Effect of post-processing conditions on polyacrylate materials used in stereolithography

Abstract

Additive manufacturing offers simple and cost-effective production of highly customizable 3D-components. One particularly interesting technology is stereolithography (SLA), which enables the fabrication of micro- and milliscale reactionware using transparent materials. In this work, the influence of 3D-printing settings such as printing angle and layer thickness and post-processing conditions, as well as the size and shape of the test samples, on the mechanical, thermal and physico-chemical properties is determined. Two photocurable acrylate resins were used for 3D-printing: Clear and High Temperature. Post-curing of the test samples was performed using several methods and varying treatment times. The tensile test results show that a higher degree of cure results in a higher tensile strength and smaller elongation. On the other hand, layer thickness and print angle have a stronger influence on the tensile strength than some of the post-curing methods. In particular, the samples printed at 45° angle with the smallest layer thickness of 25 µm were found to be the toughest. When comparing Clear and High Temperature material, it is found that the Clear samples can withstand higher stress and strain, but the samples made of High Temperature resin are more rigid and show higher Young's modulus. Differential scanning calorimerty (DSC) tests show that post-curing reduces curing enthalpy, while the glass transition temperature shifts to higher temperatures, indicating crosslinking of the polymer chains. The swelling test showed that both resins can be considered water resistant with an absorption of less than 2% within 24 h. Regarding ethanol and acetone, High Temperature resin proved to be more resistant compared to the Clear resin. The samples post-cured in the SunTest chamber also showed much lower absorption of ethanol and acetone. The contact angle measurement shows that all samples are hydrophilic, regardless of the degree of post-curing or the printing angle.