The heating blog
Composites heaters
Nobody doubts nowadays about the great advantages of composites and their increasing demand in the last decades. What was only present in specially demanding technology applications like aerospace, appears to be today a promising alternative to materials used in different industrial sectors. Automotive industry is by far the largest market for composites. Weight reduction is the greatest advantage of composite materials usage. Composites are often the material of choice in corrosive environments like chemical processing plants. Fiber reinforced composites are also replacing many traditional materials for home and architectural components like doors, wall panels and frames. Composite materials offer windmills constructors strength and flexibility through manufacturing processes with the added benefit of lightweight components. Industrial sectors like sport and recreation, marine, energy and finally, electronics, choose composites thanks to their arc and track resistance.
Composite + silicone rubber heater
When a composite needs to be heated, the standard solution is to attach a silicone rubber heater to its surface, by means of a PSA acrylic adhesive. When using this kind of heating, and specially when what is pursued is simplicity and efficiency at the same time, the following issues has to be taken into account:
- The adhesive interface between both materials is always a critical point in the heater.
- Heating asymmetry may generate dimensional tensions, which will become more important with higher thicknesses.
- As heating cannot be close to the surface that needs to be heated and most of polymers have low thermal conductivities, the temperature gradient between the surface and the heater is high.
- Assembly of the silicone rubber heater is not a simple issue.
ohmvo flexible heat
In the frame of Spanish funding (2) has developed OHMMAT NANO, a patent pending technology (3) that enables embedding in a simple way, silicone rubber heating elements in all kind of composites, without altering their outstanding properties.
The developed heating elements can be easily integrated during standard composite manufacturing processes known by those skilled-in the art, as hand and spray lay up, resin transfer moulding (RTM), resin injection moulding (RIM), sheet moulding compound (SMC), vacuum assisted resin transfer (VARTM) and prepreg autoclave curing.
The developed embeddable heating elements have as main constituents (see figure below):
- A glass cloth or PET base support,
- An electrical conductive silicone rubber with a synergical mix of electrical conductive nanofillers
- Copper electrodes for the electrical conduction.
The usual polymers and reinforcements used for the composite manufacturing are compatible with the developed heating elements. Polymer matrixes as acrylic, epoxy, melamine, phenolic, vinyl ester and urethane and reinforcements as glass, carbon and aramide fibers can be used. Depending on the final composite, the new heating technology can be applied with different material supports:
The usual polymers and reinforcements used for the composite manufacturing are compatible with the developed heating elements. Polymer matrixes as acrylic, epoxy, melamine, phenolic, vinyl ester and urethane and reinforcements as glass, carbon and aramide fibers can be used. Depending on the final composite, the new heating technology can be applied with different material supports:
A glass fiber reinforced electrical conductive silicone rubber, for FRP (Fiber Reinforced Polymer) thermoset composites.
A coated PET with an electrical conductive silicone rubber.
Electrical parameters of the heating element are obtained modifying:
- resistivity of the electrical conductive silicone rubber,
- distance between copper electrodes,
- length of the copper electrodes,
- thickness of the electrical conductive silicone coating.
