Chemical Engineering August 2020 - 30

FIGURE 2. One major area of development in sustainable coatings is waterborne formulations,
which present many benefits
application methods and can be applied
at a range of thicknesses and utilized on
multiple substrates. The main difference
between solvent-borne coatings and their
waterborne analogs is the binder system.
Solvent allows for resins to be solvated in
the coating system and aids in additive and
pigment dispersion, as well as coalescence.
Waterborne systems mainly consist of dispersions
of polymer particles and require a
stable colloidal system. While waterborne
coatings present a good opportunity as a
low-VOC option, many still contain some
level of solvent to help with surface tension
and pigment dispersion, requiring further
research to reduce solvents and regulated
materials while balancing additional performance
properties. For instance, some
basecoats on plastic substrates can suffer
from adhesion loss due to the high surface
energy of water,
reduced wet-out and a
lack of solvent to etch the substrate. Several
approaches can be used to address
adhesion issues, such as resin innovation
and formulation tools. Internal resin capability
addresses these obstacles by utilizing
chemistries to promote adhesion to diverse
substrates, choosing surfactants to aid in
reduction of surface tension, and fine-tuned
crosslinking in both one-component and
two-component coating systems. Additional
formulation tools to replace solvents,
such as flow additives, coalescents and
wetting agents, assist in balancing the necessary
properties of a waterborne system.
In addition to adhesion, appearance may
Upstream processes
Core processes
be a concern with waterborne
coatings. Solventborne
basecoats achieve
metallic flake orientation
and a high metallic appearance
due to the high volatility
of solvents and the ability
of solvents to disperse
flake pigments. Waterborne
basecoats can achieve high
metallic finishes through
careful choice of flake and
passivation, rheology control
and resin
innovation.
Even when flake orientation is achieved,
it has been historically difficult to balance
high metallic finishes and required performance
attributes, such as hardness, with
waterborne systems. In aqueous metallic
basecoats, multiple resins are often utilized
to balance both appearance and performance,
and additional formulation tools
to enhance rheological requirements for
flake orientation and stability are utilized.
Rheological effects are constantly being researched
to overcome a wide range of obstacles,
such as pigment dispersion, paint
stability and pumpability, as well as application
of emulsion-based systems.
Sustainable system integration
While many companies have been deeply
involved in sustainable coatings innovations,
the success of the industry's transition, however,
heavily depends on the effectiveness
of total solutions training. Waterborne and
high-solids, solvent-borne paint and coatings
commonly have different physical properties
than their traditional solvent-borne
counterparts, which require additional considerations
and equipment during processing.
In order to reduce the impact on users
adopting these technologies, a multi-step
process should be developed for seamless
conversion. This process includes assessing
the raw material and application requirements
for the specific paints or coatings
being used, the type of equipment required
for processing and full system training for the
workers responsible for maintaining and apDownstream
processes
End of
life
Raw material
supply
Transportation of
raw material
Packaging
supply
Production
proccesses
Transport to
user
Disposal of
packaging
Losses during
application
Product VOC
emissions
Disposal at the
end of life
FIGURE 3. A standard lifecycle assessment will highlight the stages that contribute waste of energy, materials or potential
sources of environmental impact
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Chemical Engineering August 2020

Table of Contents for the Digital Edition of Chemical Engineering August 2020