Application of polyethylene micropowder wax in powder coatings
Polyethylene wax R-(CH2-CH2) N-CH3, molecular weight 1000-5000, is white, tasteless, odorless inert material, can be melted at 104-130 degrees Celsius, can also be dissolved in solvents and resins at high temperature, but will still precipitate when cooling, its precipitation fineness is related to cooling speed: Coarse particles (5-10μm) were obtained by slow cooling, and fine particles (1.5-3μm) were precipitated by rapid cooling. In the film forming process of powder coating, when the film cooling, polyethylene wax precipitation from the coating liquid, forming fine particles, floating on the surface of the film, texture, extinction, smooth, scratch resistance; Various patterns can be obtained by proper selection of micropowder wax and coating system.
One, the effect of polyethylene powder wax:
1. Texture and extinction:
When the film is cooled, polyethylene wax particles precipitate from the film and migrate to the film surface, resulting in patterns and extinction effects. In powder coatings, different powder waxes reduce gloss differently, and can be selected according to gloss requirements. Adding 1% of micropowder wax can reduce the gloss of 60 by 5-15.
2. Scratch resistance, wear resistance, polishing resistance, engraving resistance:
Fine polyethylene wax exists on the surface of the coating in the form of dispersed particles, reducing the friction coefficient of the coating, so that when the object hits the surface of the coating, the sliding tendency is greater than the scratching tendency, reducing the tendency to be polished by friction, and maintaining low gloss durability. The dynamic friction coefficient of the film can be reduced from 0.35 to 0.25 by adding 0.5-1%. When other objects come into contact with coated products, they sometimes leave black marks on the film. The addition of polyethylene powder wax to the film can reduce this tendency or make the marks easier to erase.
3. Influence on pigment dispersion:
The micropowder wax enhanced the wetting and dispersion of pigment aggregates, and improved the coloring strength of pigments. The coloring strength of pigment can be increased 10-30% by adding 0.5-3%.
4. Influence on extrusion output:
The powder wax reduces the screw torque, adding 1% can increase the extruder yield by 5-25%.
5. Smooth and textured:
Polyethylene powder wax endows the film with excellent texture.
6. Water resistance:
Waxy film has better hydrophobicity.
7. Substrate wetting:
The separation of wax particles from the coating helps to release the gas adsorbed on the porous substrate.
Two, dosage and adding method
Polyethylene wax general dosage is 1-3%, generally added before extrusion;
Micropowder wax can be added before and after extrusion, after adding less than 1% can achieve excellent results.
1. Low molecular weight polyethylene homopolymer wax, with good extinction effect and comprehensive performance;
2. The amide modified wax increases the incompatibility and confusion in the coating components. In the hot melt state, the viscosity and surface tension of the system decrease sharply and the wax base migrates to the coating surface, which results in the formation of a dense coating film on the coating surface after curing, resulting in loss of light. Applicable except epoxy powder coatings.
3. Polytetrafluoroethylene modified polyethylene wax, good friction resistance, with high scratch resistance, smooth, texture. Wax powder containing ptfe wax, because its not melt, highlighted by individual particles on the surface, become the first line of defense against wear and tear, and from the surface wear resistance to the growth of the time, and DangTu film cooling, polyethylene wax precipitation from the coating liquid, form fine particles, floating on the surface coating, have the effect of smooth, scratch resistance, become the wear resistance of the second line of defense, The best combination of polytetrafluorin and polyethylene has the advantages of the two wax powders and has the best hardening effect.