Quality and quality assurance

Test method for porous SIPERM® materials

The functionality of porous sintered materials essentially depends on defined porosity,
uniform pore distribution, reproducible flow and sufficient mechanical stability.
These parameters cannot be ensured by visual inspection or dimensional control alone;
standard-compliant measuring methods are required that quantitatively record both the microstructure and the flow behavior.
Tridelta Siperm uses a combination of standardized test methods and material-specific
measurement series for this purpose.

For SIPERM® R, SIPERM® B and SIPERM® HP, all relevant characteristic values are determined on the basis of the relevant standards
. The tests are carried out both on reference samples of defined dimensions and on
functionally relevant areas of customer-specific components. This allows deviations to be detected at an early stage
and material batches to be clearly qualified.

Tear test – proof of tensile strength

The tensile test is carried out on standardized test specimens. It shows the deformation behavior
and the maximum tensile load before structural separation occurs. The results provide information
about the particle bonding in the sintered structure and the stability of the sintered bridges.

Typical findings from the tensile test:

• Evaluation of the sintering quality (density, binding forces in the grain structure)
• Expansion behavior of the porous plastic structure
• Recognize local inhomogeneities
• Load capacity under axial tensile stress
• Comparability between batches or quality settings

Bubble point test (DIN ISO 4003)

The bubble point test is used to determine the largest continuous pore in a porous material.
The sample is wetted with a suitable liquid and then exposed to gas
in a controlled manner. The pressure at which continuous bubbles first appear on the surface,
corresponds to the so-called “bubble point”.

This value is crucial for applications where defined separation limits or
retention levels are required. A stable bubble point over several production batches indicates a
constant pore architecture in the material. This test is regularly carried out and documented for SIPERM® materials
.

The bubble point test determines:

• the pressure at which continuous gas bubbles first pass through a porous sample wetted with liquid

• Derived from this, the largest effective pore (“largest pore size”)
• Optional qualitative information on open porosity

The following video does not show the test according to the standard, but a higher load.

Flow behavior (DIN ISO 4022)

The flow behavior describes the interaction of pressure loss and volume flow and is
decisive for filtration, aeration, degassing and compression processes. The determination is carried out on
samples of a defined thickness and area; the pressure difference before and after the sample and
the resulting volume flow are measured under fixed boundary conditions.

The measurement evaluation provides specific coefficients for each SIPERM® quality, which allow engineers to make a
reliable design. This data forms the basis for the assessment of
fluidizing surfaces, filter cartridges, extraction pipes, sensor protection components or silencers.

The corresponding characteristic values for all materials are stored in the respective data sheets.

Porometry (ASTM F316-03)

For applications with tight tolerances in terms of response times, gas diffusion or filtration efficiency
, the pore size distribution is also determined. The porometer measures the pressure thresholds at which
different pore areas are flowed through and thus provides a differentiated picture of the
material structure.

Areas of application for porometry:

• Detection of homogeneous pore distribution
• Evaluation of batch fluctuations
• Verification of safety-relevant components
  (e.g. sensors, flame arresters)

The measurement results are documented in test protocols and supplemented as required by the customer.