LPRL

Band II low observable coatings

LPRL provides additives that may be used with many types of paints for giving them low observable characteristics in band II. Current formulas are available for silicone, silicone alkyd, polyurethane, and epoxy based paints. Other varieties of paints may also be rendered low observable in the infrared. For information on how we can help you obtain infrared discretion, please contact Brett Kraabel.

In addition to providing additives, LRPL offers prepared coatings that provide infrared discretion in band II (3 -5 mm). LPRL coatings are compatible with a variety of primers, and may be applied using standard technology (e.g. spray gun).

The band II emissivity of these coatings may be tuned from 0.4 to 0.9 and are compatible with radar absorbing materials (RAM), so you are not obliged to choose between radar and infrared discretion - you can have them both!

Band II low observable coatings may be used to reduce the infrared signature of such things as:

tanks
helicopters
the super-structure of surface ships
exhaust covers
tents
camouflage nets
fighter jets
uniforms

Figure 1 displays the average emissivity between of a selection of available coatings in band II (3 to 5 mm). In addition, the average emissivity from 3.7 to 4.7 mm is shown, since many detector technologies operate in this range.

Figure 1 – The average emissivity in band II of a selection of established LPRL IR stealth coatings.

One of several independent confirmations of the potential of LPRL IR stealth coatings is shown below in Figure2, which shows the results of a thermal image measurement in band II made by Giat Industries . The sample shown is an aluminum coupon coated with a standard NATO coating. In the lower-left quadrant of the sample an LPRL IR stealth coating is deposited over the NATO coating. Since the sample was positioned vertically in an oven, there is a slight vertical thermal gradient present, so comparisons should be made between regions of the sample that are at the same vertical position. As the temperature scale is difficult to read in Figure 2, we note here that the apparent temperature difference between the LPRL coated portion of the sample and portion of the sample coated with the standard NATO coating is approximately 12 degrees Celsius (from roughly 57 to 69 degrees Celsius). This apparent temperature difference increases for higher substrate temperatures. For example, at 150 degrees Celsius, an apparent temperature difference of 16 degrees Celsius is measured between portions of the same sample when one portion is coated with an LPRL coating and the other with a NATO standard coating.

Figure 2 - Thermograph of a substrate coated with the standard NATO on top of which is deposited an LPRL IR low observable coating. Courtesy of Giat Indstries.

By combining coatings with different emissivities in a pattern, deception may be enhanced. The concept is illustrated below, where we illustrate how a tank may be coated with a thermal camouflage pattern with the aim of matching the thermal background.

Figure 3: Illustration of how coatings with different emissivities may be used to improve the match with the thermal background.

RAM Compatibility

To demonstrate the compatibility of LPRL IR coatings with RAM, we present the results of an independent measurement of the reflectivity of a polyethylene film coated with a 250 mm thick coating of LPRL IR material. The experimental arrangement to measure the reflectivity in the range from 8 to 110 GHz is shown below.

Figure 4: A schematic diagram of the experimental arrangement for measuring radar reflectivity. Courtesy of IBD GmbH.

The measurements were made at normal incidence. The results are shown below. Three different LPRL coatings were tested, brown, sand, and green. One can see that between 8 and 18 GHz the reflectivity of the PE film remains extremely low even with a coating of LPRL IR paint. The table below shows the results at 35 and 94 GHz.

Figure 5: Reflection of LPRL multipurpose coatings at near-normal incidence. Courtesy of IBD GmbH.

Table 1: The reflection at two frequencies for the LPRL multipurpose coatings shown in Figure 5. Courtesy of IBD GmbH.

	35 GHz	94 GHz

Brown	-17 dB	-11 dB
Sand	-18 dB	-10 dB
Green	-17 dB	-12 dB

Clean PE Film	-26 dB	-17 dB