Nonwovens facilitate optimum air circulation owing to their porous structure which also makes them permeable to other substances. According to DIN EN ISO 9237, air-permeability is determined by clamping a flat sample of material into a testing device and passing an air stream through it at a defined differential pressure. The flow resistance is measured.
- Automotive: Sandler nonwovens are acclaimed as open-pore upholstery materials for seating, particularly for actively ventilated climate seats.
- Technical applications: Applied as processing aids, frequently in combination with other materials, nonwovens protect delicate surfaces. Their air-permeability can be tailored to the specific application and they remain air-permeable, even when retaining other substances.
In filtration, the relevant factor is the interaction of air-permeability and the pressure drop, induced by the filter’s flow resistance. The pressure building up in front of the filter is higher than that behind the filter. A low pressure drop in combination with a high air-permeability of the filter medium reduces the amount of energy necessary to force the required amount of air through the filter—a contribution to the filter’s energy efficiency and to long-term cost-savings in the operation of the filtration plant. The durability of Sandler nonwovens further supports these savings by prolonging the filter’s operating life and reducing replacements.
The pressure drop is tested according to WSP 70.1 by measuring the filter’s flow resistance in a defined volume flow. Multiple measurements at varying volume flows can be aggregated into a curve depicting the development of the pressure drop. Sandler nonwovens are tested for this property online during production as well as by external institutes and customers. These external partners conduct tests using flat material samples as well as ready-made filters from Sandler material.
Further relevant standards on this subject are DIN 53887 and DIN EN ISO 9237.
See also: Breathability