Polyester is the workhorse coating of pre-painted aluminium coil, it can offer an economical product with reasonably good performance across the board. Polyester coatings are the basis of most internal applications of pre-painted aluminium, which asks for greater scrutiny than exterior applications, thus, high quality aesthetics, good formability and a high degree of scratch resistance are important. All of these properties can be available in polyester coatings
◆ Polyester primer and Polyester finishing coat
◆ Layering 8 - 40 µm (depending on color and application)
◆ Excellent ductility
◆ Extensive color range, high degree of gloss
◆ Limited durability regarding UV and weathering
PVDF (Polyvinylidene Fluoride)
PVDF is a highly stable resin, the PVDF resin is not affected by UV radiation, so it remains very stable for long periods in sunlight. Apart from UV resistance, it is also highly resistant to many chemicals and it has excellent stain resistance. But their resistance to damage from scratching is limited
PVDF is almost exclusively used for external wall cladding and facades. PVDF attracts a cost premium over polyester, to which the initial appearance is similar, so it is used where the long-term color durability will be appreciated, particularly for cladding and facades on prestigious buildings.
PVDF coating also can be classified as traditional PVDF and nanometer PVDF coating.
Traditional PVDF Coating, with KYNAR500 PVDF, two or three times for coating and baking, has good properties of anti-acid, anti-alkali and is durable in atrocious weather and environment, keeping 15 years no unwonted fading. In view of these facts, we recommend this paint applied for external wall cladding.
Nanometer PVDF Coating, which different with traditional PVDF is the clear coating. It contains nanometer element, which can protect panel from pollution, Because nanometer has self-cleaning effect, It easy to get rid of dust and pollution by raining or water.
◆ Excellent weathering and UV properties
◆ Very good color and gloss durability
◆ Very good corrosion and chemical resistance
◆ Very good ductility
◆ Twin coat system (uniform colors) consisting of primer and finishing layers.
◆ Layering thickness approx. 25 µm Degree of gloss (60° measuring angle): approx. 20 units (Gardner)
◆ Four coat system (aluminiumlic colors) consisting of 2 primers, base coat and transparent lacquer Layering thickness approx. 35 µm Degree of gloss (60°- measuring angle): approx. 30 - 40 units
Polyurethane coatings are chemically similar to polyesters but are capable of improvements in some areas. Polyurethanes are capable of high levels of flexibility which is often desirable for pre-painted aluminium and they also tend to be a bit more scratch-resistant than polyesters. So, for the above features, PU generally costs slightly more than Polyester, and it has become a favored option for premium interior products such as domestic appliance applications.
◆ Extreme form and temperature stability
◆ Non-flammable, non-toxic handling and processing
◆ Extremely chalk- and UV-resistant
◆ No embrittlement through light or atmospheric exposure
◆ Front face is twin coat enamelled (base and finishing coat are applied independently)
Although historically important, more recently, epoxy resins have only been used for primer paints. Adhesion to the aluminium surface and to other top-coat paint systems is very good, but epoxies tend to have limited flexibility, so their use in primers is now declining significantly in favors of polyester and polyurethane-based primer systems.
◆ Outstanding chemical resistance
◆ High flexibility
◆ Ideal for interior use
Once popular, acrylics are now used not as much as before. However, acrylics suffer from a lack of flexibility, so inEurope at least, most users have switched to polyester coatings which offer many of the same benefits in a more flexible coating. Acrylics are still used in some places, particularly for flat applications such as signage or signboards.
◆ Excellent hardness and scratch resistance
◆ Lack of flexibility
Test about color retention, gloss retention and chalking behavior of the above paint materials: