Silicone Rubber Heater Bonding Information

Silicone Rubber heaters can be applied to metal surfaces using vulcanizing, clamping, bonding and PSA.

Vulcanizing: The most effective way to apply silicone rubber heaters to metals surfaces is factory vulcanizing the heaters to the metal surface.  This is done by Birk using a proprietary process.  The metal surface is prepared and under a heat and pressure process the heater is directly vulcanized to the metal.  No adhesive is used.  This process provides a bond stronger than the heater itself and allows excellent heat transfer to the metal surface.  This process must to be done at the factory. 

Clamping:  Silicone heaters can be clamped to the surface to be heated.  Pressure plates can pressed against the heater and held in place with fasteners.  To clamp a heater to a metal surface the surface must be free from dirt and chemicals that could attack the silicone and must not have any sharp projections that could pierce the heater.  It is suggested that insulation be placed between the heater and pressure plate to direct heat towards the work surface and cushion the heater during compression.

Bonding:  Birk suggests the use of Dow Corning RTV 736 to bond silicone rubber heaters to metal surfaces. The work surface must be cleaned thoroughly with alcohol using a clean cloth. (A clean cloth means not reusing the same cloth that has already been contaminated with foreign materials.)  Use Scotch Brite® to rough the surface and clean again with alcohol and a clean cloth.  For best adhesion the surface should be primed using Dow Corning 1205.  Dow Corning RTV 736 should be spread evenly and as thin as possible over the entire surface without lumps or voids.  (Lumps and voids keep the heater away from the work surface and can cause over heating.)

Clean the heater bond surface with alcohol.  Apply the heater to the bonding surface using a soft rubber roller to remove potential air pockets. The RTV should be allowed to cure according to the direction on the label.  Do not be energized the heater for 24 hours.  RTV requires moisture to cure properly, therefore if the atmosphere is dry a humidifier should be used or simple drape a moist towel over the heater to aid curing.  Surfaces with bumps and groves cause the heater to bridge the work surface and does not provide good heat transfer.

Pressure Sensitive Adhesive:  PSA can be applied to silicone heaters for the customer to apply the heater to their product. The surface to which PSA backed silicone rubber heaters are to be applied must be cleans thoroughly as previously discussed. The heater should be applied avoiding air bubbles to any surface free of bumps and groves.  The heater should be rolled in place with a soft rubber roller to insure the entire surface is in contact with the work surface. Large heavy heaters that are supported solely with PSA are not recommended as the weight of the heater will tend to pull the heater off the work surface as temperature rises. PSA is also not recommended for application of heaters with sharp corners.  PSA does have a limited shelf life and should be used within six months of purchase.

Silicone rubber heaters can also be applied also by using eyelet, boot hooks and Velcro®.