Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023 - 43

PAINT AND COATINGS MANUFACTURING: POWDER RESINS - SUPER DURABLES
" In some applications, the end-user will want
to bend the extrusion after it's been coated for
arch-shaped or round windows, for instance.
Your typical standard durable coatings will
not take that bend without cracking. With this
coating we can bend it 360 degrees, which
means we can fold it right on top of itself and
the coating still remains intact. "
- Bob Cregg, business director, Covestro
Powder Coatings
of this system can bring the polyester powder coatings closer to a
10 year Florida outdoor durability.
" The coil coating industry is going to wrap the material back
we discovered-super durables aren't flexible, and customers
were asking for the combination of flexibility and durability, "
says Houweling. " We found that when we started working with
crystalline resins, we could improve the flexibility. We developed
a super durable flex coating resin system that uses an amorphous
resin [Uralac Premium P8000] as the highest concentration
and crystalline [Uralac Premium P9000] as the lowest. This
combination of resins improved both the flexibility, flow and the
outdoor durability. "
This formulation becomes key for several players in the
market that produce aluminum extrusions and coat 16- to 24foot
lengths, for example, before cutting the length needed for a
particular façade.
" In some applications, the end-user will want to bend the
extrusion after it's been coated for arch-shaped or round windows,
for instance, " says Cregg. " Your typical standard durable coatings
will not take that bend without cracking. With this coating we can
bend it 360 degrees, which means we can fold it right on top of
itself and the coating still remains intact. "
Houweling says that this form of flexibility has opened the
door to a new market for this powder coating resin system-the
coil coating industry. Secondly, the improved outdoor durability
up into a coil after it's been coated. That feedstock is typically
used for metal roofs, for example. But that flexibility was never
there with the standard formulations of the super durables, " says
Cregg.
Although this new formulation does improve the durability
properties, Houweling says that the mix of the two resins
will require users to pay more attention to the solution. " The
amorphous resin has a relatively high viscosity and crystalline
resin has a low viscosity. The powder coating market is used to
that, but not in this high amount. When you look at the crosslinker
HAA (five per cent), it also has crystalline materials, which
creates a big difference with the melted viscosity between the
crosslinker and the amorphous resin. Secondly, for good powder
stability, the annealing period needs to be at least two hours.
Normally, you can extrude your powder, get flakes, and start
grinding, but with this formulation you need to let it sit at room
temperature for two hours between flaking and the grinding
process as you need to let the product stabilise. "
To meet the architectural and façade industry demands,
Covestro continues to develop its polyester solutions and extend
the performance life cycle. And so far, it has been able to increase
it polyester systems to a comfortable eight-year range, according
to Cregg.
January/February 2023
43
Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023

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