Silicone Rubber heaters are constructed by vulcanizing a wire wound nickel- chrome wire or etched nickel-chrome foil between two layers of silicone rubber. Flexible heaters are regularly specified because of their light weight, thin profile, low thermal mass and flexibility. The abilities to provide an infinite array of patterns and concentrations of heat are additional characteristics. Complex shapes, contours and three-dimensional patterns are possible. Many mounting methods are available for the application of Flexible Heaters. They are available with thermostats, thermocouples, mounting holes and pressure sensitive adhesive (peel and stick).
Wire Wound Element: A fine gauge resistance wire is spiralled around a fiberglass core. The element is placed in a specifically designed pattern and vulcanized to a silicone rubber substrate. Advantages versus etched foil elements are: Physical strength; flexibility; smaller production quantity; conforms well to small radius bends and larger possible sizes.
Etched Foil Element: The manufacturing process of etched foil elements is adapted from the production of printed circuit boards. A nickel resistance alloy foil is acid etched to the specific pattern, then vulcanized to the sheath material. Advantages versus wire wound are: Higher watt densities; greater area coverage of element over heater sheath; higher production quantities and complex heat distribution.
THERMOSTATS & SENSORS
Thermostats are typically integral to the heater, encapsulated in silicone rubber and mounted in a heated area. The position is determined based upon application considerations, prototyping and testing. Thermostats separate from heater and ambient sensing thermostats in several temperature ranges are also available. Thermocouples, RTD’s, Thermistors and Thermal Fuses are normally mounted under a silicone rubber cap which is vulcanized to the heater sheath. The position can be anywhere on the heater surface.
Pressure Sensitive Adhesive (PSA) is a factory applied material for bonding Flexible Heaters to a flat, smooth surface. A peel-away protective backing allows simple field installation. The maximum element temperature for PSA use is 300°F (150°C) continuous, at no more than 5 watts per square inch. Heaters with PSA should be stored no more than 6 months before installation. Factory Vulcanizing provides excellent heat transfer from the heater element to the customer part. Strong, free of air gaps and with the longest possible heater life are advantages of Factory Vulcanizing. For field applied adhesives, an RTV Room Temperature Vulcanizing Adhesive or Contact Cement are available. Also available for Flexible Heaters are several mechanical field mounting devices such as hooks and laces, grommets and laces, spring loaded latches, snaps or velcro.