Functionalised nanosilica as an antimicrobial additive for waterborne paints

A new paper reports the use of functionalised nanosilica as a non-leaching biocide.

Water-borne paints are sensitive to humidity and susceptible to microbial attack. To prevent aesthetic bio-deterioration, biocides are used. Some of these biocides leach out from paint film during aging. Researchers now used nanosilica (NS), nanosilica modified with p-nitrophenol (PNP-NS) and silica fume (SF) as antimicrobial agents in commercial waterborne paint at 0.5–2.5 % of total solid content in paint.

Improved properties
It was observed that 2 % PNP-NS improved the antifungal properties by 100 % and 13 % compared to the control sample and commercial antifungal paint, respectively while the antibacterial property was improved by 50 % and 19 %, respectively. The algal defacement test showed more predominant values for paint with PNP-NS compared to paint with NS, SF, and commercial antifungal paint.

The X-cut adhesion, hardness, opacity and water resistance of the dry paints were evaluated after application. The viscosity and opacity of paint films were not much affected by the additives NS and PNP-NS upto 2 %. Improved X-cut adhesion, hardness and water resistance were achieved with NS and PNP-NS.

This study indicated that NS and PNP-NS are good additives to improve the antifungal and antibacterial properties of waterborne commercial paints.