Better Filtration Through Fibre Selection

Advances in filtration can come in many different ways and forms. One of the most interesting that I have come across this year has involved new developments in microfibre technology.

New microfibres are now available that offer an increased range of tunable fibre properties, including size, shape and material. By being able to vary these properties, the microfibres can be used by nonwoven manufacturers to produce filter media that can precisely meet the requirements of the end-use application. The development process works backwards from the requirements for the filter. By understanding these criteria, the right size and shape of a particular fibre can be selected and refined to produce the ideal nonwoven and filter medium.

The most commonly used polymeric materials for filter media, PET and polypropylene, can now be supplemented with others that had previously often been considered specialities for nonwovens, such as nylon, copolyesters and even PLA from renewable sources. In addition, by now being able to make microfibres at sizes of 5 microns and below, the range of options in seeking to find the right functionality in the nonwoven material is significantly improved.

However, certainly one of the most interesting way in which the properties can be affected is in the shape of the individual fibre, which can be round, flat or wedge. Here are a couple of examples. One way in which you can achieve strength in a nonwoven is from the intersection points of the fibres. If you have a round fibre that is 3 microns in diameter and a flat fibre with an effective diameter of 3 microns, then you actually get more surface contact with the flat fibre. The surface contact can create additional friction, which helps lead to strength. Another example is tortuosity. Through manipulation of the fibre shape it is possible to make a more or less tortuous path through the filter media and the properties of the filter can be fine-tuned for an application.

Filtration has come a long way from the sieve.