BS 3900-D6-1982 Methods of test for paints - Optical tests on paint films - Determination of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate using polye.pdf

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1、BRITISH STANDARD BS3900-D6: 1982 ISO3906-1980 (Including Amendment No. 1) Opacity of light-coloured paints Methods of test for paints Part D6: Determination of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate, using polyester film ISO title: Paints and varnishes Determinat

2、ion of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate (using polyester film) It is recommended that this Part be read in conjunction with the general information in the Introduction to BS3900 issued separately UDC667.613:535.345.3:535.668.1BS3900-D6:1982 This British Sta

3、ndard, having been prepared under the directionof the Pigments, Paintsand Varnishes StandardsCommittee, was published underthe authority ofthe Board ofBSI and comesintoeffect on 30November1982 BSI03-1999 The following BSI references relate to the work on this standard: Committee reference PVC/10 Dra

4、fts for comment75/52104 DC and78/51522 DC ISBN0 580 13032 0 Amendments issued since publication Amd. No. Date of issue CommentsBS 3900-D6:1982 BSI 03-1999 i Contents Page National foreword ii 0 Introduction 1 1 Scope and field of application 1 2 References 1 3 Principle 1 4 Apparatus 2 5 Sample 2 6

5、Procedure 2 7 Precision 3 8 Test report 4 Publications referred to Inside back coverBS3900-D6:1982 ii BSI 03-1999 National foreword This Part of BS3900 has been prepared under the direction of the Pigments, Paints and Varnishes Standards Committee. It is identical with ISO3906-1980 “Paints and varni

6、shes Determination of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate (using polyester film)” published by the International Organization for Standardization (ISO), and incorporates the Amendment1 published by ISO in1981. A similar test method, ISO3905 “Paints and varnish

7、es Determination of contrast ratio (opacity) of light-coloured paints at a fixed spreading rate (using black and white charts)”, has also been published by ISO but will not be implemented as a Part of BS3900 as the method is considered to be inferior to that described in this Part. Terminology and c

8、onventions. The text of the international standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has bee

9、n used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-references International standard Corres

10、ponding British Standard BS3900 Methods of test for paints ISO1512-1974 Part A1:1970 Sampling (Technically equivalent) ISO1513-1980 Part A2:1970 Examination and preparation of samples for testing (Technically equivalent) ISO1515-1973 Part B2:1970 Determination of volatile matter and non-volatile mat

11、ter (Technically equivalent) ISO2811-1974 Part A12:1975 Determination of density (Technically equivalent) ISO2814-1973 Part D4:1974 Comparison of contrast ratio (hiding power) of paints of the same type and colour (Technically equivalent)BS 3900-D6:1982 BSI 03-1999 iii ISO3905-1980, to which referen

12、ce is made in the text for information purposes only, was reviewed by the Technical Committee but, because the method it describes is inferior to that given in ISO3906, it decided not to implement the former standard. Hence there is no British Standard corresponding to ISO3905. Additional informatio

13、n. With reference to item f) of clause8, attention is drawn to the necessity to state in the test report the thickness of the polyester film if the film used was thicker than that specified in4.1. A British Standard does not purport to include all the necessary provisions of a contract. Users of Bri

14、tish 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 cover, pagesi to iv, pages1to4, an inside back cover and a back cover. T

15、his standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.iv blankBS 3900-D6:1982 BSI 03-1999 1 0 Introduction This International Standard is one of a series of standards dealing with the sampli

16、ng and testing of paints, varnishes and related products. It should be read in conjunction with ISO1512, ISO1513, ISO1515, ISO2811 and ISO2814. ISO2814 gives a simple method for comparison of opacity of paints of the same type and colour, based on measurement of the contrast ratio of films drawn dow

17、n in a prescribed manner over black and white substrates. Alternative techniques for test film preparation and measurement are specified, namely: a) direct application to black and white charts, for example Morest charts; b) application to colourless, transparent polyester film, the coated film bein

18、g subsequently placed in turn over black and white glass tiles. Because different operators using the same draw-down device may obtain paint films differing significantly in thickness, the method given in ISO2814 is not satisfactory for absolute determination of opacity. Collaborative trials between

19、 groups of experts from a number of countries have shown that reproducible results can be obtained by determination of the contrast ratio corresponding to a precisely fixed spreading rate by interpolation between measurements at two or more measured film thicknesses. The spreading rate selected in t

20、his International Standard is20m 2 /l (wet film thickness504m), considered an average for brush application of a free-flowing paint on a smooth, non-porous surface. However, for particular types of paints normally used at other film thickness ranges, for example industrial enamels and printing inks,

21、 the interested parties may agree another fixed spreading rate. Further collaborative trials indicated that the highest reproducibility was obtained by spreading paint onto polyester film b) above, although the technique of spreading on and measuring a black and white card was simpler to operate. It

22、 was not considered appropriate to combine the two techniques as alternatives within one method as was done in ISO2814 because of the major difference in reproducibility. Accordingly, two separate methods have been prepared: this International Standard deals with application to polyester film, while

23、 ISO3905 deals with application to black and white charts. 1 Scope and field of application This International Standard specifies a method to be used for determining the opacity (by contrast ratio measurement) given by paint films of white or light colours of reflectance value greater than25%, appli

24、ed at a spreading rate of20m 2 /l to colourless transparent polyester film, the reflectance being measured subsequently over agreed black and white glass plates. 2 References ISO1512, Paints and varnishes Sampling. ISO1513, Paints and varnishes Examination and preparation of samples for testing. ISO

25、1515, Paints and varnishes Determination of volatile and non-volatile matter. ISO2811, Paints and varnishes Determination of density. ISO2814, Paints and varnishes Comparison of contrast ratio (hiding power) of paints of the same type and colour. ISO3905, Paints and varnishes Determination of contra

26、st ratio (opacity) of light coloured paints at a fixed spreading rate (using black and white charts). 3 Principle The method is based on the observation that contrast ratio is an approximately linear function of reciprocal film thickness, over a restricted film thickness range which also corresponds

27、 to that used for normal application of white or light coloured paints. It is thus possible to interpolate graphically or by computation between results on films of different thicknesses, with satisfactory accuracy. Because wet film thickness cannot be determined with sufficient accuracy, the method

28、 involves determination of surface density of the dry film and a calculation of the corresponding wet film thickness. In this latter calculation, values for wet paint density and percentage non-volatile matter content are required. Determination of these values by the methods complying with the rele

29、vant International Standards has been stipulated. However, it is recognized that for certain types of paint the non-volatile matter determination according to ISO1515 does not correspond exactly to the mass changes of a film during drying under the conditions of the present test method. Any errors i

30、n results introduced by this discrepancy should be common to all laboratories and should not affect comparisons of paints of similar types.BS3900-D6:1982 2 BSI 03-1999 4 Apparatus 4.1 Substrate Untreated, colourless transparent polyester film between30 and504m in thickness and of dimensions not less

31、 than100mm 150mm. The use of thicker film is permitted by agreement between the parties. 4.2 Film applicators A series of film applicators giving a range of uniform films of wet thicknesses approximately40 to604m is required. The film laid down shall be at least70mm wide, with areas of dimensions no

32、t less than60mm 60mm and of uniform thickness over the polyester film. The application of uniform films is facilitated by the use of automatic applicators which are recommended. 4.3 Reflectometer A photoelectric instrument giving within0,3% an indicated reading proportional to the intensity of light

33、 reflected from the surface under test, and having a spectral response approximating to the product of the relative spectral energy distribution of CIE Illuminant C or D65 and the colour matching function (2) of the CIE standard observer. The value measured is R y . NOTEIt is recognized that the rel

34、ative geometrical arrangement of the illuminating beam and the light detector can affect the measurement of R y , but it is considered that variations arising from this factor in commercial reflectometers should be considerably less than the reproducibility Figure stated in clause7. In the event of

35、dispute,0/diffuse geometry, excluding specular reflection, should be used. 4.4 Template or die stamp A metal template or die stamp of dimensions not less than60mm 60mm is suitable for accurate removal of a closely defined area from a piece of polyester film. 4.5 Test plates Black and white glass pla

36、tes, each with a plane, polished surface, of at least80mm 80mm. The reflectance of the white plate shall be80 2% when measured using a reflectometer complying with4.3, and that of the black plate not more than1%. Both the black and the white glass plates should be coated on the back and edges with l

37、ight-excluding paint or adhesive tape. 5 Sample Take a representative sample of the product to be tested as described in ISO1512. Examine and prepare the sample for testing as described in ISO1513. 6 Procedure 6.1 Preparation of substrate Prepare the polyester film for coating by one of the followin

38、g methods: a) spreading it on a flat glass plate, at least6mm thick, which has first been moistened with a few drops of white spirit just sufficient to hold the film in position by surface tension; ensure that none of the liquid wets the upper surface of the film and that no air bubbles are trapped

39、under it; or b) fixing it at one end and laying it over a flat rubber block (where spiral applicators are to be used). 6.2 Preparation of coated films Immediately before application, mix the paint thoroughly by vigorous stirring to break down any thixotropic structure, taking care not to incorporate

40、 air bubbles. Apply about2 to4ml of paint, according to the film thickness required, in a line across one end of the polyester film, and spread it immediately by drawing down a suitable applicator at a steady velocity to give a uniform layer. Prepare duplicate films with each of three different appl

41、icators, chosen to give a range of wet film thicknesses from approximately404m to approximately604m. Maintain the coated films in a horizontal position until dry, for example by taping the edges to a flat substrate. The drying time (and/or stoving conditions) will depend on the type of paint materia

42、l being tested, and should be agreed by the interested parties. 6.3 Conditioning Keep the dried coated films at23 2 C and a relative humidity of50 5% for at least24h and not more than168h before the reflectance measurements are made. 6.4 Measurement of reflectance factors Fix the coated film in turn

43、 over the white and black glass plates, introducing a few drops of white spirit between the underside of the film and the glass to ensure optical contact. Measure the reflectances of each coated film at a minimum of four positions over both the black and white plates, and calculate the average refle

44、ctance factorsR Band R Wrespectively. Then calculate the contrast ratio R B /R Wfor each coated film. yBS 3900-D6:1982 BSI 03-1999 3 6.5 Determination of surface density of the dry coating Remove the coated film from the glass plate, wipe the film free from white spirit and allow it to dry. By means

45、 of the metal template and a sharp knife or precision die stamp, cut equal areas of dimensions at least60mm 60mm, from the centres of the coated polyester films. Weigh the detached pieces to the nearest1mg. Remove the paint film by the use of a solvent which has been found to have no effect on the d

46、ried mass of the polyester film, and, after thorough drying, reweigh the film. NOTEAcetone or dichloromethane are usually suitable as solvents. In cases where the dry coating is resistant to them and a solvent with greater power is required, the effect of the solvent on the mass of uncoated polyeste

47、r should be determined. Calculate the surface density of the drying coating, A A , in grams per square millimetre, by the formula A A= where 6.6 Calculation of wet film thickness and spreading rate To calculate the wet film thickness from the surface density of the dry coating, it is necessary to kn

48、ow both the density of the wet paint, as obtained by the method described in ISO2811, and the non-volatile matter content by mass using the method described in ISO1515. 6.6.1 Wet film thickness Calculate the thickness of the wet paint film, t, in millimetres, using the formula where 6.6.2 Spreading

49、rate The spreading rate SR, in square metres per litre, is the reciprocal of the wet film thickness, in millimetres, and is given by the formula and, using the formula for surface density in6.5 above, 6.7 Determination of contrast ratio for a spreading rate of20m 2 /l It is assumed that for a limited range of film thickness the contrast ratio is a linear function of the spreading rate. Therefore, the values of contrast ratio and the corresponding spreading rates obtained for each of the six films should be plotted graphically and the contrast ra