1、International Standard 721112 INTERNATIONAL ORGANIZATION FOR STANDARDIZATlONWvlEIKAYHAPOHAR OPrAHM3AL in particular, it is the only one that is really suitable for the examination of certain folded structures and other complicated weaves. Method B: Counting glass, suitable for woven fabrics with mor
2、e than 50 threads per centimetre. Method C: Traversing thread counter, suitable for all fabrics. Where the number of threads per centimetre is low, it may be convenient to express the results as the number of threads per decimetre. NOTE - Methods using parallel line gratings and tapered line grating
3、s have been given in the annex for information. These methods have not been considered accurate enough to be used as standard test methods but can be used to give rough and ready estimates for routine testing. 2 Reference IS0 139, Text/i/es - Standard atmospheres for conditioning and testing. 3 Prin
4、ciple Three methods of determining the number of threads per centimetre are specified, any of which may be used, the choice depending on the character of the fabric. The prin- ciples are as follows: Method A: A section of fabric of dimensions in accor- dance with those given in clause 4 is dissected
5、 and the number of threads counted. The threads that are counted are preferably short, 1 or 2 cm being suitabl Method B: The number of threads visible with aperture of a specified counting glass is determined. to be e. n the Method C: The number of threads per centimetre of the fabric is determined
6、with the aid of a traversing thread counter. 4 Minimum measuring distance Use the appropriate minimum measuring distance specified in the table. Table - Minimum measuring distance Number of threads per centimetre Less than 10 10 to 25 25 to 40 More than 40 Minimum measuring distance cm 10 5 3 2 Numb
7、er of threads per test piece Less than 100 50 to 125 75 to 120 More than 80 Accuracy in percentage (count to within 0,5 thread) Greater than 0,5 I,0 to 0,4 0,7 to 0,4 Less than 0,6 For the method A, take test pieces containing at least 100 threads. For narrow fabrics having a width of 10 cm or less,
8、 count all warp threads including the selvedge ends and express the result as threads per full width. When fabrics are patterned by broad areas of higher or lower density of thread spacing, select test specimens containing at least one weave repeat (see clause 10). 5 Conditioning and testing atmosph
9、ere One of the standard atmospheres for conditioning and testing textiles as defined in IS0 139 shall be used for conditioning and testing. 6 Test specimens No specially prepared specimens are required except for method A (see 7.21, but count the threads at not less than five different points select
10、ed to represent the fabric as fully as poss- ible. Expose the fabric or specimens to the standard at- mosphere for testing for at least 16 h before making the test. IS0 7211/2-1984 (E) 7 Method A - Dissection of fabric whole repeats in the measuring distance, plus the remaining in- dividual threads.
11、 Determine the number of threads in a repeat 7.1 Apparatus 7.1.1 Clamp, holding two short pins parallel and with their points being within + 0,02 cm of the minimum measuring distance specified in clause 4. Alternatively, when a clamp is not available, by analysis of the weave or dissection of the fa
12、bric. Count the number of warp threads, or the number of weave repeats, or the number of warp thread units and fractions of a unit bounded by the appropriate pair of opposite sides of the aperture. Repeat with one of the edges of the aperture parallel to the weft threads, and count the number of wef
13、t threads or weave repeats or number of weft thread units in a similar manner. 7.1.2 Two dissecting needles and 7.1.3 Heavy steel rule. If the face of the fabric is composed mainly of one set of threads, as with certain twills, sateens, etc, it may be found easier to count on the back of the fabric,
14、 where the weave design is more readily recognizable. 7.2 Procedure 9 Method C - Traversing thread counter Take five specimens at random (see clause 6) 0,4 to 0,6 cm longer than the minimum measuring distance specified in clause 4 and sufficiently wide to facilitate handling. Take care not to distur
15、b the distribution of threads, especially in a loosely woven fabric. Pass the pins in the clamp (7.1 .I) through a specimen 0,2 to 0,3 cm from each end. Remove the shorter threads (those in the direction to be counted) from the specimen outside the two pins, so that the measuring distance of fabric
16、between the pins remain. Then remove the short threads from the specimen and count them. Count any threads impaled on a pin as half a thread. It is usually convenient to employ a pair of pointed forceps to remove the threads. The threads may be arranged in groups of ten for convenience in counting.
17、9.1 Apparatus 9.1.1 Traversing thread counter, incorporating a low- power microscope, of X 4 to X 20, mounted so that it can be traversed by means of a screw over a graduated base suffi- ciently long to meet the minimum measuring distance re- quirements of clause 4. Types with an index line in the e
18、yepiece or a pointer traversing with and visible through the microscope are equally suitable. 9.2 Test procedure Use a measuring distance in accordance with clause 4. An approved alternative method where a clamp is not available is to insert two dissecting needles (7.1.2) the required distance apart
19、 by sliding their points down the appropriate graduation marks of a heavy steel rule (7.1.3) placed on edge. 8 Method B - Counting glass Lay the fabric flat on a horizontal surface and place the thread counter (9.1 .I) upon it in such a way that when the screw is turned the microscope moves across t
20、he fabric in a direction that is either parallel to the warp or parallel to the weft, depend- ing on which set of threads is being counted. Count the number of threads over the appropiate minimum measuring distance. 8.1 Apparatus 8.1.1 Counting glass, the aperture width of which shall be 2 + 0,005 c
21、m or 3 + 0,005 cm at all places. The thickness of the base plate at the edges of the aperture shall not exceed 0,l cm. . In some fabrics it is possible to see and count every thread passed by the pointer or index line as it moves across the fabric. If this is not possible, weave repeats may be count
22、ed. Begin counting from a thread in the weave repeat which can be read- ily identified. Count the number of whole repeats in the measuring distance, plus the remaining individual threads. Determine the number of threads in a repeat by analysis of the weave or dissection of the fabric. 8.2 Procedure
23、Use a measuring distance in accordance with clause 4. If the face of the fabric is composed mainly of one set of threads, as with certain twills, sateens, etc., it may be found easier to count on the back of the fabric, where the weave design is more readily recognizible. Lay the fabric flat on a ho
24、rizontal surface and place the count- ing glass (8.1 .I) on the fabric so that one of the edges of its aperture is parallel to the warp threads. 10 Calculation and expression of results In some fabrics, it is possible to see and count every thread. If Calculate the number of threads per centimetre.
25、Quote the this is not possible, weave repeats may be counted. Select a mean of individual results for each direction, that for the warp thread in the weave repeat which can be identified readily and threads as ends per centimetre and that for the weft as picks position the counting glass so that thi
26、s thread is adjacent to one per centimetre. The number of threads per square centimetre is side of the aperture of the counting glass. Count the number of given by the sum of the mean ends and picks per centimetre. 2 IS0 7211/2-1984 (E) When fabrics are patterned by broad areas of higher or lower de
27、nsity of thread spacing, determine the number of threads in each area and report the number of threads per centimetre for different areas of the pattern, 11 Test report The test report shall include the following particulars: a) a reference to this International Standard (IS0 7211/2) ; b) the standa
28、rd atmosphere used (temperate or tropical); c) the actual method used (A, B or C); d) the measuring distance used; e) the number of measurements made; f) the number of warp ends per centimetre and weft picks per centimetre and the mean value of warp ends per centimetre and weft picks per centimetre.
29、 If the fabric is pat- terned by broad areas of greater and lower density, and if required, this information can be given for each different portion of the pattern. Where the number of threads is low, it is permissible to ex- press and report the results as the number of threads per decimetre. For n
30、arrow fabrics (see clause 41, report the results as the number of threads per full width; 9) if requi red, the nu (or square decimetre) of threads Per squa re ten timetre h) details of any deviation from the method. 3 IS0 7211/2-1984 (El Annex Method using taper and parallel line gratings (Forms par
31、t of the Standard.) A.1 Method D - Parallel-line grating This method is suitable only for fabrics where thread patterns yield interference bands that are readily visible. A.1 .I Principle The number of interference bands produced when the parallel line grating is placed on the fabric is determined.
32、A.l.2 Apparatus A.1.2.1 Parallel line grating, with a length of 10 or 20 cm and with about 5 % more or less lines per centimetre than there are threads per centimetre in the cloth to be tested. If several gratings of different gauges are available, select the most suitable by trial. It is essential
33、that the lines on the grating are straight and parallel. The average number of lines per centimetre over the whole grating shall be known to O,l, and the average number of lines per centimetre at either edges of known length shall not differ from the general average by more than 0,15 %. A.l.3 Proced
34、ure Place the grating selected as most suitable on the fabric with its lines parallel to the threads to be counted. If a suitable grating has been chosen, a number of bands parallel to the edge of the grating as shown in figure 1 will be seen. Count the number of these bands along the middle of the
35、grating and divide by the length of the grating in centimetres, to obtain the mean number of bands per centimetre. Either add the number of bands per centimetre to the number of lines per centimetre of the grating, or subtract the number of bands per centimetre from the number of lines per centimetr
36、e of the grating, in accordance with the following rule. If, when the grating is rotated slightly, the bands appear to rotate in the same direction as the grating, the number of bands per centimetre must be subtracted from the lines per centimetre of the grating. If, however, the bands rotate in the
37、 opposite direction to the grating, the number of bands must be added to the lines per centimetre of the grating. A.1.4 Calculation and expression of results Where the test does not give it directly, calculate the number of threads per centimetre. Quote the mean of individual results for each direct
38、ion, that for the warp threads as ends per centimetre and that for the weft threads as picks per centimetre. The number of threads per square centimetre is given by the sum of the mean ends and picks per centimetre. 4 When fabrics are patterned by broad areas of greater and lower density of thread s
39、pacing, it may be desirable to record the number of threads per centimetre in each different portion of the pattern. A.2 Method E - Taper-line gratings This method is suitable only for fabrics where thread patterns yield interference bands that are readily visible. A.2.1 Principle The number of thre
40、ads is determined by observation of the interference pattern produced when a taper-line grating is placed on the fabric. A.2.2 Apparatus A.2.2.1 Taper-line grating, consisting of diverging lines disposed symmetrically between two parallel scales 2,5 cm apart, so that they cut off equal intercepts al
41、ong any line at right angles to the axis of symmetry. Corresponding gradua- tions on the scales are opposite one another, and the gradua- tions indicate the number of units, consisting of a line and a space, counted in a straight line from a graduation on one scale to the corresponding graduation on
42、 the other. The graduations indicate whole numbers with an accuracy of 0,5 %. The divergence of the lines should be such that the greatest and least values of lines per centimetre does not differ by more than 4 times the length of the scale in centimetres. A.2.3 Procedure Place the grating on the fa
43、bric with its long edge parallel to the threads to be counted. If a suitable grating has been chosen, there will be one point on it where the number of lines per cen- timetre equals the number of threads per centimetre. At this point a light or dark cross, which may be symmetrical or skew, will be f
44、ormed by the curvilinear pattern of the bands which ap- pear. The scale reading to which the two short arms of this cross point give the threads per centimetre. In the event of asymmetry of the cross, take the mean of the readings from both scales. The interference pattern produced by a fabric with 25 threads/cm is shown in figure 2. Often at scale readings which are multiples or fractions of the number of threads per centimetre, other patterns may be seen, but there is seldom cause for doubt in selecting the fundamen- tal one, as the others are much fainter.
