In recent years, with the increasingly strict environmental protection policy, the rapid growth of environmentally friendly coatings. Solvent-free volatile 100% UV system due to fast curing speed, low coating cost, excellent paint film performance and so on, the growth is particularly rapid, is increasingly used in floor paint, OPV and other fields.
However, it is not easy for the 100% UV system to achieve low light or even full dumbness, because the system does not contain volatiles, and the paint film shrinkage is small (only the shrinkage factor of the double-bond polymerization reaction) and difficult to
this article will introduce that by selecting the right light-reducing powder, using a "smart" formula, targeted control curing and equipment parameters, can significantly affect the degree of light-out, to obtain the ideal anti-light effect.
to take full advantage of these available influences and may even produce completely dumb coatings.
According to the thickness of the paint film, choose the appropriate anti-light powder
Usually, the traditional solvent-based coating system with the increase of film thickness, matte coating surface gloss will be increased, making the high film thickness coating system difficult to fade. However, the 100% UV cured coating gloss varies with the increase in film thickness. In a certain film thickness, gloss with the increase of film thickness and improve, to a certain film thickness, gloss will be reduced with the increase of film thickness.
as shown in Figure 1, when fine particles of light-depressing powder ACEMATT® OK 607 and ACEMATT® 3600 are added, it can be observed that the gloss increases with the thickness of the film starting from the film weight of less than 20g/
Reduced, and the addition of coarse particles of light-down powder ACEMATT® HK 440, to the film weight of 36g /
, gloss with the increase of film thickness and improve, such as further increase in film thickness, gloss will also be reduced with the increase of film thickness.
will use a model to describe the relationship between the de-lighting of the coating and the thickness of the film. The silicon dioxide anti-light powder used in the model is the ACEMATT
HK 440 for coarse particles and the
OK 607 (model only, not UV first push) for coarse particles, presented in an ideal state of uniform size spherical particles. The model is based on an 8% volume shrinkage. The shrinkage of the coating volume is accompanied by the degree of shrinkage of the anti-light powder matrix (silicon dioxide network), where relative shrinkage is defined as shrinkage efficiency.
thick coating application (55 m)
, figure 2: Assuming an
8% volume shrinkage and a 50% shrinkage efficiency, the effective volume shrinkage of
is 2 m, and the maximum height of the
paint film surface decrease is
ACEMATT® HK 440 (14.5 m), the
forms a rough paint film surface with only a small portion of the top end of the
particle, accompanied by a long-wave structure (see figure 3 green area),
resulting in a higher gloss value of 60 degrees and 85 degrees. In contrast, when using fine particles of light-down powder ACEMATT® OK 607, because the effective contraction (2
is almost half the
particle size (4.4 m) of
ACEMATT® OK 607,
the formation of rough paint film surface exposed more light powder part (Figure 3 orange area) resulting in
more obvious short-wave structure, so that the gloss of 60 degrees angle is significantly lower. However, due to the difference in height of the < film, the gloss is still high at an angle of 85 degrees. The comparison of the theoretical assumptions with the actual measured values in Figure 3 shows that the theory is valid.
thin coating application (10 m)
, Figure 4: The same 8% volume shrinkage, 50% shrinkage efficiency are assumed here, but the resulting effective contraction (the maximum height difference when the paint film surface is cured< The aCEMATT® HK 440 (particle size 14.5
of coarse particles is presented in the model in the ideal form of a single layer of coarse particles (figure 5 green area), resulting in a very significant structure, resulting in a lower gloss at 60 and 85 degrees angles. The light-killing powder ACEMATT® OK 607 of fine particles is only visible in a flat structure (the orange area of Figure 5), which results in a higher gloss at both test angles.
is applied thickly
, select a surface-treated silicon dioxide light-off powder with a fine particle size (d50<5.5 m).
The application first push ACEMATT
3600 - after polydimethylsiloxane modified fine particles of the precipitation method silicon dioxide anti-light powder, the paint system viscosity has a small impact, unstable foam, good opening effect, round particles, good scratch resistance.
thin coating, it is recommended to use d50 at 0.5-1 times the thickness of the coating film silicon dioxide anti-light powder.
the application first push ACEMATT
810 - the precipitation method of unsociated coarse particles silicon dioxide de-lighting powder, high light-down efficiency, good transparency.
Make the most of the polymerization reaction of lycopes and monomers
The factors involved in this method include: lymer, monomer, light trigger, viscosity, structural viscosity, UV spectral type, transmission speed, curing cumulative energy, curing UV intensity, temperature, etc.
present here only our conclusions and recipe recommendations from our study of influence factors. For more research details on the underlying workings, please consult our technicians for technical briefing TI 1399.
: A suitable variable is the density of the double key, which is calculated by molar mass and function. Generally speaking: higher dual-bond density, better light-down capacity. The effect of dual bond density increases as the coating becomes thicker.
: Low-lying objects with lower double-bond density and higher viscosity can also be eliminated if suitable monomers are selected. Monosomes with linear long main chain structures are conducive to lighting.
choice of light trigger is very important. "Surface dry light triggers" such as xybenzene prevent the de-lighting. Conversely, light triggers, such as BAPO, with long-wave absorption spectra help to eliminate light. A suitable light trigger mixture can also optimize the de-lighting. As the content of light triggers increases, the gloss also gradually increases.
viscosity of the structure
: the increase of the viscosity of the structure is conducive to the de-lighting.
(5) type of
spectral, transmission speed, curing cumulative energy
: radiation sources with higher spectral components in the low band, such as high-pressure mercury lamps with iron, are conducive to the demulation. If a separate radiated radon is used, the gloss decreases as the accumulated energy increases. "Low cumulative energy at low speed" is the preferred mode of operation when the required cumulative energy is achieved by setting the output and transmission speed of the (variable) radiator. It is not desirable to cure by double curing method (with a special high-pressure radiation source). For the radiation energy required for exposure, it is recommended to use a single radiation source. If several radiation sources are used in series, their radiation areas overlap.
coating: the type of substrate should also be considered for the effect of the coating's de-lighting. Preheat the applied substrate, applying areas and coatings to help dissipate light.
according to the thickness of the construction to choose the light powder, choose suitable lysate, monomer and light trigger is the easiest to achieve. The impact of system and process parameters is likely to be the most difficult to put into practice. Because in some cases, this will have economic effects or may require investment. Taking into account all the experience values, the parameters described here give the paint formulation designer a range of optimal configurations for solvent-free UV-cured coating control and de-lighting.