Desktop filament field guide: PLA, PETG, ABS, ASA, and nylon

01

Start with the service environment

Material selection begins with requirements: load and duration, impact, temperature, sunlight, moisture, chemicals, wear, electrical behavior, appearance, dimensional tolerance, expected life, and consequence of failure. A stiff display model, a sunlit equipment cover, and a wet sliding component ask different questions. NIST’s polymer-AM work focuses on structure-property relationships because the printed process history is inseparable from material performance ¹.

Treat every family comparison as a shortlist, not an approval. Ask for the exact technical data sheet, the specimen preparation and test standard, orientation, conditioning state, color or additive package, and applicable safety data. Raw polymer, injection-molded specimens, and printed coupons are not interchangeable. Build representative features and test them after the same drying, printing, annealing, machining, or conditioning planned for the delivered part.

02

PLA and PETG: accessible does not mean identical

PLA is commonly chosen for easy printing, low warping, stiffness, detail, and broad availability ⁶. Typical unmodified grades can be brittle and lose useful stiffness at temperatures encountered in hot vehicles or near equipment, but a glass-transition value from one resin sheet is not a universal service limit. Formulation, crystallinity, annealing, geometry, stress, and time matter. PLA is often excellent for models, fixtures used in mild conditions, and rapid dimensional prototypes.

PETG is a glycol-modified copolyester family often selected for toughness, strong layer adhesion, and relatively low warp ⁷. It may string, bridge less cleanly, cling aggressively to some build surfaces, and make supports difficult to remove. Water resistance of the polymer does not make a layered object automatically watertight or food-contact compliant. PETG formulations and recycling streams also differ from ordinary bottle PET, so the shared letters do not establish local recyclability.

• Choose PLA when printability, stiffness, and detail matter more than elevated-temperature or impact performance.
• Consider PETG when toughness and layer adhesion are useful and its surface and support behavior are manageable.
• Require grade-specific evidence before using either for heat, chemical, food-contact, pressure, or structural service.

03

ABS and ASA: thermal control and outdoor exposure

ABS can provide useful toughness, impact behavior, post-processing options, and higher-temperature capability than many general-purpose PLA grades ⁸. It also shrinks substantially as it cools, making enclosure temperature, draft control, bed adhesion, geometry, and internal stress important. Large parts may warp or split even when a small calibration object succeeds. Acetone vapor finishing introduces a flammable-solvent process and should never be treated as casual cosmetic cleanup.

ASA is related in use but is commonly selected for improved ultraviolet and weather resistance compared with ABS ⁹. It still requires thermal management and can emit styrene and other compounds during printing. Neither low odor nor an enclosure alone establishes acceptable air quality. NIOSH recommends controlling emissions with material selection, appropriate temperatures, source controls, ventilation, and maintained equipment ². Outdoor suitability also requires evaluation of color stability, temperature cycling, fasteners, coating, and load duration.

04

Nylon: name the polyamide and control moisture

Nylon describes a family of polyamides, including PA6, PA11, and PA12, whose moisture uptake, stiffness, ductility, impact response, heat behavior, and processing differ. Many nylon filaments are valued for toughness, fatigue resistance, wear behavior, and functional parts ¹⁰. Those tendencies do not make an unidentified nylon a certified bearing, gear, pressure component, or high-temperature material. Fillers and copolymers can move performance substantially.

Polyamides are hygroscopic. Moist feedstock can produce bubbles, rough surfaces, inconsistent flow, and altered layer bonding. Dry using the exact manufacturer’s temperature and duration, then store in a controlled dry path; one universal drying recipe can deform a spool or degrade a grade. Printed nylon can also absorb moisture during service, changing dimensions and stiffness. Test in the conditioned state that represents use, not only immediately after a dry print.

• Identify PA family, grade, additives, color, and lot.
• Record drying equipment, temperature, time, and handling after drying.
• Condition test specimens to represent the operating environment.
• Evaluate wear against the actual mating material, load, speed, lubrication, and contamination.

05

Compare honestly and make environmental claims carefully

A useful comparison matrix separates print behavior from service behavior. Include enclosure need, moisture sensitivity, tendency to warp, interface bonding, stiffness, impact, creep, temperature, UV, chemicals, finishing, emissions controls, and available test data. Avoid a single winner or universal temperature chart. Even color and recycled content can change behavior, while raster orientation and voids can dominate a printed specimen’s response. Maintain a local material library with dated specimens and repeat critical checks if a supplier changes formulation, production location, or data-sheet revision for the intended service.

Environmental labels need the same discipline. The FTC advises that broad unqualified environmental-benefit claims can be deceptive and that compostable or recyclable claims require substantiation and appropriate qualification ³. EPA explains that biobased, biodegradable, and compostable are different concepts and that local collection pathways matter ⁴. ISO likewise recommends a life-cycle approach that preserves fitness for use ⁵. A durable part that avoids repeated replacement may outperform a nominally greener material used outside its capability.

• Bio-based does not mean home-compostable.
• A recycling symbol does not guarantee local acceptance.
• Food-contact suitability depends on the complete material and manufacturing process.
• A material name is not a design allowable.