ISO INTERNATIONAL STANDARD 1890 Fourth edition 2009-06-01 Reinforcement yarns Determination of twist Fils de renfort - Détermination de la torsion Reference number ISO 1890:2009(E) @ ISO 2009 ISO 1890:2009(E) Foreword IsO (the International Organization for Standardization) is a worldwide federation of national standards bodies (IsO member bodies). The work of preparing International Standards is normally carried out through Iso technical committees. Each member body interested in a subject for which a technical committee has been International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/lEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of paten rights. IsO shall not be held responsible for identifying any or all such patent rights. ISO 1890 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13, Composites and reinforcement fibres. This fourth edition cancels and replaces the third edition (IsO 1890:1997), of which it constitutes a minor revision. The main changes are as follows: the scope has been broadened to include all reinforcement-fibre yarns; the normative references have been updated; the reference to IsO 1886 which was in the first footnote on page 3 has been removed (IsO 1886 has been withdrawn without replacement). ili INTERNATIONAL STANDARD ISO 1890:2009(E) Reinforcement yarns Determination of twist Scope This International Standard specifies a method for the determination of twist in yarns made from textile glass carbon, aramid or any other reinforcement fibres. The method applies to single yarns (one twist) and to folded or cabled yarns (two or more twists). For folded This International Standard is applicable to package-wound yarns. If the measurement is carried out on yarns taken from a beam (or warp) or from a fabric, the result is of an indicative nature only. The method is not applicable to products made from staple fibres. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated document (including any amendments) applies. Iso 2:1973, Textiles - Designation of the direction of twist in yarns and related products Iso 291, Plastics — Standard atmospheres for conditioning and testing Iso 1889, Reinforcement yarns Determination of linear density 3 Terms and definitions For the purposes of this document, the following terms and definitions apply 3.1 Z twist S twist twist in a product if, when it is held in a vertical position, the spirals or helices formed by the fibres or filaments around its axis incline in the same direction as the central portion of the letter Z or S, respectively NOTE See ISO 2:1973, Clause 2.