Abstract: A fan cooling unit (10) for cooling electronic components, such as for an air-cooled telecommunications base station, comprises a protective covering for at least the air inlet opening (11) of a casing (8) in which the electronic components are housed. The protective covering (1) has a frame (2) into which a composite filter media (3) is mounted so as to create an air-tight fit. The composite filter media (3) comprises a membrane filtration layer (20) with a porous polymeric membrane, such as expanded polytetrafluoroethylene (ePTFE), and at least one depth filtration layer (18) disposed on an upstream side of the membrane filtration layer (20). The depth filtration media layer comprises fibers having an electrostatic charge. The ePTFE membrane is preferably made from a blend of a PTFE homopolymer and a modified PTFE polymer.

Abstract: A membrane of microporous, for example stretched, PTFE is filled with particles having a size in the nanometer range. By filling with, for example, TiO2, the abrasion resistance of the membrane can be increased. Low particle size means that the original structure of the PTFE membrane with its knots and fibrils is retained, as is, consequently, the original desired properties of this material. In addition to these properties, filling of the material achieves additional properties, for example increased abrasion resistance.

Abstract: Microporous membranes are described and characterized as having a morphological microstructure of very highly elongated nodes interconnected by fibrils which form a structural network of voids or pores through the spaces between the nodes and fibrils, which voids or pores extend from one side of the membrane to the other. The membranes are highly uniform in terms of mass per volume, have very high strength and a very open microstructure.