The vapor pressure of material is an important physical property that defines the amount of vapor molecules generated at its surfaces. Materials have tendency to enter the vapor phase by sublimation (solid – gas) or evaporation (liquid – gas). The vapor pressure of material at the thermodynamic equilibrium is only a function of temperature.
The knowledge of vapor pressure is highly desirable for liquids, oils, pesticides, fertilizers and various substances in order to avoid the atmospheric accumulation of toxic compounds with a low vapor pressure. The US Environmental Protection Agency (EPA) and the European Chemicals Agency (ECH) mandate the registration of vapor pressure of certain materials, because of the impact on the environment.
Furthermore, the vapor pressure can play a vital role in manufacturing, for example organic solar films, where the progressive reduction of additives like plasticizers and UV absorbers as result of evaporation from the surface can cause unwanted decrease in their efficiency.
In this webinar, Knudsen Effusion Method and Static Method for determining vapor pressure of materials will be discussed.
 104 OECD guidline for the testing of chemicals