Eletric Heater Related

Applications Guide

Silicone Rubber/Fiberglass and Kapton Insulated Flexible HeatersFlexible heating elements have a wide range of industrial, commercial, and military applications where reliability, cost effectiveness, minimum cross-section, resistance to deterioration, and basic flexibility are critical.

Silicone Rubber/Fiberglass Heaters (see figures 1-2) are the most widely used flexible heaters. Temperature rated from -70°F to +450°F, silicone rubber resists radiation, moisture, compression set, weathering, vacuum, fungus, oils, solvents, and chemical attack. It may be factory bonded or applied with silicone rubber RTV cement or pressure sensitive adhesive systems. Various mechanical fastenings are also available.

Kapton/FEP Film Insulation (see figue2) is ideal for very precise heating requirements such as satellites and aerospace equipment. Kapton, used from -328°F to +392°F, is self-extinguishing, has double the tensile strength of fiberglass reinforced silicone rubber, and is not affected by common solvents and fluids. Kapton is almost 50% lighter than silicone rubber insulation and provides a 0.010" maximum cross-section.

Temperature Control: In the majority of applications for silicone rubber and Kapton insulated heaters, some form of temperature control must be used. See Section P for temperature controls. In some applications, electromechanical thermostats or other types of temperature control may be used. (See figures 3 and 4)

Custom Engineered Heaters: Flexible heaters can be custom made to meet your requirements for size, voltage and wattage. Built-in thermostats can also be provided on request. For more information, contact our engineering department. The following information may be helpful in determining precise heater requirements. To determine wattage requirement see Section Z.Specific Heats And Densities Of Common Heat Sink MaterialsComparison Of Materials

	Specific Density
Material	Heat* (lbs/cu in)
Aluminum & Its Alloys	0.23 0.1018
Stainless Steels	0.12 0.2895
Carbon Steels	0.11 0.2827
Copper Alloys	0.10 0.3231
Nickel & Its Alloys	0.10 0.3340
Zinc & Its Alloys	0.10 0.2589

*Btu/lb7F for cal/gm7CThe temperature shown is the internal metallic element temperature. This would be the hottest point of the heater. The test heater was suspended horizontally in still air at a 70°F ambient temperature.

Watt densities of up to 35 watts/in2 are possible when heaters are bonded to a heat sink and controlled with a thermostat or electronic control. This test is based on a bond strength test of samples of silicone rubber/fiberglass bonded to aluminum or stainless steel. The time required for bond strength to deteriorate to less than 2 pounds per inch of width of heater was considered the end point of the material.