Application of the positron annihilation method for evaluation of organic materials for cryogenic use

✍ Scribed by S. Nishijima; Y. Honda; T. Okada

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 244 KB
• Volume: 35
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(95)90913-z

✦ Synopsis

The positron annihilation method was used to evaluate the unoccupied spaces in epoxies with the aim of molecular design of epoxies for cryogenic use. The fracture toughness of commercially available epoxies was measured and compared with the lifetime TV. Evaluation by positron annihilation enabled the epoxies to be classified into two types: (I) those whose fracture toughness increases with free volume, and (2) those that do not change much with increasing free volume. The former type was understood to have systems with disordered networks, the latter, to have different crosslinking densities. The discussion suggests that the latter system is preferable for cryogenic use; it was confirmed experimentally.