Innovative Binder Technology for High-Solids Industrial Coatings
January 2016 www.coatingsworld.com Coatings World | 49
show clearly that silicone hybrid resin A,
with its increased toughness and resiliency, contributes to an improvement in the
index for stone impact resistance.
Pinhole Limit
To assess the working window of the resins,
the paint was applied wedge-wise using a
pneumatic spray apparatus (Figure 5).
Here the favorable influence of the
silicone unit in the polymer is particularly
evident. Compared with the polyester, the
silicone hybrid resin shows about 30%
less pinhole formation in a comparable
cured-coating thickness. Silicone hybrid
resins permit trouble-free application of
greater coating thicknesses.
Topcoat Appearance
The reduced tendency of silicone hybrid
resins to form pinholes is especially beneficial for the optical appearance of the applied coating, again showing the positive
effect of silicone in the paint (Figure 6).
Contact Angle
Measurement
Apart from when high-temperature-resistant coatings are required, there are
a number of reservations in the coatings
industry concerning the use of silicone
raw materials. As the new silicone hybrid
resins are also well suited for formulating
primers, contact angles of the cured coatings were measured (Table 6). The higher
the contact angle, the more difficult it is
to wet the surface with a subsequently
applied coating layer (Figure 7).
It can be seen that the silicone does
not affect the wettability; hence, the use
of silicone hybrid resins in primers does
not lead to any problems.
Cross-hatch Adhesion
Silicone units in the polymer do not affect
adhesion. Primers were formulated with
silicone hybrid resins, applied and subsequently overcoated with conventional top
coats. Additionally, coatings formulated
with silicone hybrid resins were overcoated using the same paint. Adhesion tests,
carried out to DIN EN ISO 20567, gave a
characteristic value of GT 0-1 in all cases,
as with comparable binders (Figure 8).
Impact Strength
The impact strength of the new silicone hybrid resins is clearly shown in
the Impact Test - DIN EN ISO 6272-
1/2. Figure 9 shows the results of a 1
kg weight falling from a height of 1 m
onto the coated specimen. The upper
deformation is the result of the reverse
Table 4: Resistance to liquids.
Figure 3: Salt spray test results after 1440 h.
Table 5: Stone impact test results.
Figure 7: Principle of measuring contact angle.
