Nanocoatings incognito

The coatings industry is the third major sector after cosmetics and plastics for ‘nanomaterial’ applications. Nanomaterials can be found in virtually every major global coatings sector, including plastic, wood, decorative, automotive, marine and protective finishes, where they impart a variety of useful properties. Examples include silicas or aluminas as hardeners, zinc oxides as barrier additives, titanium dioxide for photocatalytic applications and layered silicate nanoclays for their UV-reflectance and intumescent properties

However, nanomaterials have been hamstrung with health and safety concerns, confusion over terminology and a general perception as ‘materials in search of an application’, all of which need to be overcome before they can truly become the default choice for formulators.

In a recent report of the sector by consultancy firm IRL, Nanotechnology in the European Coatings Industry, a broad cross-section of nanomaterial companies were profiled according to their involvement within the sector. These companies behave like systems houses, developing high concept materials – often with the aid of government grants – which they then either license or sell directly to coatings formulators.

When asked about the current status of their business operations, many of these companies informed us that their products were in the final stages of development, with very few nanocoatings products available for purchase.

While several major chemical firms, such as BASF, BYK-Chemie and Arkema, offer their own nanomaterials, such as BASF’s COL.9 binder, they are also actively investing in other nanomaterial research companies. For example, BASF has invested in the UK firm Oxonica; Altana has a joint venture with Nanophase; and Air Products has links to Nanogate. This allows the large multinationals to experiment with the new technologies without having to invest vast sums of money setting up new R&D facilities, and gives the smaller nanotechnology ’systems houses’ the resources that only a large multinational can provide. It also shields the bigger chemical firms from any adverse publicity surrounding the technology, which is particularly valuable given the climate of scepticism regarding nanomaterials’ claimed benefits, as well as the unwelcome scrutiny they are receiving over their possible health risks.

From a health and safety perspective, the difficulties the sector faces are exemplified by the polarisation created by carbon nanotubes. These are among the most well known nanoadditives to date, due to their ability to reinforce film structure, improve scratch resistance, flaking and delamination characteristics. However, their similarity to asbestos fibres has raised serious concerns about the potential health and safety implications of including them in coatings formulations, especially as particles may be abraded during refinishing processes and released over time from the final product. Until conclusive evidence can endorse their safety, most if not all nanomaterials designed for use in coatings are viewed with suspicion.

So far, there has been marginal progress in the way of a resolution to the ongoing safety concerns. However, nearly all of the industry participants in IRL’s study agreed that there is no inherent risk of exposure to harmful moieties once the coating is cured, whereupon they become locked inside the coatings’ polymer matrices. In addition, they pointed out that when used as a raw ingredient during formulation, the materials are handled under strict health and safety protocols, much like any other potentially harmful material.

Results emerging from the German Paint and Printing Ink Association (VdL), indicate that particle release is no different to any commercially available ‘non-nano’ coating when cured. However, testing has yet to be performed on the products of finely ground nanocoatings; formulators concede that it is this test, which simulates the sanding of a coating, that could uncover any potential risk.

A second factor handicapping nanocoatings is the confusion surrounding the definition of a nanomaterial and what qualifies as a ‘nano’ coating. Scientifically, the term nanomaterial derives from the nanometre, 1x10^-9m, however, the coatings industry is awash with raw materials that qualify for such terminology. These materials, whilst not exclusively nano-scaled, do possess particle sizedistributions that can be considered as nano. Many pigments are measureable on a nanoscale, including stalwarts such as titanium dioxide and carbon black, whilst engineered polymers vital for certain types of coatings also fall into the ‘nano’ category, for example, sag control agents (SCAs) used in the automotive coatings sector.