Discussion Overview
The discussion centers on identifying materials that maintain some elasticity at cryogenic temperatures, specifically around 20 Kelvin, for use in a bladder designed to hold liquid nitrogen in a bath of liquid hydrogen or helium under pressure. Participants explore various material options and their properties under extreme conditions.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about materials that can retain elasticity at cryogenic temperatures for a bladder that could stretch or fold without cracking.
- Another suggests a stainless steel bellows tube as a potential solution and asks about the required capacity.
- A later post indicates that the bladder should ideally collapse completely and questions the viability of silicon, plastic, or rubber compounds at such low temperatures.
- Some participants express skepticism about the flexibility of plastics or rubber at 20K, suggesting that few materials would perform adequately.
- Polytetrafluoroethylene (Teflon) is mentioned as retaining some plasticity at 20K.
- Concerns are raised about nitrogen solidifying at very low temperatures, and the challenges of using materials like Kapton film are discussed, including its performance when thin and the risk of developing holes at fold points.
- Experiments with various plastics, including nylon, are noted to have failed, emphasizing the need for materials that can withstand bending stresses.
- Participants suggest that understanding the intended use of the bladder could provide better insights into material selection.
Areas of Agreement / Disagreement
Participants express differing opinions on the suitability of various materials for cryogenic applications, with no consensus reached on a definitive solution. Some materials are proposed as potentially viable, while others are deemed unlikely to perform well under the specified conditions.
Contextual Notes
Limitations include uncertainty regarding the performance of specific materials at cryogenic temperatures, the need for further clarification on the intended use of the bladder, and the potential for solidification of nitrogen and hydrogen at low temperatures affecting material choice.
Who May Find This Useful
This discussion may be of interest to materials scientists, engineers working with cryogenic systems, and researchers exploring applications involving low-temperature environments.