Among the various types of wall coverings available for a building’s exterior and interior, paint remains the most popular of all. It is cost effective, is available in a range of variants according to the surface application and offers an endless choice of colours, textures and special effect possibilities. Architect Veena Sachdev from Delhi explains, “The most economical paint finish is the cement paint which is water based and suitable for concrete, brick and plastered surfaces. As the waterproof cement paint becomes an integral part of the substrate, it prevents water penetration but allows the surface to release moisture vapors. A more advanced finish is the texture paint that consists of various resins and special additives to hold the texture after drying. These paints available in different varieties – from smooth, sand to coarse, add unique designs to the surface and also hide any imperfections in the wall or ceiling. Moreover, the special additives present in the texture paint are anti-corrosive that help protect the surface from UV damage, cracking and permanent staining. On the other hand, latex or acrylic paints use synthetic polymers such as acrylic, vinyl acrylic (PVA) or styrene acrylic as binders in different proportions which provide a non-yellowing durable finish.
“The most durable are 100% or pure acrylic emulsions that give high colour retention, chalk resistance and resistance to cracking. These paints dry quickly, are washable, stain resistant, give smoother finish and gather lesser dust. They provide sufficient protection against the extremities of heat, cold and rain as well as resistance to fungus, algae and peeling.” Berger Paints offers a range of texture finishes called Illusions which can be applied both on exterior and interior surfaces.
As per the company, the paint offers multi chrome finishes in distinct patterns and comes with enhanced washability, moisture ‘breathe out’ property for better binding and elasticity to prevent the formation of cracks. As against this, Jotun Paints100% acrylic paint, Jotashield Extreme, is formulated with advanced pigment-binder technology to deliver durability, and colour protection and enhance heat reflection. Percy Jijina, Sales Director, Decorative of Jotun India Pvt Ltd, briefing on the product says, “The application of energy saving coatings to the exteriors of building is a relatively new concept in India. The new paint has been formulated to achieve 2X heat reflectivity in any colour and is 100% lead, mercury, chromium and cadmium free.”
However, the most commonly used architectural paint product is the water based latex paint, a fast drying paint that requires only water for thinning and gives superior finish cost effectively. These paints do not fade away easily, are less likely to crack or peel and have fewer odours. Depending upon the type of binder used such as acrylic, vinyl acrylic (PVA), styrene acrylic, epoxy or polyvinyl acetate, latex paints are available in different varieties. Vinyl-Acrylic Latex paints are the least expensive, have durable colour and efficient adhesion properties. Manufacturers like Asian paints, Jotun Paints, Kansai Nerolac, Nippon Paints and Dulux offer these latex paints as well as acrylic emulsions and texture paints with their own customized variations and finishes such as semi-gloss, glossy or stone finish.
Lately, many paint companies have introduced high-quality paints that incorporate DuPont Teflon surface protector technology for enhanced performance benefits such as easy stains and dirt removal. For instance, Royale Shyne from Asian Paints features Teflon surface protector, offering enhanced durability and stain-resistance along with an anti-fungal and anti-bacterial shield. Additionally, latest elastomeric wall coatings offered by many paint companies like Sherwin Williams and Dulux are exterior acrylic latex masonry paints designed to be applied in very thick films (about 10 times as thick as regular paints). They are tough, flexible and stretch as cracks underneath open and close, thus bridging the cracks and keeping water out while maintaining a smooth appearance.
Also, with increasing environmental awareness, non-toxic, odourless paints with low or zero VOC are being manufactured. Sukhpreet Singh, Vice President of Marketing & Sales (Decorative), Kansai Nerolac Paints Ltd says, “Nerolac has introduced VOC free paints with new generation green additives and has introduced water-based decorative products which have Low –VOC content apart from being lead free. In order to recognize eco-friendly paints one must look for paints that carry the Green Seal as they meet the precise environmental standards. Paints with this designation have VOC contents below 100g/L for a non-flat finish and 50g/L for a flat finish while reflective wall coatings cannot exceed the 50g/L mark.” Alternatively, paints derived from natural raw materials like citrus peel extract, beeswax, seed oils and tree resins are not only good for indoor air quality but can also help protect the fragile ecosystem.
The High Performance Paints
The recent use of silicon based technologies in paint products has led to the development of high-performance architectural coatings that apart from UV protection also offer water resistance and permeability to water vapour. If remained trapped in masonry, they can lead to blistering and then to cracking and peeling of the paint. Silicon Paints are a transparent variety of paints that can be used as a decorative and protective coating on concrete and wooden surfaces, chipboards and bricks. As per Abhijit Roy, Managing Director, Berger Paints India Ltd, “Customers; need for paint with strong water-resistant property led to the launch of our Silicon based exterior emulsion WeathercoatAllguard. The paint is equipped with the silicon technology and secures the wellbeing of a building by providing absolute water repellence.”
Likewise, Nippon Paints, new product, Durasil, is silicon resin emulsion paint while; Shalimar Paints has introduced Self Cleaning Paint which is pure acrylic emulsion based paint with silicon additives that produce water beading effect and give the paint a self-cleaning ability. The paint imparts a glossy coat and algae and fungal resisting properties to the surface.
Another advanced product is the silicate masonry paint which is a water based sodium silicate formulation. The paint is suitable for stone, masonry, plastered surface, concrete and pebbled walls and is VOC free and breathable. It provides a matt finish that does not yellow with time and forms a hardwearing, water repellent coating that can withstand severe extremes of weather. Wacker Paints and Evonik Degussa India offer silicate resin emulsion masonry paint that combines the properties of mineral paints with synthetic-resin paints to deliver high water-vapour permeability, low water absorption and extreme longevity. As the silicone resin lines the open pores of the coating without closing them, it maintains the coating’s water vapour permeability.
An innovative paint finding popular application in offices, restaurants and classrooms is the Magnetic Paint which is pre-mixed, lead-free, water based latex paint. Very fine non rusting ferromagnetic particles are suspended in a paint to make it magnetic via a proprietary process. Sprayed or applied with a foam roller or brush, the paint can be coloured over in a desired shade. It provides a surface to hang pictures, photos, stick magnets and notes sans the need for nails. Dulux Paints, Sherwin Williams and Sanbros are some of the companies supplying magnetic paints.
Furthermore, to enhance the thermal efficiency of a building, heat reflective paints have been developed that contain physically and chemically altered solar reflective pigments to reflect infrared radiation while still absorbing the same amount of visible light. One of the examples is KoolSeal by Shrewin Williams, a highly reflective product that expands and contracts with the surface to seal out moisture and protect the surface. It provides energy saving up to 35% by reflecting almost 90% of the sun’s rays. Similarly, Dulux WeatherShield exterior paint can reduce the surface temperature of walls by upto 5oC. The Solar reflectance index (SRI) of this paint is double compared to regular exterior paints reducing the heat build-up inside the building.
Innovations in the paint industry
An important technological breakthrough in the paint industry has been the antibacterial and germ-resistant paints. Silver-based biocide widely known for providing antibacterial properties in medical devices is most commonly used in antimicrobial paints. However, its disadvantage is the high price. Some of the newer biocides Zinc pyrithione (ZPT), carbendazim (CBZ) and chlorothalonil (CTL) offer more cost effective alternative. Added to the paint, these polymers provide protection in the dry film against any fungal and algal growth. As microbial growth often stains paints and deteriorates paint properties, biocides for dry film protection help maintain paint’s physical beauty and keep microbial growth away from the coated surface. Architect & Designer VivekTalwar, Adharshila says, “While many high-quality exterior paints come with added mildewcides, fungicides and pesticides to protect the surface, lately the addition of biocide to the paints has given an added advantage of preventing bacterial growth in both interiors and exteriors. The new antibacterial paints can greatly enhance hygiene standards and public health especially in facilities such as healthcare, pharmaceuticals and schools.” Microban interior latex paints from Hirshfield, USA and Biodexwall and ceiling coating by Flexcrete Technologies Limited, UK are some of the products available internationally.
Nowadays, Nanotechnology is being applied in many industries and paint manufacturers too are exploring advantages of Nano materials in conventional paints. While traditional paints and coatings are made up of large molecules where water, dirt and other organisms can leach into the gaps and erode the surface, nano engineered paints are densely packed with robust molecules that act as a penetrative and functional barrier. As Dr. Anup Chatterjee, ex-IITian, who has used Nanotechnology to createI-CanNano paint states, “This technology is the chemical manipulation of functional paints and coatings at the molecular level to create highly resistant, long lasting and green product. Nanotechnology paints are non-toxic coating systems that can achieve better energy ratings, better indoor air quality and fewer allergy-related illnesses than the conventional paints. I-CanNanohas been certified by the paint research association, UK for being 99.99% bacteria free, 311% elastic and highly hydrophobic (79o contact angle) with very low VOC level.”
Furthermore, the growing awareness of reducing carbon footprints and improving energy costs has led to the use of Nano-technology in developing thermal insulating paints too. These paints reduce the amount of heat penetrating into the buildings, thus keeping the inner environments cool and reducing the load on air conditioning systems. The paints are induced with coated, thermally reflective ceramic micro-spheres to the acrylic paints that reduce heat transfer through the coating with 90% of solar infrared radiation and 85% of ultraviolet radiation being radiated back from the coated surface. These enhanced paints are called ceramic paints which in addition to providing protection against harmful ultraviolet rays, heat and water also reduce the transference of heat. The paint can be sprayed, rolled or brushed on any surface including roofs, is flame retardant and flexible and hence, reduces the risk of cracking. Ceramic paint looks and tints like ordinary paint as it creates a thick coating. The ceramic paint is not yet manufactured by large paint producers but is regionally available in some countries.
Next Generation Paints
An innovation under progress is the environment friendly solar paint that will help generate electricity. The invention involves development of a printable organic solar cell based on semiconducting polymer nano particles dispersed in water. Essentially, these tiny particles in suspension are a water-based paint which can be printed or coated over large areas. As per the inventor of the technology, Professor Paul Dastoor of the University of Newcastle, “In the first instance this paint coating will be put onto plastic sheets that can be placed on the roof or walls of a house. However, in longer term, it will be possible to directly paint a roof or building surface with solar paint.”
An interesting concept developed by Professor Sangmin Bae of KAIST (Korea Advanced Institute of Science & Technology) is a simple compound of plant nutrients, pulp and CMC nontoxic glue. When mixed with grass seeds, the paint can be painted onto any surface with a standard paint roller. The grass will quickly sprout and can live for more than a year, depending on the climate and the variety of grass used (mainly, ivy, moss, clover, bluegrass or fescue).
Technological developments are also underway to make paints intelligent through novel nanotechnology that turns the paint into a sensor network that’s able to detect minor structural faults before they become a severe problem. The detector paint consists of a mix of highly aligned carbon nanotubes and fly ash. When the nanotubes bend, the conductivity changes indicate that there could be a structural problem developing. The process of monitoring involves in effect a wireless sensor network. The paint is interfaced with wireless communication nodes with power harvesting and warning capability to remotely detect any unseen damage such as micro-cracks. A prototype has been developed by Dr Saafi and David McGahon, researchers at the University of Strathclyde in Glasgow, Scotland. Dr. Saafi states, “Current technology is restricted to looking at specific areas of a structure at any given time, however, smart paint covers the whole structure which is particularly useful to maximise the opportunity of preventing significant damage.” What’s more, the environment friendly paint is extremely low coat and can be simply sprayed onto any surface with electrodes attached to detect structural damage long before failure occurs.