Polyethylene wax R-(CH2-CH2)n-CH3, molecular weight 1000-5000, is white, tasteless, odorless inert material, can be melted at 104-130 degrees, also can be dissolved in solvents and resins at high temperature, but still precipitate when cooling, its precipitation fineness is related to the cooling speed: slow cooling to get coarser particles (5-10μm), fast cooling get finer particles (1.5-3μm) .
In the film-forming process of powder coating, when the coating film is cooled, polyethylene wax precipitates from the coating liquid and forms fine particles, which float on the surface of the coating film and play the role of texture, matting, slip and anti-scratch.
I. Effects of micronized pe wax
1. Texture, matting
When the coating film is cooled, polyethylene wax particles precipitate out from the coating and migrate to the surface of the coating film, producing the effect of pattern and matting; in powder coatings, different micronized waxes reduce gloss differently, and micronized waxes can be selected according to gloss requirements. Micronized wax addition 1%, 60 gloss reduction 5-15.
2. Anti-scratch, anti-abrasion, anti-polishing, anti-scoring
Microfine polyethylene wax exists in the form of dispersed particles on the surface of the coating to reduce the coefficient of friction of the coating, so that when objects collide with the surface of the coating, the tendency to slide is greater than the tendency to scratch, to reduce the tendency to be polished by friction and to maintain low gloss durability. The amount of 0.5-1% can reduce the dynamic friction coefficient of the coating film from 0.35 to 0.25. When another object touches the coated product, they sometimes leave black marks on the coating film, polyethylene micronized wax added to the film can reduce this tendency, or make the marks easy to wipe away.
3. Effect on pigment dispersion
Micronized wax enhances the wetting and dispersion of pigment agglomerates, and makes the pigment coloring intensity increase. The addition of 0.5-3% can increase the pigment coloring intensity by 10-30%.
4. Effect on extrusion output
Micronized wax makes the screw torque lower, adding 1% can make the extruder yield increase by 5-25%.
5. Smoothness and texture
Polyethylene micronized wax gives the coating film an excellent texture.
6. Water repellency
Wax-containing coating film has better hydrophobicity.
7. Substrate Wetting
The precipitation of wax particles from the coating film helps to release the gas adsorbed on the porous substrate.
II. Dosage and addition method
PE wax is generally used at a dosage of 1-3%, usually added prior to extrusion.
Micronized wax can be added both before and after extrusion, and the amount added afterwards is less than 1% to achieve excellent results.
1. Low molecular weight PE homopolymer wax, with good matting effect and comprehensive performance.
2. Modified amide wax increases the incompatibility and confusion in the coating components, in the hot melt state, resulting in system viscosity, surface tension drops sharply and wax base migration to the surface of the coating, the result is that after curing degree coating surface to form a dense coating film, resulting in loss of light. In addition to epoxy resin, powder coatings are suitable.
3. PTFE modified PE wax, good friction resistance, high scratch resistance, smoothness, texture. Wax powder contains PTFE wax, because it can not melt, with a single particle protruding on the surface, become the first line of defense against wear and tear, from the surface to grow wear-resistant time, and when the coating film cools, polyethylene wax precipitates from the coating liquid, forming fine particles, floating on the surface of the coating film, play a smooth, anti-scratch role, become the second line of defense against wear and tear. The best combine of PTFE wax and PE has the advantages of both wax powders, and the best hardening effect.
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