Study on the formulation of epoxy high Tg powder coating

Abstract: The glass transition phenomenon and its influence on the properties of coatings are expound.

Keywords: powder coating, epoxy, glass transition temperature, coating properties

0 Preface

Glass transition is an extremely important property of polymers and affects various properties of polyme.

This paper aims to study the general epoxy resin and its curing agent, filler and auxiliary agent, conduct experimental comparison, analyze the influence of various raw materials in the formulation and production process on the glass transition temperature of the coating, and develop a comprehensive performan.

1 Test part

1 Main equipment and experimental instruments

Twin-screw extruder; small pulverizer; grinding system; electrostatic spray gun; high temperature oven; impact tester; DSC differential scanning calorimeter; glass instruments such as beakers, measuring cups, glass rods, glue tip droppers,e.

2 Raw materials

Universal epoxy resin A, epoxy resin B, epoxy resin C, epoxy resin D: industrial grade, two-step method; micronized dicyandiamide: industrial grade; phenolic curing agent: industrial grade; modified phenolic Curing agent: industrial grade; acid anhydride curing agent: industrial grade; curing accelerator a: industrial grade; curing accelerator b: industrial grade; curing accelerator c: industrial grade; curing accelerator d: industrial grade; rutile titanium dioxide : Industrial Grade; Barium Sulfate: Industrial Grade; Silicon Micropowder: Industrial Grade; Mica Powder: Industrial Grade; General Pigment: Industrial Grade; General Auxiliary: Industrial Gra.

3 Powder coating and coating preparation

Carry out formula design and weigh each raw material according to the formula (see Table 1), fully premix it with a small pulverizer, and pour it into the feed port of the extrud.

4 Coating performance testing

The coating performance test and related standards are shown in Table

1 Selection of epoxy resin

During the experiment, epoxy resin A with epoxy equivalents of 400~450, epoxy resin B with 600~650, epoxy resin C with 800~950, and epoxy resin D with 1500~1800 were used, and dicyandiamide was used as the Curing agent, accelerator a is the curing accelerator, mica powder is the filler, general-purpose additives and pigments are selected, and the effects of epoxy resins with different epoxy equivalents on the coating Tg and its properties are compar.

By analyzing the data in Table 3, it can be seen that among the four selected epoxy resins, the properties of powder coatings made of resins with different epoxy equivalents are also differe.

2 Selection of curing agent

At present, the curing agents used for epoxy systems in the powder coating industry include dicyandiamide, imidazole derivatives, phenols, modified phenolic and acid anhydrides [2-

It can be seen from the above comparative analysis that the powder coating with micronized dicyandiamide as the curing system has the best comprehensive performance, followed by the acid anhydride curing system, and then the modified phenolic resin and phenolic curing syst.

3 Choice of pigments and fillers

Pigments and fillers commonly used in powder coatings mainly include titanium dioxide, barium sulfate, calcium carbonate, silicon micropowder, mica powder and so .

4 Selection of curing accelerator

During the experiment, epoxy resin A with epoxy equivalents of 400-450 and micronized dicyandiamide were used as film-forming systems for powder coatings, mica powder was used as filler, and accelerator a, accelerator b, accelerator c, Accelerator d is a curing accelerator, and the effects of these four curing accelerators on the coating Tg and its comprehensive properties are compar.

After the main formula is determined, the optimal dosage of formula materials is explored by comparing the changes of variabl.

And by analyzing the data in Table 5, it can be seen that among the four selected curing accelerators, the powder coatings prepared by accelerator a and accelerator d have the best comprehensive performance, in pencil hardness, temperature resistance test, acid and alkali resistance test, e.

5 Performance Comparison

Through the comparative analysis of epoxy resin, curing agent, filler and curing accelerator, the formula is finally determined, and epoxy high Tg powder coating can be produc.

The higher the Tg, the faster the reaction speed of the powder coating, and give the coating higher pencil hardness and better temperature resistance, acid and alkali resistance and other comprehensive properties [
The fluidized bed dipping powder coating that our company is developing has a fast reaction speed and has strict requirements on the comprehensive performance of the coating, so theoretically this high Tg powder coating can be suitable for fluidized bed dipping powder coatin.

Through trial and error, the high Tg powder coating is completely suitable for fluidized bed dip coating powder coati.

The following is a picture of the product dip coating site (see Figure

4 Conclusion

The coating Tg of the powder coating is related to the epoxy equivalent of the epoxy resin in its raw material, the type of curing agent, the type of accelerator and its amou.

The low epoxy equivalent epoxy resin/dicyandiamide curing system is used as the film-forming system, accelerator a is the curing accelerator, and mica powder is the fill.

It can meet the process and performance requirements of fluidized bed dip coating powder coatings, and has broad market prospec.