Accession Number : ADA299518

Title :   Positron Annihilation Studies of Thermoplastic LCP Composites,

Corporate Author : DUKE UNIV DURHAM NC DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE

Personal Author(s) : Naslund, Robert A. ; Jones, Phillip L.

PDF Url : ADA299518

Report Date : 03 AUG 1995

Pagination or Media Count : 4

Abstract : The time-dependent decrease in ortho-positronium (o-Ps) intensity detected in polymers during long-term positron annihilation lifetime (PALS) experiments has been extensively studied and modeled. This decrease in temperature dependent, polymer specific, source strength dependent and is noted to saturate as a function of source exposure time. Larger decreases and smaller saturation values are exhibited at lower temperatures. Additionally, at sufficiently high temperatures, a negligible decrease is detected. The time dependent decrease is recoverable at elevated temperatures. In contrast, the o-Ps lifetime component remains constant and independent of exposure time. Increasing the exposed sample volume by continuously varying the source-sample orientation dramatically decreases the reduction of o-Ps intensity.

Descriptors :   *POLYMERS, *COMPOSITE MATERIALS, *LIQUID CRYSTALS, *THERMOPLASTIC RESINS, *POSITRONS, *ANNIHILATION REACTIONS, SOURCES, LOW TEMPERATURE, RECOVERY, TIME DEPENDENCE, EXPOSURE(GENERAL), HIGH TEMPERATURE, LONG RANGE(TIME), SATURATION, STRENGTH(GENERAL), CONTINUITY, POSITRONIUM.

Subject Categories : Polymer Chemistry
      Physical Chemistry
      Radiation and Nuclear Chemistry
      Laminates and Composite Materials
      Crystallography
      Nuclear Physics & Elementary Particle Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE