Five characteristics of powder coatings
Powder Particle Size
Unreasonable particle size distribution will have adverse effects on powder spraying and coating appearance. If the particle size of the powder is too small, the utilization rate of the powder will be reduced, and if the particle size is too coarse, it is easy to produce orange peel on the surface. The sieve residue may contain impurities or coarse particles, which is easy to form pollutants or particles on the surface of the cured film.
Heavy Metal Content
High content of heavy metals will cause adverse effects on human body and environment. General control: soluble lead (PB) < 90mg / kg; Soluble cadmium (CD) < 75mg / kg; Soluble hexavalent chromium (Cr6 +) < 60 mg / kg; Soluble mercury (Hg) < 60 mg / kg.
Lower Explosive Limit Of Powder
The supplier shall inform the customer of the lower explosion limit of the powder to avoid flash explosion accidents during use, which can be carried out according to GB / t21782 4, the explosive concentration of powder is generally 30 ~ 50g / m ³ It depends on the physicochemical properties of the powder formula.
If the density is too high, it means that there are too many fillers or inorganic pigments in the powder, and the corresponding resin will be less, which is not conducive to the infiltration and dispersion of the powder during melting, and the physical and chemical properties of the film layer will also be affected after curing. If the density is too small, it means that there are too few physical pigments, which will also have an adverse impact on the strength of the film.
Powder Burning Residue
The burning residue of the powder is essentially the content of inorganic matter that cannot be burned. The inorganic matter is mainly filler and inorganic pigment, and the organic matter is mainly resin, curing agent, organic pigment and additives. If the content of residue is higher than 50%, it indicates that the resin content is too small, which will have an adverse impact on the physical and chemical properties of the cured film.
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