Silicone rubber heaters manufactured by Sinomas make it possible to achieve ennergy efficient and extremely flexible heating solutions. They takes advantage of the unique properties of silicone rubber (low thermal mass, superb electrical insulation) to provide flexible heating elements of unparalleled performance. Silicone rubber is calendared onto fiberglass cloth in a variety of thicknesses and constructions which serve as the basic insulation material for a silicone heater pad. Fiberglass gives the heater dimensional stability without sacrificing flexibility.

Generally speaking, two layers of fiberglass reinforced silicone rubber containing an etched foil element or a wire wound element are vulcanized together to form a basic silicone heating element. The main product features are:

silicone heater sample

  • Light weight, thin, flexible
  • Designed to the exact shape (including cutout) and size which conforms to the profile of customer equipment.
  • Etched foil element, uniform heating
  • -50°C to 250°C operating Temperature
  • Moisure and chemical proof, optionally IP67
  • Multiple installation method available
  • Built-in temperature sensor or digital temperature controller
  • Thermal insulation or thermal conductive overlayer
  • ISO 9001 certified system

 

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Electrical Thermal Others
Input volatge 0 - 600V AC or DC Max Temperature 250°C Mean life time > 100K hours
Watt density < 1.0 W/cm2 Min Temperature -50°C Minimum size 10x25mm
Watt tolerance ≤ ±5% Temp. Continuous ≤ 200°C Maximum size 900x3000mm
Insulation > 500M Thermal Overlayer Insulation or conductive Thickness ≤1.5mm
Dielectric > 1500V/min        
Ground mesh Optional        
Circuit design dual input voltage, three phase heater, multiple heat zone, low inductance design, etc.
Lead wires Teflon, silicone rubber, fiberglass, PI insulated cables, various plug set and termination available

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Silicone rubber heaters can be mounted in field by the following means. Please specify in advance:

  • PSA backing (Pressure Senstitive Adhesive). Acrylic PSA by 3M can withstand 149°C continuouly, and 260°C for hours. Silicone based PSA can work at 200°C continuously.
  • Filed applied RTV (Room Temperature Vulcanized) silicone sealant.
  • Magnetic mounting. Silicone rubber blended with magnetic power forms magnetic silicone rubber. They will adhere to many varieties of steel. Ideal for those situations where you need to “slap on” some heat.
  • Mechanical clamping.The rigid plate surfaces must be smooth in order not to pierce the insulation.
  • Mechanical Fastners. When the silicone rubber heater must be detachable from the cylindrical parts, several methods can be used. Various techniques routinely used with leather goods can be used on silicone rubber heaters, which include:
    • Boot hooks and springs
    • Velcro
    • Buckles and straps
    • Grommet and lacing
    • Snap fastners

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Following components can be embeded into silicone rubber heaters for temperature control. Our versatile digital temperature controllers will be introduced in a seperate page.

  • Thermal Switch are (manually or automatically) resettable thermostats with preconfigured operation temperature. It provides a low cost means of temperature control for electric heaters. Thermal switches are normally wired directly into the heater circuit. If the current draw of the heater exceeds the rating of the switch, additional power relay is needed.
    • Disc shaped snap action thermostat / thermal cutout (TCO) - automatic reset
    • Disc shaped snap action thermostat / thermal cutout (TCO) - manual reset
    • Creep action thermostat / thermal protector / thermal cutout (TCO)
    For silicone heaters with high watt density, due to the delay caused by thermal propagation to the sensing element of thermostats, the operation temperature can be a few degrees lower than the actual temperature of the devices. In other words,there will be a temperature overshoot.
  • Adjustable thermostat allows the users to adjust the temperature setting to attain a desired result. The thermostat is normally encapsulated in a silicone rubber housing. This can often be found in drum heaters and large sized heating blankets. Two types of temperature sensing elements are available for adjustable thermostats: bimetallic disc or liquid expansion temperature sensing elements. A capillary sensing probe will be required for the later case.
  • Thermal fuse (thermal cutoff) is used as high limiting protection devices to guard the load from dangerous temperatures. Please pay attention to the parameter "holding temperature" when selecting a thermal fuse. The holding temperature is the maximum temperature that the fuse can operate continuously without fatigue. It is roughly 20 degree lower than the temperature rating of the thermal fuse. The behavior of thermal fuses will be unpredictable when operating above the holding temperature.  
  • Thermocouple consists of two conductors of different materials (usually metal alloys) that produce a voltage in the vicinity of the point where the two conductors are in contact. The voltage produced is dependent on, but not necessarily proportional to, the temperature difference of the junction to other part of the conductors. Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other temperature sensors, thermocouples are self powered and require no external excitation.
  • RTD is a temperature sensor that contains a resistance element that changes resistance value as its temperature changes. By far the most common devices used in industry have a nominal resistance of 100 ohms at 0°C, and are called Pt100. Depending on the allowed tolerance of the measurement, Pt100 can be further categorized into class A, class B, class B/3, etc. Temperature controllers may require 2 3 or 4 wire input from Pt100. 
  • Thermistor is also a resistance-based temperature sensor. It can be classified into two types, depending on the sign of temperature coefficient: PTC and NTC. The thermostors used in flexible heaters generally refer to NTC.

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Following materials are available for thermal insulation of silicone rubber heaters:

  • Silicone Sponge is available in standard thickness of 3mm, 5mm, 8mm, 10mm. The maximum operation temperature is 180°C
  • EPDM is available in standard thickness: 3mm, 5mm, 8mm, 10mm, 16mm, 20mm. The maximum operation temperature is 120°C
  • Fiberglass Felt is available in standard thickness: 10mm, 20mm. The maximum operation temperature is 300°C
  • Ceramic Fiber Felt is available in thickness: 1mm - 5mm. The maximum operation temperature is 300°C
  • Aerogel Composite is available in thickness: 1mm - 5mm. The maximum operation temperature is 400°C

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waterbagheater
immersible silicone heater

Silicone rubber heaters are generally moisture proof. Additional edge processing is enough for casual water spray. If the heater pad is to operate under water permanently, the whole heater has to be press molded to avoid any exposure of fiberglass to water. In this case, the thickness of heater pad will increase to about 2.6mm. Integrated temperature sensors are also possible.

The waterproof silicone pad heaters are very useful for humid environment or fluid heating where conventional immersion heaters can't be installed due to space or mounting limit. For example we have delivered silicone heaters (2W/cm2) for portable hot water kettle and heating pad to keep the expensive plant warm in the greenhouse.

The applicable fluid includes some corrosive chemical solution. Our silicone rubber heaters have been used for SCR (Selective Catalytic Reduction) tank Adblue heating for exhaust gas emission control of diesel engine vehicles. Please consult us for chemical compatibility if you have similar demand.

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Resistance Element

etched foilSilicone rubber heater is available with etched foil elements or wire wound elements. Wire wound elements are wired manually according to pre-defined meander via the guide pins on the pattern board. Unless for irregular shaped 3D profiles or long heating tapes, wire wound technology has been phased out at SINOMAS.

The etched foil silicone rubber heater has exceptional heat transfer compared to wire wound heaters due to its large flat conductor surface. It can deliver more even heat profiles with higher watt density, providing longer service life. Beside chemical etching, for quick prototyping of large sized heating balnket, we can also produce the foil element by laser cutting.

Factory Vulcanization / Preforming

Through a controlled process of heat and pressure, silicone rubber heaters can be factory vulcanized onto plain or black anodized aluminum, stainless steel or other metal profiles / panels. The silicone rubber actually flows into the microstructure of the metal profile forming a permanent bond and allowing the most efficient heat transfer.

Factory vulcanization allows silicone rubber heaters to be designed at higher watt density and increases heater life. While the max watt density for standard silicone heater is 0.8 watts per cm2, factory vulcanization to Alunimum can support up to 3.0 watts per cm2 if the operation temperature is controlled. 

Factory vulcanized heated metal profile has suprior performance than any field installation. With in-house metal workshop and extensive supplier network, we are able to supply high quality heating solution for any type of metal profiles.

By similar process but without a heat sink, silicone rubber heaters can be factory vulcanized / pre-formed into a shape (mostly cylindrical or spiral) permanently. The preforming greatly facilitates the installation of silicone rubber heaters on pipes and cylinders of small diameter or inside heater fitting of metal drums.temperature

Temperature Rise Curve

The graph in the right illustrates the surface temperature rise of a standard silicone rubber heater with different watt densities. In the test the samples are hanged freely in an enclosed space.

The graph is supposed to give you an idea how fast the heating can be. It can't take the place of engineering calculation and test for your specific applicaiton. The temperature in the real situation will be related to many different factors.