Filament Heat Resistance Chart: HDT for Every OzFDM Material

Written by James Hill

Quick answer: Our standard PLA grades list an HDT of 53°C, PETG 68–74°C, ABS 85–98°C, ASA 88°C, PC 123°C, PC-ABS 112°C, and PA6-CF, PET-CF, PPA-CF and PPS-CF 200–245°C (ISO 75, 0.455 MPa). Use HDT to compare materials, not as a safe working limit: loaded parts and thin walls soften sooner.

A print that looks perfect on the bed can still sag on a dashboard, droop in a sunny garden or deform next to a warm motor. This page lists the heat deflection temperature (HDT) for every filament we sell, taken from the technical specifications on each product page, with one row per material and a link to the product.

What HDT measures, and how it differs from Tg and Vicat

Heat deflection temperature (HDT)

HDT is measured under ISO 75, and ASTM D648 is a similar method. A moulded test bar is supported at both ends, loaded in the middle and heated at a steady rate until it bends by a small set amount. The temperature at that point is the HDT. ISO 75-2 allows three loads: 1.80 MPa, 0.45 MPa and 8.00 MPa. A heavier load makes the bar give way at a lower temperature, so two HDT figures are only comparable when they were measured at the same load.

Every figure on our product pages is listed at 0.455 MPa (66 psi), the lighter load, except PA12-CF, which is listed at 1.8 MPa (264 psi).

Vicat softening point

The Vicat test (ISO 306 or ASTM D1525) presses a flat-ended needle with a 1 mm² tip into the sample under a 10 N or 50 N load and records the temperature at which it sinks 1 mm (Vicat softening point). It measures surface softening under a point load, not a bar bending, so Vicat and HDT figures are not interchangeable. Our product pages do not list Vicat.

Glass transition temperature (Tg)

Tg is not a load test. It is the temperature range over which the amorphous part of a plastic changes from hard and glassy to soft and rubbery, usually measured by DSC or DMA (glass transition). For amorphous plastics such as PETG, ABS, ASA and PC, useful heat resistance sits just below Tg. Semi-crystalline plastics such as nylon, PET, PPS and PP behave differently: their crystalline regions help them resist softening above Tg (crystallisation of polymers). That is one reason the fibre-filled nylon, PET, PPA and PPS grades list such high HDTs. Our product pages do not list Tg.

Why printed parts soften sooner than the chart suggests

ISO itself says HDT results do not necessarily represent maximum usable temperatures, because time and loading in real use differ from the test (ISO 75-1). For 3D printed parts, four things pull the real limit down.

• Load. The 0.455 MPa test load is light. A bracket holding weight or a clip under spring tension sees far higher local stress, so it starts to move at a lower temperature.
• Time. The test heats the bar at about 2°C per minute and stops at a small deflection (heat deflection temperature). A part in a hot car or enclosure sits at temperature for hours, and slow creep adds up.
• Structure. Test bars are solid moulded samples. Printed parts have layer lines, infill gaps and cooling stress, so less material resists the load.
• Thin walls. A thin skin over sparse infill carries higher stress and heats through faster than a thick section.

Sun adds to all of this. A dark part in direct sunlight runs hotter than the air around it, and the Victorian Government notes that the inside of a parked car can be 20 to 30 degrees hotter than outside (Better Health Channel). Leave a clear margin between the hottest temperature you expect and the HDT you choose, and more for loaded or thin parts.

OzFDM heat deflection temperature chart

Figures come from the technical specifications on each product page and are ISO 75 at 0.455 MPa (66 psi) unless the row says otherwise. Continuous use is the long-term temperature figure where one is listed. Most come from IEC 60216, a heat ageing method; a few are from UL 746B (RTI) or a typical published value for the base polymer, as stated on the listing. It comes from a different test to HDT, so read the two columns separately. Where a product page has no HDT yet, the row says See data sheet. Several of our newest grades are still awaiting verified test data from the manufacturer.

PLA family

PETG family

ABS and ASA family

Engineering filaments: PC, PC-ABS, nylon, PPA and PPS

Carbon fibre and glass fibre grades of PLA, PETG, PET, ABS and ASA

Flexible, support and other materials

How to use this chart

These are starting points. Test a part in its real location through a hot spell before relying on it.

Car interiors

If a parked car can run 20 to 30 degrees above the outside temperature, a 35°C day can put the cabin past 55°C before direct sun on the dashboard is counted. PLA (53°C) is a poor fit for anything that lives in a car, and PETG (68–74°C) is marginal for parts in the sun. ASA (88°C) is a sensible starting point for trim clips, cable holders and phone mounts, and its UV resistance helps parts that see sun every day. For parts on the dashboard itself, or anything carrying load, PC (123°C) gives more headroom.

Outdoor enclosures and garden parts

Outdoors, sunlight and heat work together. ASA is a sensible first choice for enclosures, mounts and brackets that live outside, because it pairs a higher HDT than PETG with UV resistance, and ASA-CF and ASA-GF list the same HDT in fibre-reinforced form. PETG can suit shaded, lightly loaded parts. Lighter colours absorb less sunlight than black, and electronics inside a sealed box add their own heat, so allow extra margin for a dark enclosure in full sun. Our ASA vs ABS guide covers the outdoor trade-offs.

Near motors, heated beds and hotends

Stepper motors, heated beds and enclosed print chambers keep nearby parts warm for hours. Fan ducts, motor mounts and enclosure fittings are better printed in ABS, ASA or PC than PLA, especially if you print hot materials inside an enclosure. Close to a hotend, the carbon fibre engineering grades list the highest figures (PA6-CF 200°C, PET-CF 205°C, PPA-CF 220°C, PPS-CF 245°C), but they are abrasive and need a hardened steel nozzle and a well dried spool, and PPS-CF needs a 300–350°C nozzle temperature and an enclosed printer. Whatever the chart says, keep printed parts out of direct contact with the heater block and nozzle.

Annealing for extra heat resistance

Annealing means baking a finished print below its melting point so the plastic can relax and, in semi-crystalline materials, crystallise further. Our annealing guide covers the process for PLA, PETG and ABS. The product pages for PA6-CF, PA12-CF, PET-CF, PPA-CF and PPS-CF recommend 80–100°C for one to three hours depending on the grade, and PC-ABS 100°C for one to three hours.

Expect some shrinkage or distortion, so try a spare part first. Our product pages do not say whether the listed HDTs were measured on annealed samples, so do not assume a print straight off the bed will reach them.

Shop the materials in this guide

• 1.75 mm ASA Filament - 1 KG: 88°C HDT and UV resistance for car interiors and outdoor parts.
• 1.75 mm PETG Basic Filament - 1 KG: 74°C, our highest listed unfilled PETG, for warm indoor spots.
• 1.75 mm PolyCarbonate Filament - 1 KG: 123°C HDT for loaded parts that need more headroom.
• 1.75 mm PA6-CF Filament - 1 KG: 200°C listed HDT in a stiff carbon fibre nylon.
• 1.75 mm PPS-CF Filament - 1 KG: 245°C, the highest listed HDT in our range.
• Engineering Filament: every PC, PC-ABS, nylon, PET, PPA and PPS grade from this chart.

Frequently asked questions

What is the most heat resistant filament OzFDM sells?

On listed figures, PPS-CF at 245°C, followed by PPA-CF (220°C), PET-CF (205°C) and PA6-CF (200°C). All four are carbon fibre grades that need a hardened steel nozzle and careful drying, and PPS-CF also needs a 300–350°C nozzle temperature and an enclosed printer.

Will a PLA print survive in a hot car?

Probably not for long. PLA lists an HDT of 53°C, and a parked car on a warm day can pass that. Expect warping, especially on thin or loaded parts. ASA or PC are better choices for anything that stays in the car.

Is PETG heat resistant enough for outdoor use?

Our unfilled PETG grades list 68–74°C, which can suit shaded or lightly loaded outdoor parts. For dark parts in full sun or anything under load, ASA at 88°C gives more margin and adds UV resistance.

Why doesn't the chart show Vicat or glass transition figures?

Our product pages list HDT and, for many materials, a continuous use temperature, but not Vicat or Tg. Rather than borrow generic figures that may not match our filament, we leave those columns out.

What does See data sheet mean?

The product page does not list an HDT yet, usually because the grade is new and verified test data is still to come from the manufacturer. Check the technical data sheet on the product page, and if it has no figure either, contact us before you rely on that material for heat.

Related guides

• PLA vs PETG vs ABS: Which Filament Should You Actually Use?
• ASA vs ABS: The Smarter Choice for Outdoor Prints
• Annealing 3D Printed Parts
• Building a DIY Printer Enclosure