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Home > Our Products > Permeation Measurements Method
Measurement of gas, vapors, and liquids permeation rates through plastic films or membranes using optional capabilities of enhanced gas pycnometer HumiPyc or gravimetric moisture sorption analyzer - V-GA. |
I. Manometric (pressure gradient) method for measurements of gas transport rates through plastic barriers
Method 1. After establishing vacuum on the downstream side of the sample, and
using ambient or higher pressure on the other side, the transport rates of gas
through the sample can be measured by monitoring the pressure increase in the
pycnometer chamber of known volume.
Method 2. Using ambient pressure on the downstream of the sample, and constant
higher pressure on the other side, even very resilient plastic films can be measured
as the pressure increase in the pycnometer chamber will be much less affected by
any non-zero leakage rate over prolonged time.
Method 3. Using replaceable charges in one of the adapters, the gas permeation
rates can be measured for a dry gas as well as in the presence of 100 % saturated
water vapors of selected (organic) liquids vapors.
Method 4. Using a relative humidity (RH) generator, e.g. V-Gen, the water vapor
transmission rates (WVTR) can be evaluated at different RH values from ambient
to 50 psi pressure.
Method 5. Placing a liquid on the studied membrane (at ambient pressure or
pressurized), and using vacuum on the downstream side, pervaporation rates of the
liquid though the specimen can be measured at ambient or elevated pressures.
using ambient or higher pressure on the other side, the transport rates of gas
through the sample can be measured by monitoring the pressure increase in the
pycnometer chamber of known volume.
Method 2. Using ambient pressure on the downstream of the sample, and constant
higher pressure on the other side, even very resilient plastic films can be measured
as the pressure increase in the pycnometer chamber will be much less affected by
any non-zero leakage rate over prolonged time.
Method 3. Using replaceable charges in one of the adapters, the gas permeation
rates can be measured for a dry gas as well as in the presence of 100 % saturated
water vapors of selected (organic) liquids vapors.
Method 4. Using a relative humidity (RH) generator, e.g. V-Gen, the water vapor
transmission rates (WVTR) can be evaluated at different RH values from ambient
to 50 psi pressure.
Method 5. Placing a liquid on the studied membrane (at ambient pressure or
pressurized), and using vacuum on the downstream side, pervaporation rates of the
liquid though the specimen can be measured at ambient or elevated pressures.
Calculation of gas transport rates and permeability coefficient
The volume Vc of the pycnometer chamber can be easily measured (as in regular true density measurements).
Knowing the Vc , temperature, and applying the ideal gas law, the experimentally observed pressure rise versus
time curve can be converted to volume V of gas (at STP) that permeated through the film or membrane,
yielding the curve V versus time. Since the V is a product of permeability coefficient, effective area, pressure
differential, and time divided by the thickness of the specimen, appropriate re-plotting of the curve yields the
permeability coefficient as the slope.
The volume Vc of the pycnometer chamber can be easily measured (as in regular true density measurements).
Knowing the Vc , temperature, and applying the ideal gas law, the experimentally observed pressure rise versus
time curve can be converted to volume V of gas (at STP) that permeated through the film or membrane,
yielding the curve V versus time. Since the V is a product of permeability coefficient, effective area, pressure
differential, and time divided by the thickness of the specimen, appropriate re-plotting of the curve yields the
permeability coefficient as the slope.
The HumiPyc can be easily employed as a gas
permeability tester for measurements of gas transmission rates
through membranes, plastic films, packaging materials, or other
barriers. Instead of a dedicated permeation analyzer, addition of
sample holding adapters allows for measurement of gas
transport rates using manometric (pressure gradient) method.
Considering the 24-bit resolution (less than 0.01 Pa), ability to
change the volume of pycnometer sample chamber, and large
pressure differential, a wide range of gas permeation rates can
be measured.
permeability tester for measurements of gas transmission rates
through membranes, plastic films, packaging materials, or other
barriers. Instead of a dedicated permeation analyzer, addition of
sample holding adapters allows for measurement of gas
transport rates using manometric (pressure gradient) method.
Considering the 24-bit resolution (less than 0.01 Pa), ability to
change the volume of pycnometer sample chamber, and large
pressure differential, a wide range of gas permeation rates can
be measured.
| II. Gravimetric method of permeation and pervaporation measurements |
To carry out permeation measurements using this gravimetric
sorption apparatus, the sample holding cell can be suspended on the
hang-down wire either in vertical or horizontal position. The unique
design of the cell allows for exposing the suspended membrane or
film either to the vapor or to the liquid. Water or other (organic)
liquids can be used. Using dry gas or a humidified gas source (RH
generator) with a regulated relative humidity level the permeation or
pervaporation process can be studied at different RH and temperature
conditions. Using various RH levels instead of dry gas only for
circulating through the measuring chamber, unique profiles of mass
changes vs. time can be obtained. Those profiles are invaluable for
researches studying the nature of transport processes through
membranes, plastic films, or other barriers.
sorption apparatus, the sample holding cell can be suspended on the
hang-down wire either in vertical or horizontal position. The unique
design of the cell allows for exposing the suspended membrane or
film either to the vapor or to the liquid. Water or other (organic)
liquids can be used. Using dry gas or a humidified gas source (RH
generator) with a regulated relative humidity level the permeation or
pervaporation process can be studied at different RH and temperature
conditions. Using various RH levels instead of dry gas only for
circulating through the measuring chamber, unique profiles of mass
changes vs. time can be obtained. Those profiles are invaluable for
researches studying the nature of transport processes through
membranes, plastic films, or other barriers.
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Permeation
Cell
Cell
Several types of permeation experiments can be carried out: