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LTLT
We are using GRP (glass reinforced plastic) for making low-temperature cells and supporting parts. It is cheap and easy to machine.
In the work [1] thermal expansion and thermal conductivity of glass reinforced nylon have been measured. Thermal expansion from 290K to 80K was 0.517%, and from 290K to 4K it was 0.579%.
Since we did not know the exact specification of our GRP, we remeasure its thermal expansion. We used 10mm GRP rod (RSN(771-780)) and an oxygen-free copper bar, connected together at one end with a metal clamp. At 515mm distance from this end we made marks on copper and plastic. We measured distance between the marks with accuracy better then 0.1~mm at room temperature and temperature of liquid nitrogen (80K) and got 0.233% of the total length. This should be added to thermal expansion of copper (0.302%). The result is 0.535% which is close to the value presented in the paper.
Glassfibre has been ordered from Excel [2] for the 20mK radiation shield.
Thermal expansion was measured by attaching a copper rod and putting it in liquid nitrogen dewar. At the length 630mm mutual displacement was 1.0mm (GRP shrinks less). Assuming thermal expansion for Cu is 0.302% we have GRP thernal expansion 0.143%. Note that GRP plastic sold in RS is a different material with larger thermal expansion.
[1] M. Barucci, G. Bianchini, T. Del Rosso, E. Gottardi, I. Peronic, G. Ventura,
Thermal expansion and thermal conductivity of glass-fibre reinforced nylon at low temperature,
Cryogenics, 40, 465-467 (2000)
https://doi.org/10.1016/S0011-2275(00)00067-9
[2]
Universal Glassfibre tube 65/61 mm, L100 cm, Excel (~22EUR)
https://www.exelwebstore.com/catalog/product/view/id/979/s/universaltm-glassfibre-tube-65-61-mm-l100-cm.
Thermal expansion of other materials can be found here.