Read carefully when this condition stands ...
FIG. 6. Different coating types can suffer varying degradation in optical efficiency when exposed to corrosive gases.
Environmental exposure
Comparing the performance of various products in
harsh environments can also highlight preferential product choice based on the end-use conditions. For example,
Fig. 6 illustrates the effect of
corrosive gas environments on an acrylic conformal coating, a polyurethane resin, and a silicone resin by examining the percentage reduction in luminous flux of the LED after exposure to a mixed-gas environment. These results clearly illustrate the importance of choosing the correct product for the environment.
Although the conformal coating does not deteriorate in terms of its surface insulation resistance in a corrosive gas environment, it is not an adequate protection for LEDs as it allows the gas to pass through the thin coating and penetrate the LED, thus degrading its performance over time.
A similar effect is also seen with the silicone resin; however, in this case,
despite the protection layer being considerably thicker (2 mm versus 50 μm) the gas is still able to pass through the resin and affect the LED. When you compare the result of the silicone resin to the polyurethane material, it is evident that there is a difference in performance exhibited by these two chemistry types as the silicone resin is permeable to the gas whereas the polyurethane resin, at the same thickness, is not. In such cases, an optically clear polyurethane resin, such as
Electrolube UR5634, would be the most suitable protection media to prevent the corrosive gases from adversely affecting the LED.
Such environments will not occur in an artificial horticulture facility of any size ( from a server tower case to a vast greenhouse ) ,under normal circumstances .
PU coatings are used in really harsh enviroments ( metal /petrol /gas industries ,mining ,etc ) and
are quite thick ( 0.5 to 2.5 mm ).