Preface: As a phase transfer catalyst used in the production of TGIC, the role of quaternary ammonium salt is to help open the epoxy group of liquid-phase epichlorohydrin and promote its reaction with the solid-phase cyanuric acid. The purification process such as washing and crystallization of TGIC is an important step to transfer the quaternary ammonium salt out of the system. However, poor control of the TGIC production process can lead to an increase in the viscosity of the system, and eventually after the two purification processes, many quaternary ammonium salts are still left or entrained into the finished product. This eventually leads to different batches of powder coatings made of TGIC from different manufacturers with different curing speed (gelation time).

So what are the effects of fast curing TGIC on the powder?

Leveling, matting, storage stability (chemical)

How much does different TGIC affect

Randomly selected from 8 varieties (batches) sampled in the market

	Reactivity@180℃ sec	Chlorine content wt%	Epoxy equivalent
A	275	0.53	107.53
B	246	0.60	107.53
C	300	0.49	106.38
D	271	0.45	106.38
E	292	0.45	105.26
F	354	0.45	109.89
G	255	/	/

Note The reaction activity test is the gelation time data measured by GH-2205:TGIC=93:7

Physical extinction efficiency

We know that the physical extinction of outdoor TGIC systems comes from the difference in curing speed of different combinations within the product system, and the arrival of incompatible components (acrylic, wax powder) to the surface. Too fast a TGIC reaction speed can interfere with the designed curing speed gradient and cause the system viscosity to grow too fast, ultimately leading to a lack of sufficient time for the incompatible components to float up. This affects the final effect of physical matting.

The above three curing speed gradients of TGIC matched with GH-2221 GH-2208 were used for physical matting.

TGIC	Reactivity@180℃ sec	GH-2221 4% matting agent grey gloss %@60°	GH-2208 3% matting agent grey gloss %@60°
B	246	11	17.8
C	300	9.9	14.8
D	271	10.3	14.2

As can be seen above, the difference in gloss between TGIC under the medium gloss formulation is 3%, while the difference between the very low matte formulation is about 1% gloss.

Storage stability of two-component transfer powder (including low-temperature curing powder)

Thermosetting powder coatings because of its thermosetting properties, there will also be slow cross-linking in the process of storage. And low-temperature curing, two-component matte fast components, etc. because of its catalyst content, system carboxyl, high content of epoxy groups, in storage is more likely to product slow cross-linking, when different TGIC because of the amount of quaternary ammonium salt it contains, will lead to great differences in storage stability performance.

We use C and G as a comparison here, and the system was selected as a combination of GH-4401 and GH-4409, using a general transfer formulation. Accelerated storage tests were performed in an oven at 40°C.

TGIC	Reactivity@180℃ sec	Initial Gloss % @60°	After 7 days % @60°	After 14 days % @60°
C	300	28.8	26.5	23.6
G	255	29.3	23.8	22.4

As can be seen above, the faster curing speed of TGIC in the two-component products, due to more residual catalyst fast and slow components curing speed are faster, resulting in the initial gloss is also slightly higher. After storage at high temperatures, the fast component produces more pre-gelatinization linkage leading to its gelation time shortened significantly, eventually leading to lower gloss of the coating film. And the powder made of TGIC with faster curing decreases the gloss even more significantly after storage. In particular, the gloss difference reached 2.7% at day 7. In fact, in this process the final coating film crosslinking degree will instead decline, thus unable to meet the requirements of transfer customers off paper.

Above

Users of TGIC can follow certain operating procedures for incoming material testing. In order to select the batch that meets their needs to use. To avoid the use of fast curing TGIC in situations that require matting and harsh storage conditions.