There are a number of approaches which can be adopted in the search for improved hygienic coatings. These include:
Some products such as anatase titanium dioxide (TiO2) can exhibit pollution destroying, self-cleaning, or biocidal effects, and can be regenerated by UV-, fluorescent- or even day-light. These can form the basis of future hygienic coatings, but much work is required to determine the optimum products and conditions.
Research is required to select:
Research is required to determine:
Long-term monitoring of patents and publications on photocatalytic titanium dioxide and other compounds has yielded about 500 abstracts of which about 300 relate to coating applications. Of these 300, aover 150 employ fluoro or silicone resins and many incorporate both.
Much evidence exists on the biocidal activity of metallic atoms and ions when incorporated in small quantities into coatings, including powder coatings. Some papers conclude that the addition of metals, principally silver, and metal oxides can offer synergism with photocatalytic titanium dioxide. Further information on this topic can be found in a brief article written by Ken Johns.
Where actives are incorporated in a hygienic coating there may be advantages in designing for slow and controlled release.
Micro-encapsulation can provide protection and release under certain conditions. New developments in nano-technology, thin-film coatings, and dendrimers (molecular sponges) present opportunities for novel effect coatings.
The potential exists for photocatalytic regeneration, direct biocidal activity, and UV generation of ozone in air
Ozone has a direct biocidal activity which may be applicable.
Under certain special conditions, ultasonic waves might be employed to dislodge and disrupt biofilms.
It is known that metallic ions and photocatalytic titanium dioxide can each be effective biocides alone, but they can also provide enhanced activity when used in combination. Additionally, combinations of the techniques described above may also exhibit synergistic activities.
The phrase "Cleanliness is next to godliness" is very appropriate to the current need for hygienic coatings. Whereas a coating is applied once and is expected to offer a long effective life, cleaning may be carried out daily over a period of years and may cost far more than the original coating application. Unfortunately, cleaning may often be carried out by the company offering the lowest quote and perhaps employing the least committed, lowest paid and poorly supervised workforce. Thorough supervision and control of cleaning regimes is critical.
Cleaning regimes may involve repeated, regular cycles, and aggressive abrasives and chemicals. These may have an effect on the resins and actives. It is therefore vital that the selection of coatings and cleaning systems should be designed in tandem, and tailored to specific conditions.
Future developments may include:
An advanced regime for hygienic surfaces requires efficient and rapid means of detection of biofilm contamination at the earliest stage. Traditional methods are slow, but some modern techniques may detect in-situ.
Thin-film biosensor technology is developing fast, but as yet, there is still not rapid and convenient on-site identification method.
Future possibilities may include:
There is also the possibility of polymer (dry paint) films, such as a low surface energy, robust fluoro-film. Such films could be non-porous, or with controlled porosity, and could be produced with or without additives. In such a system, there would be the possibility of the incorporation of visuals and logos.
Designer adhesives could allow for:
Furthermore, a shrink-wrap version for pipes, etc may also be possible.