Environmental aging of epoxy based stereolithography parts Part 1-Moisture transport

Current epoxy based stereolithography materials are highly hygroscopic. However, the diffusion of moisture into these materials and the effect this has on the mechanical performance of manufactured parts have not been thoroughly investigated to date. The first part of this paper will discuss the transport of moisture into representative stereolithography materials and the second part of the paper will describe the effect of the absorbed moisture on mechanical performance. Moisture transport in three different epoxy based stereolithography materials has been investigated using mass uptake experiments. The results show that anomalous (non-Fickian) diffusion occurs to varying degrees in all three materials, the characteristic uptake appearing to be pseudo-Fickian. Anomalous uptake models based on dual sorption, diffusion-relaxation and a dual Fickian model were all shown to provide an excellent fit to the data. The effects of relative humidity and sample thickness are also investigated in the paper.