I have been 3D printing parts with an Objet 30 Polyjet 3D printer for about a year now, primarily using Stratasys VeroWhitePlus UV cured model material. In general, the parts seem to become more brittle over time, which I assume is due to the parts continuing to cure due to exposure to light. However, I have also noticed that when exposed to moisture for extended periods of time the parts are prone to warping even under little strain at room temperature.
I know that the material does display thermoplastic properties to some extent, but I was wondering if someone might be able to provide me with some additional information about the long-term material properties of either this particular material or similar UV cured 3D printed plastics.
The deformation of the parts in the presence of moisture, in particular, has me really confused, so any information about why this would occur would be greatly appreciated.
In our experience, the parts will continue to cure. I don't have the chemical science background to provide proof or evidence, but I operate from an assumption that if the part requires UV rays to cure, it will continue to be reactive to UV rays after it is considered "cured".
I too have found the same brittleness over long periods of time. The only experience I have with the moisture issue would be a small component designed and built for a cable pulley in the tail section of an aircraft as a temporary solution (acting on a non-critical trim control surface). The aircraft is based down here in Houston, Texas where we get some pretty gnarly humidity. The part did begin warping after a few months but we don't have definitive information indicating it was a moisture problem, or something more structural.
I do know however, that if you aren't absolutely meticulous about cleaning ALL of that gelatin-like support material off of the part, it does wind up being more susceptible to slight deformities, and when you DO remove it all thoroughly, it is then slightly more susceptible to the brittleness issue. Not sure if I'm the only one finding this, and apologies for not having the chemical background to provide more quantitative support.