We just installed a HiBarSens tester that can measure ultra-low water vapor transmission rate – WVTR (10-6 g m-2 day-1).
Progressing with the development of new thin-film combinations of ceramic and polymer layers require that we have the capability to measure such ultra-low WVTR in our lab.
The HiBarSens equipment, provided by the company Sempa GmbH, permits the determination permeation rates of ultra-high barrier material with water in vapor or in liquid phase.
HiBarSens measurement principle
The horizontal inserted test sample divides the HiBarSens system into two compartments. The upper compartment contains a defined water vapor concentration. The lower compartment is used to measure the throughput of permeated gas. To prevent an increasing moisture concentration due to the permeation the measurement cell is perfused by a defined by pre- dried inert gas flow. The revealing equability between transported moisture to exhaust and permeated humidity through the sample, results in a constant moisture concentration in measurement cell depending at flow intensity. The system quantifies the amount of water vapor by using an optical sensor which enables the detection of permeant close to the sample.
TDLAS (tunable diode laser absorption spectroscopy) is used for extreme sensitive and selective gas detection. Herein the fact that most gas molecules absorb fractions of light at certain wavelength is used. These absorptions are characteristically for any molecule, like a fingerprint. Cross interferences with other gases are minimized by high spectral resolution and selection of appropriate wavelengths. For that reason, single TDLAS is a very sensitive measurement principle to detect trace gases.
The system uniquely offers 3 measurement modes. Beside the standard Dynamic mode, which uses a carrier gas flow through the permeation cell to ensure steady-state-conditions, it also provides two advance modes: Diffusion and Combination. Both of the advanced modes open access to measure WVTR in the 10-6 g m-2 day-1 range.