measure of all of the voids both isolated voids and interconnected voids in a sample of pressboard filaments of poly m phenylene isophthalamide mpd i having an inherent viscosity of 1 5 as measured from a 0 5 wt solution in concentrated sulfuric acid were dry spun from a solution containing 19 wt mpd i 70 wt dimethylacetamide dmac 9 wt calcium chloride and 2 wt water on leaving the drying tower the as spun filaments were given a preliminary wash with water so that they contained about 60 wt dmac 15 wt calcium chloride and 100 150 wt water based on the weight of dry polymer the filaments were washed and drawn 4 u00d7 at 90 u00b0 c in a counter current extraction draw process in which the calcium chloride determined as chloride content and dmac content were reduced to about 0 1 wt and 0 5 wt respectively the filaments were crystallized immediately after drawing by passing them over hot rolls at a temperature of about 340 u00b0 c the filaments so produced had a linear density of 2 2 decitex 2 0 denier a tenacity of about 3 7 dn tex 4 2 g denier an initial modulus of 70 dn tex 79 gpd and an elongation of 34 the filaments were cut to floc having a length of 3 4 mm 0 135 in fibrids of mpd i having an inherent viscosity of 1 5 as determined from a 0 5 wt solution in concentrated sulfuric acid were prepared substantially as described by gross in u s pat no 3 756 908 column 5 lines 34 54 stopping short of the refining step an aqueous slurry was prepared containing 1 0 wt fibrids and floc having a solid composition containing 60 wt of.