BS 2782-7 Method 740C-1996 Methods of testing plastics - Rheological properties - Polymer dispersions - Determination of white point temperature and minimum film-forming temperatur.pdf

1、BRITISH STANDARD BS 2782-7: Method 740C:1996 ISO 2115:1996 Methods of testing Plastics Part 7: Rheological properties Method 740C: Polymer dispersions Determination of white point temperature and minimum film-forming temperature ICS 83.080BS2782-7:Method 740C:1996 This British Standard, having been

2、prepared under the directionof the Sector Board forMaterials and Chemicals, waspublished under the authorityof the Standards Boardand comes into effect on 15July1996 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference PRI/21 Draft for comment 93/302775DC

3、 ISBN 0 580 25990 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/21, Testing of plastics, upon which the following bodies were represented: British Apparel and Textile Confederation British Plastics Federation Depa

4、rtment of the Environment (Building Research Establishment) Department of Trade and Industry (National Physical Laboratory) Electrical and Electronic Insulation Association GAMBICA (BEAMA Ltd.) Institute of Materials Ministry of Defence Packaging and Industrial Films Association PIRA International R

5、APRA Technology Ltd. Royal Society of Chemistry Amendments issued since publication Amd. No. Date CommentsBS2782-7:Method740C:1996 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Principle 1 5 Apparatus 1

6、 6 Procedure 2 7 Expression of results 4 8 Precision 4 9 Test report 4 Figure 1 Diagram of test apparatus given as an example 3 Figure 2 Example of a film spreader for a channelled plate 4 List of references Inside back coverBS2782-7:Method740C:1996 ii BSI 11-1999 National foreword This Method of BS

7、2782-7has been prepared by Technical Committee PRI/21and is identical with ISO2115:1996 Plastics Polymer dispersions Determination of white point temperature and minimum film-forming temperature, published by the International Organization for Standardization (ISO). The Technical Committee has revie

8、wed the provisions of the latest drafts of ISO12000 1)and ISO842to which normative reference is made in the text and has decided that they are acceptable for use in conjunction with this standard. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Se

9、rvices, BSI,389Chiswick High Road, London, W44AL. 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 obli

10、gations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1to4,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

11、inside front cover. Cross-references International Standard Corresponding British Standard ISO 123:1985 BS 6057 Rubber latices Part 2:1987 Sampling (Identical) 1) It is envisaged that upon publication ISO12000will be implemented in the UK by the publication of BS2782-7:Method740A.BS2782-7:Method 740

12、C:1996 BSI 11-1999 1 1 Scope This International Standard specifies a method for the determination of the “white point” temperature and the minimum film-forming temperature of polymer dispersions. 2 Normative references The following standards contain provisions which, through reference in this text,

13、 constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editio

14、ns of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 123:1985, Rubber latex Sampling. ISO 842, Raw materials for paints and varnishes Sampling 2) . ISO 12000, Plastics/rubber Polymer dispersions and rubber latices (natural and

15、 synthetic) Definitions and review of test methods 3) . 3 Definitions For the purposes of this International Standard, thefollowing definitions apply. 3.1 polymer dispersion polymeric material finely dispersed in a liquid phase, which is usually water. During drying, the liquid evaporates and as a r

16、esult the tiny particles are forced closer together until they touch each other depending on the type of polymer, the temperature and the possible influence of any auxiliaries present, the particles when spread out in a thin layer on a substrate interact to form either a discontinuous opaque white m

17、ass in which the polymer particles are not fused together if the temperature is insufficient to allow coalescence of the particles; or a continuous transparent layer in which the particles combine to form a homogeneous film if the temperature conditions are sufficient to allow coalescence of the par

18、ticles. NOTE 1Coalescence means uniting of particles at least partly by interpenetration of the polymer chains. 3.2 white point temperature the temperature limit below which an opaque mass, and above which a transparent film, is formed 3.3 minimum film-forming temperature the temperature limit above

19、 which a continuous homogeneous film without cracks is observed NOTE 2The white point temperature always lies a few degrees Celsius below the minimum film-forming temperature. 4 Principle A polymer dispersion is dried at a suitable temperature gradient with a current of moisture-free air and the tem

20、perature at which thecoalesced (transparent) section of the film meetsthe uncoalesced (white) section is determined. NOTE 3The required temperature gradient is obtained by applying a hot source and a cold source at some distance from each other to a metal plate (aluminium, stainless steel or copper)

21、 which may be either perfectly level and smooth or which may be channelled between the cold source and the hot source. NOTE 4To determine the film-forming temperature, one or more layers, of defined thickness, of the polymer dispersion are spread on the surface of the smooth plate or introduced into

22、 the shallow channels (starting at the end nearest the hot source). 5 Apparatus 5.1 Test apparatus (see Figure 1 for an example), consisting essentially of a rectangular plate (1) 4)which could be made for instance of aluminium, stainless steel or copper, with a thickness sufficient to guarantee a l

23、inear temperature gradient. The surface of the plate may either be perfectly smoothand polished or contain several shallow channels (5) four, for example 0,3mm deep 5) . NOTE 5To facilitate cleaning, the plate may be covered for instance by a thin aluminium foil (e.g.0,02mm thick) which is brushed o

24、n smooth with a brush and/or piece of soft felt. A few drops of glycerol between the plate and the foil promote thermal contact. The required temperature gradient may be achieved by using at one end of the plate a rheostat-controlled electrical resistance (2) as the hot source. At the other end is t

25、he cold source, consisting either of an insulated (7) container (3) holding refrigerant or of a coil inserted into the end of the plate and through which refrigerant is circulated. 2) To be published. (Revision of ISO842:1984) 3) To be published. 4) Numbers in parentheses are references to parts of

26、the apparatus shown in Figure 1. 5) Tests with smooth and channelled plates have given identical results for each of a number of different dispersions.BS2782-7:Method 740C:1996 2 BSI 11-1999 To measure the temperature gradient of the plate when equilibrium has been reached, the plate is equipped alo

27、ng its edges with evenly spaced holes(4) into which thermometers can be inserted. The first hole (10) shall be positioned at the cold end of the plate at right angles to the beginning of the channels (i.e.the beginning of the layers of dispersion). The last hole shall be near the hot source, with th

28、e other holes evenly spaced in between. The layers of dispersion, or the dispersion in the channels, is dried by directing a slight current of dry air (dried, for example, by passing it through a column packed with calcium chloride) at room temperature over the test sample(s), from the cold end to t

29、he hot end. Provision shall be made for placing a glass cover (6) above the plate, leaving a narrow gap through which the air stream can pass from one end to the other. 5.2 Temperature-measurement devices, with an accuracy of 0,1 C within the expected temperature range, predominantly between10 C and

30、+50 C. Mercury-in-glass thermometers and thermocouples which can be inserted into the holes in the plate aresuitable. Other possibilities are contact or non-contact surface thermometers or salts with defined melting points to determine the temperature gradient of the plate. 5.3 Film applicator or dr

31、awdown instrument, made of inert materials such as stainless steel or plastic, capable of producing simultaneously or successively films in the channels of a channelled plate (seeFigure 2) or films about 0,1mm thick and20mm to25mm wide on a smooth plate. NOTE 6Suitable instruments for determining th

32、e white point or the minimum film-forming temperature are available on the market. 6 Procedure 6.1 Establishment of temperature gradient Put in place the temperature-measurement devices(5.2). Adjust the temperatures of the hot source (2) and the cold source (3) to establish a suitable gradient for t

33、he test sample (polymer dispersion), such that: a) the “white point” temperature to be determined occurs in the centre section of the plate; b) the temperature range between the two extreme temperature-measurement devices (thatis between the hot and cold source) is between20 C and40 C and remains co

34、nstant during the test. The temperature gradient between the two extremetemperature-measurement devices shall beas close as possible to linear,i.e.the temperaturedifferences between successive temperature-measurement devices shall all be of the same order. The determination can be performed as soon

35、as thermal equilibrium is reached,i.e.when the temperature-measurement devices show no further variation. 6.2 Determination Apply the test sample (polymer dispersion) in a uniform layer to the top of the plate, starting from the end with the highest temperature. In the case of a channelled plate, po

36、ur into the channels, at the higher-temperature end, a quantity of the sample slightly in excess of the total capacity of the channels. Spread the material along the channels and remove the surplus with the film applicator. In case of a smooth plate, apply strips of the test sample, starting at the

37、higher-temperature end of the plate. Use a film applicator to achievethe desired layer dimensions, i.e.thickness 0,1mm and width approximately20mm to25mm. In both cases, replace the cover (6) and direct under this, from the cold end to the hot end, a current of dry air at room temperature and at a l

38、ow, constant rate of flow. Wait until there is complete separation of the section transformed into film (transparent, without cracks) and the non-coalesced section (white). Measure the distance between the first point of temperature measurement (10) and the line of separation. Note the temperatures

39、indicated by the various temperature-measurement devices in or on the plate. Plot a graph using distance intervals between devices as the abscissae and the plate temperatures as the ordinates. Determine the temperatures for the “white point” (the borderline between the white mass and the transparent

40、 film); the “minimum film-forming temperature” (thelowest temperature where a continuous, homogeneous film without cracks is formed).BS2782-7:Method 740C:1996 BSI 11-1999 3 Figure 1 Diagram of test apparatus given as an example (the plate in this diagram is channelled but this feature is not essenti

41、al)BS2782-7:Method 740C:1996 4 BSI 11-1999 If a surface thermometer is used, the white point and the minimum film-forming temperature can be determined directly by reading the scale of the instrument. NOTE 7If the temperature gradient is linear, it is unnecessary to plot a graph since the result wou

42、ld be a straight line. Carry out the determination at least in duplicate. If the difference between the determinations exceeds2 C, discard the results and repeat the test. 7 Expression of results Record the temperatures obtained from the graphs or directly from the surface thermometer. Calculate the

43、 mean of the individual results, rounding to the nearest degree Celsius. 8 Precision Following accurately the procedure specified, it is possible to attain the following: a) repeatability: 2 C; b) reproducibility: 4 C. 9 Test report The test report shall contain at least the following information: a

44、) a reference of this International Standard; b) sufficient information to identify completely the polymer dispersion tested; c) the type of test apparatus used and the test conditions; d) the laboratory temperature; e) the results of the test, expressed as values for the “white point temperature”,

45、the “minimum film-forming temperature”; f) any deviations from the procedure specified; g) any unusual features noted during the test; h) the date and place of the test. Figure 2 Example of a film spreader for achannelled plateBS2782-7:Method740C:1996 BSI 11-1999 List of references See national fore

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