1.What is the root cause of color fading/variation?
Ultraviolet rays in sunlight are the main culprit for the aging of organic coatings and the degradation of pigments. Ultraviolet rays have high energy and can destroy the chemical bonds of resin molecules in the coating and the structure of pigment molecules.
2.What is the difference in UV resistance among different resins?
PVDF (polyvinylidene fluoride): The best UV resistance. The C-F bond energy in its molecular structure is extremely high (up to 485 kJ/mol), which can effectively resist the damage of ultraviolet rays. PVDF resin itself is very stable and degrades very slowly. High-quality PVDF coatings can provide excellent color retention, and the color change is very small even after long-term exposure to strong sunlight.
HDP (high durability polyester): The molecular structure is modified on the basis of ordinary polyester and high-efficiency UV absorbers, light stabilizers and pigments with excellent weather resistance are added. Its UV resistance and color retention are significantly better than ordinary polyester, close to the level of PVDF, but may be slightly inferior to top PVDF in the long run. High cost performance.
SMP (silicon modified polyester): Silicone components are introduced into polyester resin. Silicone elements improve the heat resistance and flexibility of the coating. Its UV resistance and color retention are better than ordinary polyester, but usually not as good as HDP and PVDF. The higher the silicone content, the better the performance.
Ordinary polyester: The most economical and commonly used, but the UV resistance is relatively weakest. Under strong or continuous ultraviolet radiation, resins and pigments are more susceptible to photo-oxidative degradation, resulting in color fading, darkening (may darken before chalking), and early and obvious chalking. The color retention period is relatively short.
3.What is the difference between pigment grade and stability?
Even when using the same resin (such as PVDF), the color durability of the coating depends greatly on the weatherability level of the pigment used. ◦ High-performance pigments: Inorganic pigments (such as certain metal oxides) or organic pigments with special structures designed for durable outdoor applications, with excellent light fastness (not easy to fade) and weather fastness (resistance to environmental erosion). They are more expensive. ◦ Ordinary pigments: Poor light fastness and weather fastness, easy to decompose or chemically change under the action of ultraviolet rays, resulting in rapid fading or shifting of color (such as red to pink, blue to gray). ◦ Key point: Top-grade coating materials (such as PVDF, HDP) must be paired with high-performance pigments to achieve their best color retention effect. Poor-quality pigments will drag down the performance of the entire system.
4.What is the difference between coating integrity and chalking resistance?
The material determines the ability of the coating to resist environmental erosion (acid rain, pollutants, moisture). ◦ Materials with strong corrosion resistance (such as PVDF): They can better protect the internal pigment particles from being exposed and washed away. Even if the surface resin ages very slowly, it is also very resistant to chalking, and the pigment is not easily lost due to chalking, and the color can be "locked" in the coating for a longer time. ◦ Materials with weak corrosion resistance (such as ordinary polyester): The coating is more easily damaged by the environment, and the surface may chalk faster. Chalking not only causes the surface gloss to decrease and the touch to be rough, but more importantly, it causes the pigment particles on the surface to fall off, directly causing the color to fade and turn white (exposing the underlying color or primer).
5.What is the difference in color durability?
PVDF coating: Performs best in standard tests (such as QUV, Xenon Arc) and in actual applications. It usually guarantees ΔE < 5 (the threshold of change that can be detected by the human eye) for 10-15 years or even longer. Many high-quality products can still maintain acceptable appearance for 20-30 years under normal conditions. It is particularly suitable for occasions with extremely high requirements for color stability (such as high-end building exteriors, landmark buildings). ◦ HDP coating: Excellent color retention, usually can provide a good color retention period of 7-15 years or even longer, and the performance is close to PVDF, which is a very cost-effective choice. ◦ SMP coating: The color retention is better than ordinary polyester, but weaker than HDP/PVDF. It is usually expected to have good medium-term performance in moderate environments (such as 5-10 years). ◦ Ordinary polyester coating: The color retention is relatively limited. In strong sunlight environments, it may fade or discolor more significantly within a few years (such as 3-7 years). Suitable for projects with low requirements for long-term color stability or limited budgets.