Revealing interactions of layered polymeric materials at solid-liquid interface for building solvent compatibility charts for 3D printing applications

Poor stability of 3D printed plastic objects in a number of solvents limits several important applications in engineering, chemistry and biology. Due to layered type of assembling, 3D-printed surfaces possess rather different properties as compared to bulk surfaces made by other methods. Here we study fundamental interactions at the solid-liquid interface and evaluate polymeric materials towards advanced additive manufacturing. A simple and universal stability test was developed for 3D printed parts and applied to a variety of thermoplastics. Specific modes of resistance/destruction were described for different plastics and their compatibility to a representative scope of solvents (aqueous and organic) was evaluated. Classification and characterization of destruction modes for a wide range of conditions (including geometry and 3D printing parameters) were carried out. Key factors of tolerance to solvent media were investigated by electron microscopy. We show that the overall stability and the mode of destruction depend on chemical properties of the polymer and the nature of interactions at the solid-liquid interface. Importantly, stability also depends on the layered microstructure of the sample, which is defined by 3D printing parameters. Developed solvent compatibility charts for a wide range of polymeric materials (ABS, PLA, PLA-Cu, PETG, SBS, Ceramo, HIPS, Primalloy, Photoresin, Nylon, Nylon-C, POM, PE, PP) and solvents represent an important benchmark for practical applications.


Supplementary_Movie_S1.mp4
This video illustrates the effect of the extrusion multiplier on the stability of FDM parts made of PLA in dichloromethane. For comparison, the effect of the solvent on the extruded part is shown. All parts have the same dimensions and similar weight. Three FDM parts were manufactured with different extrusion multiplier values: 0.8; 0.9; 1.0. That is, this experiment demonstrates the stability of FDM parts manufactured with extrusion multipliers that are most commonly used in practice of FDM printing. A brass cylinder was used as an indicator. A video is a time-lapse shot taken at 6 seconds intervals during 1.0 hour. During the shooting, 600 individual frames were obtained, which were then combined into this video at a frame rate of 25 fps.

Supplementary_Movie_S2.mp4
This video also demonstrates the effect of the extrusion multiplier on the stability of FDM parts made of PLA in DCM media. Unlike the Movie-S1 video, this video shows parts made with increased extrusion multipliers: 1.1; 1.2; 1.3. An extruded part is selected for comparison. All parts are characterized by almost the same dimensions and weights. The indicator is a brass cylinder. A video is a time-lapse shot taken at 6 seconds intervals during 1.0 hours. During the shooting, 600 individual frames were obtained, which were then combined into this video at a 25 fps frame rate.

Supplementary_Movie_S3.mp4
This video shows various types of degradation of FDM products made from various materials. Disintegration of the FDM parts is shown by the example of a PLA material filled with copper particles in a methylene chloride medium. Delamination is displayed using PLA filled with copper particles in acetone. True dissolution is characteristic of SBS in methylene chloride, and swelling is shown by the example of Primalloy material in toluene. All destruction models presented in this video were shot using the time-lapse method of photoshooting. The time-lapse was 3 seconds; the total duration of the shooting was 80 minutes. The resulting 1600 frames were combined into a video with a 25 fps frame rate.

Supplementary_Movie_S4.mp4
This video shows the absence of the influence of Archimedes force on the destruction time of FDM parts when using indicator beads of different masses. In the experiment steel beads and glass beads of the same size and FDM parts made of PLA were used. The experiment was performed in methylene chloride media. Three different volumes of solvent were used for each type of beads: a small volume into which a smaller part of the bead was immersed; the average volume into which most of the bead was immersed; the large volume into which the entire bead was immersed. In all cases, the destruction of the part occurs at about the same time. The video was obtained as a result of time-lapse shooting at 6 seconds intervals during 2.5 hours. Obtained 1500 frames were combined in a video with a 25 fps frame rate.

Supplementary_Movie_S5.mp4
This video shows the absence of the influence of the shape of the indicator loading on the dynamics of the destruction of FDM parts. FDM parts are made of PLA. The tests were carried out in methylene chloride media. A steel bead and a brass cylinder were used as an indicator loading. Both loads have the same weight. The loss of part integrity in experiments with different loads occurs almost simultaneously. The video is the result of time-lapse shooting, taken at 6 seconds time-lapse during 1.5 hours. The resulting 900 frames were combined in a video of 25 fps frame rate. Table S1. FDM parameters used in this study for a set of materials.                               14. Experiments in water media Figure S41. Snapshot of the experiment in water in the beginning. Figure S42. Snapshot of the experiment in water after 1 h. Figure S43. Snapshot of the experiment in water after 20 h. Table S2. Qualitative analysis of stability of FDM parts made of different materials in organic and inorganic liquid media: (•) material is stable during experimental time i. e. shape of the part does not change; dissolution of outer layers of material does not occur; (•) material is not stable during experimental time, change of shape is observed, dissolution (DS), disintegration (DI), or/and delamination (DL) of the part occur; (•) material is moderately stable during experimental time: its swelling (SW) or slight dissolution of outer layers are observed, shape of the part does not change.