Samenvatting
Adding carbon particles to a polymer network to prepare conductive elastomers is a common strategy to obtain cheap, robust materials, with high thermal and chemical resistance and good dimensional stability. However, despite being so popular for its low price and ease of manufacturing, very few efforts have been made towards improving its sustainability. In this work, we tackled this gap by adding conductive fillers into a bio-based self-healing polymer matrix cross-linked by Diels-Alder cycloaddition.The final goal is to obtain an ink based on this polymeric matrix with healing capacity and carbon black filler to synthesize stretchable self-healing conductive composite materials to manufacture sensors for smart textiles and soft robotics via screen-printing technique.
The design of the material has been done at various levels of development. Starting by doing simulations of the Diels-Alder reactions to understand the healing behaviour. The
composites are made from a self-healing polymeric matrix based on castor oil, liquid bismaleimide BMI698, carbon black 260G filler, and organomodified nanoclay C15A. A
Design of Experiments and study of the variability factor of Taguchi L9 is done to evaluate the impact of the stoichiometric ratio, the fraction of carbon black and nano clay, on the healing and electrical conductivity properties. The behaviour of conductive composites is evaluated for its application as piezoresistive sensors through quasistatic and dynamic tests. Finally, inks based on the conductive composite are synthesized and applied to a stretchable textile using screen printing.
It is found that adding fillers in the polymeric matrix, despite increasing the conductivity, has a stiffening effect and reduce the healing capacity. An increase in the healing
temperature improves the mechanical properties recovery, however electrical conductivity is efficiently recovered after healing. Composites show a complex piezoresistive behaviour (non-linear). However, they are likely to be use as linear response sensors when strained between 3% and 25% with a GF of -1.065+0.008. Sensors present few hysteresis and drift under dynamic loading making that it could be necessary a periodic calibration. After a fatidic damage, and healing process, the conductivity and sensor performance are recovered. The screen-printing method has shown a good potential for obtaining sensor on textiles. In general, screen-printed conductive self-repairing materials can be a technology that opens the door to obtaining sensors with complex shapes, which can also be extrapolated to an industrial scale. In addition, the use of self-healing polymers networks allows to take advantage of elastomers outstanding properties but in a way that is more aligned with sustainability, since they are capable of being recycled and offer a longer life cycle.
| Datum prijs | 29 jun 2023 |
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| Originele taal | English |
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| Begeleider | Joost Brancart (Co-promotor), Guy Van Assche (Promotor) & Aleix Costa Cornellà (Advisor) |