PLA or HT? Which high-temperature filament can stand heat and stress better?

In my last article, I went over the basics of working with high-temperature 3D printer filaments. In this article, I'll put both HT and PLA (polylactic acid) filament through two of three separate homemade tests.

The three experiments I conducted were designed to test the two filaments in terms of strength and heat resistance while controlling as many outside factors as possible.

I’m sure that ColorFabb has a very sophisticated, very expensive testing machine that tests their filament in a completely controlled environment. Unfortunately, I do not have access to such a machine, so my testing devices will be built out of materials you can purchase from your local hardware store.

Oven Test

The first experiment was designed to test the heat resistance of the two filaments. I put two rings, one in HT and one in PLA, side by side on a cookie sheet and put them in an oven. Then, I started ramping up the heat. The following picture shows the two models after the test.

Both models (HT on the left and PLA on the right) after the oven test

Frankly, I was very surprised by the outcome. At exactly 100 degrees Celsius, I pulled the models out of the oven and attempted to cut them using a butter knife. Both models held up in exactly the same fashion, so I put them back in the oven and again turned up the heat.

The interesting outcome occurred at 300 degrees Fahrenheit. The black HT ring was malleable and folded in on itself, while the white PLA ring appeared unfazed by the high temperature. This could be a product of the HT filament being more pliable overall, but it is not the “High Temperature” resilience that I expected.

What is important to note is that this experiment was not conducted under the operating specs explicitly set forth by the manufacturer. The HT filament's exact claim is that the filament retains its strength up to 100 degrees Celsius, and the filament folded under significantly more than that. Even though I will talk about verifying that exact claim in the final article in this series, this first test is not a standout performance by the HT filament.

Hammer Drop Test

The second test I conducted was purely a strength test. To test the strength of the filament, I mounted the each ring in a vice and repeatedly dropped a four-pound sledgehammer on them. Here is a layout of the testing machine:

The ColorFabb_HT model in the testing setup

Of course, the optimal way to test the ring would be to hang successive weights on it until it failed, but I felt that this method was much safer in that it did not involve heavy weights suddenly falling to the ground.

I started by dropping the hammer on the print from a short height and successively raised the hammer, one inch at a time. If the print survived all of those drops, I would repeatedly drop the hammer from the highest point and record how many hits it survived. The following two videos show each print having the hammer dropped on it.

The HT (left) and PLA (right) models reaching their respective breaking points in the stress test

This is the test that the HT filament truly stood out in. The PLA couldn’t survive even one drop from the highest point, while the HT model survived through twenty-two drops. Honestly, I’m surprised that ColorFabb doesn’t market the product as primarily higher-strength because the improvement over standard PLA is unprecedented.

One of the main attributes that makes the HT filament more shock resistant is its inherent softness. This may have been a detriment during a pure heat test, but when a weight is dropped on it, the HT filament is more “bouncy” and is able to absorb the energy much more effectively. Even other filaments designed for strength, such as carbon fiber composites, are much more rigid and would not be able to handle the shock as well. The difference would be similar to dropping a hammer on a rubber ball instead of a raw egg.

In the next article, we will talk about testing the heat resistance and strength simultaneously, as well as an overall analysis about how each filament performed.

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