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Thermal contraction of Vespel SP-22 and Stycast 1266 from 300K to 4K
RESEARCHAND TECHNICALNOTES Thermal contraction of Vespel SP-22 and Stycast 1266 from 300K to 4K G.W. Swift and R.E. Packard
The use of Vespel SP-22 polymide resin 1 and Stycast 1266 epoxy 2 as construction materials is becoming common in low temperature apparatus. Vespel SP-22 has a thermal conductivity nearly as low as graphite, 3 yet is more easily machined and is much stronger; Stycast 1266 bonds well to metals, and its transparency and low viscosity greatly simplify casting procedures. A knowledge of the coefficient of thermal contraction of such construction materials is often necessary for proper design of low temperature devices. We present here data on the total thermal contraction of these two materials, measured relative to OFHC copper, from room temperature to dry ice, liquid nitrogen, and liquid helium temperatures.
Dial indicator
The simple pushrom dilatometer used to make the measurements is shown in Fig. 1. The test piece and the copper reference pieces are 0.01 m diameter by 0.27 m long rods, and are immersed in liquid in a dewar flask. Expansion or contraction of the test piece relative to the copper is transmitted to the dial indicator outside the dewar by the stainless steel pushrod and support tubes. These tubes are cut from the same piece of stock to ensure that their thermal contractions will be identical. The dial indicator 4 is an ordinary machinists' gauge with a resolution of 5 x 10-6m and total range of 2 x 10 -2 m.
Stainless steel pushrod tube Stainless steel support tubes
Since the dilatometer measures the difference in contraction between the reference and test rods, it is necessary to add the contraction of the reference to the observed differential contraction to fred the contraction of the test piece. OFHC copper was chosen as the reference material because its contraction is well documented and because there seems to be negligible variation in contraction from sample to sample.S'6 The apparatus is checked by cooling to 77 K with test pieces of 304 stainless steel and of OFHC copper. As expected, no differential contraction is observed with the copper sample, within the resolution of the dial indicator. The contraction observed for the stainless steel agrees with previous work 7 to within I%. The authors are at the Physics Department, University of California, Berkeley, CA 94720, USA.
Test piece OFHC copper
Dewar flask \
Fig. 1
Sketch of the apparatus
0011-2275/79/060362-02 $02.00 © 1979 IPC Business Press 362
CRYOGENICS. JUNE 1979
0
LIIHE iNORE (RVOTROnI(5 is
200
mo
The Answer
400
[]
= .4~ 600
800 I~ I000
[]
For all of your CRYO6ENIC NEEDS!
SP-22 1266
I
12OO
0
I00
200
:500
Temperature, K Fig. 2 Thermal contraction of Vespel SP-22 and Stycast 1266. The curve for copper (included for comparison) is from reference 5
The data on isotropic Vesepl SP-22 and Stycast 1266 are shown in Fig. 2 and Table 1. The Stycast 1266 4 K datum agrees with previous work. s The dflatometer is very inexpensive and easy to build and to use, and its accuracy o f AL/L ~ 2 × 10 -s is adequate for many applications. T a b l e 1.
(1 -
LT/L296)
x 105 (Twice Actual Size)
Vespel SP-22 195K
289+2
Stycast 1266 596
77 K
558
1035
4K
633
1150+2
We would like to thank the DuPont Company for making available the Vespel SP-22. This work was supported in part by NSF grant DMR-76-82934.
References l 2 3 4
Dupont Company, plastic Products and Resins Department, Wilmington, Delaware 19898 Emerson and Cuming, Inc, Dielectric Materials Division, Canton, Mass Locatelli, M., Arnaud, D., Routin, M. Cryogenics 16 (1976) 374 Type 8241-942, Brown and Sharpe Mfg Co, Kingstown, R.I. 02852
5
6 7 8
Rubin, T., Altman, H.W., Johnston, H.L. J Amer Chem Soc 76 (1954) 5289 White,G.K. AIP Conference Proceedings 17, Thermal Expansion (1973) 1 Altman, H.W. Coefficients of Thermal Expansion of Solids at Low Temperatures, Part IV, Tech Rep 264-28, Ohio State Univ Research Foundation Veuro, M.C. Thesis, Helsinki University of Technology, Helsinki, Finland
Lake Shore Cryotronics, Inc. combines over 10 years of experience in the development and manufacture of Cryogenic Thermometry and Instrumentation with the latest stateof-the-art techniques to give you the answer to your everyday needs. • Carbon Glass Resistance Thermometers • Si & GaAs Diode Sensors • Capacitance Sensors • Germanium Resistors • Thermocouples • Platinum Resistors • Digital Thermometers & Controllers • Liquid Level Controllers & Indicators • Accessories • Engineering • Complete Calibration Services 30mKto380K • Closed Cycle refrigerator systems • Continuous flow Helium Cryostat systems
F o r details and literature umite, call, or t e l e x
O
LRHE SNORE [R¥OTROnIES,IIIL
6 4 E a s t W a l n u t St. Westerville, Ohio 43081 (614) 891-2243 Telex: 24-5415 Cryotron WTVL
Contact us direct, or our representatives
In Europe: Cryophysics Oxford, England (865) 722824 Darmstadt, W Germany (6151 ) 74081
CRYOGENICS . JUNE 1979
Geneva, Switzerland (22) 329520 Versadles,France (1) 9506578
363
The use of Vespel SP-22 polymide resin 1 and Stycast 1266 epoxy 2 as construction materials is becoming common in low temperature apparatus. Vespel SP-22 has a thermal conductivity nearly as low as graphite, 3 yet is more easily machined and is much stronger; Stycast 1266 bonds well to metals, and its transparency and low viscosity greatly simplify casting procedures. A knowledge of the coefficient of thermal contraction of such construction materials is often necessary for proper design of low temperature devices. We present here data on the total thermal contraction of these two materials, measured relative to OFHC copper, from room temperature to dry ice, liquid nitrogen, and liquid helium temperatures.
Dial indicator
The simple pushrom dilatometer used to make the measurements is shown in Fig. 1. The test piece and the copper reference pieces are 0.01 m diameter by 0.27 m long rods, and are immersed in liquid in a dewar flask. Expansion or contraction of the test piece relative to the copper is transmitted to the dial indicator outside the dewar by the stainless steel pushrod and support tubes. These tubes are cut from the same piece of stock to ensure that their thermal contractions will be identical. The dial indicator 4 is an ordinary machinists' gauge with a resolution of 5 x 10-6m and total range of 2 x 10 -2 m.
Stainless steel pushrod tube Stainless steel support tubes
Since the dilatometer measures the difference in contraction between the reference and test rods, it is necessary to add the contraction of the reference to the observed differential contraction to fred the contraction of the test piece. OFHC copper was chosen as the reference material because its contraction is well documented and because there seems to be negligible variation in contraction from sample to sample.S'6 The apparatus is checked by cooling to 77 K with test pieces of 304 stainless steel and of OFHC copper. As expected, no differential contraction is observed with the copper sample, within the resolution of the dial indicator. The contraction observed for the stainless steel agrees with previous work 7 to within I%. The authors are at the Physics Department, University of California, Berkeley, CA 94720, USA.
Test piece OFHC copper
Dewar flask \
Fig. 1
Sketch of the apparatus
0011-2275/79/060362-02 $02.00 © 1979 IPC Business Press 362
CRYOGENICS. JUNE 1979
0
LIIHE iNORE (RVOTROnI(5 is
200
mo
The Answer
400
[]
= .4~ 600
800 I~ I000
[]
For all of your CRYO6ENIC NEEDS!
SP-22 1266
I
12OO
0
I00
200
:500
Temperature, K Fig. 2 Thermal contraction of Vespel SP-22 and Stycast 1266. The curve for copper (included for comparison) is from reference 5
The data on isotropic Vesepl SP-22 and Stycast 1266 are shown in Fig. 2 and Table 1. The Stycast 1266 4 K datum agrees with previous work. s The dflatometer is very inexpensive and easy to build and to use, and its accuracy o f AL/L ~ 2 × 10 -s is adequate for many applications. T a b l e 1.
(1 -
LT/L296)
x 105 (Twice Actual Size)
Vespel SP-22 195K
289+2
Stycast 1266 596
77 K
558
1035
4K
633
1150+2
We would like to thank the DuPont Company for making available the Vespel SP-22. This work was supported in part by NSF grant DMR-76-82934.
References l 2 3 4
Dupont Company, plastic Products and Resins Department, Wilmington, Delaware 19898 Emerson and Cuming, Inc, Dielectric Materials Division, Canton, Mass Locatelli, M., Arnaud, D., Routin, M. Cryogenics 16 (1976) 374 Type 8241-942, Brown and Sharpe Mfg Co, Kingstown, R.I. 02852
5
6 7 8
Rubin, T., Altman, H.W., Johnston, H.L. J Amer Chem Soc 76 (1954) 5289 White,G.K. AIP Conference Proceedings 17, Thermal Expansion (1973) 1 Altman, H.W. Coefficients of Thermal Expansion of Solids at Low Temperatures, Part IV, Tech Rep 264-28, Ohio State Univ Research Foundation Veuro, M.C. Thesis, Helsinki University of Technology, Helsinki, Finland
Lake Shore Cryotronics, Inc. combines over 10 years of experience in the development and manufacture of Cryogenic Thermometry and Instrumentation with the latest stateof-the-art techniques to give you the answer to your everyday needs. • Carbon Glass Resistance Thermometers • Si & GaAs Diode Sensors • Capacitance Sensors • Germanium Resistors • Thermocouples • Platinum Resistors • Digital Thermometers & Controllers • Liquid Level Controllers & Indicators • Accessories • Engineering • Complete Calibration Services 30mKto380K • Closed Cycle refrigerator systems • Continuous flow Helium Cryostat systems
F o r details and literature umite, call, or t e l e x
O
LRHE SNORE [R¥OTROnIES,IIIL
6 4 E a s t W a l n u t St. Westerville, Ohio 43081 (614) 891-2243 Telex: 24-5415 Cryotron WTVL
Contact us direct, or our representatives
In Europe: Cryophysics Oxford, England (865) 722824 Darmstadt, W Germany (6151 ) 74081
CRYOGENICS . JUNE 1979
Geneva, Switzerland (22) 329520 Versadles,France (1) 9506578
363