Photo: Reactive Surfaces
ance in a number of ways. Magnetic, antimicrobial, antistatic, photocatalytic (self-cleaning), optical, surface energetics and many other attributes can be enhanced or affected with the use of nanomaterials. Many companies have
commercialized products for the industry in pursuit of such
benefits.1 The unique nature of nanomaterials, however,
has raised concerns about the potential environmental,
health and safety hazards they might present. Some early
studies on carbon nanotubes have underscored this concern.2 Both the European Commission and the U.S.
Environmental Protection Agency (EPA) have initiated programs to investigate this issue. 3
While nanomaterials have attracted much interest from
academia and industry, many researchers have elected to
explore new mechanisms for incorporating more traditional materials as functional additives. 4 One technique is to
encapsulate these materials—often monomers, catalysts,
dyes or pigments—in microcapsules that are designed to
trigger/degrade under certain conditions. Upon their
release, the additives undergo a chemical reaction or physical response to the conditions that initiated the capsule
decomposition. Other additives have been incorporated to
indicate changes in the coating as opposed to repairing or
maintaining functionality. Such indicators may include
thermochromic, photochromic and piezoelectric pigments,
which have been designed for use in paints as sensors.
Passive functional materials have been included to guard
against microbial attack such as specially designed silver,
calcium hydroxide and titanium dioxide.
The use of such additives shows great promise, but there
are limitations. Functional materials for use in paints and
coatings must be carefully selected to meet a number of criteria. Specifically, such additives must:
• be compatible with the other coating ingredients;
• have little or no impact on general coating performance;
• survive the production process;
• be stable under typical storage conditions on the shelf
and in the film;
• consistently respond to relevant stimuli; and
• repeatedly respond to stimuli within a commercially-rea-sonable time frame.
With the growing market demand for “greener” coating
products, these additives as well as their manufacturing
processes must also be environmentally friendly.
Engineering such products can be a challenge.
tions or increase structural integrity are, or soon will be,
available to formulators.
CHOICES, CHOICES, CHOICES
Much of the research on functional coatings to date has
focused on the development of novel additives that perform
defined tasks once they are incorporated into the film. Such
additives include not only engineered biomolecules such as
proteins and enzymes but also nanomaterials and encapsulated specialty chemicals.
When reduced to the nanoscale, certain substances
(nanomaterials) exhibit unique chemical and physical
properties and are capable of enhancing coating perform-
NATURALLY THE BEST CHOICE
Biomolecules—also referred to as biocompounds, biocomponents or bioadditives—represent a third class of functional
additives that meet all of these criteria as has been demonstrated by a number of researchers in both industry and
academia. Biocompounds, such as peptides and proteins,
with the potential for use as functional additives are well
known and have been used for many years in a variety of
industries outside paint and coatings such as detergent
enhancement additives, tanning processes and food processing. In addition to being biodegradable, bioengineered
additives operate under mild conditions, produce no toxic
