1、March 2010 Translation by DIN-Sprachendienst.English price group 14No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS
2、19.120!$rd“1617965www.din.deDDIN ISO 14887Sample preparation Dispersing procedures for powders in liquids (ISO 14887:2000)English translation of DIN ISO 14887:2010-03Probenvorbereitung Verfahren zur Dispergierung von Pulvern in Flssigkeiten (ISO 14887:2000)Englische bersetzung von DIN ISO 14887:2010
3、-03Prparation de lchantillon Procdures pour la dispersion des poudres dans les liquides (ISO 14887:2000)Traduction anglaise de DIN ISO 14887:2010-03www.beuth.deIn case of doubt, the German-language original shall be considered authoritative.Document comprises 28 pages02.10 DIN ISO 14887:2010-03 2 Co
4、ntents Page National foreword 3 Introduction 4 1 Scope 5 2 Normative reference 5 3 Terms and definitions .5 4 Symbols and abbreviated terms 6 5 Examination of the dry powder 7 6 Selection of a liquid and trial dispersion 7 7 Examination of the dispersion .8 8 Identification of possible dispersing ag
5、ents . 10 9 Optimization of the dispersion method 16 10 Maintenance of dispersion stability during sample handling 19 Annex A (informative) Alternative dispersion-stability tests. 20 Annex B (informative) Commercial dispersing agents in the various dispersing agent categories 22 Bibliography. 27 A c
6、omma is used as the decimal marker. DIN ISO 14887:2010-03 3 National foreword This standard has been prepared by Technical Committee ISO/TC 24 “Sieves, sieving and other sizing methods”, Subcommittee SC 4 “Sizing by methods other than sieving”. The responsible German body involved in its preparation
7、 was the Normenausschuss Bauwesen (Building and Civil Engineering Standards Committee), Working Committee NA 005-11-42 AA Partikelmesstechnik (Sp ISO/TC 24/SC 4). A discussion of various terminological issues is necessary. First, it is apparent that the term “dispersion” differs in meaning in German
8、 and English. In German the overall designation “Dispersion” referring to material systems having a solid dispersion phase and a liquid continuous phase has not found wide acceptance up to now. Rather, the term “disperses System” as defined in the German terminology standard DIN 66160:1992-09 is mor
9、e frequently used, as are the terms “Suspension”, “Schlamm”, “Schlicker” and “Paste”, depending on the application. In the international use of the term “dispersion” a clear distinction does not seem to be made between the manufacturing of a dispersion and the action of changing states. In German th
10、is distinction is made more clear by the different terms “Dispergieren/Dispergierung”. Therefore, in the German version of this standard the (fluid) dispersion system is always designated a “Suspension” and the act of making and handling such systems is termed “Dispergierung”. Difficulties can also
11、occur in the use of the term “agglomerate”, which in the present standard is clearly distinguished from the term “aggregate” in the “Terms and definitions” clause, although this term is not used again in the text. In the meantime, definitions of the two terms as defined here have been laid down in t
12、he document DIN CEN ISO/TS 27687:2008. The general term “clump” is translated in the German version as the more understandable, but non-standard term “Zusammenballung” in its more general sense. Attention is drawn to the possibility that some of the elements of this document may be the subject of pa
13、tent rights. DIN (and/or DKE) shall not be held responsible for identifying any or all such patent rights. DIN ISO 14887:2010-03 4 Sample preparation Dispersing procedures for powders in liquids Introduction The evaluation of particle size distribution is of crucial importance for research projects,
14、 product development, process control, quality control, and other technical activities where particle size effects are important. Paints, inks, filled plastics, ore processing, pharmaceuticals, agricultural and cosmetic products depend on accurate particle size analysis for their commercial producti
15、on. A typical powder is composed of clumps of “primary“ particles that are held together by weak or strong forces. The size of clumps remaining after the powder has been wetted into a liquid depends in part on how much energy has been expended in breaking up these clumps. Since a clump responds to m
16、ost particle sizing methods as a large particle would, the presence of clumps in incompletely dispersed samples skews the reported particle size distribution to larger sizes than if all the clumps were broken up. A particle size analysis is useful only if the sample is prepared so that the particles
17、 are in a well-defined degree of dispersion, preferably one in which most clumps are fully deagglomerated and in which the particles do not reagglomerate or adhere to the walls of the sample container during the time required for analysis. While “complete“ dispersion to primary particles is often de
18、sired, it is important to remember that in many cases the most useful information is obtained when the sample is not fully dispersed. For example, if a customer blends the powder into a liquid using a low-shear process that does not break moderately strong bonds in the clumps, the quality control te
19、sts for powder intended for that customer should use similarly low shear during sample preparation and analysis. Because of the impurities present, the equipment available for breaking up clumps, the methods used for particle size analysis, and the dispersing agents available for testing may vary fr
20、om one site to another, the procedure developed at one site by applying the guidelines in this International Standard may differ from (but be as valid and as useful as) that developed at another site for the same powder. A list of references for further study, including standards for evaluation of s
21、ome of these more complex systems, is given in the bibliography. Annex A discusses some of the complications that arise when the powder has a surface treatment or soluble components; when the liquid contains ionic or polymeric solutes; when the dispersing agent contains minor ingredients. Annex B co
22、vers the classification of commercial dispersing agents in the various dispersing agent categories. DIN ISO 14887:2010-03 51 Scope This International Standard was developed to help particle size analysts make good dispersions from powder/liquid combinations with which they are not experienced. It pr
23、ovides procedures for wetting a powder into a liquid; deagglomerating the wetted clumps; determining if solution composition can be adjusted to prevent reagglomeration; selecting dispersing agents to prevent reagglomeration; evaluating the stability of the dispersion against reagglomeration. This In
24、ternational Standard is applicable to particles ranging in size from approximately 0,05 to 100 m. It provides a series of questions on the nature of the powder and liquid involved. The answers are used with charts that guide the user to generic dispersing agents that are likely to be suitable for di
25、spersing the powder in the liquid. This International Standard applies only to the preparation of simple, dilute dispersions (less than 1 % by volume solids) for particle size analysis. It does not deal with the formulation of complex and commercial mixtures highly loaded with solids, such as paints
26、, inks, pharmaceuticals, herbicides and composite plastics. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of
27、these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document refer
28、red to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 8213:1986, Chemical products for industrial use Sampling techniques Solid chemical products in the form of particles varying from powders to coarse lumps. 3 Terms and definitions For the purpose
29、s of this International Standard, the following terms and definitions apply. 3.1 agglomerate assemblage of particles which are loosely coherent SEE floc (3.5) 3.2 aggregate assemblage of particles rigidly joined together NOTE Because of the confusion which exists in the use of the above terms they a
30、re used sparingly throughout the text. DIN ISO 14887:2010-03 6 3.3 clump assemblage of particles which are either rigidly joined or loosely coherent 3.4 critical micelle concentration CMC concentration of dispersing agent above which micelles will form 3.5 floc assemblage of particles which are very
31、 loosely coherent SEE agglomerate (3.1) 3.6 primary particles units that are to be measured in the particle size analysis, in general harder to break than clumps 3.7 Tyndall effect light scattered perpendicular to a beam of light passing through a liquid that contains particles 4 Symbols and abbrevi
32、ated terms For the purposes of this International Standard, the following symbols and abbreviations apply. SVVolume-specific surface area (m2/kg) CMC Critical micelle concentration (mol/m3) IS Ionic strength (mol/m3)N1)M1,3Complete 1-th moment of the density distribution of particle volume PEO Polye
33、thoxy = (-CH2-CH2-O-)n PPO Polyisopropoxy = (-CH2-CH(CH3)-O-)npHisopH at which the zeta potential is zero for an amphoteric surface (which is positively charged at lower pH and negatively charged at higher pH) pKapH at which half the hydrogen ions from acid groups are ionized pKbpH at which half the
34、 hydroxide ions from base groups are ionized 3,iq Density distribution of particle volume xiUpper particle size of the i-th particle size interval (m) m Micrometer Zeta potential V Registered trade name. N1) National footnote: 2ii21IS zc=(NIST Special Publication 960-3). DIN ISO 14887:2010-03 75 Exa
35、mination of the dry powder 5.1 Sampling Sampling shall comply with the requirements specified in ISO 8213, unless a method specified in a national standard or mutually agreed upon by the analyst and client takes precedence. Sample preparation shall always be done consistently so that repeated prepar
36、ations based on replicate samples of a batch of powder (which was carefully mixed before being sampled or subdivided into samples) give closely comparable results. 5.2 Clump size range and particle size range Sprinkle the dry powder on a microscope slide and examine it using an optical microscope at
37、 200 magnification or other suitable magnification. Put a cover glass over the powder on the microscope slide and tap the cover glass lightly with a spatula (take care to avoid breaking the cover glass) to see how easy it is to crush the clumps. Note the approximate size range of the clumps that are
38、 not broken up by such crushing. If the majority of the particles are smaller than 1 m, use a transmission or scanning electron microscope to observe and characterize the particles. 5.3 Shape and surface roughness; their variation with size Note whether the surfaces of the fundamental particles are
39、spherical or crystalline, smooth or rough, porous or nonporous. Determine whether all the sizes of particle have the same morphology. If the particles are very rough or porous, obtain an experimental measure of the volume-specific surface area (m2/kg). If this value is large compared to the area com
40、puted for spheres with the powders particle size distribution then an unusually large amount of dispersing agent (compared to a similar size distribution of spherical nonporous particles) may be required to stabilize the dispersion. NOTE The volume-specific surface area of spheres may be calculated
41、from 1,36VSM= (equation 35 in ISO 9276-2) where 1, 3 3 ,11lnniiiixMqx=(equation 31 in ISO 9276-2) 6 Selection of a liquid and trial dispersion 6.1 Selection of a liquid The analyst shall list the liquids that are commonly used for dispersing the solids for the selected method of particle size analys
42、is and shall strike from the list any that fail to satisfy the following criteria. If the method is sedimentation, the liquid shall have a specific gravity that differs sufficiently from that of the powder to permit the use of this method. If the method is light scattering, the liquid shall have a r
43、efractive index (at the analytical wavelengths) that differs sufficiently from that of the powder to permit the use of this method. The liquid shall have negligible reactivity with the powder. The liquid shall not swell or shrink the particles by more than 5 % in diameter. The liquid shall provide a
44、 solubility of less than 5 g of powder per 1 kg of liquid. DIN ISO 14887:2010-03 8 NOTE This is to minimize Ostwald ripening that could cause the particle size distribution to change during the measurement time. The liquid shall have a change in the solubility (for the powder) with temperature of le
45、ss than 0,1 mg/l per kelvin, or the temperature shall be controlled throughout the preparation and analysis to keep the solubility from changing by more than 0,5 mg/l. NOTE If the particle size analysis method requires 10 mg of powder dispersed in 1 litre of liquid, a temperature rise of 5 K (from a
46、n ultrasonic probe or particle-analysis instrument warmth) would cause the dissolution of 1 mg or 10 % of the powder. 6.2 Preparation of a test paste of the powder Put two drops (or 0,1 g) of the liquid on an etch-roughened glass plate (“frosted“ glass). Blend in a roughly equal amount of powder by
47、sprinkling powder on the liquid surface and rubbing it into the liquid using a circular motion of a 10 mm wide spatula, applying a moderate amount of pressure (sufficient to read 1 kg on the scale of a balance). The objective is to wet all the powder surfaces and to break up all clumps of powder int
48、o primary particles. The high concentration of solids provides crowded conditions that favour collision between clumps and breakup into primary particles. These crowded conditions will also favour flocculation unless the particles repel one another. 6.3 Preparation of a dilute dispersion of the powd
49、er Make a dilute dispersion (4 % by mass) from the concentrated paste by adding a few drops at a time of the liquid and blending in with the spatula until 50 drops (about 2,5 g) of liquid have been added. This quantity should be sufficient for examination with a microscope. If a larger quantity is required for other types of test, the analyst shall follow the instructions given in 7.2. 7 Examination of the dispersion 7.1 Evaluate for under- or over-grinding Examine the dilute dispersion using an optical microscope (for particle
