Future-Oriented Experimental Characterization of 3D Printed and Conventional Elastomers Based on Their Swelling Behavior

Abstract

The present study investigates different elastomers with regard to their behavior towards liquids such as moisture, fuels, or fuel components. First, four additively manufactured materials are examined in detail with respect to their swelling in the fuel component toluene as well as in water. The chemical nature of the materials is elucidated by means of infrared spectroscopy. The experimentally derived absorption curves of the materials in the liquids are described mathematically using Fick’s diffusion law. The mechanical behavior is determined by uniaxial tensile tests, which are evaluated on the basis of stress and strain at break. The results of the study allow for deriving valuable recommendations regarding the printing process and postprocessing. Second, this article investigates the swelling behavior of new as well as thermo-oxidatively aged elastomers in synthetic fuels. For this purpose, an analysis routine is presented using sorption experiments combined with gas chromatography and mass spectrometry and is thus capable of analyzing the swelling behavior multifacetted. The transition of elastomer constituents into the surrounding fuel at different aging and sorption times is determined precisely. The change in mechanical properties is quantified using density measurements, micro Shore A hardness measurements, and the parameters stress and strain at break from uniaxial tensile tests.

The effect of water ingress on additively manufactured electrodes

“…Perhaps under-appreciated by electrochemists is the inherent permeability of polymer materials towards small molecules, with PLA representing a particularly poor barrier compared to other common polymers. 12 Such solvent ingress often results in swelling of the polymer, which can lead to structural damage 13 to and changes in bulk mechanical properties 14 of the polymer. These physical changes might well prove to be of concern to electrochemists, for example because swelling could change the electroactive area of the electrodes.…”

The Design of 4D‐Printed Hygromorphs: State‐of‐the‐Art and Future Challenges

“…For instance, most studies consider squares specimens of material with parallel printing paths. [ 8,58,87,278 ] Other studies however consider dog bone specimens, [ 277,279 ] or the specific shape of the coupon for which the material is developed for [271]. Finally, a precise evaluation of the range of variation of humidity should be part of a standardization of the measurement techniques.…”

“…Moreover, measurements of the hygro-deformation need to be carried out in an appropriate medium. For instance, Loos et al [277] have characterized the absorption using an Archimedes-type of measurement in toluene. In a similar way to the mechanical properties, the assessment of the influence of the humidity on the CME is important to improve the reliability of design models for hygromorphs.…”

“…Reference Material Measurement Scale RH range Properties Vonk et al (2020) [280] Hydrogel filament Full field topography Phase (filament) 10%-90% Hygroscopic strain Faust et al ( 2021) [281] Nylon & short carbon fibers Laser line probe Phase (filament) Dry%-52% Hygroscopic strain Hiendlmeier et al (2022) [77] Superabsobent in-house resin Mechanical swelling equilibrium Layer Dry%-100% Hygroscopic Strain Kreider et al ( 2021) [279] Polyamid & short carbon fibers CT-scanner Layer Ambient RH%-100% Volume change Loos et al ( 2021) [277] Elastomer Archimedes Layer Ambient RH%-100% Volume change Lv et al (2018) [271] Hydrogel Fluorescent Microscope Layer Ambient RH%-100% Swelling ratio…”

The influence of printing parameters on the mechanical properties of 3D printed TPU-based elastomers

“…This impairs both the final quality of the parts and the extrusion process, sometimes leading to the interruption of the print jobs [10]. The influence of liquid media on printed geometries and their resulting mechanical behaviour was investigated in Loos et al [11]. Bruère et al [12] examined the under-extrusion related to the feeding system and caused by moisture absorption by the filament prior to printing.…”