IS 1670 : 1991 Textiles - Yarn - Determination of breaking load and elongation at break of single strand

1 Scope

1.1 This standard prescribes method for determination of breaking load andelongation at break of yarn using constant-rate-of-traverse,constant-rate-of-loading and constant-rate-of-extension machines. Since for anyfibre type breaking load is approximately proportional to the linear density,strands of different sizes are compared by converting the observed breaking loadto breaking tenacity (centinewtons or millinewtons per tex).

1.1.1 The method prescribed in this standard is applicable to monofilamentand multifilaments other than tyre cords and industrial yarns, and spun yarns(single, plied or cabled) made from all kinds of textile fibres or their blendswith the exception of yarns that stretch more than 5.0 percent when tension isincreased from 0.5 to 1.0 g (5 to 10 mN) per unit linear density of the yarn intex.

1.1.2 This standard is designed primarily for yarn in package form but can beused for single strands removed/extracted from a woven/knitted fabric.

1.1.3 This standard does not cover textured yarns and fancy yarns.

1.1.4 This test method offers two options with respect to moisture content ofthe specimens at the time of testing.

1.1.4.1 Option 1 - Conditioning to moisture equilibrium in the standardatmosphere for testing textiles ( see IS 6359 : 1971).

1.1.4.2 Option 2 - Testing in wet condition. Tests on wet specimens areusually made only on yarns which show a less strength when wet or when exposedto high humidity, for example, yarns made from animal fibres and man-made fibresbased on regenerated and modified cellulose. Wet tests are made on flax yarns todetect adulteration by failure to gain strength.

1.1.5 This method also offers three options for the physical confirmation ofthe specimen.

1.1.5.1 Option A - Straight (see Note 4).

1.1.5.2 Option B - Knotted (see Notes 1, 2 and 3).

1.1.5.3 Option C - Looped (see Notes 1 and 3).

Note - 1 The reduction in strength due to the presence of a knot or loop isconsidered a measure of brittleness of yarn. If a textile yarn is looped orknotted, its tensile strength may reduce. This can arise when a yarn is bent toa small radius of curvature (as in sewing or knitting) or knotted (as in themanufacture of nets). In order to assess the importance of these effects, loopstrength and knot strength are described.

Note - 2 The knot strength test as described in this standard is not intendedto assess the efficiency of any given type of knot for joining together twoseparate lengths of yarns.

Note - 3 Elongation in a knot or loop test is not known to have anysignificance and is not usually recorded.

Note - 4 unless otherwise indicated, `single-strand strength' is assumed torefer to a straight, conditioned specimen (Option 1A).

2 References

IS 570 :1964 Methods for determination of universal count ofjute yarn

IS 681 :1964 Methods for determination of universal count ofwoollenand worsted yarns

IS 1070 :1977 Water for general laboratory use

IS 1315 :1977 Method for determination of linear density of yarnsspunon cotton system

IS 3920 :1985 Methods for sampling of cotton yarn for determinationofphysical characteristics

IS 6359 :1971 Method for conditioning of textiles