PERFORMANCE OF TITANIUM DIOXIDE (TIO2) PHOTOCATALYTIC COATING IN SINGAPORE

Abstract

The self-cleaning coating known as Titanium Dioxide (TiO2) coating was one of the solutions to clean the façade of tall buildings which in turn decreased the frequency for façade maintenance. The function of TiO2 self-cleaning coating on building façade had been discussed widely in the last decade. However, few studies and reviews were carried out on the application of the coating in buildings in Singapore. Therefore, this study intended to provide analysis and reviews on the few pioneer TiO2 self-cleaning coating case studies in Singapore in terms of performance, cost and management issues. Moreover, this study identified the important criteria to achieve successful performance of TiO2 self-cleaning coating specifically in Singapore.

Two tests were conducted for the evaluation of the performance of TiO2 coating. The water contact angle test were most suitable for the monitoring of the performance of TiO2 coating on non-porous and smooth surfaces such glass and aluminium, where upon irradiation of sunlight, the water spread out instead of beading. This test was not suitable for concrete and painted surfaces due to their porous and water absorbing nature. However, it was shown to be suitable for granite stone surfaces after a longer duration of sun’s irradiation.

The methylene blue test was also only suitable for glass, aluminium and stone surfaces, where upon irradiation of sunlight for 2 hours, the blue dye discolourised indicating the formation of hydroxyl ions to break down organic stains. This test, to monitor the performance of the coating, was also found to be unsuitable for the porous concrete and painted surfaces.

Six case studies of TiO2 coated façade were analysed in depth to evaluate and review the performance of the technology in Singapore. Four successful cases comprised of Tokio Marine Centre, a bungalow, National Museum of Singapore and Singapore Supreme Court. The two unsuccessful cases were Pacific Plaza and Nanyang Technological University Art, Design and Media School (NTU ADM). The main reasons of success and failure of the coating were due to technology of application, location and age of building. The information was collected through interview, site visits, questionnaires and secondary resources. To conduct the research and analysis, the Facilities Managers, Architect Firm and TiO2 Coating Supplier were interviewed to collect relevant data and in-depth details. Site visits to the Pacific Plaza, Tokio Marine Centre, NTU ADM were conducted to verify and investigate the performance of the TiO2 self-cleaning coatings. Questionnaires were sent to the Facilities Managers of the six case studies to obtain insightful evaluation and performance assessment.

Finally, a performance checklist was derived from the interviews, experiments and case studies to provide a guide for objective evaluation of the building and good practice to ensure the success performance of the TiO2 coating. The criteria for the success of TiO2 coating include type of substrate; location of building; design favourable to photocatalytic action; dry weather and dry spells; application of photocatalytic coating; age of building; tampering of coating; presence of silicone residue; and excessive wear and tear.