Selection of fillers and pigments in high temperature resistant powder coatings

Because powder coatings have the advantage of close to zero VOC emissions, they have become a rapidly developing field in the entire coating and coating industry, and their rapid development has been driven by the current national green and sustainable development background

In recent years, China has gradually become the world's main production base for cookers, ovens, exhaust pipes, etc.

The so-called high-temperature and heat-resistant powder coatings refer to powder coatings that have been subjected to a long-term exposure of more than 300 ° C, the coating film is not damaged, can still maintain appropriate mechanical properties, and play a protective role.

According to the heat-resistant characteristics and technical characteristics of the coating film, heat-resistant powder coatings can be divided into ordinary heat-resistant and high-heat-resistant powder coatings.

The heat-resistant powder coatings can withstand temperatures above 400°C.

01 Application areas and performance requirements

High temperature powder coatings are widely used in power stations, power stations, metallurgy, petroleum, chemical industry, food and other fields, such as: BBQ ovens, high-power lighting covers, heating pipes, hot blast stoves, ovens, motorcycle exhaust pipes, chimneys, etc.

Taking the BBQ oven as an example, most of the substrates are cold-rolled steel plates, and a few are cast aluminum.

The coating film not only needs to meet the conventional performance requirements such as impact, hardness, bending, adhesion, acid and alkali resistance, aging, etc.

Another example is the high temperature resistant powder coating for vehicle exhaust pipes, the operating temperature can reach 350~550 ℃, and the coating film should not have appearance defects such as cracks, cracks, blistering, chalking, etc.
, color difference value, loss rate, etc.
Agreed, the color is mainly black
.

02 Choice of filler

1 mica powder

Mica powder is a kind of natural fine-grained muscovite, monoclinic crystal, scaly, with silky luster
.
Adding mica to the formula can improve the UV resistance of the coating film and improve the weather resistance of the coating film
.

The flaky result can not only improve the compactness of the coating film, prevent the infiltration of water, improve the water resistance, acid and alkali corrosion resistance and good insulation of the coating film, but also improve the heat shielding effect of the coating film, which can improve the coating film.
Heat resistance
.

2 talc powder

Talc, also known as hydrous magnesium silicate, is crushed from talc ore.
The fine particles of talc are needle-like crystals with a greasy feeling and can be used as a thixotropic filler
.

It has a certain influence on the melt fluidity of powder coatings and has a certain influence on leveling.
It is often used for texture powder, and the addition amount should not be too much.
Talc powder can improve the hardness, weather resistance and corrosion resistance of the coating film.
The -OH in talc powder can add additional Improve film adhesion
.

3 Hollow Beads/Hollow Beads

Hollow microbeads are inert hollow spherical particles with high hardness and high strength.
The main components are silicon dioxide and aluminum oxide, the diameter is 0.
2-400μm, and the appearance is off-white.
The hollow microbeads have the following characteristics:

(1) Small surface area, which can reduce the amount of resin used;

(2) Low slaughter and good fluidity have little effect on leveling;

(3) It can improve the hardness of the coating, scratch resistance and corrosion resistance;

(4) Can be extinct;

(5) Improve the thermal insulation, water resistance and high temperature resistance of the coating film;

(6) Absorb ultraviolet light and improve the weather resistance of the coating;

(7) The hardness, heat resistance and wear resistance of the coating film can be improved
.

4 Quartz powder/silica etc.

Quartz powder has high Mohs hardness, acid resistance, alkali resistance, wear resistance and non-toxicity, and has good electrical insulation, which can improve the hardness and heat resistance of the coating film, but the addition amount should not be too much, which will cause extrusion difficulties
.

Silica Mohs hardness is 5.
4-6, oil absorption is 100%-200%, it has the characteristics of light resistance, high temperature resistance, acid resistance and alkali resistance, and has the characteristics of matting, anti-sagging and improving the fluidity of powder coatings.
Too much, otherwise it will cause extrusion difficulties, often used in heat-resistant powder coatings
.

03 Selection of heat-resistant pigments

When the temperature is higher than 250°C, ordinary organic pigments will change color or even decompose.
Therefore, only inorganic pigments, such as iron oxide black and graphite, can be selected in the formula of heat-resistant powder coatings, considering the discoloration resistance and the overall comprehensive performance of the coating
.

Iron oxide black and graphite are the best black pigments.
They not only have good resistance to high temperature discoloration, but also do not affect the mechanical properties of the coating.
In addition, aluminum powder, stainless steel powder, and iron powder can also be added to the formula coating film.
hot sex
.

For heat-resistant powder coatings, the resin used as the base material should have good thermal stability.
If the filler is selected properly, many properties of the coating film can be greatly improved.
Different fillers play different roles in the coating.
Relying on resins or fillers cannot achieve high temperature resistance requirements
.

In addition, the combination of various fillers can obtain the coating film with the best comprehensive performance, such as the combination of mica, talc, and hollow microspheres can improve the cracking resistance of the coating film
.