Accession Number : ADA302546

Title :   Long-Term Influence of Physical Aging Processes in Epoxy Composites.

Descriptive Note : Contract rept.,

Corporate Author : ADVANCED RESEARCH AND APPLICATIONS CORP SUNNYVALE CA

Personal Author(s) : Kong, Eric S.

PDF Url : ADA302546

Report Date : FEB 1981

Pagination or Media Count : 34

Abstract : The long-term properties of amorphous, glassy materials, including the crosslinked thermoset of network epoxies, have been demonstrated to change as a function of annealing time at a temperature below the material's glass transition temperature, Tg (1, 2). This sub-Tg annealing process is typically accompanied by a volume recovery phenomenon known as physical aging (3, 4). A polymer cooled from above its Tg is in a non-equilibrium state which possesses excess values in free volume as well as excess values in state functions such as volume and enthalpy. The molecular basis for this non-equilibrium behavior arises from the quenching of free volume into the polymer system due to the inability of the polymer chains to achieve their equilibrium conformation as the temperature of the system is lowered through Tg. That is, due to the rapidly increasing viscosity as Tg is approached, the molecules essentially undergo a log-jam effect and excess free volume is quenched within the system.

Descriptors :   *AGING(MATERIALS), *EPOXY COMPOSITES, VOLUME, ANNEALING, RECOVERY, NETWORKS, MOLECULES, PHYSICAL PROPERTIES, MATERIALS, POLYMERS, EQUILIBRIUM(GENERAL), GLASS, LONG RANGE(TIME), QUENCHING, TIME, CROSSLINKING(CHEMISTRY), TRANSITION TEMPERATURE, CHAINS, NONEQUILIBRIUM FLOW, EPOXY COMPOUNDS, VISCOSITY, ENTHALPY, THERMOSETTING PLASTICS, CONFORMITY.

Subject Categories : Polymer Chemistry
      Laminates and Composite Materials
      Plastics
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE