What is Paint?
Paint is a material, designed to be applied to a wide range of surfaces, to impart beauty and protection that will dry to give
a solid film.
What goes into Paint?
1.Pigments
Finely ground powders: naturally occurring minerals or synthetically produced. They provide:
Colour and special effects
Opacity - (coverage / hiding power)
Filling properties
Sandability
Adhesion
Durability and corrosion resistance
Aluminium pigment
Extenders (Matting Pigments) Used for filling, sanding, adhesion and corrosion resistant properties
Extenders are translucent and therefore have poor opacity
How do matting pigments work ?
Low pigment/polymer ratio Polymer rich smooth surface High reflectance >90% @ 60 Deg
High pigment/polymer ratio Rough surface profile High degree of light scattering reflectance <5% @ 60 Deg
Pearls and Multi coloured pigments
2.Resin Resin is the backbone of paint.….and is needed for :
成膜
包裹颜料
耐久
光泽
流平性
黏附力
抗化学物质
Polymers (Resin or Binder)
Provide Cohesive force
Provide Adhesive force
Impart physical and chemical properties e.g. hardness, flexibility and chemical resistance
3.Additives These are materials added in small quantities to give or improve certain specific characteristics…..
UV Absorbers – Durability
Flow additives – Levelling
Anti-Settle agents
Driers and Catalysts
Plasticisers
4.Solvents/Thinners Volatile material needed to….
Reduce Viscosity
Change speed of dry/flash-off
Types used and quantity depends on:
Type of paint
Weather - Hot / Cold
Type of drying process - Air Dry / Baked
Size of job
Typical Solvents
Aliphatic Hydrocarbons e.g. White Spirit
Aromatic Hydrocarbons e.g. Xylene
Ketones e.g. Methyl Ethyl Ketone Esters e.g. Butyl Acetate
Alcohols e.g. Butanol
Water
Polymer Technology
The type of polymer used will affect many of the properties of the paint
Most significantly, the drying processes can be greatly affected by these choices
Paint Drying Process
The different drying processes found include:
Lacquer Dry
Oxidation
Chemical Reaction
Lacquer Dry Paints
Nitro-cellulose or Acrylic Lacquer Paints
They are 1 Pack paints (1 Pack = 1 Component)
Have no pot life (pot life = usable life)
Easy to use
Good polishability
Rapid dry
Low solids
High material usage
Do not need heat assistance for drying
Dry by simple evaporation of solvents
Paints That Dry Through Oxidation
Known as Alkyd paints
They are 1 Pack paints
No heat required for drying
These paints dry by
Solvent evaporation
Reaction with oxygen in the air
Slow drying
Made using mild solvents
Relatively inexpensive raw materials
Lower durability than 2 Pack paints
Poor polishability
Paints That Dry Through Chemical Reaction
2K (2-Komponent) 2-Pack Paints are a typical example
These consist of a paint pack + hardener
The paint and hardener must be packaged separately to prevent them from reacting together
The components will start to react from the moment they are mixed together
Application of heat by hot air or Infra Red will increase the speed of reaction and will reduce the time needed to complete the reaction (cure time)
Solvent may be added as 3rd component to achieve the correct application viscosity
These paints dry by
Solvent evaporation
Chemical reaction
Speed of cure can be controlled
Pot Life becomes important factor
High gloss
Good durability
High solids
High build
Low bake/Infra Red finish
Only technology capable of meeting Aerospace industry standards
Typical polymer systems used in Aerospace Coatings
Nitrocellulose - Dopes for fabric covered aircraft
Acrylic, Single component - Exterior topcoats for military aircraft
Epoxy/Polyamide - Anti-corrosive primers
Epoxy/Polyamide - Interior topcoats
Polyester/Isocyanate - Interior and exterior topcoats, military and civil
Acrylic/Isocyanate - Exterior decoration for civil aircraft