TY - THES

T1 - Development of electrically conductive resins for DLP printing applications

AU - Feigl, Viktoria

N1 - embargoed until 25-05-2028

PY - 2023

Y1 - 2023

N2 - Developing electrically conductive photopolymer composites and using them with digital light processing 3D printing for the additive manufacturing of multi-material structures could revolutionize the electronics industry in the near future. To approach this goal, electrically conductive polymers were prepared in this thesis by adding electrically conductive fillers. In the course of this, both, the base resin and the filler system were optimized. Due to their viscosities, suitable for incorporating filler, one epoxy and one acrylic resin were selected for the experiments. In the rheological measurements, it was found that processing at 50 °C gives clear advantages in terms of viscosity and the degree of filling that can be achieved. Dendritic copper particles together with carbon nanotubes were used as filler system. Although a higher concentration of filler facilitated a higher electrical conductivity, it also led to a stronger absorption of light and thus, to a decrease of the photochemical reaction kinetics. This was not only shown in photo-differential scanning calorimetry results, as the enthalpy decreased strongly, but also in 3D printing tests. Due to the reduction of the light penetration depth it was not possible to cure resin layers with higher layer thickness efficiently. It was also found that the electrical conductivity does not only depend on the filling degree but also on the matrix and the photoinitiator content. A higher concentration of photoinitiator gave better electrical conductivities but could also bring a positive effect on the photopolymerization rate and the printing time. During all experiments, the selected epoxide resin and the acrylate system were compared as a matrix and the same conclusion was found several times. The acrylate resin, due to its higher reactivity in radical-mediated photopolymerization, led to a faster and more exothermic reaction, less required energy for curing and higher electrical conductivity of the cured materials. With this research, a foundation for future studies could be laid and essential information on achievable filler concentrations with the resins used could be obtained.

AB - Developing electrically conductive photopolymer composites and using them with digital light processing 3D printing for the additive manufacturing of multi-material structures could revolutionize the electronics industry in the near future. To approach this goal, electrically conductive polymers were prepared in this thesis by adding electrically conductive fillers. In the course of this, both, the base resin and the filler system were optimized. Due to their viscosities, suitable for incorporating filler, one epoxy and one acrylic resin were selected for the experiments. In the rheological measurements, it was found that processing at 50 °C gives clear advantages in terms of viscosity and the degree of filling that can be achieved. Dendritic copper particles together with carbon nanotubes were used as filler system. Although a higher concentration of filler facilitated a higher electrical conductivity, it also led to a stronger absorption of light and thus, to a decrease of the photochemical reaction kinetics. This was not only shown in photo-differential scanning calorimetry results, as the enthalpy decreased strongly, but also in 3D printing tests. Due to the reduction of the light penetration depth it was not possible to cure resin layers with higher layer thickness efficiently. It was also found that the electrical conductivity does not only depend on the filling degree but also on the matrix and the photoinitiator content. A higher concentration of photoinitiator gave better electrical conductivities but could also bring a positive effect on the photopolymerization rate and the printing time. During all experiments, the selected epoxide resin and the acrylate system were compared as a matrix and the same conclusion was found several times. The acrylate resin, due to its higher reactivity in radical-mediated photopolymerization, led to a faster and more exothermic reaction, less required energy for curing and higher electrical conductivity of the cured materials. With this research, a foundation for future studies could be laid and essential information on achievable filler concentrations with the resins used could be obtained.

KW - 3D printing

KW - DLP

KW - Digital Light Processing

KW - multimaterial printing

KW - electrically conductive fillers

KW - dendritic copper particles

KW - CNT

KW - electrically conductive composite

KW - electrically conductive resin

KW - photopolymerization

KW - resin-filler-system

KW - photoreactivity

KW - UV light shielding

KW - printability

KW - 3D Druck

KW - DLP

KW - Digital Light Processing

KW - Multimaterial Druck

KW - elektrisch leitfähiger Füllstoffe

KW - dendritische Kupferpartikel

KW - CNT

KW - elektrisch leitfähige Komposite

KW - elektrisch leitfähige Harze

KW - Photopolymerisation

KW - Harz-Füllstoff-System

KW - Photoreaktivität

KW - UV Lichtabschirmung

KW - Druckbarkeit

M3 - Master's Thesis

ER -