Dynamic Vapor Sorption 101: What, why and how?
Water is ubiquitous. Those who study the physical world or manufacture materials within it will eventually be forced to acknowledge moisture’s impact on the substances they work with.
More specifically, water – both in a material and around it – is a crucial factor in determining how and where a product or material can be used, when it will degrade, what (if any) treatments or coatings it needs, or if it needs to be entirely reformulated.
Moisture can’t be safely ignored – so how can its impact be measured and accounted for?
Through vapor sorption analysis.
What is dynamic vapor sorption (DVS)?
The goal of vapor sorption analysis is to learn how much of a solvent – usually water – is adsorped or desorped by a material and how quickly that happens.
To find this out, a sample of the material is placed in an environment where the amount of solvent vapor (humidity) can be controlled and adjusted. Changes in the sample’s weight are then measured and used to calculate how much vapor it adsorps or desorps.
Dynamic Vapor Sorption (DVS) is one popular way to analyze vapor sorption. Up until a few decades ago, a slow, manual process involving desiccators was the primary method of vapor sorption analysis. In 1991, Daryl Williams developed DVS to reduce the massive amount of time and manual labor that was required to get meaningful data.
How dynamic vapor sorption works
There are several types of DVS devices, but most are similar in their mechanism of action.
A typical Dynamic Vapor Sorption device holds a sample in a temperature-controlled chamber. It then uses humidified or desiccated air to bring the chamber to a set relative humidity level. Once the sample comes to equilibrium (assumed by weight) with the chamber’s relative humidity level, its change in mass is recorded. The device then repeats the process with increased or decreased relative humidity levels and records further changes. After the needed data points are collected, some DVS devices will use them to generate an isotherm.