Acrylic Fiber, Orlon
This is an Orlon acrylic fiber. Orlon is a trademarked product of the E. I. DuPont Nemours Company. The low
birefringence and small diameter of the fiber results in the low first order white interference color seen here. Orlon has
a birefringence of about -0.002, and a bilobate (dog-bone) cross-section.
Acrylic fiber is derived from petrolium products. It is formed by drawing the polymer in solution through a spinneret into
a bath where it solidifies from the outside in. This results in less than a circular cross-section because the outside
polymerizes first and is drawn more rapidly though the bath than the interior of the fiber that is still liquid. The
draw-rate and process affects the fiber diameter, birefringence, and the cross-sectional shape, from nearly round, to bean
shaped, to dog-bone, to slightly crinulate. Acrylic fiber was commertially producted starting in about 1944.
Significance in the Environment:
This is a common clothing fiber.
Acrylic fiber has a refractive index along its length of about 1.50 to 1.53 and perpendicular to its length of about 1.50
to 1.53. It has a birefringence of about 0.002 to 0.012 and a negative sign of elongation. It may exhibit slight irregular
striations along its length due to the crinulate cross-section of the fiber, one depression along its length in the case of
the dog-bone cross-section, or appear to vary in diameter due to a bean shaped cross-section.
DuPont Company Techinical Bulletin X-156: IDENTIFICATION OF FIBERS IN TEXTILE MATERIALS, December 1961.