National Bureau of Standards

Library, E-01 Admin. Bldg.

NBS MISC. PUBL 260-1

1

Standard Reference Materials:

VISCOSITY OF A STANDARD

LEAD-SILICA GLASS

U.S. Department of Commerce

National Bureau of Standards
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UNITED STATES DEPARTMENT OF COMMERCE • John T. Connor, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Standard Reference Materials:

VISCOSITY OF A STANDARD

LEAD-SILICA GLASS

A. Napolitano and E. G. Hawkins

Institute for Materials Research

National Bureau of Standards Washington, D.C.

National Bureau of Standards Miscellaneous Publication 260-11

Issued November 7, 1966

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 25 cents
Library of Congress Catalog Card Number 66-60039
PREFACE

Within the framework of the NBS Institute for Materials

Research the area of standard reference materials is a broad

and important one, including the preparation,, characterization and distribution of a wide variety of materials in such

diverse fields as metallurgy , polymers and inorganic

materials. In carrying out such a program there is much

interaction with representatives of industry and science s beginning with discussions as to which primary standard

materials will do most to advance technology, the furnishing

of materials and fabrication of samples., and the characterization and certification of the materials by cooperative

efforts. The many groups participating in a standards

program are very interested in detailed information on specific aspects of the program — but to date there has

been no publication outlet for such written discussions.

To meet this need, NBS Miscellaneous Publication 260

has been reserved for a series of papers in the general area

of "standard reference materials". This series will present

the results of studies and investigations undertaken within

the Institute for Materials Research with emphasis on the

preparation and characterization of standard reference

materials. This subject-oriented series will provide a means for rapid dissemination of this detailed information

and we hope will stimulate the use of standard reference

materials in science and industry.

W. Wayne Meinke, Chief

Office of Standard Reference Materials.

iii
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from foreign countries should include an additional one-fourth of the purchase price for postage.

iv
CONTENTS

PAGE

1 0 INTRODUCTION , „ . . . . 8 . 1

2. GLASS SAMPLE

. 2

3. APPARATUS AND METHOD OF MEASUREMENT . 5 Laboratory A 0 . 5 Other Participating Laboratories „ . . 5

4. RESULTS o . . . . c 5 Viscosity Measurements Made at NBS (Lab. A) . . . 5 Viscosity Measurements Made at Participating

Laboratories . . . „ 10

Softening^ Annealing and Strain Points . . . 0 . 22

5. SUMMARY . . . 23

6. ACKNOWLEDGMENT 23

7. REFERENCES 2k

LIST OF TABLES

TABLE NO.

1. Viscosities of five samples of glass

selected from glass No. 711 6

2. Fulcher equation constants ..... 7

3. Comparison of temperatures corresponding to specified viscosities calculated from Fulcher

equation parameters for each of the five

samples 8

4„ Comparison of values of log]_o *\ and standard

deviations calculated at 500 and 1200 °C from

the data of each participating laboratory ... 9

5. High temperature viscosities of glass

No. 711 o 11

v
LIST OF TABLES (con't)

TABLE NO. PAGE

6. Low temperature viscosities of glass

No. 711 . 12

7. Fulcher equation constants from the data

submitted by each laboratory l4

8. Comparison of temperatures for specified

viscosities calculated from appropriate

Fulcher equation parameters „ . 15

9. High temperature viscosities of glass No. 711

(restrained sphere,, Lab. C) . . . „ 19

10. Softening 3 annealing,, and strain points of

standard glass No. 711 22

LIST OF FIGURES

FIGURE NO.

1. Index variation of Standard Glass No. 711 ... 3

2. Differences in observed and calculated log-j_o

viscosities of participating laboratories

on Standard Glass No. 711 16

3. Observed values of logio viscosity plotted

against the function of temperature

4255/T °C - 152.1 (700-1400 °C) 17

4. Observed values of log]_o viscosity plotted

against the function of temperature

4255A °C - 152.1 (460-600 °C) 18

5. Comparison of log-j_ 0 viscosities obtained

by the restrained sphere and rotating cylinder

methods on Standard Glass No. 711 20

6. Comparison of log-iQ viscosities obtained by

the beam-bending (heating and cooling cycles)

and fiber-elongation methods on Standard Glass

No. 711. Equilibrium values of log]_o viscosity

beyond log^g ^ = 12 as obtained by several

laboratories are also compared with the

Fulcher equation (extrapolated) ........ 2i

vi
STANDARD REFERENCE MATERIALS:

VISCOSITY OF A STANDARD LEAD-SILICA GLASS

A. Napolitano and E. G. Hawkins

Institute for Materials Research

National Bureau of Standards

ABSTRACT

The viscosity of a lead-silica glass has been measured at the National Bureau of Standards and seven other

laboratories. Determinations were made in the range of

10 2 to lO1^ poises (1350-400 °C). Measurements were

made by the rotating cylinder,, restrained sphere, fiberelongation, and beam-bending methods. The results have

been critically evaluated and the glass has been issued

as Standard Reference Material No. 711.

Key words: Beam bending, fiber elongation, glass

,

glass standard, glass viscosity, lead-silica glass,

restrained sphere, rotating cylinders, standard, standard

reference material, viscosity, viscosity standard.

1. INTRODUCTION

In a previous paper [l] the viscosity of a standard

soda-lime-silica glass, No. 710 was reported as part of th

program of physical property measurements on a series of

glasses for calibrating instruments and comparing results

between laboratories. As a continuation of this program,

this report concerns the viscosity of another commercial

glass, a lead-silica type, that has been measured at the
National Bureau of Standards and seven other participating

laboratories

.

The lead-silica glass was selected as an additional

standard because it duplicated another important type of

commercial glasses that are made in large quantities. It can

be produced as a homogeneous glass and is stable in storage.

The results submitted by the participating laboratories,

as well as those of the National Bureau of Standards , have

been analyzed and tabulated in a "Certificate of Viscosity

Values" and the glass has been issued as Standard Reference

Material No. 711.

2 0 GLASS SAMPLE

Every effort was made at the start to obtain a quantity

of glass of the lead-silica type with the greatest possible

homogeneity throughout the lot. The lot consisted of lj500 kg

of glass in the form of bars having a cross-section of about

5 cm by 5 cm and ranging in length from 45 cm to 60 cm. The

bars were marked with the hour of manufacture and numbered

consecutively to show the sequence of production. Except for

one short period at the beginning of the production run, figure 1, there was no break in the continuous process. The

bars numbered 76-79 inclusive were discarded by the producer

because the index was outside the specified limits. The bars

numbered 1-46 were also not included in the shipment by the

producer because they were either off index or were discarded

for other reasons

.

List of participating laboratories which made viscosity and

other property measurements on Standard Reference Material

No. 711: Bausch & Lomb, Inc., Rochester, N. Y.; Brockway

Glass Co., Inc., Brockway, Pa 0 ; Corning Glass Works, Corning,

N. Y. ; Emhart Manufacturing Co e , Hartford, Conn.; General

Electric Co., Cleveland, Ohio; National Bureau of Standards,

Washington, D 0 C. (Lab Q A); Owens-Illinois, Toledo, Ohio;

Owens-Corning Fiber Glass Corp., Granville, Ohio; Thatcher

Glass Manufacturing Co., Inc., Elmira, N 0 Y.

2
CDW

•H

in ^t- go

CD 00

CD N -N0l±3VdJ3d dO X3QNI

3
The homogeneity of the glass xvas checked by measuring the

index of refraction (N^-line) on specimens taken from about

every 20 kg. This corresponded to an average of two index

samples for every hour of the production run. The specimens were measured [2] both in the condition as received and after

they all had been given the same heat treatment. These index

measurements are shown in figure 1. Also shown in figure 1 are the index measurements reported by the producer.

The variation in index of refraction of the 1J00 kg of

glass was determined to be -.0002 after fine annealing at the

National Bureau of Standards. Such a variation in index for

such a large quantity of glass is within acceptable tolerances.

It was subsequently found that no significant variation in

viscosity was associated with those portions of glass having

different indices (Lab. A). Even though the uniformity of

index is not necessarily a unique indicator of uniformity of

composition., it is most unlikely that in a continuous production of such a large quantity of glass with no deliberate

changes in batch composition^ that a significant change in

composition would not be reflected by an associated significant change in index. This has been discussed previously [l].

The chemical composition of the glass as analyzed by one

of the participating laboratories was as follows:

Si0

2

- 46.0 %

PbO - 45.32

K

20 - 5.62

Na

2

0 - 2.50

R

2 0

3

- O.56

As a further check on the uniformity of the lot., five samples were selected from the lot for viscosity measurements.

This glass is not intended as a standard for chemical

analysis

.

Laboratory E.

4
3. APPARATUS AND METHOD OF MEASUREMENT

3.1 Laboratory A The measurement of viscosity at the National Bureau of

Standards was made by the rotating cylinder and fiber elongation methods. The equipment for these measurements has been

described in detail in the previous papers [l_,3].

3.2 Other Participating Laboratories

All of the other participating laboratories that made

viscosity determinations at high temperatures used the rotating cylinder method. The techniques and modifications in the

method of making these measurements have also been reviewed

briefly in the previous work [l]. Laboratories C 9 F and G used a Brookfield RVT viscometer to make torque measurements.

In addition to the rotating cylinder data^ laboratory C submitted another set of data made by the restrained sphere

method [4],

With one exception those laboratories that submitted data

for low temperatures (below the softening point) used the fiber

elongation method. Laboratory D made measurements by a beambending method [5] and data was obtained over the range of

viscosities log-j_Q o to log^

Q

14 poises . Measurements were

made by laboratory D while the temperature was being held

constant and also while the glass was being heated and cooled

at a constant rate.

4. RESULTS

4.1 Viscosity Measurements Made at NBS (Lab. A)

The results of viscosity measurements on five samples

selected from the lot of glass are given in table 1. Two

samples (figure 1), bars No. 50 and No. 353 were taken from

regions of lowest index of refraction,, bars No. 130 and

One poise is 1 g/cm s which is equal to 0.1 kg/m s.

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No. 280 from regions where the rate of change of index was increasing and decreasing respectively, and, finally, bar

No„ 205 from the region of highest index. (The uniformity of

these samples was such that the viscosity values were within

-2% of the mean at the high temperatures.)

The data from both the low temperature fiber elongation

method and the high temperature rotating cylinder method for

each of the five samples were combined and fitted to the

Fulcher equation [6] by a least squares calculation*. This

equation has the form:

Log10 V = A+B/T-T

q

(1)

where T = temperature in °C

ti = viscosity in poises

and A, B, and T

Q

for each of the five samples and also for the

five samples combined are given in table 2. Table 2. Fulcher equation constants.

Bar No. Laboratory A (NBS) A B T

0 50 -1.653 4319 146.5

130 -1.637 4295 148.4

205 -1.655 4318 148.0

280 -1.663 4330 146.0

353 -1.651 4310 147.6 Combined -1.654 4317 147.0

The values reported in this paper were obtained by a method

suggested by R. W. Dougles [7]. Equation (1) was written

in the form:

T log1Q n = T

q log1Q n + AT + C where C = B - AT , and the usual least squares

method was used to obtain estimates of T . A and C. The

values in table 3 and 8 agree, to the number of significant

digits reported, with values obtained by the Gauss-Newton

iterative method applied to the model, as given in equation

(l), although the coefficients differed somewhat (maximum

difference was 2.2 standard deviation).

7
Using these constants, temperatures for specified log^Q

viscosity values were calculated and are given in table J. Inspection of table 5 reveals that the reproducibility of

temperatures at certain log-^Q viscosities between samples is

within 1 °C. Because of this reproducibility temperatures

are cited to the nearest .1 °C throughout this paper.

Table 3. Comparison of temperatures corresponding to specified viscosities calculated from Fulcher

equation parameters for each of the five

samples

.

Temperature °C Bar No.: 50 130 205 280 353 Combined

Log1Q n 1.90 1362.0 1362.8 1362.5 1361.2 1361.4 1361.8

2.00 1328.7 1329.4 1329.3 1328.0 1328.2 1328.5

2.25 1253-0 1253.4 1253.6 1252.5 12-52.5 1252.9 2.50 1186.4 1186.7 1187.7 1186.0 1186.0 1186.3

2.75 1127.4 1127.5 1128.1 1127.1 1127.0 1127.3 3.00 1074.7 1074.7 1075.5 1074.5 1074.3 1074.7

3-25 1027.3 1027.3 1028.2 1027.3 1027.1 1027.4 3.50 984.6 984.5 985.5 984.6 984.4 984.7 3.75 945.8 945.7 946.8 945.9 945.7 945.9 4.00 910.5 910.4 911.5 910.6 910.4 910.6 4.50 848.4 848.3 849.5 848.5 848.3 848.5

5.00 795.6 795.6 796.8 795.8 795.7 795.8

5.50 750.3 750.2 751.4 750.4 750.4 750.5 6.00 710.8 710.8 712.0 711.0 711.0 711.1

6.50 676.2 676.3 677.4 676.4 676.4 676.5 7.00 645.6 645.7 646.8 645.8 645.8 645 .-9 8.00 593.9 594.1 595.2 594.1 594.2 594.2 9.00 551.9 552.2 553-2 552.0 552.3 552.2 10.00 517.1 517.5 518.4 517.2 517.6 517.5 11.00 487.8 488.3 489.2 487.9 488.3 488.2

12.00 462.8 463.4 464.2 462.9 463.4 463.2

Two representative temperatures were selected to determine

the overall precision of measurement and to compare the two

methods of measuring viscosities, rotating cylinder at 1200 °C

•and fiber elongation at 500 °C.

8
The log10 viscosity values along with their standard

deviations (from the Fulcher equation) for each of the five

samples and also for the five samples combined for the repre- sentative temperatures, 1200 and 500 °C are given in table

For both temperatures, 1200 and 500 C, the log10

Table 4. Comparison of values of Log]_o n and standard

deviations calculated at 500 and 1200 °C from

the data of each participating laboratory.

Laboratory- Bar No.

Lo^

120'

A

B

CDE

FG

H

aCombined

Combined

50 130

205 280

353 Combined

A-H u except

2.447

2.447 2.450

2.445 2.444 2.446

2.436

2.412 2.431 2.421

2.443 2.559 2.448

2.440

.004

.005

.003 .006 .004

.005 .005

.006

.005 .010

.006

.003

.033 .012

Laboratory

Log „ n 500°°C 0 Bar No. 50 10.565 .060 130 10.579 .035 205 10.612 .027 280 10.569 .045 353 10.579 .025 Combined 10.575 .040 10.580 .015 10.619 .030 10.633 .073

A

B

CDEFG

H . Combined, A-H

Combined, except

10.612 10.610 10.610

,022

.056

.056

^No data. Equation 2 Equation 3

viscosity values for each sample may be said to agree with the

corresponding values from the combined equation (five samples)

using plus or minus one standard deviation from the value of

log^Q viscosity of each sample and from the combined equation

as the test of agreement. Since -these samples were selected

1 1

1 11 1 1 1 1

1 These standard deviations as well as the others given in

Table 4 were computed by combining deviations in the ranges

where the changes in the function are small, which were 1075-1375 °C and 475-600 °C, respectively.

9
from the lot where the index of refraction showed the greatest

spread, figure 1, it may be concluded that the combined

equation represents to within its uncertainty the log1Q viscosity of any of the five samples and also it is assumed of any

other sample selected from the lot.

The proportional error of measured viscosity is a function

of temperature, the standard deviation of the viscosity being

about 1.2$ at 1200 °C and about 10% at 500 °C. The measurements

at the higher temperatures by the rotating cylinder method are more precise by a factor of eight than those at the lower

temperatures by the fiber elongation method.

4.2 Viscosity Measurements Made at Participating

Laboratories

The results of viscosity measurements submitted by each

participating laboratory are given in table 5 (high temperature data) and table 6 (low temperature data). The data

obtained by the restrained sphere method (Lab. C) and that by

the beam-bending method using the heating and cooling rates

(Lab. D) were not used in the analysis of the data.

The data submitted by each laboratory was fitted to the

Fulcher equation by the least squares calculation in the same manner as that used for Laboratory A and the values of the

constants A, B, and T

Q

derived from each each laboratory's

data are given in table 7. A comparison of the data from each

laboratory is given in table 8 by calculating temperatures for

specified values of log^Q viscosity using these constants.

The data from all of the participating laboratories was combined and fitted to the Fulcher equation. This gave:

log1Q rj = -1.607 + 4249/T°C-152.2 (2)

The values of log1Q viscosity and their standard deviations for the two representative temperatures T = 1200 °C and

T = 500 °C for each laboratory and for the combined data were determined and are given in table 4. 10
Table 5. High temperature viscosities of glass No. 711.

Rotating cylinder

Laboratory B Laboratory C Laboratory D

o Temp . C Log^Q n obs 1 emp . 0 0

1 emp . 0

t.op n obs 767.2 5.332 oAA n Voo . U

0 c on 3-580 Aoc t. 095.1 A "IOC 814.

4

; on 0

4. 010 n nn / c 10L4 .

5

0 0 00 3-283 O/O c r42.

5

5. 553

on c L olp . 0 4 821 1 non c 1U/U. 50 n 00 ooj 0 /«4.2 c no c 5.0/5 900.0 4.093 1114.0 2.771 825.9 4.659

onn A 4.U09 1 nAo 1 1 cy A ±_Lp4.o O CO c 2. ?9;> 0/7 y A 074.0 y OQO. 4.238

O OA "1 980 . 10 1 on 3-489 12UU . 4O IT3 931.

5

0 onn 3 • 8U9 OOO O 98 / .2 Q 1 On 3 .48U 1244.

5

O O CO oo y i 3-534

i no A "7 3 .213 1 no 0 c 1U28.

2

"3 Ol A 3 • 210

n no o o 1038.3 0 i no 3 .192 "1 0 no n 10 92.

9

o oon 2 . 889

in/ o q Q 1 Ao 3 • 102 110 1 1 Ao y ( .

4

0 cAq 2. 900 11U2 1 1 no &. o

O QAA 2 . OOO n om 0 12U1.

8

2 .428 1117.2 2.798 1236.0 2.294

1194.4 2.455 1269.6 2.182

1200.0 2.437 1306.6 2.061

1249.4 2.243 1343.0 1.947 1255.6 2.229 1375.1 1.859

1303.3 2.064

1314.4 2.031

1354.4 1.894 Laboratory E Laboratory F Laboratory G 748 5.517 921 3.90 924.4 4.00

806 4.862 961 3.63 963.9 3.75

902 4.021 1015 3.29 1003.9 3.50

992 3. 408 1066 3.04 1050.0 3.25

1092 2.868 1122 2.77 1098.9 3.00

1192 2.464 1181 2.52 1152.8 2.75

1254 2.235 1237 2.30 1213.9 2.50

1301 2.070 1292 2.12 1283.3 2.25

1357 1.900 1362.8 2.00

It is noted in table 4 that the value of log1Q viscosity

at 1200 °C for laboratory G is three standard deviations

higher than the value of log1Q viscosity from the combined

data. If the high temperature data from Laboratory G (no low

temperature data submitted) is discarded then the above

equation becomes:

log10 v = -1.621 + 4255/T°C-152.1 (3)

11
Table 6. Low temperature viscosities of glass No. 711.

Fiber elongation

Laboratory B Laboratory C Laboratory H

1 eilip . Li T no- n r>T*iG 1 emp • Li TJj°g^Q n obs Torrrri 1 ClIip . Li " §]_Q n OD5

1 nA 1 a

t).UO . X ±4. //CU 499. r 1 9 9A7 111 n 1 9 Q9H no 7a

4-1-7 • f 1 ^ qAa 11 7 £9 1 1 7 0 44r -L/C 19 . A^n OpU

, ~ r ~a

435.

3

1J-9"3

. <c<cJ_ 991 ; 7Q A 4r 7.0 1 1 "59A -L-L . 9<cO 49D.O ; Kk n 19 0/ 1; -Ld . ^49

L SO 0 -I-*- 1 ? • 9^9 sen i+79 l> 10. 865 A 70 0 11. 710

47 S 0

a

11. 501 496 7 10 . 720 471 5 11.250

488.

6

a 10.980 505.7 10.409 499.5 10.620

505.8 10.361 511.6 10.222 508.0 10.340

522.2 9.877 516.6 10.047 534.0 9.570

532.5 9.599 527.9 9.726 557.0 8.870 551.9 9.022 542.9 9.260 568.5 8.590

559.4 8.825 562.3 8.776 574.0 8.420

593.3 8.023 563.6 8.733

584.5 8.237

aTime held at indicated temperatures before viscosity measurements were made are as follows: 4O6.I, 137 hrs.; 419.7, 92 hrs.; 435-3

,

24 hrs.; 450.0, 16 hrs.; 475-0, 15 hrs.; and 488.6, 2 min.

Heating

mp. °C Log1Q n obs

515 10.068

520 9-996

520 9-954

520 9.849

525 9.806

525 9-795

525 9.732

530 9.662

530 9.640

530 9.610

535 9.530

535 9.498

535 9.493

540 9.417

540 9.386

Beam bending

Laboratory D Cooling

Temp. °C Log10 n obs

520 9.986

517 10.127

513 10.179

509 10.371

505 10.538

500 IO.740

495 10.892 490 11.072 480 11.425

475 11.650

470 11.872

465 12.057

460 12.190

460 12.220

460 12.248

Equilibrium

Temp. °C Log1Q n obs 416 14.137 425 13-760 428 13-638

436 13.140

445 12.736 458 12.185 465 11.901

469 11.845 470 11.773

476 11.603 476 11.550 482 11.436

483 11.340

485 11.170

487 11.179 12
Table 6. Low temperature viscosities of glass No. 711

(con' t)

.

Beam bending

Laboratory D Heating Cooling Equilibrium

Temp. °C Log 0 nobs Temp. °C Log

10 n obs Temp. °C Log

1Q

n obs

540 9.334 455 12.373 491 10.988

545 9-301 455 12.422 497 10.728

545 9.253 455 12.456 503 10.567

550 9.164 450 12.577 503 10.425

555 9.041 450 12.640 509 10.217

560 8.901 450 12.656 512 10.324

565 8.774 445 12.790 515 10.072

565 8.751 445 12.811 516 10.182

570 8.654 445 12.836 521 9.899

570 8.587 440 12.987

575 8.498 440 13.000

575 8.449 440 13.004

580 8.348 440 13.000

580 8.314 435 13.161

585 8.233 435 13.201

590 8.149 435 13.179

595 8.045 430 13.340

600 7.931 430 13.365

605 7.803 430 13.334

610 7.692 425 13.505

420 13.689

415 13.823

410 13.965

405 14.107

400 14.265

395 14.442 390 14.619

The values of log10 viscosity at 1200 and 500 °C along with

their standard deviations from equation (3) for, all laboratories (except G) are also given in table 4. In the last

column of table 8 temperatures at the specified log-^o viscosities are given using equation 3.

13
e 7. Fulcher equation constants from the dat submitted by each laboratory.

nange , u A B T—0

40U— I An i q An ±j)OU -1.654 4317 U7.0 /, 7^ 1 q An 4 r p—J-J5DU -1.753 4440 140.0

A7n locn -1.659 4264 152.7

y.An -1. 526 4106 I62.3 745-1360 -1 . 404 3866 -L07 , <t 920-1300 -1.587 4238 148.4

925-1365 -1.830 4871 90.1

470- 575 -5.341 7482 31.0

460-1375 -1.607 4249 152.2 460-1375 -1.621 4255 152.1

Laboratory

A

aB

CDE

FG

H K

Combined, A-H

Combined, except G'

^Data from five samples combined. Equation 2 Equation 3 The calculated log^Q viscosities from 460 to 1^80 °C,

using equation 5j are represented by a straight line at zero ordinate in figure 2. The differences in the observed and

calculated log10 viscosities ( A l°g10

17 ) of each laboratory's

data using this equation are shown in figure 2. The arbitrary

limits i{5 °C and ^10$ viscosity in poises have also been shown

for this glass to indicate the magnitude of scatter [1].

The scatter in the observed log1Q viscosities with this

glass was considerably greater than those of the soda-limesilica glass. This is especially true at the lower temperatures where the results obtained by the two methods (fiber

elongation and beam bending) overlap each other and show an equal amount of scatter. For these lower temperatures only

the data obtained at equilibrium are shown in figure 2. The observed values of logjg viscosity obtained by each

laboratory have been plotted against the function of temperature 4255/T°C-152. 1 from equation 3. The high temperature

data (rotating cylinder method) is shown in figure 5 and the

low temperature data (fiber elongation and beam-bending method]

is shown in figure 4. 14
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3

15
I o

<3l .IT)

If

S

CO

LU

pp CD CD QQ O <<<

< 1 1 1 cr LU Li_ o

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16
r * n \5 13 6.5 Orn—|

1 r TEMPERATURE 10" * x °C

II 9

PARTICIPATING LABORATORIES.

O A- LAB A E- LAB • B-LAB X F- LAB

C-LAB G - LAB

A D-LAB

3.0 3.5 4.0 4.5 5.0 VALUES OF

5.5 6.0 4255

6.5 7.0 7.5 8.0 T°C - 152.1

Figure 3. Observed values of log^o viscosity plotted

against the function of temperature

4255/T °C - 152.1 (700-1400 °0) o

17
TEMPERATURE IO'

2 x°C

6.00 5.50 5.00 4.75 4.60

.00-

PARTICIPATING LABORATORIES.

O A-LAB A D-LAB • B-LAB + H-LAB

C-LAB

9.00 10.00 11.00 VALUES OF

12.00

4255

T°C-I52.

13.00 1400

Figure 4. Observed values of log]_o viscosity plotted

against the function of temperature

4255/T °C - 152.1 (460-600 °C).

18
A comparison of the results (see table 9) by the restrained sphere method (Lab. C) and equation 3 is made in figure 5. The solid line curve represents calculated values from equation 3. The average departure of the results by the restrained sphere from those of the rotating cylinder is -3-5$ with

one point off by -10$ and another off by -20% in viscosity.

This is considered a relatively good agreement between the

two methods

.

Table 9. High temperature viscosities of glass No. 711

(restrained sphere, Lab. C).

Temp °C L° 8ion obs Temp °C Lo§10

n obs 889 4.144 1061 3.026

920 3.840 1064 3-073

932 3,827 1095 2.877

962 3-589 1118 2.749

987 3.442 1146 2.632

1009 3-317 1170 2.574

1037 3.168

In the round robin tests made with the first Standard

Reference Material No. 710, Hagy [5] made a comparison of the

beam-bending and fiber elongation methods of measuring viscosities and found that the two methods were in agreement. With

this glass , No. 711* at equilibrium temperatures, the beambending data showed a little more scatter i.e. -18$ in viscosity as compared to -15$ by the fiber elongation method

(table 4). Since both methods of measuring viscosity cover essentially the same range of temperatures it is possible to derive a best curve from the data with a standard error of

-14$ in viscosity (-1.5 °C ) at the lower temperatures.

The beam-bending data obtained while the sample was being

cooled and heated is shown in table 6 and plotted in figure 6. 19
Q3AU3S80 A1IS03SIA 0I 901

20
620 580 540 500 460 420 380

TEMPERATURE - °C Figure 6. Comparison of logio viscosities obtained by the

beam-bending (heating and cooling cycles) and fiberelongation methods on Standard Glass No. 711. Equilibrium values of log10 viscosity beyond log10 1. = 12

as obtained by several laboratories are also compared

with the Fulcher equation (extrapolated).

.21
The results are compared to the values calculated from equation

3 (table 8) with values extrapolated beyond log^ 12. In addition, viscosity values made under equilibrium conditions

above log-^Q 12, are also shown in figure 6. If these data,

above log10 12, obtained under equilibrium conditions, had

been included in the original least square calcualtion the

data would not fit the curve (Pulcher equation) at the high

temperatures (low viscosity) and at the low temperatures

(high viscosity) as well as it does using only the data between log1Q 2 and l°g10 12 • 4.3 Softening, Annealing and Strain Points

The softening, annealing and strain points were determined by five participating laboratories and are given in table

10. The definition of these points and methods of determining

them are given in ASTM Standards [8,9].

Table 10. Softening, annealing, and strain points of

standard glass No. 711.

Temperature °C Laboratories

A D E F I Average

Softening point 603 602 599 603 603 602 Annealing point 433 431 429 432 435 432 Strain point 393 393 389 387 396 392

22
5 . SUMMARY

(1) NBS has established an additional Standard Reference

Material for viscosity of glass: No. 711 (Lead-Silica).

(2) Viscosity measurements have been made on this glass

by eight participating laboratories. The temperature range

covered was 390 to 1375 °C . The rotating cylinder, restrained

sphere, fiber elongation and beam bending methods were used.

(3) A viscosity temperature curve was determined from

these measurements by fitting the data points to the Fulcher

equation by the method of least squares.

(4) The softening, annealing and strain points of this

glass have been determined by five participating laboratories.

6 . ACKNOWLEDGMENT

The authors express their sincerest thanks to all

participating laboratories for their cooperation in making

viscosity measurements on this glass. They also wish to acknowledge the help received from Pedro B. Macedo and Janace

A. Speckman in setting up the computer programs.

23
7 . REFERENCES

Napolitano, A. , and Hawkins, E. G. , "Viscosity of a Standard Soda-Lime-Silica Glass" , NBS J. of Res. Part A, September-October 1964.

National Bureau of Standards Technical News Bulletin,

"An Improved Refractometer " , 135 (1953); 38, 63

(1954).

Napolitano, A. , Macedo, P., and Hawkins, E. G. , "A Wide

Range (Up to 10 10 poises) Rotating Cylinder Viscometer"

NBS J. of Res. Part A, September-October 1965

Fenstemacher , J. E., and Ryder, R. J., "An Improved

Restrained Sphere Viscometer", Bull. Am. Ceram. Soc.

43, 134 (1964).

Hagy, H. E c , "Experimental Evaluation of Beam-Bending

Method of Determining Glass Viscosities in the Range

10° to 10!5 Poises", J. Am. Ceram. Soc. 46, [2], 93

(1963). —

Fulcher, G. S., "Analysis of Recent Measurements of

Viscosity of Glasses", J. Am. Ceram. Soc. _8, [6], 339

(1925).

Proceedings of the Society of Glass Technology. Report

by the Physical Properties Committee of the Society of

Glass Technology, XI, pp 58-104 (1956).

ASTM Standards, I96I; "Softening Point of Glass", ASTM

Designation: C338-57, PP 695-698.

ASTM Standards, I96I; "Annealing Point and Strain Point

of Glass", ASTM Designation: C336-54T, pp 645-650.

24
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