Characterizing Today's Materials — Discovering Tomorrow's™

Gravimetric Water Vapor Sorption Analyzers

Water content, water sorption kinetics, and percent water uptake are all characteristics of interest to material scientists. Water sorption behavior plays an important role in the development and use of many common and advanced materials. Some examples include:

 

Aquadyne DVS

. 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 are fully automated, gravimetric, one (Aquadyne DVS-1) or two (Aquadyne DVS-2, DVS-2HT) sample dynamic vapor sorption instruments. They measure 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 of the Aquadyne DVS-2. DVS-2HT 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. Sample(s) can be pre-dried in situ at up to 85°C (DVS-2) in a flow of dry gas. The software supports multiple users with password-controlled access.

   
Dynamic Vapor Sorption

 

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.

 

"Ask for these PowderTechNotes:
57 Using The Aquadyne DVS to Date Archaeological Material.
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44 Water Vapor Sorption by Milk Powders

 

SPECIFICATIONS

Balance heads:

 

2(DVS-2, DVS-2HT), 1(DVS-1)

Balances, type:

 

ultrasensitive electronic microbalances

Balance capacity(each):

 

5g

Balance capacity(combined):

 

10g (DVS-2, DVS-2HT only)

Dynamic weighing range(each):

 

-500mg to +500mg, 0 to +1000mg

Dynamic weighing range(combined):

 

-1000mg to +1000mg, 0 to +2000mg (DVS-2, DVS-2HT only)

Weighing resolution:

 

0.1µg

RH range:

 

<2% - 98% (depending on temperature)

RH resolution:

 

0.1%

RH accuracy :

 

± 0.8% RH at 25°C

Sample chamber temperature range:

 

<10 - 80°C (DVS-2), 10 - 85°C (DVS-2HT), 15-60°C (DVS-1)

Sample chamber temperature stability:

 

± 0.1°C

Balance head temperature :

 

Up to 85°C (DVS-2) , 90°C (DVS-2HT), 75°C (DVS-1)

Gas flow rates:

 

0 - 200 cm3/min (mass flow controllers)

Viewing port / sample chamber door

 

heated, triple-glazed

Data acquisition rate:

 

adjustable, up to 12 points per minute

Sample pan material:

 

silica

Water reservoir capacity:

 

46 ml