Complete Textile Glossery (U to V)

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U

ULTIMATE TENSILE STRENGTH: See TENSIL STRENGTH.
ULTRASONIC QUILTING: See PINSONIC® THERMAL JOINING MACHINE.
ULTRAVIOLET DEGRADATION: Weakening or deterioration caused by exposure to
ultraviolet rays of sunlight or artificial light.
ULTRAVIOLET RESISTANCE: Ability to retain strength and resist deterioration on exposure
to sunlight.
UNCRIMPING ENERGY: See CRIMP ENERGY.
UNDRAWN TOW: See DRAWN TOW.
UNDRAWN YARN: Extruded yarn (filaments), the component molecules of which are
substantially unoriented. Undrawn yarn exhibits predominantly plastic flow in the initial stages
of stretching and represents an intermediate stage in the production of a manufactured yarn.
UNEVEN DYEING: A fabric dyeing that shows variations in shade resulting from incorrect
processing or dyeing methods or from use of faulty materials.
UNEVEN SHRINKAGE: A wavy, warpwise condition in the fabric that prevents it from lying
flat on a horizontal surface.
UNEVEN SURFACE: An irregular surface characterized by nonuniformity in the physical
configuration of the yarns or fibers making up the surface of the fabric.
UNEVEN YARN: A yarn that varies in diameter to an abnormal degree.
UNFINISHED WORSTED: A worsted fabric with a relatively soft hand and a light nap.
UNIDIRECTIONAL FABRIC: A fabric having reinforcing fibers in only one direction.
UNION CLOTH: A term describing a fabric woven from two or more types of yarn. For
example, a union cloth may have a cotton warp and a wool filling. (Also see COMBINATION
FABRIC.)
UNION DYEING: See DYEING.
UNOPENED STAPLE: Staple fiber in bunches or clusters in the bale in such a condition that it
will not process smoothly through carding and subsequent operations in the spun-yarn plant.
UNRELAXED YARN: See RELAXED YARN.
UPDRAFT METIER: A dry spinning machine in which the air flow within the drying cabinet is
countercurrent to the yarn path (upward).
UPTWISTER: A machine used for twisting yarns in an upward path from a rotating vertical
supply package to a horizontal take-up package. Used for spun yarns and to a small extent for
adding twist to some filament yarns.
UPTWISTING: The process of twisting yarn on the uptwister. The yarn to
be twisted, which has been wound on a balanced support package, is placed
on a revolving spindle. The yarn form the revolving supply package is fed
upward through a gathering eye or guide, over a stop motion and a tension
bar or bars, through a traversing guide, and onto the revolving collecting
package.
URETHANE: The name of a group of organic chemical compounds or
resins built from isocyanate, a very reactive material that liberates gas during
reaction to produce foams of various types. Two types of compounds that
react with isocyanate to form foam are polyesters and polyethers.
Polyurethanes are used for foams and in other compounds in fiber form. The polyester variety
should not be confused with polyester fibers. (Also see SPANDEX FIBER.)
USTER TESTER: An instrument that provides a continuous measurement of the variation in
weight per unit length of sliver, roving, and yarn.
UV ABSORBERS: Polymer additives that absorb light in the UV region or that trap radicals
produced in fiber during photooxidation. They provide stabilization against actinic degradation.
Some critical applications include geotextiles, recreational surface polymers and fibers, tenting
tarpaulins, etc.
V
VARIANT: A manufactured fiber modified in polymer configuratio
n or by additive during
manufacture, resulting in a change in the properties of the fiber. Examples are flame-retardant
variants, deep-dyeing variants, high-tenacity variants, low-pilling variants, and cotton-blending or
wool-blending variants.
VAT DYES: See DYES.
V-BED FLAT-KNITTING MACHINE: A latch-needle weft-knitting machine with two
needlebeds at a 90° angle to each other in the form of an inverted V. Each needlebed is at a 45°
angle to the horizontal. These machines are used primarily to produce collars, sleeves, sweater
strips, and rib trims.
VECTRAN® FIBER: Manufactured fiber spun from Celanese Vectra® liquid crystal polymer.
These fibers have high-temperature resistance, high strength and modulus, and high resistance to
moisture and chemicals, with good property retention in hostile environments. They are used as
matrix fibers for advanced composites and as reinforcing fibers in advanced composites, ropes
and cables, and in electronics applications.
VEGETABLE FIBER: A textile fiber of vegetable origin, such as cotton, kapok, jute, ramie,
and flax.
VELOUR: 1. Generally, a soft, closely woven fabric with a short, thick pile, weighting about 10
to 20 ounces per yard and made in a plain or satin weave. Velour is usually made of cotton or
wool, or with a cotton warp in wool, silk, or mohair velour. It is also made in blends of spun
manufactured fiber and wool. Velours are used for coats, draperies, upholstery, powder puffs,
and other pile items. 2. A felt with velvet-like texture used for men’s and women’s hats.
VELVET CARPET: A woven carpet in which the pile ends are lifted over wires that are
inserted in the same manner as the filling and that cut the pile as they are withdrawn.
VELVETEEN: A fabric with a low filling pile made by cutting
an extra set of filling yarns woven in a float formation and bound
to the back of the material at intervals by weaving over and under
one or more warp ends.
VELVET FABRIC: A warp-pile woven fabric with short, dense
cut pile that produces a rich fabric appearance and soft texture.
Two methods are used for weaving velvets. In the double-cloth method, two fabrics are woven
face to face with the pile ends interlocking. A reciprocating knife cuts through these pile ends to
produce two separate pieces of velvet. In the second method, pile ends are lifted over cutting
wires that are inserted with the filling and that are withdrawn to cut the pile. Velvet is produced
in a wide range of constructions and types. Originally made of silk, but now also of cotton or
manufactured fibers giving fabrics that are sometimes washable. The fabric can be specially
finished to make it crush-resistant and water-repellent or it may be embossed or patterned by
burn-out printing.
VERTICAL FLAME TEST: See FLAMMABILITY TESTS.
VIBROSCOPE: An instrument for determining the mass per unit length of a fiber.
VINAL FIBER: A manufactured fiber in which the fiber-forming substance is any long chain
synthetic polymer composed of at least 50% by weight of vinyl alcohol units and in which the
total of the vinyl alcohol units and any one or more of the various acetal units is at least 85% by
weight of the fiber (FTC definition). Vinal fibers show good chemical resistance but soften at
comparatively low temperatures. Vinal fibers are used for apparel, industrial goods, and fishnets.
VINYL: A univalent radical, (CH2=CH-), derived from ethylene.
VINYLIDENE CHLORIDE: A chemical material obtained from ethylene, a petroleum product,
and from chlorine. It is used for the manufacture of textile monofilaments and film. It is more
commonly identified in the U.S. as saran. (Also see SARAN FIBER.)
VINYON FIBER: A manufactured fiber in which the fiber-forming substance is any long chain
synthetic polymer composed of at least 85% by weight of vinyl chloride units (FTC definition).
VISCOMETER: A device designed to measure the viscosity (resistance to flow) of the fluid.
Many types exist from simple calibrated glass tubes to extensively instrumented, on-line shear
viscometers.
VISCOSE PROCESS: 1. One of the methods of producing rayon. (Also see RAYON FIBER).
2. The chemical process used in the manufacture of cellophane. (Also see VISCOSE
SOLUTION).
VISCOSE RAYON: One type of rayon. It is produced in far greater quantity than
cuprammonium rayon, the other commercial type. (Also see RAYON FIBER.)
VISCOSE SOLUTION: The solution obtained by dissolving cellulose xanthate in caustic soda,
from which viscose filaments and cellophane are produced.
VISCOSITY: The internal flow resistance of a fluid. (Also see INTRINSIC VISCOSITY and
RELATIVE VISCOSITY.)
VOILE FABRIC: A sheer spun cloth that is lightweight and soft. It is usually made with
cylindrical, combed yarn. Voile is used for blouses, children’s wear, draperies, bedspreads, etc.
VOLATILE: Readily vaporized at a relatively low temperature.
VOLATILITY: Property of having a low boiling point or temperature of sublimation at normal
pressure. Likewise, having a high vapor pressure at ambient conditions.
VOLUME RESISTIVITY: The ration of the potential gradient parallel to the direction of
current flow in a compound to the current density after a specified time of voltage application.
VULCANIZATION: See CURING, 2.

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