Polyethylene wax R - n - CH3 (CH2 - CH2), molecular weight, 1000-5000 is white, tasteless, odorless inert substances, can melt, 104-130 degrees Celsius, can be dissolved in solvent and resin in high temperature, but still precipitate during cooling, it precipitation of fineness is associated with cooling speed: slow cooling get a coarser particles (5-10 microns), rapid cooling precipitation finer particles (1.5 3 microns). In the film forming process of powder coating, when the film cools, polyethylene wax precipitates from the coating solution, forming fine particles, floating on the surface of the film, play a texture, extinction, smooth, scratch resistance purposes; A variety of patterns can be obtained by properly selecting the system of powdered wax and coating.
One, the effect of polyethylene powder wax:
1. Texture and extinction:
When the coating cools, polyethylene wax particles precipitate from the coating and migrate to the surface of the coating, producing the effect of pattern and extinction. In powder coating, different micro powder wax to reduce the glossiness is different, can choose micro powder wax according to the glossiness requirements. The amount of micro powder wax is added by 1%, and the gloss of 60 is reduced by 5-15.
2. Anti-scratch, anti-wear, anti-polishing, anti-engraving:
The fine polyethylene wax exists on the surface of the coating in the form of dispersed particles, which reduces the friction coefficient of the coating. When the object collides with the surface of the coating, the tendency of sliding is greater than the tendency of scratching, and the tendency of being polished by friction is reduced, thus maintaining the low gloss durability. The dynamic friction coefficient decreased 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. Polyethylene powdered wax added to the film can reduce this tendency or make the marks easy to erase.
3. Influence on pigment dispersion:
The powdered wax can enhance the wetting and dispersing of pigment aggregates and enhance the pigment coloring intensity. Adding 0.5-3% can increase pigment coloring strength by 10-30%.
4. Influence on extrusion output:
Micro powder wax reduces screw torque, adding 1% can increase extruder yield by 5-25%.
5. Smooth and textured:
Polyethylene powder wax endows the film with excellent texture.
Wax coating has better hydrophobicity.
7. Wetting of substrate:
The precipitation of wax particles from the film facilitates the release of gas adsorbed on the porous substrate.
Two, dosage and adding method
The general dosage of polyethylene wax is 1-3%, which is generally added before extrusion.
Micro-powdered wax can be added before and after extruding. Excellent results can be achieved when adding less than 1% after extruding.
1. Low molecular weight polyethylene homopolymer material wax, with good extinction effect and comprehensive properties;
2. Amide modified wax increases the incompatibility and confusion of coating components. In the hot melt state, the viscosity and surface tension of the system decrease sharply, and the wax base migrates to the surface of the coating. Applicable except for epoxy resin 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 ptfe and polyethylene, possesses the advantages of the two kinds of wax powder, add hard work best.