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In recent years, with the increasingly strict environmental protection policy, environmental protection paint rapid growth. 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 a 100% UV system to achieve low light or even full dumbness, because it does not contain volatiles, and the paint film shrinkage is small (only the shrinkage factor of the double-bond polymerization reaction) and difficult to
city China
.
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.
1
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 gloss in 100% UV-cured coating 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 adding fine particles of light powder ACEMATT® OK 607 and ACEMATT®3600, it can be observed that from the film weight of less than 20g/
m
2
, the gloss increases with the thickness of the film and Reduced, and the addition of coarse particles of light-down powder ACEMATT® HK 440, to the film weight of 36g /
m
2
, 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 ACEMATT
®
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
i.e.
paint film surface decrease is
2
μ
m.
ACEMATT® HK 440 (14.5 m), the
forms a rough paint film surface with only a small portion of the top end of the
powder
particle, accompanied by a long-wave structure (see figure 3 green area),
to
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
m)
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 height difference of the < coating film, the gloss at an angle of 85 degrees is still high. 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 below: The same 8% volume shrinkage, 50% shrinkage efficiency, the resulting effective contraction (the maximum height difference when the surface of the paint film is cured) is <0.5 m, the effect of volume shrinkage on the de-lighting becomes insignificant, and the particle size of the photon itself is greatly enhanced. The aCEMATT® HK 440 (particle size 14.5
sm)
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.
conclusion
(1) when
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.
(2)
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.
2
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 findings and recipe recommendations from our study of the factors. For more research details on the underlying workings, please contact our technicians for technical briefing TI 1399.
Conclusion
(1)
Lymer
: 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.
(2)
monomer
: Low-lying objects with lower double-bond density and higher viscosity can also be de-lighted if suitable monomers are selected. A monosome with a linear long main chain structure is conducive to lighting.
(3)
lightener:
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 amount of light trigger increases, so also the gloss increases.
(4)
viscosity of the
: 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.
(6)
of the
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.