Development of a PMMA/TiO2/LO nanocomposite for aquatic environments

Abstract

Structures and vessels exposed to water are susceptible to corrosion and fouling due to multiple factors such as the complex biology present in these environments. Hence, it is important that new materials are investigated, combining durability and anti-fouling properties. To tackle this, the work in this project investigated a nanocomposite material, that consisted of a polymethyl methacrylate matrix and titanium dioxide nanoparticles encasing linseed oil as the dispersed phase. The development of the material and evaluation of its durability, anti-fouling properties and leaching of ions into the environment were the main objectives of this project. Samples were prepared using the doctor blade technique, applying a film containing 8.6, 14.8 and 28.3 wt% titanium dioxide nanoparticles on to glass substrates. To assess the durability of the material, salt-spray testing was conducted to simulate environmental conditions while leaching testing was carried out in deionised water. Prior to the salt-spray testing, the weight, wettability and surface roughness of the samples were assessed. These properties were also assessed just after the salt-spray testing and after two weeks. Optical microscopy was conducted to assess the self- healing capabilities of the material. The results showed that contact angle as well as the surface roughness of the nanocomposite increased with an increase in wt% of the nanoparticles. After salt-spray testing, the contact angle decreased while the surface roughness increased. This trend continued after the two weeks were allowed to assess any self-healing. It was noted that the nanocomposite was prone to degradation as well as showing significant adherence issues. Trends towards self-healing properties were noted within the 28.3 wt% samples that underwent both salt-spray testing as well as the leaching testing, but this was not conclusive. The liquid from leaching testing was extracted and analysed using inductively coupled plasma mass spectrometry. The leaching testing indicated that the 28.3 wt% samples leached less than 1 ng/mL of titanium ions. The anti-fouling tests conducted involved assessing the growth inhibition of the nanocomposite against both marine and freshwater algae. All the samples exhibited anti-fouling properties that were not significantly different to PMMA. They showed sufficient growth inhibition against the freshwater algae while being less effective against the marine algae, showing differing results for the latter. The material developed was not durable as would be necessary for the aquatic environment. However, the nanocomposite provided good anti-fouling properties while keeping Ti ion leaching into the environment below the threshold.