Günther Hartwig - Böcker

This was the third meeting in the series of special topical conferences on Non-Metallic materials at low temperatures. The first meeting was in Munich in 1978, the second in Geneva (1980) and so Heidelberg 1984 seemed an obvious time to review some of the hopes and objectives of the earlier meetings. It is also appropriate to consider the changing needs of the cryogenic community and how best the theory and practice of Non-metallic materials can be applied to suit this dynamic young science. The aims and objectives of the International Cryogenic Materials Board in sponsoring this meeting remain the same. Namely, to provide a forum where practicing Engineers can meet with materials suppliers and researchers in an attempt to ensure that a real understanding exists between the two sides of the Cryogenic Materials Community. In this atmosphere, real problems can be addressed together with full discussions of tried and tested practical solutions. It is in this way that knowledge and confidence may grow hand in hand with the logical growth of the industry.

Most descriptions of polymers start at room temperature and end at the melting point. This textbook starts at very low temperatures and ends at room temperature. At low temperatures, may processes and relaxations are frozen which allows singular processes or separate relaxations to be studied. At room temperatures, or at the main glass transitions, many processes overlap and the properties are determined by relaxations. At low temperatures, there are temperature ranges with negligible influences by glass transitions. They can be used for investigating so-called basic properties which arise from principles of solid state physics. The chain structure of polymers, however, requires stringent modifications for establishing solid state physics of polymers. Several processes which are specific of polymers, occur only at low temperatures. There are also technological aspects for considering polymers at low temperatures. More and more applications of polymeric materials in low­ temperature technology appear. Some examples are thermal and electrical insulations, support elements for cryogenic devices, low-loss materials for high­ frequency equipments. It is hoped that, in addition to the scientific part, a data collection in the appendix may help to apply polymers more intensively in low­ temperature technology. The author greatly appreciates the contributions by his coworkers of the Kernforschungszentrum Karlsruhe in measurement and discussion of many data presented in the textbook and its appendix. Fruitful disccussions with the colleagues Prof. H. Baur, Prof. S. Hunklinger, Prof. D. Munz and Prof. R.

This volume emphasizes the importance of first understanding cryogenic properties in order to comprehend the room temperature properties of polymers. The author describes the necessary modifications for polymers and their applications to the most important thermal, mechanical, and dielectric properties. Other chapters discuss the correlation between polymer structures and properties, the phonon structure of polymers, separation of components influenced by glass transitions and 'basic properties' related to solid state physics, and the influence of tunneling processes on properties at very low temperatures. Polymer Properties at Room and Cryogenic Temperatures also features an extensive appendix with key data on all the properties considered in the text. This volume is an important and useful text for students, scientists, lecturers, and engineers in the area of polymer science.

Cryogenics is an emerging technology filled with promises. Many cryogenic systems demand the use of nonmetallics and composites for adequate or increased performance. Thermal and electrical insulations, potting for superconducting magnets' mechanical sta­ bility, and composite structures appear to be some of the most significant applications. Research on nonmetallics at cryogenic temperatures has not progressed to the degree of research on metals. Nor can room temperature research be extrapolated to low tempera­ tures; most polymers undergo a phase transformation to the glassy state below room temperature. Research by producers, for the most part, has not been prac­ tical, because, except for LNG applications, the market for large material sales is not imminent. There are, however, many government­ stimulated developmental programs. Research on nonmetallics thus is dictated by development project needs, which require studies orien­ ted toward prototype hardware and specific objectives. As a result, research continuity suffers. Under these conditions, periodic topical conferences on this subject are needed. Industry and uni­ versity studies must be encouraged. Designers and project research material specialists need to exchange experiences and data. Low­ temperature-oriented research groups, such as the National Bureau of Standards and the Institute for Technical Physics - Karlsruhe, must contribute by assisting with fundamentals, interpreting proj­ ect data, and contributing to project programs through their materials research.