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1、INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXAYHAPOAHAR OPrAHM3AMR I-IO CTAHAAPTHSAMM Pi , y-q - 3; ” yj; : ;k.f ; .t .I ,;, y! ,$ ?yj. $, .$.A.,i , l Glass - Viscosity and viscometric fixed points - Part 8 : Determination of (
2、dilatometric) transformation temperature IS0 7884-8 First edition 1987-12-15 Reference number IS0 7884-8 : 1987 (E) Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 08:40:59 MDTNo
3、 reproduction or networking permitted without license from IHS -,-,- Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technic
4、al 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, govern- mental and non-governmental, in liaison with ISO, also take part in the work. Draft International Stand
5、ards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approval by the member bodies voting. International Standard IS
6、0 7884-8 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and related apparatus. Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwis
7、e stated. 0 International Organization for Standardization, 1997 l Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 08:40:59 MDTNo reproduction or networkin
8、g permitted without license from IHS -,-,- INTERNATIONAL STANDARD IS0 7884-8 : 1987 (E) Glass - Viscosity and viscometric fixed points - Part 8 : Determination of (dilatometric) transformation temperature 0 Introduction International Standard IS0 7884, Glass - Viscosity and viscometric fixed points,
9、 consists of the following separate parts : Part 7 : Principles for determining viscosity and viscometric fixed points. Part 2 : Determination of viscosity by rotation viscometers. Part 3 : Determination of viscosity by fibre elongation viscometer. Part 4 : Determination of viscosity by beam bending
10、. Part 5: Determination of working point by sinking bar viscometer. Part 6 : Determination of softening point. Part 7 : Determination of annealing point and strain point by beam bending. Part 8 : Determination of (dilatometricl transformation temperature. 1 Scope This part of IS0 7884 specifies a me
11、thod of determining the (dilatometric) transformation temperature tg of a glass by means of the thermal expansion method. This temperature character- izes a certain glass transition range from the elastic brittle (low temperature) state to the viscous (high temperature) state of glass. The transform
12、ation temperature has been found useful for specifying cooling programmes and estimating the upper temperature limit of applicability of the respective glassware. NOTE - The more direct viscometric method of annealing point and strain point determination (see IS0 7884-7) serves similar purposes. The
13、 determination of the transformation temperature fg might be con- venient if a suitable device for determining the coeffrctent of thermal expansion is available in the laboratory. dN.s * 1 dPa.s = 1 x = 1 P (P is the symbol for poise) 2 Field of application This method is applicable to all glasses o
14、f normal bulk- production compositions. Generally, the transformation temperature ts falls in the range from 350 to 800 “C, depending on the type of glass. 3 References ISO 7991, Glass - Determination of coefficient of mean linear thermal expansion. IEC Publication 5841, Thermocouples - Part 7 : Ref
15、erence tables. 4 Definition For the purposes of this part of IS0 7884, the following defini- tion applies. transformation temperature ts of glass : The temperature corresponding to the point of intersection of two tangents, drawn from the low-temperature branch and the high- temperature branch of th
16、e dilatometer curve (see clause 5 and figure I). NOTE - The transformation temperature lg corresponds to a dynamic viscosity of the order of 1013.3 dPa.s*. No exact relation exists be- tween to and the fixed points L9f3 and L9f4 according to IS0 7884-7. For usual silicate glasses, r9f3 is 5 to 10 X
17、higher than tg. For some special cases (e.g. borosilicate glasses with high SiO2 content) rPf3 is up to 30 “C higher than tg. However, rYf3 can be up to 20 OC lower than tg (e.g. in the case of crown glasses having an La203 content). In these extreme cases the annealing point L9f3 is the more approp
18、riate informa- tion about cooling programmes required and the temperature limit of applicability of the respective glassware. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 08
19、:40:59 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7884-8 : 1987 (E) 5 Principle 7.2 Pretreatment The transformation temperature is determined by measuring the change in length, related to the length at initial temperature, of a rod made from the glass under test wi
20、th temperature. The relative change in length is plotted against the temperature fdilatometer curve). The dilatometer curve is determined for a defined rate of temperature increase. From this dilatometer curve the transfor- mation temperature is determined by a graphical procedure as shown in figure
21、 1. 6 Apparatus 6.1 Dilatometer, capable of the determination of changes in length of the specimen to 2 x 10-s x I0 (i.e. 2 pm per 100 mm). NOTE - Differential dilatometers may also be used. The reference curves may be evaluated directly, taking the first minimum as tg, or they may be redrawn as sho
22、wn in figure 1 and evaluated as described in clause 5. The contact force shall not exceed 1 N. This force shall not act via conical tips or conical end faces of the test specimen, but only via contacts of planes with spherical faces whose radii of curvature shall be not less than the rod diameter of
23、 the test specimen. 6.2 Furnace, compatible with the dilatometer assembly, for temperatures up to 50 OC above the expected transformation temperature. 6.3 Furnace control device for the desired rate of temperature increase of (5 + 1) Wmin in the range above 200 OC. The temperature distribution withi
24、n the furnace during the increase shall be smoothed to such an extent that devi- ations over the whole length of the test specimen remain less than 5 OC. 6.4 Temperature measuring device (e.g. thermocouple type E, J or K according to IEC 584-l 1, capable of determining the mean temperature of the sp
25、ecimen to f 2 OC. 6.5 Recording device for the change in length and for the temperature. 7 Test specimen 7.1 Shape The shape of the test specimen depends on the form of the specimen holder of the dilatometer assembly. The test specimen length shall be at least 5 x 104 times the resolution of the ext
26、ensometer . The test specimen shall be a rod with a cross-section of about IO to 25 mm2, and in any case of such a value that the stress arising from the contact force of the dilatometer remains less than 0,l N/mm? This is to avoid viscous or elastic deforma- tions of the rod during the test. The te
27、st specimen shall be annealed before the test by heating it to about 30 OC above the estimated transformation temperature and then cooling it to about 150 OC below the estimated transformation temperature at a cooling rate of (2 + 0,2) Wmin, followed by further cooling in draught-free air to room te
28、mperature. In figure 2 an example of a dilatometer curve is shown for an in- sufficiently annealed specimen. Such a curve, however, can be used for preliminary estimation of the value of the transforma- tion temperature prior to a repeated annealing procedure as specified in the preceding paragraph.
29、 8 Procedure The whole of the following procedure shall be performed twice. If no deformation takes place in a test specimen, it may be re- tested after re-annealing (see 7.2). Insert the test specimen at room temperature into the dilatometer and set the extensometer. Heat the test specimen from 200
30、 “C at a constant rate of temperature increase of (5 f 1) Wmin and record the temperature t and the related change in length. Correct for a possible temperature difference between the specimen and the hot junction of the thermocouple as caused by the temperature increase. NOTE - The amount of the co
31、rrection may be found empirically from appropriate runs of the dilatometer in accordance with IS0 7991, working on a glass with a sufficiently higher transformation temperature lg. 9 Expression of results 9.1 Evaluation of transformation temperature If not recorded directly, plot the relative change
32、 in length against the temperature as shown in figure 1. Draw the tangent to the low-temperature branch of the dilatometer curve at a point about 150 OC below the estimated transformation temperature. NOTE - A slight deviation from that temperature results generally in changes of less than 1,5 OC in
33、 transformation temperature. Draw the tangent to the high-temperature branch of the dilatometer curve at the point of inflection (see figure 1). Read from the graph the temperature that corresponds to the point of intersection of the two tangents. If the values of this temperature found in both runs
34、 of the test differ by not more than 5 X, then take the arithmetic mean and round it to the nearest entire degree Celsius. This is the transformation temperature. If the difference between the results of both runs is greater than 5 “C, then repeat the whole test on a new sample. 2 Copyright Internat
35、ional Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 08:40:59 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7884-8 : 1987 (E) 9.2 Precision Repeatability : 3 OC Reproduc
36、ibility : 6 “(2 IO Test report The test report shall include : a) reference to this part of IS0 7884; b) description of the sample; c) method of sampling; d) number of test specimens; e) method of preparation and form of the test specimens; f) type of apparatus used; g) corrections applied; h) multi
37、ple use of test specimens; i) transformation temperature, tg, in degrees Celsius; j) any changes observed in the glass during and/or after measurement. 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not
38、 for Resale, 04/27/2007 08:40:59 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO7884-8:1987(E) E $ s : Q 5 k & .G & $5 4 -5 z i= 2 $3 2 2 i+ . d / 0 z / + I 4 I 1 l521C I I I 0 450 500 550 Temperature t, C Figure 1 - Example of a dilatometer curve and the evaluation of
39、transformation temperature (521 “C in this case) of a glass Temperature t, OC / /- quenched Figure 2 - Example of the dilatometer curve of a glass in the annealed and in a quenched state 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA T
40、echnical Standards 1/9972545001 Not for Resale, 04/27/2007 08:40:59 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7884-8 : 1987 (E) UDC 666.11.01 : 532.13 Descriptors : glass, tests, determination, thermodynamic properties, dilatometry. Price based on 4 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 08:40:59 MDTNo reproduction or networking permitted without license from IHS -,-,-