Formation of the Porous Structure of Cigarette Filters

An originaI method based on permeability measurement is applied to studying the formation of the porous interstitial structure of cigarette filters. Using this method, it is shown that the porous structure of a filter is formed in the course of the filling process which is accomplished by compression of the filter material without significantly modifying the specific structure of this material. In the filling process, the elements of the filter material are assembled in the filter by imbrication. A given filter materiaI is characterised by the specific volume that it takes up when its elements are assembled at the compression Iimit without any crushing. A filter material is, moreover, characterised by the mode of assembling of its elements in the formation of the porous interstitial structure of a filter. The permeametric method allows us to define this characteristic. The results can be applied to the choice of filter material and to the determination of the optimum filling rate permitting the rapid development of a cigarette filter with fixed characteristics.