Prepainted steel coils coating is mainly classified as two parts. One is Primer coating, the other one is finish coating.
Primers Classification of Prepainted Steel Coil Coating:
The classicisation of the primer includes epoxy, polyester, acrylic acid, polyurethane, etc.
Usually speaking, the chosen of the primer shall be matched with the end usage, environment condition, processing stage and finish coat. The thickness of the primer is usually 5~7 um.
Following is the detail introduction of some often-using primer:
(1) Epoxy primer:
The epoxy primer owns strong adhesion to the base metal and good properties in waterproof, alkali-proof and chemical resistance, which is the original primer for the prepainted steel coil. However, its flexibility is poorer than other primers.
(2) Polyester primer:
The primer own strong adhesion to the base metal and excellent flexibility, which is relatively sensitive to damp environment, but chemical resistance is poorer than that of epoxy primer.
(3) Water-soluble acrylic acid primer
This primer owns strong adhesion, excellent flexibility, lower organic solvent and low-temperature curing.
(4) Polyurethane primer
The primer of this kind has excellent chemical resistance, durability and flexibility.
Finish Coating Classification of Prepainted Steel Coil Coating:
Among all the ingredients of coating, resin and pigment mainly effect for duration. The primers usually is polyester (PE), silicon modified polyester(SMP), Poly Vinylidene Fluoride (PVDF), High Durability Polyurethane(HDP), etc.
(1) Polyester (PE)
The finish coating of PE has strong adhesive force, a variety of colours, wide scope of properties in formation and durability outdoors, moderate chemical resistance and low cost.
(2) Silicon Modified Polyesters (SMP)
The membrane of the finish coat of this kind has excellent rigidity, abrasion resistance, thermal resistance, good outside durability, chalking resistance, high retention of colour, ordinary flexibility, moderate cost, etc.
(3) High-Durability Polyester (HDP)
The finish coat of this kind has excellent retention of colour, resistance of ultra-violet radiation, strong outdoors durability, chalking resistance, strong adhesion to the base metal, plenty of colours chosen and relatively lower cost compared to the same quality.
(4) Poly Vinylidene Fluoride (PVDF)
The finish coat of this kind features in its excellent retention of colour, resistance of ultra-violet radiation, outdoors durability, chalking resistance, resistance to solvent, formability, good dirt resistance, but colours chosen limited and high cost.