Synthetic down

A synthetic fiber thermal insulator material in the form of a cohesive fiber structure, which structure comprises an assemblage of:

• (a) from 70 to 95 weight percent of spun and drawn, synthetic polymeric microfibers having a diameter of from 3 to 12 microns;
• and
• (b) from 5 to 30 weight percent of synthetic polymeric macrofibers having a diameter of 12 to 50 microns,
• characterized in that at microfiber/macrofiber contact points said microfibers are bonded to said macrofibers and at macrofiber/macrofiber contact points said macrofibers are bonded to said macrofibers, the bonding being such that the macrofiber component does not lose its structural integrity and the density of the resultant structure is within the range of 0.2 to 1.0 lb/ft.sup.3, the thermal insulating properties of the bonded assemblage being equal to or not substantially less than the thermal insulating properties of a comparable unbonded assemblage, and in that said material has a radiation parameter defined as the intercept on the ordinate axis at zero density of a plot of K.sub.c P.sub.f against P.sub.f less than 0.075 (Btu-in/hr-ft.sup.2 -.degree.F.) (lb/ft.sup.3) and an apparent thermal conductivity K.sub.c measured by the plate-to-plate method according to ASTM C518 with heat flow down of less than 0.5 Btu-in/hr-ft.sup.2 -.degree.F.