sides of the container the temperature of the air is 80 u00b0 c at the level of the receiving conveyor the fibers are deposited in a continuous sheet about 50 cm in width formed by long fibers which are dry and to a large extent cross linked the degree of cross linking may be varied by adjusting the suction to control the temperature at the bottom of the basket at an output of composition of 255 kg day the quantity of fibers recovered is 166 kg day the diameters of the fibers are from 2 to 19 u03bcm the histogram of the diameters is of a very restricted gaussian type with an average diameter of 7 micrometers the average resistance to traction is established at about 300 mpa the volumetric mass of the sheet is approximately 20 kg m 3 and its thermal conductivity is of the order of 35 mw m u00b0 k for a thickness of 80 mm the fibers originally obtained may be completely cross linked by passage through a stove at 120 u00b0 c for 5 minutes fibers which have not been completely cross linked may present a certain thermoplasticity this may be used to advantage to form a self bonded sheet for this purpose the sheet obtained is subjected to a temperature of the order of 220 u00b0 c for 3 minutes under slight compression the sheet thereby obtained has a cohesion which enables it to.