Assessment of Microfadometry as a tool for the rapid identification of photosensitive polymer based additive manufacturing materials.
 
Carolien Coon, Jacob Llewelyn Thomas, Matija Strlic1

 
Developments in digital technologies are transforming the way we produce, interpret and care for art. Additive Manufacturing (AM) allows artists and conservators to create and replicate in a way not possible before and as such 3D printed objects are forming part of museum collections – either as artworks, surrogate objects or for use in conservation. The expiration of Rapid Prototyping (RP) patents led to quick developments in AM systems and materials are becoming more and more complex. Currently the most advanced systems are evolutions from the stereolithographic process. Using inkjet technology, high-resolution multi-material colour printing is now possible resulting in a single print incorporating a range of material properties. This presents a conservation challenge, as very little is known about the long term stability of these materials.  Experimental materials are also being made commercially available at competitive prices but only for brief periods of time.
 
Previous studies into the photostability of AM polymers proved photopolymers to be amongst the least stable AM materials. Photo-initiators and the ratios of base polymers in hybrid systems play a significant role in material stability. Simply re-printing is not always a viable option, due to it not being sustainable and also due to post-processing or digital preservation issues. The scope of new and experimental materials available on the market with unknown compositions highlights the need for a method to rapidly assess the stability of objects or part of objects as they enter collections.
 
Microfade testing (MFT) has successfully been used to identify light sensitive dyes or pigments present in museum collections. If applicable to plastic AM materials, MFT would be an excellent tool for surveying 3D printed artworks entering collections as it provides quick responses and is micro-destructive. Initial assessments using Xenon MFT to identify photosensitive AM were unsuccessful. Exposing photosensitive AM materials to accelerated light degradation at 17 Mlx resulted in mechanisms atypical to ambient conditions due to limited oxygen diffusion, thus preventing valid extrapolation to real conditions. Reciprocity testing with LED MFT at light intensities between 0.8 – 0.18 Mlx resulted in increased proportionality in reaction rates. These results as well as investigations into MFT in anoxia and oxygenated environments are presented and the potential of UV-Vis MFT as an analytical tool to study the photochemistry of AM materials will be explored.