1、BRITISH STANDARD BS 2782-5: Method 521A: 1992 Methods of testing Plastics Part 5: Optical and colour properties, weathering Method 521A: Determination of haze of film and sheet IMPORTANT NOTE. Before reading this method it is essential to read BS 2782-0, Introduction, issued separately.BS2782-5:Meth
2、od 521A:1992 This British Standard, having been prepared under the directionof the Plastics and Rubber Standards Policy Committee, was published underthe authority of the Standards Board and comes into effect on 31 March 1992 BSI 08-1999 The following BSI references relate to the work on this standa
3、rd: Committee reference PRM/21 Draft for comment 91/37442 DC ISBN 0 580 20462 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/21, upon which the followin
4、g bodies were represented: British Plastics Federation British Steel Industry British Telecommunications plc British Textile Confederation Department of Trade and Industry (National Physical Laboratory) EEA (the Association of Electronics, Telecommunications and Business Equipment Industries) Electr
5、ical and Electronic Insulation Association (BEAMA Ltd.) Electrical Installation Equipment Manufacturers Association (BEAMA Ltd.) GAMBICA (BEAMA Ltd.) Ministry of Defence Packaging and Industrial Films Association PIRA Plastic Industrial Containers Association RAPRA Technology Ltd. Yarsley Technical
6、Centre Ltd. Amendments issued since publication Amd. No. Date CommentsBS2782-5:Method 521A:1992 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Principle 1 4 Apparatus 1 5 Test specimens 2 6 Test conditions 2 7 Procedure 2 8 Calculation 2
7、 9 Test report 3 Appendix A Derivation of formulae for calculation of haze 4 Figure 1 Essentials of apparatus 2BS2782-5:Method 521A:1992 ii BSI 08-1999 Foreword This British Standard has been prepared under the direction of the Plastics and Rubber Standards Policy Committee. It supersedes Method 515
8、A given in BS2782:1970 which is withdrawn by amendment. WARNING NOTE. This British Standard does not necessarily detail all precautions necessary to meet the requirements of the Health and Safety at Work etc. Act 1974. Attention should be paid to any appropriate safety precautions and the method sho
9、uld be operated only by trained personnel. 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 not of itself confer immunity from legal obligations
10、. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to4 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.BS2782-5:M
11、ethod 521A:1992 BSI 08-1999 1 1 Scope This British Standard describes a method of test for measuring the light transmitting properties, and from these, the light scattering properties,i.e. haze, of planar sections of transparent plastics film and sheet. 2 Definitions For the purposes of this British
12、 Standard the following definitions apply. 2.1 direct transmittance the ratio of the radiation passing through the barrier without deviation, to the incident radiation 2.2 haze that percentage of transmitted light which in passing through the specimen, deviates from the incident beam by more than 2.
13、5 on average, by forward scattering 2.3 total luminous transmittance the sum of the direct transmittance and the haze 3 Principle A collimated incident light beam passes through an integrating sphere and out through an exit port closed by an absorbent light trap. Any light scattered by the instrumen
14、t alone is detected by a photocell positioned at right angles to the beam after multiple reflections in the sphere. With a specimen in position 1 (seeFigure 1), the photocell detects the total light scattered by the specimen and the hazemeter. With the sphere in position 2 (see Figure 1), similar me
15、asurements without and with the specimen will give a measure of the total luminous transmittance. From these four measurements the haze expressed as a percentage is calculated. 4 Apparatus 4.1 Hazemeter, constructed essentially as shown in Figure 1 and having the following characteristics. The integ
16、rating sphere used to collect the transmitted flux may be of any diameter, so long as the total port area does not exceed4% of the internal reflecting area of the sphere. The entrance and exit ports shall be centred on the same great circle of the sphere and there shall be at least 170 of arc betwee
17、n the centre of the entrance port and the centre of the exit port. The axis of the irradiating beam shall pass through the centres of the entrance and exit ports. The exit port shall subtend an angle of 8 at the centre of the entrance port. The photocell or photocells shall be positioned on the sphe
18、re 90 10 from the entrance port. The interior wall of the sphere adjacent to the exit port shall be designed to be used as a reflectance standard. The angle of rotation shall not exceed 10 . The specimen shall be illuminated by a substantially unidirectional beam and the maximum angle which any ray
19、of this beam makes with its axis shall not exceed 3 . The beam shall not be vignetted at either port of the sphere. When the beam is unobstructed by a specimen, its cross section at the exit port shall be approximately circular, sharply defined and concentric within the exit port, leaving an annulus
20、 of 1.3 0.1 subtended at the entrance port. NOTEIt is important to check the unobstructed beam annulus dimensions whenever apertures or focus are changed. When the specimen is placed immediately against the integrating sphere at the entrance port, the angle between the normal to its surface and the
21、axis of the beam shall not exceed 8 . The surfaces of the integrating sphere, the baffles and the reflectance standards shall be matt white and of similar reflectance. The photoelectric cell used to measure the radiant flux within the sphere shall give output measurements proportional within1% to th
22、e incident flux over the range of intensity used. There shall be no reading when the sphere is dark. When the light trap is in position at the exit port and no specimen is present the beam shall be totally absorbed. With the light trap in position the photocell output shall be less than1% of the ful
23、l scale reading. The light source shall be a tungsten or tungsten halogen lamp appropriately filtered to give the colour temperature of one of the CIE 1)recommended illuminations, A, C or D65, the selection of filter being reported. The photocell shall have a spectral response approximating to the V
24、(2) response of the eye. 1) International Commission on Illumination, Central Bureau, Kegelgasse, 27, A-1033 Vienna, Austria.BS2782-5:Method 521A:1992 2 BSI 08-1999 The baffles shall be designed so that light may not pass directly from the illuminated area of the sample to the photocell or, when the
25、 sample is not present, from the illuminated area of the sphere wall to the photocell. 5 Test specimens Each test specimen shall be large enough to cover a25mm 25mm aperture with an overlap, but small enough to be tangential to the sphere walls. NOTE 1A disc 38mm in diameter is suitable. The test sp
26、ecimen shall have approximately plane-parallel surfaces free of dust, grease, scratches or blemishes. There shall be no visibly distinct internal voids or particles unless it is specifically desired to measure the contribution to haze due to these imperfections. NOTE 2The effect of surface defects m
27、ay be eliminated by immersing the specimen in a clear liquid of the same refractive index. The test specimens shall be conditioned at23 2 C and505% r.h. for not less than16h prior to the test. 6 Test conditions The tests shall be carried out in a laboratory atmosphere of23 2 C and 50 5% r.h. 7 Proce
28、dure NOTEIt is important that the detailed instructions issued by the makers of the hazemeter are followed at all times. 7.1 Maintain the light trap in place for all readings, and only remove it for checking the annulus dimensions (see clause 4). 7.2 With the sphere in position 1 (see Figure 1) and
29、the light source switched off check that the photocell output reads zero. 7.3 With the sphere in position 1, switch on the light source. With no specimen at the inlet port, measure the photocell output I 1 . NOTEThis reading should be close to zero. 7.4 With the sphere in position 2 and with no spec
30、imen in position, measure the photocell output, which is the incident intensity I 2 . 7.5 With the sphere in position 2, place a specimen in position at the inlet port. Measure the photocell output, which is the total light transmitted by the specimen I 3 . 7.6 Leave the specimen in place. Rotate th
31、e sphere to position 1 and measure the photocell output, which is the light scattered by the instrument and the specimen 14. 8 Calculation NOTEThe derivation of these formulae are given in Appendix A. 8.1 Calculate and record the total luminous transmittance T 1from the following expression. Figure
32、1 Essentials of apparatus T 1 I 3 I 2 - =BS2782-5:Method 521A:1992 BSI 08-1999 3 Calculate and record the diffuse luminous transmittance T 2from the following expression. Calculate the haze expressed as a percentage in accordance with the following expression. 9 Test report The test report shall inc
33、lude the following information. a) a complete identification of how the test specimen(s) were prepared, including manufacturers code, grade and form; b) a reference to this British Standard, BS 2782-5:Method 521A; c) thickness of the specimen in micrometres to the nearest micrometre; d) the type of
34、light source used and the type of filter used; e) the type of instrument used, including the make and model number; f) the average total luminous transmittance T 1and the average diffuse luminous transmittance T 2to the nearest0.001; g) the haze expressed as a percentage to the nearest0.1%. Indicate
35、 when average values are quoted; h) the name of the test house; i) the date on which the tests were conducted.BS2782-5:Method 521A:1992 4 BSI 08-1999 Appendix A Derivation of formulae for calculation of haze A.1 The total luminous transmittance T 1is the ratio of all transmitted light to the total i
36、ncident light: since I 4is now the light scattered by the specimen only. A.2 If the light scattered by the instrument, I, is zero, then the diffuse luminous transmittance T 2is the ratio of the light scattered by the specimen to the incident light: since I 4is now the light scattered by the specimen
37、 only. A.3 If I 1is not zero, then the total scattered light I 4is greater than the light scattered by the specimen by an amount proportional to I 1and equal to I 1times I 3 /I 2 . The corrected amount of light scattered by the specimen will then be: I 4 I 1 (I 3 /I 2 ) which is substituted for I 4i
38、n equation 2. A.4 Substituting for I 4in equation 2 gives a corrected expression for the diffuse luminous transmittance T 2 . A.5 The haze is given by the ratio of diffuse luminous transmittance T 2to total luminous transmittance T 1 , expressed as a percentage. A.6 Ideally I 1is zero and then the h
39、aze expressed as a percentage is 100(I 4 /I 3 ). It is important that I 1 /I 2remains a small correction if large errors are to be avoided. (1) (2) T 1 I 3 I 2 - = T 2 I 4 I 2 - =5 blankBS 2782-5: Method 521A: 1992 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the in
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