Filter media with irregular structure and/or reversibly stretchable layers
Articles and methods relating to filter media are generally provided. In some embodiments, a filter media has an irregular surface structure. For instance, the filter media may comprise a plurality of peaks that are irregular in one or more ways. A ratio of a peak height standard deviation to an average peak height may be greater than or equal to 0.05, and/or a ratio of a peak spacing standard deviation to an average peak spacing may be greater than or equal to 0.08. In some embodiments, a filter media comprises a non-woven fiber web having a layer thickness of greater than 0.3 mm and/or a stiffness of less than or equal to 100 mg.
1. An article, comprising:
a first layer and a second layer, wherein:
the first layer has an average surface height of greater than 0.3 mm;
the first layer is held in an undulated configuration by the second layer;
the second layer is formed from a reversibly stretchable material;
the average surface height is an average of relative heights of each point in a relative surface topography with respect to a reference height; and
the reference height is a height at which 95% of the points making up a measured surface topography are above and 5% of the points making up the measured surface topography are below.
2. The article of claim 1 , wherein the article is a filter media.
3. The article of claim 2 , wherein the first layer is a meltblown fiber web and/or is carded.
4. The article of claim 2 , wherein the first layer is a non-woven fiber web.
5. The article of claim 2 , wherein the article has an air permeability of greater than or equal to 20 CFM.
6. The article of claim 2 , wherein the first layer has an air permeability of greater than or equal to 2 CFM.
7. The article of claim 2 , wherein the article has a gamma of greater than or equal to 15, and wherein the gamma is defined as (−log 10(initial penetration %/100)/initial pressure drop, mm H 2 O)×100.
8. The article of claim 2 , wherein the first layer is charged.
9. The article of claim 2 , wherein the second layer is a mesh and/or a film.
10. The article of claim 2 , wherein the first layer is a film.
11. The article of claim 2 , wherein the second layer is capable of undergoing a reversible stretch of at least 50% along at least one axis.
12. The article of claim 2 , wherein the article comprises a support layer that holds the first layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the layer.
13. The article of claim 2 , wherein the second layer comprises fibers and/or strands.
14. The article of claim 13 , wherein the fibers and/or strands comprise an elastomer.
15. The article of claim 13 , wherein the strands are not in direct contact with each other.
16. The article of claim 2 , wherein the article has a hydraulic gamma of greater than or equal to 15.
17. The article of claim 2 , wherein the article has a dust holding capacity of greater than or equal to 50 g/m 2 as determined by a Multipass Filter Test based on ISO 16889 (2008).
18. The article of claim 2 , wherein the first layer is impregnated with a binder.
19. The article of claim 2 , wherein the article comprises a third layer, wherein the second layer is laminated to the third layer, and wherein the third layer prevents the second layer from being capable of undergoing a reversible stretch.