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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 1 7
1 4
SURFACE ENGINEERING
NEW COATINGS PROTECT
PIPE INTERIORS
Axalta Coating Systems, Houston,
recently developed two new high tem-
perature, corrosion-resistant internal
pipe coatings. Nap-Gard 7-0017HT and
7-0017VHT Black Beauty FBE products
are thermosetting epoxy powders de-
signed to provide excellent chemical
resistance when operating in tempera-
tures to 200°C (392°F).
Corrosion caused by carbon diox-
ide and hydrogen sulphide, often found
in sour crude oil, is a major challenge
for the oil and gas industry. These high
glass transition temperature, internal
pipe coatings are designed to combat
this problem. When properly applied
with Nap-Gard 7-1808 primer, the new
coatings exhibit extreme corrosion pro-
tection against high levels of H
2
S, CO
2
,
and methane, even at elevated tem-
peratures and pressures.
axaltacs.com.
CHEMICAL VAPOR DEPOSITION
PRODUCES BIODEGRADABLE
POLYMERS
Researchers from the University
of Michigan, Ann Arbor, Northwestern
Polytechnical University, China, and
the Karlsruhe Institute of Technology,
Germany, introduced the first chemi-
cal vapor deposition (CVD) method to
produce degradable polymers. Biomol-
ecules or drugs can be attached using
special side groups, which allows coat-
ing of biodegradable implants.
The achievement was made using
two special types of monomers—the
BRIEF
MetaSOL nanotechnology coatings from
MetaShield LLC
, N.Y., provide a 1.2% (absolute) efficiency boost for triple junction solar
cells, according to an independent research study. The material is a nanoparticle embedded, glass-based coating that increases
efficiency using advanced light trapping technology. The formula is sprayed directly onto a solar cell’s existing antireflective coating
and hardens at room temperature, forming a transparent ~200 nm glass film.
metashield.com.paracyclophanes usually used for this
process were combined with cyclic ke-
tene acetals. While classic polymers
based on paracyclophanes are con-
nected exclusively through carbon-car-
bon bonds, the ketene acetal converts
during polymerization so that ester
bonds are formed within the polymer
backbone. Such bonds can be broken in
aqueous environments.
“The speed of degradation de-
pends on the ratio of the two types of
monomers as well as their side chains,”
explains lead researcher Jörg Lahann.
“Polar side chains make the polymer
film less hydrophobic and accelerate
degradation because water can pene-
trate more easily. The speed of degra-
dation can thus be tailored to the in-
tended use.” Tests show that neither the
polymer nor its degradation products
are toxic.
For more information: Jörg Lah-
ann,
lahann@umich.edu,
www.umich.edu.
BUG EYES INSPIRE REFLECTIVE
MATERIALS
Retroreflective materials, includ-
ing some tapes and road paints, work
by bouncing light back toward the orig-
inal source, such as a car’s headlights,
making them bright and easy to see.
Existing retroreflectors are typically
made with glass microbeads andmicro-
prisms. Dyes, pigments, or plastic layers
are often added for color. However, they
tend to reduce light reflection and col-
ors can fade over time. Researchers at
the National Chung Hsing University,
China, and colleagues turned to the
compound eyes of insects for a newway
to address these limitations.
An array of glass microspheres was
evenly coated with smaller balls of sili-
ca, resulting in a brilliantly colored, ret-
roreflective material. Color can be ad-
justed by changing the size of the silica
crystals and brightness can be boosted
by adding layers. At 250 nm and 40 lay-
ers deep, crystals appear bright green
and reflect more light than commercial
coatings with no color. In addition to
boosting the brightness of objects for
safety reasons, researchers say that by
reflecting rather than absorbing light,
the material could be applied to build-
ings to reduce the urban heat-island
effect.
www.nchu.edu.tw/en-index.php.The structure of bug eyes (top) is inspiring
colorful reflective materials (bottom).
Courtesy of the American Chemical
Society.
New high temperature, internal pipe
coatings protect against corrosion.
Courtesy of Axalta.