Takeaway: Polyurea coatings have some unique
advantages that set them apart from other types of coatings; they also have
some limitations and special requirements to apply them properly.Polyurea
coatings have some unique advantages that set them apart from other types of protective coatings. They also
have some limitations and special requirements in order to properly apply them.
This article examines eight questions that must be answered when considering
these coatings.
1.
What is Polyurea?
Polyurea is an elastomer substance derived from step-growth polymerization, which involves combining a synthetic resin and isocyanate reactive materials. Thus, the reaction of an isocyanate
part with a resin blend component part through the step growth process of
polymerization produces polyurea.Various formulations of resins and isocyanates
can provide the desired setting time, moisture resistance, pigmentation, flame retarding properties and other unique features.
A hybrid coating is
polyurea blended in polyurethane in predetermined proportions. The hybrid coating provides
certain physical properties of the pure polyurea at a lower cost.
1.
How do Aliphatic Polyurea Differ from Aromatic
Polyurea?
Polyureas derived from aromatic diisocyanates are distinguished by ultraviolet (UV) light
sensitivity.Sunlight exposure or artificial UV light can cause deterioration of
the polyurea's physical properties and color changes such as darkening and chalking. Aromatic polyurea is a low cost alternative but is not appropriate
as a top coat; it can be adequate for a base coat application.Polyureas derived from aliphatic
diisocyanates can resist color change due to sunlight exposure and maintain
their physical properties even under UV exposure conditions. They are preferred
for outdoor applications because they can improve aesthetics with a glossy
appearance and can be used at lower film thicknesses of around 30 mills. However, they are expensive when
compared to aromatic polyureas, due to the complicated processing involved. Additional info found at bedliner.
1.
What are the Unique Features of Polyurea?
There is no coating system that can successfully replace polyurea in all respects,
due to its unique physical properties and durability. However, it's surface preparation requirements are very stringent.Polyurea
protects wooden, concrete and steel surfaces and structures from abrasion and corrosion damage. It can help preserve a
deteriorating concrete structure and help repair and keep canals intact. It
resists scratches, chemicals, oils and salts in commercial and industrial floor applications. It can
also preserve boats and other vessels by providing protection from cracking and
deterioration.Advantages of polyurea coatings include:
● Very fast
setting (curing time typically 2 to
5 minutes) depending upon the formulation
● Excellent
abrasion and scratch resistance
● Very stable resistance to weather and
environmental conditions
● Very beneficial
elongation
characteristics
● Can be applied
in variable temperature conditions, even in high humidity
● Stable heat
resistance up to 130°C (266°F) and short term rating of 220°C (430°F)
● Coating
thickness can be finely controlled
● Very effective bonding on correctly
prepared surfaces of wood, cement, concrete and metals
● Excellent chemical resistance
● Feasibility of
low viscosity, thus enabling
mixing and spraying at desired temperatures
● Can be
formulated for a very high tensile strength up to 4350 psi
1.
What is the Polyurea Market Outlook?
The global market size in
2015 for all coatings and paints was USD $141.58 billion. Of that, polyurea
coatings were greater than USD $500 million, with the construction sector
making up 40% of the market share. The global polyurea coating consumption in
2014 was 114.3 kilotons. The global market size in 2017 for polyurea coatings
rose to USD $684 million.Polyurea's market size is growing rapidly, partly due
to it being approved as an eco-friendly low volatile organic
compound coating (low VOC).
Substitution of cheaper epoxies and other coatings by eco-friendly polyuria coatings is
expected to cause a spurt in demand for polyurea. The global market share is
expected to reach USD $1.59 billion by 2022.Hybrid polyuria products are
expected to be a major contributor to the polyuria market size because they are
less expensive and have good abrasion resistance and adhesion to concrete and metallic surfaces. However,
hybrid polyurea products may be lacking in moisture resistance as well as high temperature resistance as compared to pure polyuria coatings. (Learn more about
the polyurea market in the article The History and
Industry Adoption of Polyurea Coating Systems.)Faster growth in developing countries with their
increasing need to protect infrastructure investment, machinery parts,
equipment and machine tools could contribute to growth in demand. Higher
moisture resistance and the quick setting properties of polyuria could generate
demand for its use in containment liners, roof top coatings, bridges, offshore structures and car
parking lot applications.By region, North America has had a dominant market
share, whereas Asia-Pacific is expected to grow faster than other regions due
to government-funded infrastructure projects in China and India as well as
foreign investment in various sectors of the economy.
1.
How does Polyurea Compare to Epoxy and
Polyurethane?
Compared to epoxy coatings,
polyurea is greatly superior in moisture resistance, UV resistance (for aliphatic coatings), abrasion resistance, chemical
resistance, temperature resistance and durability. It also has a quicker cure
time.Compared to polyurethane, polyurea has superior durability, chemical resistance
and moisture resistance.
1.
What are the Significant Applications for
Polyurea Coatings?
There are numerous
application that benefit from polyurea coatings, including the following:Automotive industry and material handlingThe auto industry has used polyurea coatings for more than
three decades. The coating is popular because of its impact resistance and
other mechanical properties.Polyurea provides abrasion protection in mining and
construction equipment, and for lining dumpers that are used for abrasive
materials such as coal and metallic ores. It protects conveyors and rollers of
conveyor systems that transport abrasive coal, stones and metallic ores.It is
also used for bed liners for large commercial vehicles and material handling
trucks.Pipelines, pumps and
irrigation systemsPolyurea provides
corrosion and abrasion protection of pipelines that carrying abrasive and
corrosive materials. It is applied as base coating to prevent cathodic disbonding.It is used as a pump coating to reduce cavitation and erosion, and to improve pump output. (For more on this topic, see
Erosion Corrosion:
Coatings and Other Preventive Measures.) It is also used to line aquaculture tanks and ponds,
and for canal repairs and leakage proofing.Defense
and security sectorsDue to
their proven impact resistance, ability to absorb explosive energy, durability
and quick setting features, polyurea coatings and linings easily find use in
the defense and security sectors.Polyurea's application in ballistic missile
system is well documented. As a military equipment coating, polyurea can
contract and expand with changes in ambient temperature and form a moisture
tight seal. Coatings will be free of scratches, dents and abrasion damage, all
while ensuring an attractive glossy appearance. A spray coating of polyurea on truck bed liners can reduce vibration and
contribute to safety. Coating military buildings with polyurea can minimize
damage due to bomb blasts.HealthcareIn a hospital environment, ideally the floor and wall
coverings will be resistant to viruses and bacteria because there is a constant
risk of patients acquiring a secondary infection. Cracks, crevices and
scratches on the floor can cause moisture seepage and spread dangerous
diseases.Polyurea coatings seal cracks and prevent scratches that might
otherwise occur due to frequent scrubbing, thus minimize the risk of bacterial
propagation. These coatings can help maintain sterile conditions in surgical
areas, intensive care units and neonatal care units.Surfaces
of steel and concrete bridgesPolyurea
is used for the initial coating and as a repair/maintenance
coating because of its fast
curing ability, impact resistance, and elongation and tensile strength.
Polyurea’s structure (molecular chain) makes it an elastomer of high
durability. This is the secret of its suitability in construction and other
fields.Polyurea coatings can prevent the collapse of concrete structures by
effectively repairing a deteriorating portion of the concrete structure and by
providing a protective seal around cracking and deteriorating concrete.
1.
What Application Methods are Best for Polyurea?
Four application methods
are currently used:1. High pressure hot
sprayThis method consists of:
● Preparing the
surface
● Mixing the
component parts
●
Performing the coating application
The high pressure method is
chosen for very high volume coating jobs. Formulators must prepare a lower viscosity
coating at operating temperature to ensure a favorable flow of the fluid within
the machine and a uniform thickness on the surface.During initial surface
preparation, oily contaminants and dirt must be removed by means such as abrasive sand blasting. Surface should be checked for cleanliness to ensure
strong adhesion of the polyurea coating. This is a critical step to ensure the
coating's durability.In the mixing stage the prescribed pressure and
temperature range must be maintained. Component dosing and mixing must be done
with precision. The spray system must be designed to maintain pressure as well
as temperature.The formulated mixture is sprayed on the clean de-dusted
surface. The first coat is produced directly on the surface. A second coat is
applied to ensure a leak-proof barrier.Machines used for polyurea spray
coatings must be able to maintain temperatures up to 80°C (176°F) and pressure
up to 210 bars.2. Warm spray coating This method is chosen when the volume of the spray coating
job is medium and formulators are able to ensure a low viscosity of fluid mix
below 60°C (140°F).3. Low pressure cold
spray In the case of cold spray,
formulators must ensure low viscosity at ambient temperatures to enable spray
coating. This is a convenient method for small surface area jobs and repairs.4. Other methods Roller or brush on methods are used when spraying is not
feasible, such as a small pipe interior coating.
1.
What are the Limitations and Critical Issues
for Polyurea Coatings?
Polyurea coatings do have
some limitations and special considerations.Because the coating is highly
reactive and quick-curing, setting of the coating without adequate wetting out
time can cause poor adhesion to the substrate. Formulators must ensure complete
wetting out of the surface before the coating sets. It is a tricky
situation.Aromatic polyurea coatings may react to UV radiation, resulting in
color changes and chalking. The aesthetics are negatively affected by UV
radiation. For those applications that require visual appeal, aliphatic
polyurea must be used.Hot spray applications require specialized and
sophisticated spray equipment that are able to generate high pressures and high
temperatures. Technicians must be specifically trained for this
task.Formulation, primer selection and stringent surface preparation are all
critical steps for success.
