PTC rubberUS patent 8,367,986 is a

silicone rubber Silicone rubber is an elastomer (rubber-like material) composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations ...

which conducts electricity with a

resistivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

that increases exponentially with increasing temperature for all temperatures up to a temperature where the

grows to infinity. Above this temperature the PTC rubber is an

electrical insulator An electrical insulator is a material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons which cannot readily move. Other materials—semiconductors and conductors—conduct electric current ...

. PTC rubber is made from

polydimethylsiloxane Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its ...

(PDMS) loaded with

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 1 ...

s. PTC stands for

Positive temperature coefficient A temperature coefficient describes the relative change of a physical property that is associated with a given change in temperature. For a property ''R'' that changes when the temperature changes by ''dT'', the temperature coefficient α is def ...

Properties

If the

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

strength inside the material is large enough (typically larger than 30 V/mm), the carbon nanoparticles trigger a

quantum mechanical Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, qua ...

tunneling effect Quantum tunnelling, also known as tunneling (American English, US) is a quantum mechanics, quantum mechanical phenomenon whereby a wavefunction can propagate through a potential barrier. The transmission through the barrier can be finite and de ...

current to flow through the material. The contribution from a large number of small tunneling effect currents can add up to macroscopic currents in the range of

ampere The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...

s. The quantum mechanical tunneling effect inside the material is highly temperature dependent. The current decreases exponentially with increasing temperature. This means that the resistivity of the material grows exponentially with increasing temperature. At a specific temperature the quantum mechanical tunneling effect current ceases. At temperatures higher than this the PTC rubber is an electrical insulator and no electrical current can flow through it. This temperature can be adjusted between 32 and 176 F (0 and 80 C) during the production of the PTC rubber. Hence, PTC rubber is a PTC material with very strong PTC characteristics. In fact, PTC rubber has the strongest PTC effect of all known materials, and over a wide temperature range. It has PTC properties for all temperatures.

Applications

The PTC rubber can be rolled into thin sheets and laminated with

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

. The copper is in turn connected to a voltage to provide the electrical field inside the material necessary to trigger the

. The sheets can be formed into any shape and size. PTC rubber sheets can be used as thin flexible

PTC heater A positive temperature coefficient heating element (PTC heating element) or self-regulating heater is an electrical resistance heater whose resistance increases significantly with temperature. The name self-regulating heater comes from the tendency ...

s. These heaters will provide high power when they are cold and rapidly heat up themselves to a constant temperature and remain there virtually unaffected by changes in the ambient conditions. They can be powered with any voltage between 5 and 230 V, AC or DC. The PTC rubber material is a

self-regulating heater A positive temperature coefficient heating element (PTC heating element) or self-regulating heater is an electrical resistance heater whose resistance increases significantly with temperature. The name self-regulating heater comes from the tendency ...

. It produces the same amount of heat in each point of the heater as is conducted and radiated away from the heater to the object it is attached to, and its surroundings. It is in constant thermal equilibrium with the environment, point by point. A measure of the power produced by the heater is actually a measurement of the

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

between the heater and the object. Hence, it can be used as a heat transfer sensor.

References

{{Reflist Silicones Siloxanes Solid state engineering