Mimic Polypropylene

I am prototyping some small parts for a customer and they will eventually be injection molded in Polyproylene Homopolymer resin. Before we build hard tooling we want to print some parts in the Form2 and do general fit and function tests on the parts. I have several different Form2 resins and a UV curing station. I am wondering if anyone can help point me towards the best practices to achieve as close to PP parts as possible. Al;so, does anyone know the specific temperature at which well cured resin will soften? I want to experiment with printing cores and cavities to injection mold, but need to stay below the “softening” temperature on the printed materials.

cured parts are not thermoplastics, so will not ‘melt’, per se. somewhere on the forum a year or more back was discussing how it tends to burn with exessive heat. what is the temp of PP @ injection? why not put the core in the over to see if it can withstand that temp for some period?

RE: emulating PP in cured resin; these resins are more acrylic-like when cured. The closest you’ll get to PP will be Tough, or a combination of that and potentially clear and/of flex. Search for Tuff and Tufflex in this forum for experiments I’ve done.

Thanks for the info, I will research the Tufflex posts to better try to understand.

You seem to be doing the types of experimentation I will enjoy doing. If you were looking to make a printed part like polypropylene what resin mix would you try? The parts we are making are for the pharmaceutical market so if you have an pill bottle and lid, that is the approximate results we are looking for. Water bottle caps are very similar as well but a bit softer than the pharma parts.

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I would like to see Formlabs release more resins that mimic different plastics as well.
The original Flex was a fail. I do not know of a plastic that is similar to a stale gummy bear. The V2, I have not printed in yet.
The tough is ok. It has its applications.
More options please. As long as it is not marketed and available to the Form 2 only…

Just for my own sanity I wanted to check. You aren’t planning on putting printed parts in or near an injection molding press are you? The only outcomes I can think of with that combination are expensive, messy, and dangerous.

@DavidRosenfeld The Flexible V2 is a giant step forward, request a sample print, it will make you want a bottle!

Duh! No.

I have a bottle of V2. It is sitting on my shelf. Maybe I will ask for a sample to give me an idea of the improvements and how to better utilize it.
I just got a sample of the new white. I am not sure I like it. It is better then the original but not what I was expecting.


This is from a year and a half ago.

Using printed cores and cavities is definitely going to be the mainstream way to produce high-quality prototypes from the correct plastics.

What we need are resins that can withstand the heat (mostly) and pressure (somewhat less so) associated with the process. Because these cores/cavities are basically an insert inside the standard mold halves, pressures are contained within the block. Inrush pressure will stress small sections of the printed components, but this can be mitigated with a slower injection profile which is fine for low volume parts. I would wager that the heatsink-like effect of the larger mold block will be reduced, due to the more insulating effect of the printed core/cavity. This in turn will keep the melt in a more liquid state longer, allowing longer shot times, and thus less inrush pressure will be required to fully fill the mold.

From the article:

Thanks for the link that’s really awesome stuff! I’ll dive in more when I’m not on the clock :wink:

Successfully proven wrong by the Objet once again. Common FL let’s get some IM-grade resin in the users hands (totally kidding that’s really niche).

Sorry everyone for the left turn this has taken from the OP.