Opening roller

A rapidly rotating roller, which is covered with pins or card clothing, used to separate sliver into individual fibres. This type of unit is incorporated in the feed section of most open-end spinning machines.

Optical Brightener

1. A colorless compound that when applied to fabric absorbs the ultraviolet radiation in light but emits radiation in the visible spectrum. 2. Fluorescent materials added to polymer in manufactured fiber production that emit light in the visible spectrum usually with a blue cast.

Optical brightening agent

A substance that when added to a substrate increases the apparent reflectance in the visible region by converting ultra-violet radiation into visible light and so increases the whiteness or brightness.

Optical Properties

A general term used to refer to the relations of yarn or fibers with light. It includes such parameters as birefringence refractive index reflectance optical density etc.

Optimum Twist

In spun yarns a term to describe the amount of twist that gives the maximum breaking strength or the maximum bulk at strength levels acceptable for weaving or knitting.

Ordinary beald

A form of weaving in which warp threads are made to cross one another between the picks.
Note 1: The simpler types of lightweight fabric produced by this method of weaving are known as 'gauze'.
Note 2.. It may be necessary to use:
(i) an caser motion to control the tension of the crossing ends during the formation of the crossed shed;
(ii) a shakes. motion to provide a partial lift to the standard lieald to bring the threads approximately level and thus facilitate crossing.
Note 3.. In simple ]cello weaving, one thread, generally called a crossing or leno end, L (see Fig. 1), is caused to lift alternately on one side and then on the opposite side of the other thread, usually referred to as the standard end, G, so as to produce 'crossed' or 'open' sheds. If the standard end is lifted a 'plain shed' (occasionally referred to as an 'ordinary shed') is formed.Healds B and C (B working in conjunction with A on certain picks) are responsible for the operations of crossing and lifting thread L relative to thread G. A suitable name for B is front crossing heald, and for C, back crossing heald, with D referred to as the standard heald and A as the doup.

Ordinary lay

A laid rope (see lay 3) in which the direction of twist in the roping yarn and the finished rope are the same, and in which the direction of lay of the strand is in the opposite direction.

Organdie

A plain-weave transparent fabric of light weight and with a permanently stiff finish.

Organdy

A very thin transparent stiff wiry muslin fabric used for dresses neckwear trimmings and curtains. Swiss organdy is chemically treated and keeps its crisp transparent finish through many launderings. Organdy without chemical treatment loses its crispness in laundering and has to be restarched. Organdy crushes or musses but is easily pressed. Shadow organdy has a faint printed design in self-color.

Organic cotton

Cotton grown under cotiditions prescribed by one of various local or regional organic certification schemes. (See also transitional cotton.)

Organize Yarn

Two or more threads twisted in the singles and then plied in the reverse direction. The number of turns per inch in the singles and in the ply is usually in the range of 10 to 20 turns. Organzine yarn is generally used in the warp.

Organza

A stiff thin plain weave fabric made of silk nylon acrylic or polyester organza is used primarily in evening and wedding attire for women.

Organzine

Silk yarn used as warp for weaving or for knitting, comprising single threads that are first twisted and then folded together two, three, or four-fold, and then twisted in the direction opposite to that of the singles twist.

Orientation

1. Parallelism of fibres, usually as a result of a combing or attenuating action on fibre assemblies, causing the fibres to lie substantially parallel to the axis of the web or strand which they constitute.
2. A predominant direction of fibrils and/or linear macromolecules in the fine structure of fibres.
Note 1: In manufactured fibres, orientation is usually parallel to the fibre axis as the result of extrusion, stretching, or drawing. In natural fibres the predoniinailt direction is determined during growth, for example a helix around the fibre axis in cotton.
Note 2.. Unoriented structures are those in which orientation is absent. Disoriented structures are those in which orientatioti has been reduced or eliminated as a result of a disrupting treatment.

Orifice

Generally an opening. Used specifically to refer to the small holes in spinnerets through which the polymer flows in the manufacture of fibers.