EN 14370-2004 en Surface active agents - Determination of surface tension《表面活性剂 表面张力的测定》.pdf

1、BRITISH STANDARD BS EN 14370:2004 Surface active agents Determination of surface tension The European Standard EN 14370:2004 has the status of a British Standard ICS 71.100.40 BS EN 14370:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 1

2、 December 2004 BSI 1 December 2004 ISBN 0 580 44935 1 National foreword This British Standard is the official English language version of EN 14370:2004. The UK participation in its preparation was entrusted to Technical Committee CII/34, Methods of test for surface active agents, which has the respo

3、nsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “In

4、ternational Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a

5、 British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related internation

6、al and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 14, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last

7、 issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN14370 September2004 ICS71.100.40 Englishversion SurfaceactiveagentsDeterminationofsurfacetension AgentsdesurfaceDterminationdelatension superficielle GrenzflchenaktiveStoffeBestimmungd

8、er Oberflchenspannung ThisEuropeanStandardwasapprovedbyCENon1July2004. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnat

9、ional standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestat

10、usast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUn

11、itedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2004CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.EN14370:2004:EEN 14370:2004 (E) 2 Contents page

12、 Foreword. 3 1 Scope. 4 2 Normative references. 4 3 Principle. 4 4 Apparatus 4 5 Preparation of apparatus . 7 6 Sample preparation 8 7 Procedure 9 8 Expression of results. 10 9 Precision 12 10 Test report. 13 Bibliography . 14 EN 14370:2004 (E) 3 Foreword This document (EN 14370:2004) has been prepa

13、red by Technical Committee CEN/TC 276 “Surface active agents”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 2005, and conflicting national stand

14、ards shall be withdrawn at the latest by March 2005. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany,

15、 Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 14370:2004 (E) 4 1 Scope This document specifies test methods for the determination of surface tension of liqu

16、ids, particularly surface active agent solutions. The methods are suitable for determining the static surface tension of liquids, for example inorganic and organic liquids and solutions. 2 Normative references The following referenced documents are indispensable for the application of this document.

17、 For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 304, Surface active agents Determination of surface tension by drawing up liquid films 3 Principle The force, F, exerted either by the

18、surface tension on a plate which is brought vertically into contact with the liquid and is completely wetted by it (static method) or which is necessary to pull a horizontally suspended stirrup or ring out of the liquid surface (quasi-static method) is measured (see 1 and 2). The surface tension is

19、obtained by calculation (see Clause 8). In the static method, the plate is stationary so that an equilibrium value is obtained. The quasi-static method requires movement of the ring or stirrup. By using sufficiently small and slow changes in ring or stirrup position during the measurement, deviation

20、s from equilibrium are minimised. 4 Apparatus 4.1 Tensiometer The tensiometer shall be designed for a plate, stirrup or ring, and shall consist mainly of two parts: a) support for the sample vessel in the form of a small horizontal platform which can be moved up and down, for example using a microme

21、ter screw; b) apparatus for measuring the force exerted on the plate, stirrup or ring; the uncertainty of measurement shall not exceed 10 -6N, which corresponds to a maximum error of 0,1 mg in determining the mass. NOTE Instead of a torsion balance, a lever balance or an electronic balance (laborato

22、ry, analytical or microbalance) can be used as an alternative. To obtain higher efficiency and reproducibility, an automatic tensiometer incorporating a balance, motor- driven platform and evaluation unit should be used. 4.2 Plate The plate shall consist of platinum or platinum/iridium sheet. It sha

23、ll be about 20 mm long, about 0,2 mm thick and at least 10 mm high, and shall be roughened to improve its wetting power. NOTE Satisfactory roughening can be achieved by sandblasting, by rubbing with emery or by sintering a platinum black layer onto the platinum sheet. The plate shall be suspended at

24、 a point in the axis of symmetry. The platinum, platinum/iridium plate shall have an effective height of at least 10 mm to keep wetting errors as low as possible (see Figure 1). EN 14370:2004 (E) 5 4.3 Stirrups Stirrups shall be made of platinum or platinum/iridium wire. The measuring wire shall hav

25、e a diameter of (0,1 0,01) mm and a length of 10 mm to 40 mm; the two branches shall be at least 10 mm long. NOTE Two small platinum balls may be attached to the lower ends of these branches as counter-weights, or, alternatively, the lower ends may be joined by a platinum wire (see Figure 2 for an e

26、xample). Dimensions in millimetres Figure 1 Dimensions of plate Dimensions in millimetres Figure 2 Stirrup 4.4 Ring The ring shall consist of platinum or platinum/iridium wire with a thickness not greater than 0,4 mm and a mean circumference of 60 mm (for example: inner diameter 18,7 mm, outer diame

27、ter 19,5 mm). It shall be suspended horizontally from a wire loop on a metal rod, which joins it to the tensiometer (see Figure 3 for an example). EN 14370:2004 (E) 6 Dimensions in millimetres Key 1 Metal rod 2 Wire loop 3 Ring Figure 3 Measuring ring for the tensiometer 4.5 Sample vessel The sample

28、 vessel for the liquid under test shall be a glass vessel, which is suitable for use in a thermostat. It shall have a sufficient capacity for the liquid, which, if necessary, shall be protected from evaporation. It shall be constructed such that the temperature of the gas phase above the liquid can

29、also be kept constant by thermostat. There is no need to use a thermostat for measurement at room temperature. The sample vessel shall consist of a cylindrical glass container with an internal diameter of at least 45 mm, for use with the ring method, stirrup method or plate method. NOTE If a vessel

30、of less than 45 mm diameter needs to be used (for example, if only small amounts of sample are available), wall effects can cause an error in the surface tension measurement. The magnitude of this error depends on the distance between the wall of the vessel and the edge of the ring or stirrup. EN 14

31、370:2004 (E) 7 5 Preparation of apparatus 5.1 Cleaning Clean the glass vessels carefully, first by thorough preliminary cleaning using a suitable solvent, for example 2-propanol or propanone. Then rinse them repeatedly with freshly double distilled water and dry them. Clean and rinse the plates, sti

32、rrups or rings in the same manner, and then heat them briefly to incandescence in a methanol or ethanol flame (the latter may be preferred since it has a low vapour pressure and higher flash point), preferably a non-luminous natural gas flame, ensuring they are only heated to red heat and never to w

33、hite heat. NOTE Should the plates, stirrups or rings become contaminated with residues, for example from silicones or cationic surface active agents, it may be preferable to clean with a sulfo-chromic acid mixture or as specified in ISO 304. 5.2 Measurement preparation 5.2.1 Principle The zero setti

34、ng of the apparatus is checked, and the tensiometer is adjusted such that results can be reliably read off from the display as millinewtons per meter. 5.2.2 Levelling Level the apparatus by adjusting the screws at the foot of the apparatus using suitable aids, for example a spirit level placed on th

35、e tensiometer support. A protective covering against drafts may be used. NOTE The apparatus should be mounted via rubber feet on a stone slab of about 30 kg to avoid the effect of mechanical impact and vibration (for example building vibration). 5.2.3 Zero setting Adjust the zero point of the tensio

36、meter, taking into account the following: a) if a plate is used: the zero point of the apparatus shall be adjusted after mounting the plate in the air; b) if a stirrup is used: the zero point of the apparatus shall be adjusted at the depth of the immersed stirrup at which the maximum force is read o

37、ff. Such, no correction for the buoyancy due to the volume of the immersed connection wire or the two platinum balls is necessary (see 7.2). NOTE This can be achieved, for example, if, when reaching the maximum force, either the lamella spread from the measuring wire is destroyed, or if, without lam

38、ella formation, the tensiometer platform height corresponding to the maximum force is set with the micrometer screw (see 4.1 a); c) if a ring is used: the zero point of the apparatus shall be adjusted after mounting the ring in air. EN 14370:2004 (E) 8 5.2.4 Calibration procedure Calibrate the torsi

39、on balance using either of the following two methods: a) place riders of known mass between 0,1 g and 1 g on the plate, stirrup or ring. The method is time-consuming, but the potential error is very low. Use equation (1) to determine the apparatus factor, a , by which the measurement values shall be

40、 multiplied: a r a = (1) where l m r r g = (2) m r is the mass of the rider, in grams; g is the acceleration due to gravity (981 cm/s 2 ); l is the wetted periphery of the plate, stirrup or ring, that is twice the length plus twice the thickness of the plate, or twice the length of the stirrup test

41、wire, or twice the mean circumference of the ring, in centimetres; ais the tensiometer reading after the rider is placed on the plate, stirrup or ring, in millinewtons per metre; b) use pure substances whose surface tension is known exactly. The density of the pure calibration substance has to be th

42、e same as that of the sample fluid in order to avoid different buoyancy. This method is quicker, but less reliable. Use equation (3) to determine the apparatus factor, b , by which the measurement values shall be multiplied: g o b = (3) where ois the theoretical value of the surface tension, in mill

43、inewtons per metre; gis the measurement value of the surface tension, in millinewtons per metre. NOTE Automatic tensiometers can be calibrated via a potentiometer setting such that subsequent conversion of the readings is not necessary. 6 Sample preparation Use double distilled water to prepare aque

44、ous solutions. During measurements, keep the solution temperature constant to within 0,5 C at a value which ensures a homogeneous (single phase) solution at the given concentration; micelles shall not be considered as a separate phase in this context. If there is an upper miscibility limit (for exam

45、ple a cloud point with aqueous ethylene oxide adducts), choose a temperature below this limit for the measurements. Always choose a measurement temperature EN 14370:2004 (E) 9 suited to the respective problem. Measurements at room temperature are the least problematic. Thermostat the sample in the a

46、pparatus during measurement using a thermostating jacket. NOTE 1 A difference in temperature of 1 C causes a change of at least 0,1 mN/m; with pure water, the following relationship applies: C m mN, = T 15 0(4) Since the surface tension of solutions changes with time and the effect of the chemical n

47、ature of the surface active agent, its concentration and its adsorption capacity are of importance in these changes, it is not possible to specify an exact time to begin the measurement procedure. It is therefore be necessary to measure the surface tensions repeatedly as a function of time and thus

48、of the age of the surface. After a time, which is characteristic of each system, no more changes in surface tension are observed, since equilibrium has been established. NOTE 2 For time-dependent measurements, the static method using a plate will be the method of choice. If automatic tensiometers are used, quasi-static and static measurements can be recorded as a function of time, for example, using x/t recorders. The surfaces of surface active agent solutions are extremely sensitive to contamination due to atmospheric dust or solvent vap