Positron Annihilation Spectroscopy: A Nondestructive, Submicroscopic Characterization Technique for Structural Polymers

Abstract

Positron annihilation lifetime spectroscopy (PALS) has been used to characterize as extruded and aged LEXAN polycarbonate. The long-lived component of the PALS analysis is attributed to orthoPositronium (oPs) pick off annihilations. The oPs pickoff component lifetime and intensity decrease as the result of the aging heat treatment, and this decrease is associated with a decrease in the free volume site size and concentration in glassy polycarbonate due to aging. Isothermal relaxation experiments performed over the range 12 C to 30 C performed on as-extruded and aged polycarbonate indicate that the relaxation kinetics are significantly different, and are consistent with a decrease in molecular mobility as the result of aging. An activation energy for structural relaxation of 8.2 kcal/mole for aged polycarbonate versus 3.0 kcal/ mole for unaged polycarbonate was determined. The relaxation kinetics observed using PALS is related to the structural state and molecular mobility of the polymer.

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Document Details

Document Type
Technical Report
Publication Date
Nov 16, 1989
Accession Number
ADA217748

Entities

People

  • Phillip L. Jones

Organizations

  • Duke University

Tags

Communities of Interest

  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Abstracts
  • Energy
  • Engineering
  • Heat Of Activation
  • Intensity
  • Kinetics
  • Materials
  • Materials Science
  • Mechanical Engineering
  • Military Research
  • Mobility
  • Physical Properties
  • Positrons
  • Relaxation Time
  • Scientists
  • Spectroscopy
  • X-Ray Diffraction

Fields of Study

  • Physics

Readers

  • Materials Science and Engineering.
  • Molecular Photonics/Laser Physics
  • Polymer Science and Engineering.