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1、BRITISH STANDARD BS 2782-6: Method 643A: 1976 Methods of testing Plastics Part 6: Dimensional properties Method 643A: Shrinkage on heating of film intended for shrink wrapping applications IMPORTANT NOTE. Before reading this method it is essential to read the foreword, general introduction and instr
2、uctions to BS 2782, issued separately. UDC 678.5/.8:678.01:536.416:620.192.52 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 643A:1976 BSI 08-1999 The following BSI references relate to the wo
3、rk on this standard: Committee reference PLC/17 Draft for comment 68/11485 ISBN 0 580 09092 2 A British Standard does not purport 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 n
4、ot of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in
5、the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 643A:1976 BSI 08-1999i Contents Page 1Sco
6、pe1 2References1 3Principle1 4Apparatus1 5Test pieces1 6Conditioning1 7Procedure1 8Test report1 Figure 643 A.1 Specimen holder2 Figure 643 A.2 Light wire mesh cage with lid2 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Co
7、py, (c) BSI ii blank Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 643A:1976 BSI 08-19991 1 Scope This method describes a procedure for determining the extent to which plastics films shrink w
8、hen heated in an unrestrained state. For films of different materials, appropriate test temperatures are specified. It should be appreciated that for some materials, the shrinkage obtained in industrial use may differ from the values obtained by this test method. The shrinkage of film as determined
9、by this method is usually measured in two directions at right angles to each other in the plane of the film. 2 References The following British Standards are referred to in this method. BS 2782:1975, Methods of testing plastics Foreword, general introduction and instructions. BS 3412, Polyethylene m
10、aterials for moulding and extrusion. 3 Principle The method consists of heating a measured length of film in a bath at a stated temperature, remeasuring and calculating the percentage reduction in length. 4 Apparatus The following apparatus is required. 4.1 Heating bath, of depth sufficient for the
11、test piece to be fully immersed and containing a liquid that will not affect the material under test at the test temperature nor decompose at this temperature.1) It shall be possible to control the temperature of the bath to within 0.5 C of the specified temperature. 4.2 Test piece holder, that will
12、 permit the test piece to be fully immersed in the liquid in the bath e.g. a pair of metal tongs or the device, made from heavy-gauge wire, shown in Figure 643 A.1 or a light wire mesh cage with lid as shown in Figure 643 A.2. 4.3 Stop watch 5 Test pieces Use a 10 1 mm wide test piece. If the appara
13、tus shown in Figure 643 A.1 is used, cut the test piece 100 mm in length plus an amount necessary for holding it. Mark the test piece (for example, by drawing a line across its width) at a distance of 100 1 mm from one end. If the apparatus shown in Figure 643 A.2 is used, cut the test piece 100 1 m
14、m in length. Use five test pieces for each direction of testing (see paragraph on direction of testing in BS 2782: Introduction:1975). 6 Conditioning Unless otherwise specified, the test pieces do not require to be conditioned. 7 Procedure Immerse the test piece fully for 20 1 s in the bath, at the
15、temperature specified below for the material (see note 1). Remove the test piece from the bath and, without delay, place it horizontally (see note 2) on a sheet of absorbent material, such as tissue or blotting paper, to cool. Measure the distance from the end of the test piece to the mark or the to
16、tal length of the test piece, as appropriate, to the nearest 1 mm (l1mm). Express the shrinkage on heating of the test piece as a percentage of the original length (100 mm), i.e. as (100 l1) %. Report the shrinkage in a particular direction of the material under test as the mean of the values obtain
17、ed on the five test pieces cut in that direction (see note 3). NOTE 1It is intended to add to the list of test temperatures as experimental evidence becomes available for films of other compositions. NOTE 2If the test pieces are held in a vertical position to cool they may stretch and give a false r
18、esult. NOTE 3The length of the test piece is normally reduced by the heat treatment, in which case the shrinkage is reported as a positive value. If the test piece extends under the heat treatment, the shrinkage is reported as a negative value. 8 Test report The report shall include the following pa
19、rticulars. a) The shrinkage on heating of the material for each direction of testing. b) The direction of the long axis of each group of test pieces in relation to some feature of the film. 1) Glycerine or silicone oil is a suitable liquid. PVC film90 0.5 C Polyethylene film of density not greater t
20、han 0.925115 0.5 C Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 643A:1976 2 BSI 08-1999 c) Temperature of test. d) The individual test results. e) The method used to hold the test piece. Fig
21、ure 643 A.1 Specimen holder Figure 643 A.2 Light wire mesh cage with lid Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank University, London South Bank University, Tue Dec
22、12 08:42:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6: Method 643A: 1976 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the i
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