Recent research has confirmed that the resistance to ultraviolet rays and the physical-mechanical properties of the finished product depend on the quantity of carbon black and its dispersion, so it is necessary as well as economically advantageous to establish exactly the quantity. The electric oven reaches the maximum temperature of 1100°C, controlled on a digital display. Microprocessor thermoregulator and two thermocouples for the controls of the sample and the oven temperature.