The heat-stretching of Polifen yarn is nonuniform: fibre sections with a linear density less than the mean are deformed to a greater extent than sections which have a linear density above the mean.
The nonuniformity of Polifen yarn with respect to linear density increases by a factor of 1.5 to 2 during the heat-stretching process.
Translated from Khimicheskie Volokna, No. 2, pp. 24–25, March–April, 1983.