It’s all walls and ceilings

This Issue This is a part of the Exteriors and interiors feature

By - , Build 166

Far from just bringing colour to our walls, paint is a multi-talented marvel. It can glow, retard flames, kill bugs, conduct light and can double as a whiteboard.

THE TWO prime functions of interior paints are to provide added aesthetics and improved hygiene over the raw surface. The improved hygiene primarily comes from the increased cleanability of the painted surface. Changing tastes and increased expectations have impacted on even these basic requirements – but more on that later.

It has long been recognised that the sheer area covered by walls and ceilings within the built environment offers the potential to bring other benefits. For example, in the late 60s, all of the 70s and much of the 80s, textured ceiling sprays – based mainly on vermiculite and perlite – were used very effectively as anti-condensation paints. They were also equally effectively for noise moderation and contributed to fire retardancy.

Paint that can protect from fire

The paint industry has a long history of increasing the fire retardance of flammable interior surfaces by the application of intumescent coatings. These potent little chemical factories start melting under the heat generated by an initiating fire. Simultaneously, specially selected ingredients within the coating react with each other, causing the melt to foam and swell. This foam, many times the thickness of the original paint film, then turns into a highly protective char that protects the substrate from fire.

Intumescent paints typically come in a somewhat limited colour range, and their scrub and stain resistance are not quite as good as the best standard wall paints. These drawbacks seem to overwhelm the fact that they can save lives.

Cool multi-function paints

Additional functions within an interior paint coating are a huge marketing tool in China. The first multi-functional paint was marketed as being 2 in 1. Within weeks, the opposition launched 3 in 1, and the race was on! Current leaders claim 10 in 1 where, like a number of CVs one reads, every little feature gets star billing. I do not denigrate this approach – it serves to highlight many of the benefits that are often taken for granted in modern paints.

Glow-in-the-dark paints

Some of the more spectacular add-on properties include luminescence or the ability to glow in the dark. There are various chemistries involved in luminescence, which focus on the key property of afterglow. With the simplest and cheapest iterations, the afterglow may last for only a few minutes whereas the most active will continue glowing for several tens of minutes – even an hour or two.

While the former may be seen as more novelty paints suitable for stencilling say the moon and stars on a child’s bedroom ceiling, the latter can play a serious safety role, for example, in highlighting escape routes in the event of loss of electrical power.

Magnetic paints

Magnetic paints – which are not magnetic at all but provide an iron-rich substrate to which magnets will be attracted – also fall more into the novelty area, providing surfaces that can be decorated with fridge magnets. They also provide the paint chemist with the novelty of a paint that can itself rust, against which internal protection must be provided.

Write-on paints

Blackboard paints offer a traditional method of giving dual use to wall areas. Transformation of whole wall areas, using write-on style overcoats, into white or coloured boards is a more interesting technology.

These coatings are clearly related to exterior graffiti-resistant coatings. However, the resistance properties need to be delivered from a waterborne system as the strong solvents usually associated with the exterior product can simply not be tolerated indoors.

The products are designed for easy, dry erasability of whiteboard markers. The surfaces are resistant to permanent markers, but these need to be removed with meths or a meths and water mixture.

Surface smoothness is important for best erasability as in an absence of air bubbles from the surface. Producing a matt product remains a challenge!

Fight against bugs and formaldehyde

Using wall surfaces in the fight against bacteria is mainstream in Japan and China and has some traction in niche areas in this part of the world. There are a few methods of achieving this, the majority of which involve the use of bactericidal additives.

For materials that have a long-term ability to kill bugs, it is crucial to select bactericides with low mammalian toxicity or sensitivity. Silver is highly favoured, but that is also not without issue as it can cause some discolouration – particularly in thermal areas.

These coatings do not preclude normal cleaning, as a build-up of dead bacteria will isolate the bactericidal surfaces from fresh bacterial settlement.

Still in the health area, formaldehyde abatement is very much to the fore, again especially in China and Japan. Fortunately, and somewhat serendipitously, one of the self-crosslinking chemistries used in acrylic enamels has the ability to react with and to denature formaldehyde. Due to the nature of film formation in acrylics, a vast excess of the cross-linking group must be used in order to achieve its designed purpose, leaving behind a substantial amount for mopping up formaldehyde.

The property is finite, and when it is depleted, the paint loses this additional protective property. However, it does perform a very useful service especially as the paint is typically used when formaldehyde levels are generally at their highest during a new build or refurbishment.

It will bring light

Another addition to the multi-functionality of paint coatings is the recent launch in New Zealand of a decorative paint incorporating a conductive layer. Coupled with some very smart electronics, the paint responds to specific touch signals that can effect a subsequent action. These actions can turn on a light in an unfamiliar environment or trigger an alarm if the collapse of someone in an aged care institution is detected.

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