1、BRITISH STANDARD BS3424-20: 1987 Testing coated fabrics Part20:Method23: Method for determination of dimensional changes on mechanical relaxation at zero tension IMPORTANT NOTE. It is recommended that this Part be read in conjunction with the information in Part0 “Foreword and general introduction”
2、UDC677.077.652:678.066.2:677.017.22:53.091/.096BS3424-20:1987 This British Standard, having been prepared under the directionof the Rubber StandardsCommittee, was published under the authority ofthe Board of BSI and comes intoeffect on 30 January 1987 BSI 04-1999 The following BSI references relate
3、to the work on this standard: Committee reference RUM/13 Draft for comment85/40619DC ISBN 0 580 15484 X Foreword During the processing, production and subsequent batching and rolling operations carried out in the manufacture of a coated fabric, strains are introduced which are, at various times duri
4、ng the manufacturing process, alleviated, re-introduced, increased or maintained for varying periods of time. These strains are unlikely to be constant throughout the entire length of the roll. When, for example, the coated fabric is batched or re-wound after manufacture, the tension introduced into
5、 the coated fabric will tend to be greater when the roll is being wound at or near its maximum diameter than when it is at its minimum diameter. This difference in tension or strain may be even greater when the machinery being used is spindle driven, so that the surface speed of the roll being wound
6、 increases as its diameter increases. Even with surface driven rolls, i.e.when the surface speed of the roll being wound is constant, the tension introduced may vary depending upon the type of let-off motion employed on the feed supply. In addition to these variables, as the coated fabric is exposed
7、 to elevated temperatures during its processing, the finished product normally contains less than its normal moisture content. When, therefore, the coated fabric is unrolled and allowed to relax in a normal atmosphere under zero tension, the processing tensions or strains tend to decay and/or equali
8、ze and the coated fabric may absorb moisture. This decay of processing tensions and moisture uptake often result in dimensional changes occurring. It is these dimensional changes that this method of test seeks to measure. This Part supersedes method23 of BS3424:1973. A British Standard does not purp
9、ort to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front c
10、over, pages i and ii, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue
11、 CommentsBS3424-20:1987 BSI 04-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Apparatus 1 4 Procedure 1 5 Calculation and expression of results 1 6 Test report 2 Figure 1 Position of gauge marks on the surface of the coated fabric for determination of dimensional changes
12、on mechanical relaxation at zero tension 2 Publications referred to Inside back coverii blankBS3424-20:1987 BSI 04-1999 1 1 Scope This Part of BS3424 describes a method for determining the dimensional changes occurring when a coated fabric is allowed to relax mechanically under zero tension in the s
13、tandard atmosphere for conditioning and testing. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle The roll of coated fabric under examination is unrolled along a horizontal flat surface and gauge marks are made in either the width or th
14、e length directions or both. The coated fabric thus marked is exposed for24h under zero tension in the standard atmosphere for conditioning and testing, after which the distances between the pairs of reference marks are measured and the dimensional changes determined. 3 Apparatus 3.1 Rule. A steel t
15、ape, graduated inmm, complying with BS4035. 3.2 Flat surface. A clean, horizontal flat surface of at least2.5m in length and a width at least100mm wider than the material under test. It shall be free of rough areas likely to prevent the coated fabric moving freely. 4 Procedure 4.1 Marking Without no
16、ticeably increasing the tension in the material, unroll the coated fabric on the flat surface(3.2), with the substrate side uppermost in the case of single-face coated fabrics. Without delay ensure that the material is flat and mark the upper surface, as shown in Figure 1, as required, i.e.in the lo
17、ngitudinal or transverse directions or both or in the centre only, relevant to clause5 a),5 b),5 c),5 d) or5 e) as required. The distance between pairs of marks in the longitudinal direction shall be2m, avoiding the first and last metre, and no marks shall be within50mm of a selvedge. Measure and re
18、cord to the nearest mm the distance between the marks. 4.2 Condition Expose the material for at least24h under zero tension in the standard atmosphere for conditioning and testing specified in method4 (i.e.BS3424-2). 4.3 Measure Measure and record the distances to the nearest mm between the marks ma
19、de as described in4.1 and record the difference, if any. 4.4 Re-roll Re-roll the coated fabric on to a new cloth centre and carry out the procedure described in4.1, 4.2 and4.3 at the other end of the roll. 5 Calculation and expression of results Calculate any shrinkage or extension in the material a
20、s a percentage of the original dimension, as follows: a) % dimensional longitudinal change (left hand) ; b) % dimensional longitudinal change (centre) ; c) % dimensional longitudinal change (right hand) ; d) % dimensional transverse change (running end) ; e) % dimensional transverse change (end) ; w
21、here L 1 is the original dimension in the longitudinal direction between gauge marks A and F, taken at4.1; L 2 is the dimension, being the largest deviation from L 1 , of the two measurements taken at4.3 and4.4; C 1 is the original dimension in the longitudinal direction between gauge marks B and E
22、taken at4.1; C 2 is the dimension, being the largest deviation from C 1 , of the two measurements taken at4.3 and4.4; R 1 is the original dimension in the longitudinal direction between gauge marks C and D taken at4.1; R 2 is the dimension, being the largest deviation from R 1 , of the two measureme
23、nts taken at4.3 and4.4; T 1 is the original dimension in the transverse direction between gauge marks A and C taken at4.1; L 2 L 1 ()100 L 1 - = C 2 C 1 ()100 C 1 - = R 2 R 1 ()100 R 1 - = T 2 T 1 ()100 T 1 - = E 2 E 1 ()100 E 1 - =BS3424-20:1987 2 BSI 04-1999 6 Test report The test report shall inc
24、lude the following information: a) the description of the coated fabric; b) the percentage dimensional change in the longitudinal direction. If there is any difference in the percentage dimensional change across the width of the coated fabric, i.e.at5 a),5 b) or5 c), report all three results; c) the
25、 percentage dimensional change in the transverse direction. If there is any difference in the percentage dimensional change along the length of the coated fabric, i.e.at5 d) or5 e), report both results; d) a reference to this method of test, i.e.method23 of BS3424-20; e) any deviation from the stand
26、ard test procedure. T 2 is the dimension, being the largest deviation from T 1 , of the two measurements taken at4.3 and4.4; E 1 is the original dimension in the transverse direction between gauge marks F and D taken at4.1; E 2 is the dimension, being the largest deviation from E 1 , of the two meas
27、urements taken at4.3 and4.4. Figure 1 Position of gauge marks on the surface of the coated fabric for determinationof dimensional changes on mechanical relaxation at zero tensionBS3424-20:1987 BSI 04-1999 Publications referred to BS3424, Testing coated fabrics. BS3424-2:Method4, Conditioning and sel
28、ection of test specimens. BS4035, Specification for linear measuring instruments for use on building and civil engineering constructional works. Steel measuring tapes, steel bands and retractable steel pocket rules. BS3424-20: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitut
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