Dynamic Vapor Sorption (DVS) Analysis
The dynamic vapor sorption method is used in laboratories world-wide to examine the intriguing moisture sorption behaviour of materials. DVS is used in the industry as well as in academia. It is applied in pharmaceutics for salt-screening and to analyse polymorphism. In food research it is used in stability and shelf-life studies as well as to investigate moisture migration between ingredients in a food product. DVS helps to develop sophisticated packaging materials by measuring the water vapor permeability of films and foils. It is also a valuable tool to asses the caking behaviour of powdered and granular material during transport, storage and handling. In building physics it is used to analyse water uptake and release of insulation and construction materials made of wood, plaster, fibres or concrete. In the electronic industry moisture induced failure of componenents is of interest. Originally developed for pharmaceutical research, dynamic vapor sorption nowadays is used in a continuously growing number of DVS applications.
Dynamic vapor sorption methodThe basic operation principle of a gravimetric sorption analyser is to measure the change in mass over time of a sample that is kept in an environment of controlled and constant temperature and relative humidity. Change in mass takes place either by water sorption (uptake) from the surrounding air to the sample or water desorption (release) from the sample.
Sorption kinetics curve – single humidity stepAfter a change in relative humidity, e.g. to a higher humidity, uptake or release of water by the sample is determined gravimetrically by means of a microbalance at defined time intervals. At the early stage of sorption/desorption, the change in weight is large. Over time, the process approaches an equilibrium and the change in weight is continuously getting smaller.
Sorption cycle – multiple humidity stepsWhen the sample weight is finally stable, it is at equilibrium with the surrounding atmosphere. The measurement is then continued at the next humidity step (lower or higher relative humidity). Typically, one or more complete sorption/desorption cycles (sorption from low to high RH and desorption from high to low RH) in small RH steps are done.
Sorption IsothermThe individual equilibrium data points from all humidity steps of the sorption/desorption cycles are used to generate the sorption isotherm. The sorption isotherm is the relationship between the water content of a sample and the relative humidity of the ambient air at a particular temperature.
Dynamic Vapor Sorption Instruments
ProUmid manufactures and sells two series of multi-sample dynamic vapor sorption instruments that cover all kind of moisture sorption applications.