Shafiq Randhawa Technical consultant Polyurethane skyep- taha.shafiq87

1. Two component PU coating
system
The most frequently recommended
products for two-component coatings
applications are
polyisocyanates and polyols. In addition,
for some applications the polyol and
aromatic polyisocyanates may also be
appropriate.

2. Properties
 The properties of a two-component polyurethane
coating depend on certain factors,
 such as the degree of branching of the reaction
partners,
the content of the reactive groups themselves,
physical state of the raw materials

3. Properties (cont.)
A further possibility for modifying the film properties is to
use the same polyol and vary the quantity of the
polyisocyanate. By “undercrosslinking,” which means using
an NCO to OH ratio less than 1.0 / 1.0, the
polyurethane film generally becomes softer and perhaps
more flexible, less weather resistant, and less
resistant to solvent and chemicals.

4. Properties ( cont)
 On the other hand, by
“overcrosslinking,” using an NCO to OH
ratio
greater than 1.0 / 1.0, the resultant films
tend to be harder and more chemical
resistant.

5. Curing of two component
 the curing of two-component polyurethane
coating systems can be carried out at
room temperature.
 The drying times can vary considerably
depending on the types of polyols and
polyisocyanates used.

6. Curing
 aliphatic polyisocyanates have low
reactivity by nature and longer drying
times as compared to aromatic
polyisocyanates. The incorporation of
0.005% dibutyltin dilaurate, 0.2% zinc
octoate can shorter the drying time.

7. CURING POINT
The following points Should be noted
1. Both components must be mixed
together thoroughly.
2. The reaction which begins immediately
upon mixing results in a gradual to rapid
viscosity increase.
3. The increase in viscosity eventually
leads to a gelation of paint

8. Application of Two component PU
Coating
 Application by air, airless, or
air-assisted airless spray.
 electrostatic spray, brush and roller
coating.

9. Moisture- Curing one component
Pu coating
 Adducts of polyisocyanate/polyol
combinations with an excess of
isocyanate groups (prepolymers) can
crosslink with atmospheric moisture to
give insoluble higher molecular weigh
polyurethane. This reaction describes the
curing principle for moisture-curing
polyurethane coatings.

10. Properties of one component
moisture cure pu coating
 Curing or drying properties
The one-component coatings based on
aliphatic isocyanates
(HDI, IPDI) generally need longer drying
times than those based on aromatic
isocyanates (TDI, MDI). The drying times
depend not only on the temperature, but
also on the amount of
atmospheric moisture present.

11. Properties of one component
moisture cure Pu coating
 With very low absolute moisture content,
the drying times may be increased.
 The aliphatic polyisocyanate based
moisture-cured coatings often require
metal catalysts (such as dibutyltin
dilaurate) to provide reasonable cure
times.

12. Properties ( Cont.)
 Weathering Properties
It depend on the type of isocyanate used.
Coatings based on TDI or MDI have a
tendency to yellow in the light and show a
relatively rapid loss of gloss on
weathering.

13. Properties ( Cont)
 those based on HDI and IPDI, are light
stable. Depending
on the composition, these one-component
coatings may be equivalent in gloss
retention and chalk resistance to two-
component polyurethane,
polyurethane coatings have very good
mechanical properties.

14. Pigmented one component
Coating
 Due to the sensitivity of one-component
coatings to moisture, a special technique
has to be followed .
The formulation is divided into four step
 1. Weighing
2. Pre dispersing
3. Dispersing in the sand mill
4. Filling

15. Application
 Moisture-curing coatings based on the De
polyisocyanates are normally applied by
brushing or
spraying. Dip coatings and curtain coating
cannot generally be used because of the
extended contact between the liquid
coating and atmospheric moisture.

16. Application (cont)
 Unpigmented one-component coatings
are used primarily for wood substrates
such as parquet flooring and
other indoor wood flooring applications.
Another area of application is for the
sealing or coating of concrete
floors, and decorative seamless floors.

17. Application ( Cont)
 Pigmented one-component coatings can
be used for anticorrosion coatings for
metal,
 for the coating of concrete substrates,
 and for various other decorative and
protective coatings.

18. Formulating Aids
 1- Modifiers-
 these are added to improve specific
application properties (leveling
agents or thickeners, for example),
Products such as a cellulose acetate
butyrate, low molecular weight acrylic
resins, and polyvinyl chloride/polyvinyl
acetate copolymers are suitable
modifiers.

19. 2- Solvent
 aromatic hydrocarbons such as toluene,
and xylene.
 special care should be taken when
selecting the solvents.
Any solvent chosen must not contain
hydroxyl groups.
 Solvents which contain reactive groups
such as amines should not be used since
they react with isocyanate groups.

20. Pigments
Inorganic Pigments
 White: Titanium dioxide
 Yellow: Iron oxide yellow, nickel and chrome
titanates, chrome and cadmium yellows
 Brown: Iron oxide brown
 Red: Iron oxide red, cadmium red
 Black: Iron/manganese mixed metal oxide
black, iron oxide black, some carbon blacks
 Blue: Mixed metal oxide blue
 Green: Chrome oxide green

21. Organic Pigments
 Blue: Phthalocyanine blue
 Green: Phthalocyanine green
 Red: Perylene and quinacridone red
 Yellow: Monoazo, isoindoline,
monoarylide yellow

22. Leveling Agent
 Cellulose acetate butyrate or low
molecular weight acrylic resins .
 Polyvinyl acetate, copolymers of
PVC/PVAC, and some urea resins may
improve leveling properties .
 Silicone and polymeric fluids and fluoro
chemical additives can improve flow by
lowering the surface tension of the coating
material

23. Thickening Agent
 Suitable thickening agents are copolymers
of vinyl chloride and vinyl acetate,
precipitated silicas,and bentonite clay.
 If an increase in viscosity is desired,
copolymers of vinyl chloride and vinyl
acetate can be added to the
polyol solution in quantities of 5-10%
based on solid binder.

24. Thickening agent(Cont)
 Bentonite clay thickeners are used in
additions of up to 1.5% on solid binder to
prevent the settling of pigments and
extenders. These agents are best
suspended with solvents into a gel before
use.

25. Air Release Agent
 Air release agents are particularly useful
for the prevention of blistering during
application by brush or roller
coating. Modified polysiloxanes and other
types of polymeric additives are commonly
used as defoamers and air release
agents.

26. Catalysts
 Catalysts are used in one- and two-
component polyurethane coatings to
shorten the curing time,
especially in those containing aliphatic
polyisocyanates.
 Various metal compounds such as
dibutyl tin dilaurate and zinc octoate are
commonly used catalysts in both two-
component coatings and one component

27. Catalyst ( Cont)
 Excessive catalyst levels can also have a
detrimental effect on film
appearance, property development, and
on exterior durability.

28. Polyurethanes
 Polyurethanes are formed by the
reaction between a polyisocyanate and
hydroxyl (-OH) containing resin blend

29. Polyurethanes
 Disocyanate can be aromatic or
aliphatic
 Wide variety of formulations

30. Polyurethanes
 Conventional 2-part (thin film)
 Waterborne formulations
 Moisture cure polyurethane single
component
 End product can be polyurethane or
polyurea chemistry
 100% Solids/Elastomeric

31. Polyurethanes
 Conventional 2-part (thin film)
 Slower cure, longer pot life
 Waterborne formulations
 Use water dispersible polyisocyanates
 Paint Specification
 “Two-Component Weatherable Aliphatic
Polyurethane Topcoat, Performance-Based”

32. Polyurethane Paint
 Weathering levels for color and gloss
 Level 1 (<1000 hrs or <24 months)
 Level 2 (<2000 hrs or < 48 months)
 Level 3 (>2000 hrs or > 48 months)
 Color: max 2.0 ∆E, Gloss: max loss 30

33. Polyurethanes
 Typically aliphatic
 Slower cure
 Excellent color and gloss retention
 Good chemical/solvent resistance
 Good hardness/abrasion resistance

34. Polyurethanes
 100% Solids/Elastomeric
 Typically aromatic
 Fast cure
 Hi build, up to 100+ mils

35. Polyurethanes
 100% solids polyurethane properties:
 Elongation/flexibility
 Excellent chemical/solvent resistance
 Moisture sensitive application
 Can be applied in low temperatures (below
freezing)
 Low VOC

36. Polyureas
 Formed by the reaction between an
isocyanate component and an amine-
terminated (-NH2) resin blend

37. Polyureas
 Isocyanate can be aromatic or aliphatic
 Aromatic resins will yellow but not crack
 Aliphatic resins have excellent
weatherability
 Wide variety of formulations possible
through particular resin blend
 Typically 100% solids

38. Polyureas
 100% solids polyurea properties:
 Elongation/flexibility
 Excellent chemical/solvent resistance
 Not sensitive to moisture during application
 Can be applied in low temperatures (below
freezing)
 Thermal shock resistance
 Minimize down time
 Low VOC

39. Polyureas
 Polyaspartic ester based polyureas are
a newer technology
 Resin blend based on aliphatic
polyaspartic ester
 Can have much slower reaction time
 Thinner film application
 Typical use is analagous to conventional
polyurethanes

40. Polyurethane/Polyurea
Hybrids
 Hybrid coatings are formed by the
reaction between an isocyanate
component and a resin blend
component
 Resin blend may contain amine-terminated
and/or hydroxyl-terminated polymers
 Wider range for reaction time and
performance properties

41. Polyureas
 Fast cure
 Moderate cure
 Hybrid systems
Paint Specification
 “Two-Component Aliphatic Polyurea
Topcoat Fast or Moderate Drying,
Performance Based”

42. Polyurea Paint
 Type 1: Fast Drying (less than 30
minutes)
 Type 2: Moderate Drying (30 minutes to
2 hours)
 Weathering levels

43. Polyurea Paint
 Weathering Levels
 Accelerated weathering levels
 1A – 500 hours, max 2.0 ∆E, 20% gloss loss
 2A – 1000 hours, max 3.0 ∆E, 30% gloss loss
 3A – 2000 hours, max 3.0 ∆E, 40% gloss loss
 Outdoor weathering levels
 1N – 12 months, max 2.0 ∆E, 35% gloss loss
 2N – 24 months, max 3.0 ∆E, 50% gloss loss

44. Polyurea Paint
 Other tests
 Solvent Resistance
 No visible topcoat removal (100 double rubs)
 Pull-Off Adhesion
 Average (3 pulls) ≥ 600 psi
 Minimum 500 psi

45. Polyurethane vs Polyurea
 Polyureas are faster cure, e.g. seconds
 Polyureas not moisture sensitive
 Polyurethanes cure slower but are
moisture sensitive
 May have fewer adhesion problems
with polyurethanes

46. Surface Preparation
 Steel
 Abrasive blast cleaning t
 Angular surface profile

47. Surface Preparation
 Concrete
 Abrasive blast cleaning
 Profile/roughening required
 Specialized primer may be necessary
 Check moisture content

48. Application Equipment
 Thin film polyurethanes and polyureas
(polyaspartics)
 Conventional or airless spray
 100% solids polyurethanes and
polyureas
 Plural component spray

49. Application Equipment
 Plural component spray equipment
 Heats and mixes resin (part A) and curing
agent (part B) components automatically in
correct proportions
 Paint mixture travels directly to spray gun
for immediate application
 Some coatings may be brush/roller
applied

50. Application Equipment
 Plural component spray equipment
 Storage to deliver unmixed material
 Proportioning Device
 Pressure Pump
 Mixing Device
 Static mixer or air impingement
 Delivery system (spray gun)
 Flushing system

51. Application Equipment
 Plural component application
 Equipment as recommended by coating
manufacturer
 Requires trained/licensed applicators
 Involve coating manufacturer technical
representative for projects
 Single application (multiple passes)

53. Application Equipment

54. Application Equipment

55. Application Equipment

56. Polyurethane Applications
 Roof coatings
 Pipe
 Tank interior/exterior
 Truck bed liners
 Railcars
 Parking decks
 Anti-graffiti coatings
 Caulk/joint/sealant materials

57. Polyurea Applications
 Roof coatings
 Pipe
 Tank linings
 Truck bed liners
 Railcars
 Parking decks
 Caulk/joint/sealant materials

58. Polyurethane Systems
 Conventional polyurethane for steel
structures (exterior tank, bridges)
 Surface preparatiion
 Application:
 Zinc primer @ 3 – 5 mils DFT
 Epoxy intermediate @ 4 – 6 mils DFT
 Aliphatic polyurethane @ 3 – 5 mils DFT

59. Polyurethane Systems
 Waterborne polyurethane for steel
/concrete (anti-graffiti coating)
 Surface preparation: abrasive blast cleaning
 Application:
 Sealer/primer for concrete
 2 coats waterborne urethane primer @ 2 – 3 mils
DFT/coat
 2 coats waterborne urethane finish @ 2 – 3 mils
DFT/coat

60. Polyurethane Systems
 Waterborne polyurethane properties
 Tensile strength: 5950 psi
 Elongation: 150%
 Taber abrasion: <45 mg loss/1000 cycles
 Graffiti resistance: Level 3, ASTM D6578

61. Polyurethane Systems
 Waterborne polyurethane chemical
resistance
 MEK double rubs, 300+ cycles
 Gasoline: no effect after 7 days
 50% NaOH: no effect after 24 hours
 10% HCl: no effect after 24 hours
 Toluene: no effect after 4 hours

62. Polyurethane Systems
 Steel pipe (exterior) coating
 Surface preparation: SP 10, profile 2.5 mils
minimum
 Application:
 100% solids polyurethane @ 13 – 15 mils DFT

63. Polyurethane Systems
 Concrete tank lining
 Surface preparation: ASTM D4259/ ICRI
03732, CSP 5
 Application:
 Epoxy primer @ 5 – 7 mils DFT
 100% solids elastomeric polyurethane @ 60 – 80
mils DFT

64. Polyurethane Systems
 Elastomeric polyurethane properties
 Shore A hardness: 60
 Adhesion to concrete: 350 psi
 Elongation: 400%
 Tear strength: 150 psi
 Tensile strength: 900 psi

65. Polyurethane Systems
 Elastomeric polyurethane chemical
immersion
 Acetic acid, 10%
 Hyrdochloric acid, 10%
 Methanol
 Nitric acid, 10%
 Phosphoric acid, 10%
 Sulfuric acid, 30%

66. Polyurea Systems
 Steel tank lining
 Surface preparation: SP 10, profile 3 mils
 Application: 100% solids aromatic
elastomeric polyurea @ 60 – 80 mils DFT

67. Polyurea Systems
 Elastomeric polyurea properties
 Shore D hardness: 50
 Elongation: 250%
 Tensile strength: 2125 psi
 Tear strength: 390 psi

68. Polyurea Systems
 Elastomeric polyurea chemical immersion:
 Acetic acid, 10%
 Ammonium hydroxide, 20%
 Hydrochloric acid, 10%
 Phosphoric acid, 10%
 Sulfuric acid, 10%

69. Polyurea Systems
 Concrete tank lining
 Surface preparation: SP 13 / ICRI 03732,
CSP 3-5
 Application:
 Epoxy primer @ 3 – 5 mils DFT
 100% solids aromatic polyurea @ 60 – 100 mils
DFT

70. Polyurea Systems
 Steel structures (exterior tank, bridges)
 Surface preparation: SP 10, profile 2-3 mils
 Application:
 Zinc primer @ 3 – 4 mils DFT
 Aliphatic polyaspartic @ 6 – 9 mils DFT

71. Polyurea Systems
 Polyaspartic properties
 Abrasion resistance: 90 mg loss/1000 cycles
 Adhesion: 825 psi
 Corrosion weathering: 15 cycles ASTM
D5894, Rating 10 blistering/corrosion
 Freeze/thaw: 30 cycles, no adhesion loss

72. Polyurea Hybrid Systems
 Concrete floor coating
 Surface preparation: abrasive
blasting/mechanical roughening
 Application:
 Epoxy primer @ 3 – 5 mils DFT
 100% solids elastomeric polyurea hybrid @
30+ mils DFT

73. Polyurea Hybrid Systems
 Elastomeric polyurea hybrid properties
 Shore D hardness: 60
 Tensile strength: 2300 psi
 Elongation: 100%
 Tear resistance: 330 psi
 Taber abrasion: 25 mg/1000 cycles

74. Summary of Key Points
 Polyurethanes
 Thin film conventional and waterborne
 Single component moisture cure
 100% solids thick film
 Polyureas
 100% solids thick film
 No moisture sensitivity
 Thin film polyaspartics

75. Summary of Key Points (cont.)
 Blast cleaning generally required
 Plural component application for 100%
solids polyurethane/polyurea
 May allow for low temperature
applications
 Minimize down time

76. Polyurethane and Polyurea
coating
 Questions?