ISO-7884-1-1987.pdf
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1、IS0 7884-l INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXAYHAPOAHAR OPTAHl43AIJWl IlO CTAHAPTMSAklM .;p&;j ,: : : . 9 Y, ,; _, S-II . , “ yf t ;.: Y: ;1;4 ,!.-, 5. f” o is the surface tension in millinewtons per metre. For Q = 2
2、,5 g/cm3 and o = 300 mN/m the viscosity is da = 107.6 dPas In most cases Of2 lies close to that value; it shall be used if the values of Q and cr are unknown. In extreme cases qf2 ranges from 107,5 to 108 dPas. The softening point can also be determined by the method described in IS0 7884-2. 3.3.3 a
3、nnealing point rYf3: The temperature determined in accordance with the method described in IS0 7884-7. NOTE - From the beam bending method a non-equilibrium viscosity of 1O1a,2 dPas is assigned to the annealing point. From various measurement techniques, a non-equilibrium viscosity of 101s to lots.2
4、 dPas has been found to approximate to the viscosity at the annealing point. 3.3.4 strain point r9f4: The temperature determined in accor- dance with the method described in IS0 7884-7. NOTE - From the beam bending method a non-equilibrium viscosity of 1014.7 dPas is assigned to the strain point. Fr
5、om various measurement techniques, a non-equilibrium viscosity of 1014,5 to 1014J dPas has been found to approximate to the viscosity at the strain point. NOTE - The order of magnitude of the constants for technical glasses is as follows : A = - 100 (decadic logarithm of viscosity in decipascal seco
6、nds) B = 103T c = 102oc 4.2 Determination of the constants Three pairs of measured temperatures and equilibrium viscosities i = 1, 2, 3, covering the range of the measurement and separated sufficiently from each other, are chosen to calculate the constants of the VFT-equation by means of equa- tions
7、 (3) to (5) : c=v, + (192 - l9,) . it93 - L91) * (lg 43 - lg 472) (lY2 - V,) . (lg 1/3 - Ig tll 1 - h93 - I. ( therefore, any change in composition of the glass should be avoided as far as possible, in particular by taking the following precautions : - do not grind to powder (to avoid water adsorpti
8、on); - do not heat above the measuring temperatures if possi- ble, or heat only for as short a time as possible (to avoid loss of volatile components); - do not heat for a long time within the temperature region of maximum rate of crystallization; - select pieces without inhomogeneities, inclusions
9、or bub- bles. 1) Pythagoras IS an example of a suitable product supplied by W. Haldenwanger Technische Keramik GmbH I: 0,015 0 700 7,80 4:6 0,020 0 600 10.74 883 0,036 0 950 I,86 23 0,011 2 850 3,38 4,l 0,017 6 103 750 5,55 7,4 0,032 0 “short” i: 7,78 12,6 0,054 8 IO,66 13,4 0,058 0 600 1354 13,4 0,
10、058 0 5 / Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:47:14 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7884-l : 1987 (E) As an example for a typ
11、ical technical glass (reference glass DGG 1, see table 31, table 2 gives a survey on the influence of the error in viscosity introduced by rounding the constants of the VFT-equation. Table 2 - Influence on error introduced by rounding constants A, B and C Rounding of constants A, B, C Temperature Re
12、lative error (Arlr) x 100 % in the case of constant to . significant to the nearest . . . ff A B C figures unit(s) in the last digit OC maximum maximum maximum 1400 0,oz 0,Ol 5 2 800 0.02 O.J 0,03 560 0.08 0,ll 1400 0,05 0.02 5 5 800 0,06 0,lO 0,08 550 0,19 0.28 1400 or1 0,04 4 1 800 O,l 02 02 550 0
13、,4 33 1400 02 O,l 4 2 800 02 0,4 0,3 550 0.8 1,1 1400 0,5 4 5 800 0.6 I,0 % 550 1.9 2:8 1400 Or4 3 1 800 12 ii? 1,6 550 3:9 5,5 6 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=Defense Supply Ctr/9960866100 Not for Resale, 04/24/2007 10:47:14
14、 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7884-l : 1987 (E) Annex B Examples of certified reference glasses for viscometric calibration (This annex does not form an integral part of the standard.) The tabulated certified reference glasses (CRG) NBS 709 to NBS 717
15、 are available from the National Bureau of Standards, Washington (see NBS Special Publication 260) and the certified reference glass (CRG) DGG I from the Deutsche Glastechnische Gesellschaft (DGG), MendelssohnstraB 75-77, D-6000 Frankfurt/M. 1, Germany, F.R. The certified reference glasses (CRG) NBS
16、 710, 711 and 717 are supplied as rectangular-shaped bars, and are certified for viscosity values between 102 and 1012 dPas. They are supplied to check the performance of high-temperature viscosity equipment (rotating cylinders) and low-temperature viscosity equipment (fibre elongation, beam bending
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