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Mylar straws from PPG and Pressure test

Mylar straws from PPG and Pressure test. Chiho Wang, Seog Oh Duke University. Mylar straws from PPG. 6 μ m Mylar + 6 μ m polyester adhesive + 6 μ m Mylar. Nomex wraps inside the straw for mandrel release Refrigerant type lubricant on mandrel (no Silicon)

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Mylar straws from PPG and Pressure test

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  1. Mylar straws from PPGand Pressure test Chiho Wang, SeogOh Duke University

  2. Mylar straws from PPG • 6 μm Mylar + 6 μm polyester adhesive + 6 μm Mylar. • Nomex wraps inside the straw for mandrel release • Refrigerant type lubricant on mandrel (no Silicon) • 25 pieces made: 5mm ID x 150 cm length Chiho Wang & Seog Oh

  3. Pressure test • 4 straws on 15 psi N2 Chiho Wang & Seog Oh

  4. Leak rate • Pressure drop = 0.1757 psi / day @ ~15psi (no env. corr.) • Leak rate = 0.00813 mBar/Bar/min • 1 straw: volume = 29.45 cm3, surface = 235.62 cm2 • Leak rate / straw = 29.45 * 8.13E-6 / 60(sec) = 4E-6 cc/sec PSI Chiho Wang & Seog Oh

  5. Permeability • Permeation Q = k p A / d • Q = permeation: cc/sec • P = pressure: atm • A = surface area: cm2 • D = thickness: cm • K = permeability: cc/sec cm-2 cm atm-1 • 4E-6 cc/sec = k * 1 atm * 253.62 cm2 / 18E-4 cm • K = 2.8E-11 cc/sec cm-2 cm atm-1 @ 15°C Chiho Wang & Seog Oh

  6. Comparison • J. Vac. Sci. Technol. A, Vol 12, No. 4, Jul/Aug 1994 • Temperature dependence : • Our K at 15°C, 2.8E-11, is a factor of 6 smaller than 1.8E-10 • If corrected for temperature, our value is even smaller. • Note: in this table, aluminized Mylar has higher permeability than plain Mylar in CO2 !! Chiho Wang & Seog Oh

  7. Discussion • O2 and H2O diffusion into straws might compensate permeation of N2 out of straws(?) • Polyester adhesive might be more gas tight than Mylar(?) • Residual of lubricant on straw wall might reduce the permeation(?) • Will aluminizing Mylar help gas leak? • More study is needed. Chiho Wang & Seog Oh

  8. Plan • Add ~700 gram weight and continue the pressure test with 20 psi - to test the mechanical integrity. Chiho Wang & Seog Oh

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