Oxygen Absorber at 200-350 deg F For Curing Photopolymer

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In summary, when curing a photopolymer in an anoxic atmosphere, at what temperature does carbon react with and absorb oxygen?
  • #1
Basic Question:

I am trying to heat cure a photopolymer for a couple of hours at 350 deg F in an anoxic atmosphere. My idea was to seal the part in aluminum foil with charcoal to absorb the oxygen, but was not sure that the carbon and oxygen would react at that temperature.

Extra Background Info For The Extra Curious:

I'm working with a 3D printer that uses a light cured polymer (B9 Creator). 3D models are sliced into layers and projected one at a time into a vat of photopolymer. It starts the reaction and cures the model just enough to make it solid. Any more and the light would bleed into the next layer. Once a part is printed, it's washed with IPA to remove liquid polymer and then fully cured. The cured model is placed in a gypsum based investment and the polymer is burned out of the mold for casting.


The polymer is reacting with the investment. Gypsum based investment utilizes a complex chemical reaction. Normally, water is mixed with the powder and a slurry is poured into the mold. The water and binder harden the slurry into a solid. The next reaction completes the hardening. If you heat the model at a specific rate, water is expelled and the cristobalite expands at a rate that maintains dimensional stability.

One way that the polymer interferes with the investment is through thermal expansion. If you fully cure the polymer with a UV light box, the model will undergo thermal expansion. Thicker cross sections will break down the investment just as the cristobalite begins to expand.

The other way it interferes is if you opt to heat cure the model. Heat will complete the reaction initiated by light and allow the model to undergo thermal expansion prior to being in the investment. However, heat cured models will interfere with the investment's chemical reaction leaving a rough surface finish.

Recently, someone tried curing the models by heating submersed models in baby oil (microwave). The results are reportedly perfected. My theory is that the heat plus anoxic environment are making the model thermally and chemically inert. I would like to test this by sealing them with aluminium foil and oven curing them in an anoxic atmosphere.
  • #3
Thanks Greg. To phrase as simple as possible, at what temperature does carbon react with and absorb oxygen?
  • #4
I don't know about the carbon, but that would not be my first approach. A reaction would also heat up the carbon, with the risk of starting a fire.

If oxygen is the problem: do you have access to nitrogen, dry ice or something else you can use to flush your heat chamber?
EricM81 said:
However, heat cured models will interfere with the investment's chemical reaction leaving a rough surface finish.
What about some special treatment of the surface after curing?
  • #5
At higher temps to prevent oxidation, we use a kind of steel foil with charcoal to absorb oxygen, which is why it was my first thought for doing it at 350 def F with aluminium foil.

Fire is not a problem. This is in a commercial burnout oven that's made to allow airflow and burn out all of the carbon in the chamber.

I can bathe it in argon while I seal the foil. That will give me a near oxygenless environment for testing, but if successful it's not a great long term solution.

Surface treatments have varying levels of success. Plus they're hard to apply in a thin layer evenly without pooling. You tend to lose detail, sub 1mm holes get filled in, etc. If only you could electroplate a polymer.

1. What is an oxygen absorber?

An oxygen absorber is a small packet or sachet containing iron powder, salt, and activated carbon. It is used to remove oxygen from the surrounding environment, which helps to preserve the freshness and quality of various products.

2. What is the purpose of using an oxygen absorber at 200-350 deg F?

The purpose of using an oxygen absorber at 200-350 deg F is to facilitate the curing process of photopolymer materials. The high temperature helps to accelerate the chemical reactions involved in the curing process, while the oxygen absorber helps to create an oxygen-free environment, which is essential for the photopolymer to cure properly.

3. How does an oxygen absorber work?

An oxygen absorber works by reacting with the oxygen in the surrounding environment. The iron powder in the absorber combines with the oxygen to form iron oxide, while the salt helps to activate the iron powder. The activated carbon then absorbs any remaining moisture, creating a low-oxygen environment that is ideal for preserving the freshness of various products.

4. What are the benefits of using an oxygen absorber at 200-350 deg F?

Using an oxygen absorber at 200-350 deg F offers several benefits. Firstly, it helps to protect the photopolymer from oxygen, which can interfere with the curing process and affect the quality of the final product. Additionally, the high temperature helps to speed up the curing process, reducing the overall production time. Lastly, an oxygen absorber can also help to extend the shelf life of the cured photopolymer by preventing the growth of microorganisms that require oxygen to survive.

5. Are there any safety precautions to consider when using an oxygen absorber at 200-350 deg F?

Yes, there are some safety precautions to keep in mind when using an oxygen absorber at 200-350 deg F. It is essential to handle the absorber with caution, as the iron powder can be flammable. Additionally, it is crucial to keep the absorber away from children and pets, as it can be harmful if ingested. It is also essential to follow the recommended temperature range and avoid exposing the absorber to extreme heat, as it may cause the packet to rupture and release its contents.