1、 ISO 2013 Guidelines for the characterization of dispersion stability Lignes directrices pour la caractrisation de la stabilit des dispersions TECHNICAL REPORT ISO/TR 13097 First edition 2013-06-15 Reference number ISO/TR 13097:2013(E) ISO/TR 13097:2013(E)ii ISO 2013 All rights reserved COPYRIGHT PR
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4、E) ISO 2013 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 T erms and definitions . 1 3 Basics of stability . 3 3.1 Stability Summary 3 3.2 Characteristic features with regard to dispersion stability 4 3.3 Alteration of the state of a dispersion . 4 4 Characterizing t
5、he change of the state of a dispersion . 6 4.1 General comments . 6 4.2 Direct methods 7 4.3 Correlative methods . 8 4.4 Procedures to accelerate the evaluation of long-term stability 8 5 Prediction of the shelf life of a dispersion 10 5.1 General comments 10 5.2 Comparative analysis 10 5.3 Predicti
6、ve analysis 10 Annex A (informative) A compilation of relevant international and national standards 12 Bibliography .14 ISO/TR 13097:2013(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prepa
7、ring International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in l
8、iaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC
9、Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives Attention is drawn to the possibility that som
10、e of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declara
11、tions received. www.iso.org/patents Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. The committee responsible for this document is ISO/TC 24, Particle characterization including sieving, Subcommittee SC 4, Particle charac
12、terization.iv ISO 2013 All rights reserved ISO/TR 13097:2013(E) Introduction Stability with respect to changes in relevant product specifications and product performance is important in industry and for end users. Various terminologies are used to reflect different phenomena as well as different use
13、r perspectives. In the literature and in practice, one frequently finds terms such as dispersion, suspension or emulsion stability, demixing or separation stability, sedimentation or creaming stability, physical stability, colloidal stability, and kinetic stability. This Technical Report focuses on
14、instability driven by thermodynamics and does not include phenomena that are due too, e.g., radiation, chemical or enzymatic reactions 1)or are related to the growth/metabolism of biological organisms like bacteria. These phenomena are often described as photo, UV or irradiation stability, thermal o
15、r chemical stability of one or the other constituent, enzymatic or microbial stability, etc. The Technical Report concerns general aspects of stability test methods, acceleration procedures and data evaluation. In addition, recommendations of instrument manufacturer, information from the scientific
16、or user community as well as from regulatory bodies are intended to be taken into account. 1) Chemical and physical properties are often interrelated. ISO 2013 All rights reserved v Guidelines for the characterization of dispersion stability 1 Scope This Technical Report addresses the stability char
17、acterization of liquid dispersions (suspensions, emulsions, foams and mixtures thereof) for applications, such as new product design, optimization of existing products, quality control during processing and during usage of the product. The stability of a dispersion in the sense of this Technical Rep
18、ort is defined in terms of the change in one or more physical properties over a given time period. Stability can be either monitored (determined) in real time or predicted on the basis of physical quantities related to stability. In the case of very stable dispersions, procedures that accelerate the
19、 changes under consideration or accelerated aging tests administered over a shorter time scale can be appropriate. Shelf life can be estimated based on the observed rate of the change in the physical property and the user-required specifications for the product. Guidelines are given for choosing rel
20、evant measurements that can be used for the ranking, identification and quantification of instability. 2 T erms a nd definiti ons For the purposes of this document, the following terms and definitions apply. 2.1 agglomeration assembly of particles in a dispersed system into loosely coherent structur
21、es that are held together by weak physical interactions Note 1 to entry: Agglomeration is a reversible process. Note 2 to entry: Synonymous with coagulation and flocculation. SOURCE: ISO 14887:2000, 13.1, modified text altered; IUPAC Gold Book, 2modified 2.2 aggregation assembly of particles into ri
22、gidly joined structures Note 1 to entry: Aggregation is an irreversible process. Note 2 to entry: The forces holding an aggregate together are strong, for example covalent bonds or those resulting from sintering or complex physical entanglement. Note 3 to entry: In common use, the terms aggregation
23、and agglomeration are often applied interchangeably. SOURCE: ISO 14887:2000, 13.2, modified text has been altered; ISO 26824 3 2.3 coalescence disappearance of the boundar y bet ween t wo particles (usually droplets or bubbles) in contact, or bet ween one of these and a bulk phase followed by change
24、s of shape leading to a reduction of the total surface area Note 1 to entry: The flocculation of an emulsion, namely the formation of aggregates, may be followed by coalescence. SOURCE: IUPAC Gold Book 2 TECHNICAL REPORT ISO/TR 13097:2013(E) ISO 2013 All rights reserved 1 ISO/TR 13097:2013(E) 2.4 cr
25、eaming rise (separation) of the dispersed phase in an emulsion due to the lower density of the dispersed phase (droplets) compared to the continuous phase Note 1 to entry: Creaming velocity has a negative sign as particle movement is opposite to the acting force. 2.5 dispersion in general, microscop
26、ic multi-phase system in which discontinuities of any state (solid, liquid or gas: discontinuous phase) are dispersed in a continuous phase of a different composition or state Note 1 to entry: If solid particles are dispersed in a liquid, the dispersion is referred to as a suspension. If the dispers
27、ion consists of two or more liquid phases, it is termed an emulsion. A suspoemulsion consists of both solid and liquid phases dispersed in a continuous liquid phase. SOURCE: Hackley et al. 4 ; IUPAC Gold Book, 2modified 2.6 dispersion stability ability to resist change or variation in the initial pr
28、operties (state) of a dispersion over time, in other words, the quality of a dispersion in being free from alterations over a given time scale Note 1 to entry: In this context, for instance agglomeration or creaming represents a loss of dispersion stability. SOURCE: IUPAC Gold Book 2 2.7 f lo c c u
29、l at ion assembly of particles in a dispersed system into loosely coherent structures that are held together by weak physical interactions Note 1 to entry: The term flocculation is used frequently to denote agglomeration facilitated by the addition of a flocculating agent (e.g. a polyelectrolyte). N
30、ote 2 to entry: See 2.1. 2.8 f lot at ion migration of a dispersed solid phase to the top of a liquid continuous phase, when the effective particle density is lower relative to the continuous phase density Note 1 to entry: It may be facilitated by adhering gas bubbles, for example dissolved air flot
31、ation, or the application of lipophilic surfactants (e.g. in ore processing). 2.9 particle minute piece of matter with defined physical boundaries Note 1 to entry: A physical boundary may also be described as an interface. Note 2 to entry: A particle may move as a unit. SOURCE: ISO 14644-5:2004, 53.
32、1.7, modified Note 1 is different and Note 2 has been added; ISO/TS 27687:2008, 6modified Notes 1 and 2 have been altered and Note 3 has been deleted. 2.10 Ostwald ripening dissolution of small particles and the redeposition of the dissolved species on the surfaces of larger particles Note 1 to entr
33、y: The process occurs because smaller particles have a higher surface energy, hence higher total Gibbs energy, than larger particles, giving rise to an apparent higher solubility.2 ISO 2013 All rights reserved ISO/TR 13097:2013(E) SOURCE: IUPAC Gold Book 2 2.11 phase inversion phenomenon whereby the
34、 phases of a liquid-liquid dispersion (emulsion) interchange such that the dispersed phase spontaneously inverts to become the continuous phase and vice versa, under conditions determined by the system properties, volume ratio and energy input SOURCE: Yeo et al. 7 2.12 phase separation process by wh
35、ich a macroscopically homogeneous suspension, emulsion or foam separates into two or more new phases SOURCE: Yeo et al. 7 2.13 sedimentation settling (separation) of the dispersed phase due to the higher density of the dispersed particles compared to the continuous phase. The accumulation of the dis
36、persed phase at the bottom of the container is evidence that sedimentation has taken place Note 1 to entry: In the case of a dispersed liquid (emulsion), droplets can sediment if their density is higher than that of the continuous liquid phase (e.g. water in oil emulsion). SOURCE: IUPAC Gold Book 2
37、2.14 shelf life recommended time period during which a product (dispersion) can be stored, throughout which the defined quality of a specified property of the product remains acceptable under expected (or specified) conditions of distribution, storage, display and usage SOURCE: Gyeszly 8 3 Basics of
38、 stability 3.1 Stability Summary Stability is the capacity of a dispersion to remain unchanged with respect to predefined stability criteria over a given time under stated or reasonably expected conditions of storage and use. It depends therefore on the application. For instance a cosmetic emulsion
39、may be considered stable if no oil phase formation is observed during a period of three years. On the other hand, natural fruit juice can exhibit pulp settling without any reduction in quality. There is no universal method or technique to quantify all stability aspects due to the complexity of stabi
40、lity related phenomena. Therefore, it is always necessary to define: a) stability metrics: properties of the state or behaviour of a dispersion which should be monitored according to the demanded specific product qualities. b) stability criteria: deviations from the initial properties at production
41、date, which are acceptable. Shelf life is defined in terms of the alteration of stability metrics. In general, faster alteration leads to shorter shelf life. In order to meet the predefined stability criteria of very stable products, analytical techniques having high resolution/sensitivity need to b
42、e used and procedures can be required in order to accelerate the alteration. However, because of the interrelated physical, physico-chemical and chemical properties of a liquid dispersion, adequate acceleration methods should be chosen and validated in the context of a specific product. ISO 2013 All
43、 rights reserved 3 ISO/TR 13097:2013(E) 3.2 Characteristic features with regard to dispersion stability Generally speaking, dispersions are thermodynamically unstable. 9However, for a dispersed system, the rate of change in its state may be acceptably low and therefore it exhibits kinetic stability.
44、 Kinetic stability may be improved by electrostatic, steric or electrosteric stabilization, or particle coating, as well as by pickering or rheological additives to the continuous phase. The state of dispersion stability depends upon numerous interrelated physical, physico-chemical and chemical para
45、meters, and its nature is therefore complex. The parameters may be categorized as follows: a) volume or mass concentration of dispersed phase (e.g. spatial homogeneity, diluted or concentrated); b) state of the continuous phase (e.g. density, viscosity, surface tension, chemical potential, quality o
46、f solvent); c) state of the dispersed phase (e.g. size, shape and density distribution, as well as viscosity of droplets, deformability of particles, structure of particulate surface); d) interaction between particles/droplets (e.g. electrostatic and van der Waals force, steric and depletion force);
47、 e) interaction between dispersed and continuous phase (e.g. wettability, interfacial tension, surface and volume rheology, solubility, dissolvability, network formation). The volume concentration of the dispersed phase of a dispersion is one of the primary requirements of any product design and it
48、should be homogenous within the entire product during the entire life span. In general, the higher the volume concentration, the higher the physical stability (e.g. less phase separation). Formulators have to achieve product specifications and sufficient dispersion stability as demanded by the appli
49、cation or customer. This is accomplished by choosing the state of the dispersed phase (e.g. size distribution, shape, density match, restrictions to oversize, surface charge and coating) and the appropriate behaviour of the continuous phase. Traditionally, electrostatic stabilization has been principally used. Today, polymeric additives are commonly employed to tailor properties of the continuous phase of innovative products. Two essential aspects with regard to dispersion stability are particle-particle interactions
