The global chemical industry is a big deal. A very big deal. In 2017 it was worth in the region of $4.3 trillion. In the UK alone it generated £55 billion and delivered over £8.8 billion of value to the economy.^ Think of the industry, and formulation chemistry will be at the heart of it. (For clarity, formulation chemistry is the mixing of compounds/substances that do not react with each other but produce a mixture with the desired characteristics/properties to suit a particular application/use).
Fully understanding the relationship between a surface and how it reacts to a coating is fundamental to developing ever-more-innovative solutions. The world’s biggest and best minds continue to chase the holy grail of a coating that can do anything that is required of it.
Levels of investment in new chemical formulations continue to grow exponentially, and the area of surface engineering, and particularly coatings, is no exception. Surface engineering focuses on the modification of the surface properties of metallic and non-metallic components in order to affect its function. Common uses are the galvanising of steel and the enamelling of metallic glass such as that used on kitchen hobs. In the coatings industry, the major change that has taken place during the last 40 years has been the adoption of new coating technologies. These new technologies include waterborne (thermosetting emulsion, colloidal dispersion, water-soluble) coatings, high-solids coatings, two-component systems, powder coatings, and radiation-curable coatings.
There are many examples of robust coatings that do specific jobs very well – the paint industry have for many years produced coverings that are durable, particularly for the commercial sector, by using certain additives to create longer-lasting solutions. Similarly, the use of types of polymers can increase the level of viscosity or binding to the surface that has been painted. The solution in which the formulation is suspended is also critical; paints may be water, latex, oil, acrylic or epoxy based, and the higher the levels of durability required (think car body vs house interior wall) the higher the cost.
Other applications that utilise certain formulae to create specific characteristics are Thermochromic and Photochromic paints, that can react to changes in heat and light respectively.
Inks and Dyes
There are a huge number of inks available of different compositions to suit different circumstances. Ink used for newspapers or paperback novels must be cheap and have the consistency of a thick sludge to properly feed through the ink rollers of a printing press. Good colour quality is required for glossy magazines. As well as colour composition, appropriate ink flow is important for pens and computer printers. The performance and formulation of a good photocopier or laser printer toner depends upon its electrostatic properties.
Dyes, natural or synthetic (dyestuffs) are used to colour fabric materials, and like inks come in many different compositions. In recent years more diverse dyes have been produced to offer a particular type of reaction – the most common of which have been Thermochromic.
Silica is the new black
Traditionally compounds such as Metal Organic Frameworks (MOFs), Layered Double Hydroxides (LDHs) and Molecular Imprinted Polymers (MIPs) have been the mainstay of coatings tech, but increasingly the use of silica and silica-based compounds are being utilised to create different types of coating – and different characteristics.
Silica is also big business – in 2017 7.2 million metric tonnes of it was produced globally (of which China accounted for 4.8 million metric tonnes, about two-thirds)*. Silica functions in paints and coatings as a great low-cost extender. As in other applications, silica is desirable for its chemical inertness which allows for good acid, chemical, and heat resistance. Along with its chemical inertness silica’s hardness improves abrasion resistance in coatings such as paints.
The use of nanoparticles
One new area of interest is nanotechnology, with tens of thousands of patents issued already just for the coatings industry. Very small ceramic or metallic particles can be added to paint formulations to modify specific properties (e.g., scratch, wear, corrosion and UV resistance) in highly specialized applications. At nano-level, the sizes of the particles means the ratio of surface area to mass becomes significant, giving the particles unique properties.
Some of the futuristic applications are nanotubes for electrically conductive coatings and to increase the speed of reaction of thermosetting resins; buckyball coatings for machine parts; metals for conductive coatings in inks, and specialist functionalised colloidal silica nanoparticles. The technology is limited mainly to highly specialized applications because of the high cost per unit volume needed to reduce the size of particles and the need to add surface modifiers to keep the particles from agglomerating. Recent research efforts have been focused primarily on functionalizing the particle surface of the nanoparticles to make them more compatible with the coating resin systems, so that easy dispersion, low viscosity, and covalent bonding between the particles and resins are achieved.
However, functionalised colloidal silica nanoparticles are now available in market; they are discrete in nature, are porous, can be suspended in alcohol as well as water and most importantly can be functionalised to provide different characteristics. This could be particularly useful in industries such as additive manufacturing, paint manufacturing and academic research.**
Whatever the future holds, one thing is clear – the search for the perfect coating that doesn’t require re-application, is cost-effective and kind to the planet continues, and is already changing our world in ways we can’t even begin to imagine.
^(Chemical Industry Association 2015)