TY - THES

T1 - Development of Conductive Polymer Composites for the Material Extrusion of Dielectric Elastomer Actuators

AU - Steinert, Thomas

N1 - no embargo

PY - 2022

Y1 - 2022

N2 - The research in actuators for special operations has strongly increased in the last decades and gathered high attention. To fulfil different requirements, actuators appear in many different variations. Lately the potential of Dielectric Elastomer Actuators (DEAs) has shown promising results. A key objective of the study was to improve the conductivity of the electrode materials for DEAs with the same flexibility as commercially available materials. Within the COMET-Modul Chemitecture the research was supported in corporation with the Polymer Competence Center Leoben (PCCL) GmbH. As an additive manufacturing process, material extrusion was used to manufacture the DEAs. Silver coated carbon fibres were determined to be the most promising filler type in this application by pre-tests. The chosen matrix was a thermoplastic elastomer (TPE)-type from the company BASF. Conductive Polymer Composites (CPCs) in the form of filaments were produced using different filler contents, and material qualification was achieved by tensile tests, microscopy, and electrical resistance measurements. Based on the first results using pure silver coated carbon fibres as filler, these electrodes performed better than the reference materials. Compared to the reference, the CPC with 15 vol.% silver coated carbon fibres achieved the same displacement of 110 % with a voltage of 2.8 kV (reference material needs 5.4 kV). This meant that half as much voltage was needed to achieve the same displacement. For the resistance measurement an impulse of 2 kV was needed though to achieve conductivity. For the actuators, however, that was not a problem, as they were powered by higher voltages (> 2 kV). Being used as actuators as well, the electrodes were improved so that they could also be used in heating applications at low voltages (< 1 kV). Even though the improved CPCs had a better electrical conductivity, their additive manufacturing proved to be quite challenging. This was caused by the electrically conductive fillers, which also increased thermal conductivity. As a result, the produced filaments could not be printed since they softened too early in the printer and were no longer extrudable. In order to counteract this problem, a different matrix was used. The TPE matrix was replaced by an electrically conductive matrix (TPE + special carbon structure) to reduce the thermal conductivity. Neither of these methods worked, as the material was still too soft and the conveying system in the printer was too abrasive for the filament. In conclusion, the improved electrodes for actuators achieved the in advance set goal, but the developed materials could not be used for heating.

AB - The research in actuators for special operations has strongly increased in the last decades and gathered high attention. To fulfil different requirements, actuators appear in many different variations. Lately the potential of Dielectric Elastomer Actuators (DEAs) has shown promising results. A key objective of the study was to improve the conductivity of the electrode materials for DEAs with the same flexibility as commercially available materials. Within the COMET-Modul Chemitecture the research was supported in corporation with the Polymer Competence Center Leoben (PCCL) GmbH. As an additive manufacturing process, material extrusion was used to manufacture the DEAs. Silver coated carbon fibres were determined to be the most promising filler type in this application by pre-tests. The chosen matrix was a thermoplastic elastomer (TPE)-type from the company BASF. Conductive Polymer Composites (CPCs) in the form of filaments were produced using different filler contents, and material qualification was achieved by tensile tests, microscopy, and electrical resistance measurements. Based on the first results using pure silver coated carbon fibres as filler, these electrodes performed better than the reference materials. Compared to the reference, the CPC with 15 vol.% silver coated carbon fibres achieved the same displacement of 110 % with a voltage of 2.8 kV (reference material needs 5.4 kV). This meant that half as much voltage was needed to achieve the same displacement. For the resistance measurement an impulse of 2 kV was needed though to achieve conductivity. For the actuators, however, that was not a problem, as they were powered by higher voltages (> 2 kV). Being used as actuators as well, the electrodes were improved so that they could also be used in heating applications at low voltages (< 1 kV). Even though the improved CPCs had a better electrical conductivity, their additive manufacturing proved to be quite challenging. This was caused by the electrically conductive fillers, which also increased thermal conductivity. As a result, the produced filaments could not be printed since they softened too early in the printer and were no longer extrudable. In order to counteract this problem, a different matrix was used. The TPE matrix was replaced by an electrically conductive matrix (TPE + special carbon structure) to reduce the thermal conductivity. Neither of these methods worked, as the material was still too soft and the conveying system in the printer was too abrasive for the filament. In conclusion, the improved electrodes for actuators achieved the in advance set goal, but the developed materials could not be used for heating.

KW - Conductive Polymer Composites

KW - Dielectric Elastomer Actuators

KW - Softrobotics

KW - Materialextrusion

KW - leitfähige Polymerkomposite

KW - dielektrische Elastomer-Aktuatoren

KW - Materialextrusion

U2 - 10.34901/mul.pub.2023.69

DO - 10.34901/mul.pub.2023.69

M3 - Master's Thesis

ER -