We've just been going through a rather lengthy patent application submitted by Eduardo Napandensky and Diana Ravich - and the patent is assigned to Objet Geometries, one of the top line commercial 3D printer manufacturers. The patent describes a mysterious new print material that has new color and strength properties.
Specifically, this is the abstract:
Described is a composition for solid freeform fabrication (SFF) at a given dispensing temperature. The composition comprises: a curable component having a monofunctional (meth)acrylic functional group; a photo-initiator, and a sulfur-containing additive. The viscosity of the composition, as measured at the given dispensing temperature, changes by no more than 3 cps during 30 days of aging at 40.degree. C.
But what's the nature of this invention?
UV curable acrylic based compositions for SFF, for example FullCure.RTM.720 (from Objet Geometries Ltd, Israel) have a characteristic yellow tint. In some UV curable compositions, the yellow tint is present both before and after curing, while in other compositions, the yellow tint appears only during the curing process. Although the source of the yellow tint is not completely understood, the photoinitiator type and concentration influence the resulting material color. While some photo initiators have a strong color, e.g., I-369, resulting in an undesirable material color even at low photo initiator concentrations, other photo initiators, e.g., Darocure TPO, have much less color, but are required to be used at high concentrations in order to impart the composition sufficient reactivity, thus also resulting in a negative impact on the cured material's color. Other color sources are the color of the raw materials themselves, raw material contaminations as well as additives, e.g., radical scavengers, added in order to impede polymerization of the raw materials during the production process or in order to impede spontaneous polymerization over time during storage.
In addition to the undesirable yellow tint produced by the use of photoinitiators at high concentrations, high photoinitiator concentrations also have a negative affect on the cured material's mechanical properties. For example, a high photoinitiator concentration tends to produce materials with inferior mechanical properties, such as lower tensile strength, compared to the tensile strength of the same material with a lower concentration of the respective photoinitiator.
What appears to be invented in this case is a new material that uses less sulphur (preferably 1% as opposed to 5%), which does two things:
- Improves color quality by reducing the yellow tint
- Improves mechanical strength by reducing the percentage of mechanically weak sulphur
As this is a patent application, we're not sure when this material might appear on their product shelf. Perhaps it already is, but it doesn't say in the application.