It is a good idea to do a little research before decidng which filaments to choose for printing models that will live outdoors. Did you know there are test results that filament manufacturers list on Technical Data sheets regarding resiliency? Two criterias to look for are Heat Deflection temperature (HDT) or Vicat softening temperature. Data about one or the other is usually given.

By way of explaining HDT, imagine you have a plastic ruler. That ruler can hold its shape pretty well at room temperature. HDT is how hot that ruler can get before it starts to bend and droop under its own weight. It’s basically the temperature at which the plastic gets soft enough to sag. Think of it like this: the hotter it gets, the weaker the plastic becomes. HDT tells you the temperature where it gets weak enough to noticeably bend.

This first table gives general information about filaments. Heat deflection temperature can vary depending on the manufacturer and specific formulation of the filament.The values in the table represent a general range.

Filament	HDT
PLA (Polylactic Acid)	50°C – 60°C (122°F – 140°F)
ABS (Acrylonitrile Butadiene Styrene)	85°C – 100°C (185°F – 212°F)
PETG (Polyethylene Terephthalate Glycol)	65°C – 80°C (149°F – 176°F)
Nylon	Varies depending on specific type (60°C – 260°C / 140°F – 500°F)
Polycarbonate (PC)	140°C – 150°C (284°F – 302°F)

Some filament manufacturers utilize Vicat softening temperature tests to measure the temperature at which a model made with the filament loses it stiffness and softens. “The Vicat softening point is closer to the actual melting or softening point of the polymer. Vicat softening temperature is typically always higher than the HDT for a polymeric material as the penetration load is always higher than a bending load on a material specimen.”¹

This second table offers a list of specific brand filaments and their HDTs or VICATs. Use it to lead you in the right direction for finding the best filament to print your outdoor project.

Brand	Flilament	HDT or VICAT
FormFutura	High Gloss PLA ColorMorph	± 58° C (136.4°F) VICAT
FormFutura	Tough PLA	± 57° C (134.6°F) VICAT
Push Plastic	High Heat +Tough PLA	95.3°C (203.54°F) HDT
eSun	ABS+	73°C (163.4°F) HDT
FormFutura	EasyFil ABS	± 103° C (217.4°F) VICAT
Filamatrix	PETG	65°C (149°F) HDT
Filamatrix	Zenith PETG Copolymer	71°C (159.8°F) HDT
PolyMaker	PolyMax PETG	82°C (179.6°F) VICAT
Filamatrix	Nylon Carbon Fiber	147°C (296.6°F) HDT
Filamatrix	Nylon Glass	152°C (305.6°F) HDT
Push Plastic	Carbon Fiber Nylon	172°C (341.6°F) HDT
Push Plastic	Polycarbonate	107°C (224.6°F) HDT
Raise3d	Premium Polycarbonate	117°C (242.6°F) VICAT

1. Kartik Srinivas, “Heat Deflection Temperature (HDT) and Vicat Softening Temperature Testing.” ADVANSES, 24 Feb. 2022, https://advanses.com/heat-deflection-temperature-vicat-softening-temperature/#:~:text=The%20Vicat%20softening%20point%20is,load%20on%20a%20material%20specimen.