PTC stands for Positive Temperature Co-efficient, an inherent characteristic of a selected material. It means that the electric resistance of the said material increases with the increase of the temperature as shown in Figure 1.
PTC films refers to such films with the desirable PTC characteristic and inks used to form these such films, are referred to as PTC Inks.
PTC films are generally used as heating elements which mainly provide infra-red radiation to the environment which are known as PTC heating films.
Distinguished from other regular heating elements whose electric resistances are relatively constant, a PTC heating film is capable of controlling the temperature itself, by regulating its heating power via its electric resistance response to temperature.
The science behind this self-regulation is based on the principal of the Ohm Law: [I = V/R, and P=I*V =V*V/R, where I is current, V is Voltage, R is Resistance, P is power).
At low temperatures, its resistance is lower, so its heating power is larger resulting in the temperature quickly increasing. While the temperature increases, its resistance rises as well and therefore decreasing its heating power at the same time.
During a short period and certain temperature, its heating power decreases to point where it simply balances the energy loss of the system, maintaining a constant.
In our proprietary PTC film, the PTC characteristics are scientifically achieved by controlling the distance between conducting domains (particles of carbon black mostly) through the designed thermal expansion of the polymeric binder employed in our PTC inks in nano-scale and in quantum fashion.
At a lower temperature (below Tg), the polymer chains are mainly frozen. Their thermal expansion is limited, so the carbon particles are closer to each other which offers high conductivity (low resistivity).
When the temperature increases, polymer chains start to move and stretch and when the temperature approaches its Tg, its expansion increases dramatically, so does the distance between carbon particles, thus as a result, the conductivity quickly decreases (resistivity quickly increases), so does its heating power.
没有评论:
发表评论