An important challenge faced by the automotive industry concerns the so-called overspray, when excess paint particles disperse and contaminate the surrounding environment. To minimise the potential damage caused by overspray to the painting robots, these are often protected by polyester covers. However, their hydrophilic nature leads to paint absorption, requiring their often replacement and subsequent waste generation. A promising solution to deal with this problem is to impart the covers with superhydrophobic properties. In superhydrophobic surfaces, the drops of water are almost
spherical, so they will readily roll off. When exposed to paint particles, the paint should behave similarly, not having time to be absorbed.
In this work, several modification strategies were explored to impart polyester fabrics with highly hydrophobic features through the combination of nanomaterials (silica and alumina nanoparticles) to introduce a micro/nano roughness and the use of low surface free energy compounds (stearic acid and hexadecyltrimethoxysilane). Results showed that, overall, the immobilisation of polyester samples with nanomaterials alone increased the water contact angle, but the water droplets did not roll from the surfaces. Such hydrophobic features were attributed to the increase in fibres' roughness, as evaluated by SEM analysis and roughness measurements. When nanomaterials were combined with hydrophobic agents, the hydrophobic properties of polyester fabrics improved synergistically, as evidenced by the increase in the water contact angle but also by the decrease in the water sliding angles. It was also possible to conclude that any of the modification strategies improved the fabric’s ability to resist the effects caused by overspray, as there was a significant reduction in the amount of paint absorbed. Results also suggested that the approaches with the lowest sliding angles had better resistance against the effects caused by overspray. The durability of the best effective treatment was evaluated by measuring the water contact angle after 70 washing cycles, and results showed that hydrophobicity could be preserved even after being subject to these harsh conditions.
In conclusion, combining nanostructured materials with hydrophobic agents holds great potential to create highly hydrophobic features and subsequent resistance to overspray. This minimizes the need for frequent replacements, reduces painting process delays and costs and reduces the waste produced.