The thermal conductivity of high modulus Zylon fibers between 400 mK and 4 K

Abstract

Zylon is a synthetic polyurethane polymer fiber featuring very high mechanical strength. Measurements of the thermal conductivity λ Z ( T ) of high modulus Zylon fibers at temperatures between 400 mK and 4 K were performed to assess if they can be successfully employed in the design of high performance suspension systems for cold stages of adiabatic demagnetization refrigerators. The linear mass density of the yarn used in these measurements amounts to 3270 dtex, which is also a measure for the yarn’s cross section. 1 A linear mass density of 1 tex is equivalent to a yarn mass of 1 g/km. High modulus Zylon has a density of 1.56 g/cm 3. 1 The experimental data for the thermal conductivity was fitted to a function of the form λ Z = ( 1010 ± 30 ) · T 1.30 ± 0.03 pW mm dtex - 1 K - 2.3 . This result was normalized to the breaking strength of the fibers and compared with Kevlar. It shows that Kevlar outperforms Zylon in the investigated temperature range. At 1.5 K, the thermal conductivity integral of Zylon yarn is twice as high as the thermal conductivity integral of Kevlar yarn with the same breaking strength.