Bc. Lucie Reinšteinová

The work focuses on the synthesis of the siloxene nanofiller and its subsequent use in the preparation of poly(ε-caprolactone)/siloxene (nano)composites via in situ polymerization and melt blending. The siloxene nanofiller was synthesized by deintercalation of calcium silicide. Conditions for the polymerization of ε-caprolactone containing dispersed siloxene were optimized—tin(II) 2-ethylhexanoate was found to be the most suitable one. Subsequently, (nano)composites were prepared. Thermal properties, mechanical properties, and the dispersion of the filler within the polymer matrix were studied. Increasing the filler content led to an increase in the glass transition temperature by up to 6, even though the molar mass decreased exponentially as the siloxene acted as a transfer agent during polymerization. Finally, biocompatibility and cytotoxicity tests were conducted, which represent an essential part of evaluating potential biomaterials. The tests confirmed the bio-inertness of the samples and ruled out their cytotoxicity.

The aim of this work is to advance further the development of an environmentally friendly method of manufacturing printed circuit boards (PCBs) using recycled and recyclable 3D printable polymers as an insulating substrate and electrically conductive pastes for the conductive pattern. Previous iterations of this alternative process development were focused on the automatic dispensation of ink from the cartridge to create the conductive pattern. To reduce the time required for production, increase the accuracy of the process, and make it much more implementable in practice, screen printing was employed for the creation of a conductive pattern in this study. Two conductive pastes were used in this study: a silver-based paste and a copper-based paste. For the protection of the patterns against degradation, two different methods were tested: overprinting with another polymer layer by 3D printer and coating with an acrylic varnish. To test the functionality of surface treatments and their effect on the circuit's reliability, samples were placed in a desiccator at 99% relative humidity. The results, however, showed that the effect of the tested surface finish is negligible, and the durability of the conductive patterns under a humid environment is given primarily by the paste itself. The silver-based paste showed no significant change after 125 days in the desiccator. On the contrary, complete degradation of the copper-based patterns occurred after only 6 hours in the desiccator. Despite being more environmentally friendly, the copper-based paste is not practically usable from this point of view without significantly more robust surface protection, such as plating. Therefore, the silver-based pastes will be utilized in further continuation of this project.