Fingerprint Resistance Test Of powder Coatings

Powder coatings have the advantages of energy saving, environmental protection and excellent performance. Compared with traditional liquid coatings, powder coatings have the advantage of solvent-free evaporation. However, in the actual spray curing process, a small number of small molecular substances will still evaporate, and the most common phenomenon is "smoking" phenomenon in the curing process. Another phenomenon is simply ignored, that is the "fingerprint" phenomenon.

For example: for a sprayed workpiece, if the worker touches the coating directly when he leaves the workpiece, the phenomenon of "fingerprints" will easily occur; maybe if the workpiece is defective, the second spraying solidifies, and there is no second spraying, the fingerprints of the previous touch often appear, and the fingerprints are very significant; if the second spraying happens to be the place touched by the previous hand, the adhesion between the coatings will also have problems. This kind of "fingerprint" phenomenon can be seen everywhere, especially in bright products. On the one hand, the main reason for this phenomenon is that the low molecular weight substances contained in polyester resin are separated from the coating surface in the process of preparing powder coatings for application, resulting in "fingerprint" phenomenon.

Milestone Industrial Co. Ltd. is a new product specially developed for "fingerprint" phenomenon. It mainly studies the fingerprint resistance of powder coating from the perspective of polyester resin composition. A kind of fingerprint resistant polyester resin is prepared from terephthalic acid, isophthalic acid, neopentyl glycol and so on. The influence of raw material monomer and composition process on fingerprint resistance is studied. The specific process is as follows:

1) Basic formula of resin synthesis

2) Resin synthesis process

The first stage: put the alcohol (NPG, eg, CHDM, BEPD, TMP) into the reactor, heat it to 120 ℃, wait for the alcohol to melt, start the stirring, then put TPA and fc2001 into the reactor, slowly raise the temperature to 248 ℃, and keep the temperature until the acid value is 6-10mgkoh / g;

In the second stage, the temperature was reduced to 190-220 ℃, IPA and ADA were added in turn, the reaction temperature was raised to keep the reactants clear, the acid value was measured by sampling, and the temperature was reduced to 230 ℃ after reaching 43-47 mgKOH / g;

The third stage: Vacuum polycondensation at - 0.096mpa for 2h, determination of acid value and viscosity, cooling to 180-200 ℃, adding additives, maintaining for 0.5h. It is the polyester resin used in this study.

3) The synthetic polyester resin, curing agent TGIC, leveling agent, pigments and fillers, benzoin, etc. were evenly mixed according to the formula proportion, and then extruded and pressed by twin-screw extruder. After cooling, the powder coating was prepared by crushing and sieving.