Paint is both a functional and aesthetic element of the built environment. Improved paint technology offers a variety of functional advances, including structural reinforcement and better indoor air quality.
Typically, paint includes pigments, binders, and solvents. Here’s what they do:
- Pigments: provide the color for the paint.
- Binders: the base ingredient(s) that adhere(s) to the material being painted. The binder is usually a durable coating for the material, as well as a vehicle for the pigment.
- Solvents: in a liquid paint, solvents such as water or mineral spirits carry the binder and pigment then evaporate.
In addition, other substances can be added for specific purposes, such as texture or reflectivity.
Graphene is a one-atom thick layer of carbon arranged in a honeycomb pattern. Among its many properties, graphene is 100 to 200 times stronger than steel, and it conducts electricity better than copper. Paint that includes graphene can function as a structural component, and in the future may be able to function as a “photovoltaic paint.”
Structurally, the material is already in use. A Spanish company has combined graphene with limestone to create a paint called Graphenstone that’s used on older buildings. The company, Graphenano, has also proposed using the paint on the crumbling opera hall in Valencia, Spain. Just eight years old, the stunning building’s exterior finish started peeling off in high winds last December. The graphene paint is intended to act as a reinforcing mesh at the molecular level, and its flexible nature prevents cracking and peeling.
Graphene can also repair itself when damaged. Researchers at the University of Manchester, UK, including Konstantin Novoselov, one of the original discoverers of graphene and a Nobel laureate, bombarded damaged graphene sheets with pure carbon. The carbon atoms automatically filled in the gaps in the hexagonal structure of the graphene and restored its strength. This offers the potential for damaged graphene in structures to be repaired relatively quickly and simply.
Graphene’s conductivity also lends itself to production of electricity. Novoselov’s team has also produced paper-thin wafers made from graphene and other thin materials that conduct electricity on par with today’s typical photovoltaic cells. Adding graphene to paint, Novoselov said, may enable them to create paint that generates electricity for the building, an approach similar to solar sensitive nanoparticles.
Researchers at Spain’s Institute of Photonic Science have also worked with graphene, and said its low resistance to electron flow makes it a more efficient material for photovoltaic cells. Compared to silicon-based panels, the current standard, graphene-based photovoltaic cells may be 60 per cent more efficient. These developments have the potential to make solar electricity for the built environment vastly cheaper and more accessible.
Volatile Organic Compounds (VOCs) and Biocides in Paint
Solvents evaporating are one of the issues with VOCs, or volatile organic compounds. Modern paints may contain hundreds or thousands of chemicals, some of which are toxic to humans. Low-VOC and no-VOC paints reduce the number of VOCs, making them healthier for both installers and the occupants or users of the building. Here are the standards for paints:
Latex and flat-finish paints
- Low-VOC is classified as containing less than 250 grams of VOCs per litre
- VOC-free paint is classified as containing less than five grams per litre
- Low-VOC paint contains less than 380 grams per litre
Even VOC-free paint can contain toxic chemicals, however. Most commercially made paints include additives that inhibit the growth of mold, mildew, bacteria, and fungus. Some of those additives, such as triclosan, methylosothiazolin (MIT), and benzisothiazolin-3-one (BIT), are implicated in a variety of adverse health reactions.
One paint manufacturer, Alistagen Corporation, has created an antimicrobial paint that uses calcium hydroxide in place of chemical biocides. Calcium hydroxide, often called slaked lime or builders’ lime, is a naturally occurring mineral that is effective against mold, mildew, algae, fungi, and bacteria. The US EPA registered the paint, Caliwel, for use on hard surfaces in 2002, and for use in HVAC systems in 2003. The calcium hydroxide in the paint has an effective life of six years, according to the company.
In addition to removing VOCs, one company has produced a new paint additive that it says can clean polluted air. Dow Chemical, developer of the product, said the acrylic polymer in their paint additive bonds to formaldehyde molecules and locks them into the paint. It reacts chemically with formaldehyde in indoor air, transforming the formaldehyde into “an inert and harmless vapor.”
Formaldehyde is an organic chemical and known carcinogen commonly used in paper products, plywood and fibreboard products, and many personal care products found in the home. According to the Australian Government’s Department of Health, formaldehyde is toxic by inhalation, touch, and swallowing. Formaldehyde can irritate the nerves in the nose and eyes, resulting in teary eyes, blocked sinuses, sore throat, and runny nose.
Dow Chemical spokesman Stan Cook said the paint additive goes beyond past reductions in VOCs and other chemicals by “not just reducing paint emissions but functionally removing other indoor pollutants, such as formaldehyde, emanating from other sources in homes and buildings.”