 2,000-2,200 MPa |
| Heat Deflection | 80-180°C | 70-80°C | 95-105°C |
| UV Resistance | Poor (degrades) | Moderate | Excellent |
| Chemical Resistance | Good (oils, fuels) | Excellent (acids, bases) | Good (general) |
| Impact Strength | Excellent | Good | Good |
| Moisture Absorption | High (2-8%) | Very Low | Very Low |
| Cost per Part | $$$ | $$ | $$ |
Numbers vary by specific grade and print settings. These are representative ranges from production parts, not datasheet maximums.
When to Use Nylon
Nylon is the workhorse for mechanical parts. It’s tough, wear-resistant, and handles repeated impact and vibration better than almost anything else you can print.
Best for:
- Load-bearing brackets and mounts
- Wear surfaces: bushings, guides, sliding contacts
- Under-hood automotive parts (heat + vibration + oil exposure)
- Snap-fit assemblies that need to flex without breaking
- Parts that take repeated impact
Nylon absorbs moisture from the air, which actually increases its impact resistance slightly but reduces stiffness. For parts that need to stay dimensionally stable in humid environments, use a sealed or coated nylon, or consider one of the reinforced variants.
Reinforced options: Carbon fiber nylon (CF-PA) adds 2-3x stiffness at minimal weight gain — ideal for structural brackets and housings. Glass fiber nylon (GF-PA) splits the difference between CF and standard: better impact resistance than CF-nylon, better stiffness than plain nylon.
When to Use PETG
PETG is the practical choice for chemical environments and cost-sensitive production runs. It prints reliably, resists most common chemicals, and costs less per part than nylon.
Best for:
- Chemical exposure: lab equipment, cleaning solution contact, food-adjacent applications
- Transparent or translucent parts where visual clarity matters
- Cost-sensitive production runs where you need “good enough” mechanical properties
- Parts exposed to moisture (near-zero absorption vs. nylon’s 2-8%)
- Medical and food-contact applications (FDA-compliant grades available)
PETG’s main limitation is heat. At 70-80°C heat deflection, it’s not suitable for anything near engines, heaters, or sustained sun exposure in enclosed spaces. It’s also softer than nylon — fine for static loads, less ideal for wear surfaces.
Reinforced options: Carbon fiber PETG adds stiffness and improves the heat deflection temperature by 10-15°C. Glass fiber PETG is less common but available for applications needing chemical resistance with added rigidity.
When to Use ASA
ASA is what you use when your part lives outside. It’s essentially ABS with UV stability — same general mechanical properties, but it won’t yellow, chalk, or become brittle after months of sun exposure.
Best for:
- Outdoor enclosures and housings
- Automotive exterior parts: mirror caps, trim pieces, vent surrounds
- Signage and display mounts
- Garden, marine, and agricultural equipment
- Any part exposed to sustained UV radiation
ASA also handles temperature cycling well. Parts that go from freezing nights to hot afternoons won’t warp or crack the way PLA or even PETG might over time. Its chemical resistance is reasonable for general exposure — not as strong as PETG against specific acids, but fine for rain, road salt, and cleaning agents.
Reinforced options: CF-ASA is available but less common. For outdoor structural parts that need more stiffness, we usually recommend switching to CF-nylon with a UV-resistant coating rather than reinforced ASA.
How to Decide
Start with the environment, not the part geometry:
- Will it be outside? → ASA
- Will it touch chemicals? → PETG
- Will it carry load, wear, or vibrate? → Nylon
- Is it cost-sensitive with moderate requirements? → PETG
- Does it need to survive above 100°C? → Nylon (or CF-nylon for stiffness)
If your part crosses categories — outdoor and load-bearing, for example — that’s where material selection gets interesting. Usually one requirement dominates, but sometimes you need reinforced variants or a two-material approach.
What About Blends and Specialty Filaments?
We see a lot of “nylon-like” or “engineering PETG” filaments marketed online. Most of them are fine for hobby printing but don’t have the consistency or verified properties you need for production parts. We stock specific industrial grades with known, repeatable properties. When we quote a material, we can provide the actual datasheet for that exact grade.
Not Sure? Ask.
Send us your use case — where the part lives, what loads it sees, what it’s replacing. We’ll recommend a material and print a test part so you can validate it in your actual application before committing to a production run. No charge for the material recommendation. Test parts are billed at standard rates.
That’s the fastest way to get from “which material?” to “this one works” without guessing.