Aquadyne DVS Gravimetric Water Sorption Analyzer from Quantachrome

Water sorption behavior plays an important role in the development and use of many common and advanced materials. Some examples include:

  • Stability of pharmaceutical excipients and drug actives
  • Drying and storage of grains
  • Texture and shelf life of food products
  • PEM fuel cell components
  • Mortar, grout and other cementitious materials
  • Paper and coatings
  • Hydrophobic surface treatments
  • Microporous and nanostructured carbons

The Aquadyne DVS is a fully automated, gravimetric, dual sample water vapor sorption analyzer. It measures adsorption and desorption isotherms of water vapor both accurately and sensitively, including sorption kinetics, with minimal operator involvement. The weight(s) of one or two sample(s) is/are constantly monitored and recorded as the relative humidity is automatically varied by the blending of dry carrier gas with a saturated gas stream. The dual balance design allows increased analysis throughput, side-by-side comparison with known or reference materials, or an extended mass range for a single sample. The independently temperature-controlled balance head environment ensures long term stability. The small sample chamber ensures rapid changes in sample atmosphere conditions when the relative humidity is altered during an analysis. Samples can be pre-dried in situ at up to 80°C in a flow of dry gas. The software supports multiple users with password-controlled access.

Measurement Capabilities

  • Isotherms: Mass change as a function of changing relative humidity, increasing mass during adsorption (increasing RH%), decreasing mass during subsequent desorption (decreasing RH%).
  • Kinetics: time-dependent sorption studies give the rate of sorption.
  • Effect of Temperature: isotherms and kinetics change as a function of temperature. Can be used to yield sorption enthalpies.

Applications/results

  • Deliquescence: certain salts exhibit the property of dissolving in self-adsorbed water.
  • Equilbrium moisture content: quantitatively the amount of water associated (adsorbed/absorbed) with the material under given atmospheric conditions of temperature and relative humidity. (Organic materials may be subject to molding according to atmospheric humidity, for example).
  • Hysteresis working range: adsorption and desorption usually differ by hysteresis - this gives a range of stability in which subsequent sorption cycles produce no change in equilibrium moisture content.
  • Hydrophobicity/philicity: the shape of the isotherm reveals relative strength of affinity between water and the surface, due to polar or other chemical interactions.
  • Micropore investigations: even hydrophobic materials can take up moisture if their pores are small enough.
  • Crystallization phenomena: certain amorphous materials will undergo crystallization as a function of water sorption due to, for example, shifts in glass transition points.
  • Sample form: sorption kinetics can be altered by the physical form of a material - powder, granule, pellet, tablet, monolith etc.

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