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1/212 MATERIALS PERFORMANCE October 2012 NACE International, Vol. 51, No. 10

M A T E R I A L M A T T E R SM A T E R I A L M A T T E R S

Researchers with materials producer

Cabot Corp. (Billerica, Massachusetts)

and paint manufacturer Tnemec Co.(Kansas City, Missouri) have combined

their expertise to develop a new class of

uid-applied thermal insulation coating

systems that utilize the properties of silica

aerogel particles to deliver the perfor-

mance of a thermal insulator with the

flexibility of a coating. These water-

borne, highly thermally insulative coat-

ings (HiTICs) provide an option for in-

sulating surfaces that typically are not

insulated because of oddly shaped geom-

etry, severe service environments, or

concerns that corrosion under insulation

(CUI) may occur.

Silica aerogel is a solid, porous mate-

rial traditionally formed when liquid is

drawn from a silica gel under high tem-

perature and high pressure through a

process known as supercritical drying.

This process slowly removes the liquid

and replaces it with a gas without collaps-

ing the solid component, and the result is

New thermal insulation coating systems utilize

properties of silica aerogel

Silica aerogel particles are composed of more than 90%

air trapped within a highly porous structure. Photo

courtesy of Cabot Corp.

The infrared photo illustrates the surface temperatures of the

tanks. The tank on the left is coated with a standard coating and

the tank on the right is coated with an aerogel-based HiTIC. The

contents of both vessels are controlled to 60 C, however the

tank with the HiTIC has a cooler surface temperature. Photo

courtesy of Cabot Corp.

a ne, porous silicon dioxide (SiO2) struc-

ture. The manufacturing process allows

control of the materials porosity, poresize, and distribution. According to the

Lawrence Livermore National Labora-

tory, aerogels are a class of materials that

exhibit the lowest density, thermal con-

ductivity, refractive index, and sound

velocity of any bulk solid. Aerogel is often

used for thermal insulation in a blanket

form that is wrapped around piping and

covered with cladding.

The Tnemec HiTICs are formulated

with surface-treated amorphous silica

aerogel in particle form, manufactured

by Cabot Corp., to lower the thermal

conductivity of the surface to which the

coating is applied. Each aerogel particle

is composed of more than 90% air

trapped within a highly porous structure

that essentially resembles a birds nest

comprised of nanometer-size silica

strands, explains James Pidhurney, global

commercial manager of Cabot Aerogels

coatings business.The structures average

pore size is ~20 nm, which is smaller than

the mean path of air, so air molecules are

contained within the pores between thesilica strands and cant come into contact

with one another and transfer energy to

one another. If an aerogel particle is

broken, the fragments still retain the po-

rous structure and its properties.This

makes aerogel twice as insulating as still

air and very good at inhibiting conductive

heat transfer, Pidhurney notes. The sur-

face area of the aerogel particles is also

hydrophobic, which make the particles

very resistant to water inltration.

The ability to reduce heat transfer

between objects, known as thermal insu-

lation, is described as thermal conductiv-

ity. The aerogel particles have an ex-

tremely low thermal conductivity

measurement of ~12 mW/(m-K), which

is an indication of their high insulating

capabilities. When the aerogel particles

are used in large volumes (e.g., 70% by

volume) in a coating formulation to dis-

place resins that have a relatively high

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2/2NACE International, Vol. 51, No. 10 October 2012 MATERIALS PERFORMANCE 13

A pipe fange is coated with the aerogel-based HiTIC. Photo courtesy o Tnemec.

thermal conductivity

measurement [e.g.,

300 mW/(m-K)], theend result is a coating

with a thermal conduc-

tivity measurement be-

tween 30 to 50 mW/

(m-K), which is up to

10 times more insulat-

ing than standard

paint, says Pidhurney.

When applied to

piping, tanks, valves,

and other steel struc-

tures in industrial fa-

cilities as part of a com-

plete insulating coating

system, the aerogel-

containing HiTICs,

which can be formu-

lated as acrylic or ep-

oxy coatings, are able

to lower surface temperatures to protect

against the potential risk of burns from

skin contact as well as reduce the sub-

strates thermal conductivity to help

maintain temperatures of stored or con-

veyed materials, says Andy Hoffman,

Tnemec market support manager, Indus-

trial Market. These aerogel-based coat-

ings can be applied at a very high dry lm

thickness (DFT) per coat. The insulating

capability of insulating coating systems

with the HiTICs is comparable to bulk

insulation in terms of their R-value/in.

T h e

R-value/in for the epoxy and acrylic

HiTIC is 2.9 and 4.1, respectively. This

compares to an R-value/in of 3.2 to 3.8

for loose-ll cellulose, 2.2 to 2.7 for loose-

ll berglass, and 3.0 to 3.3 for loose-ll

rock wool.1

The HiTIC coating systems are able

to withstand substrate temperatures up to

400 F (204 C) and can be spray-applied

to surfaces with temperatures