Predicting Interfacial Gap Thermal Conductance under Non Isothermal Free Volume Relaxation States
Non-isothermal free volume relaxation shrinks interface polymers, drops contact pressure, and spikes thermal gap resistance during cooling cycles.
Structural Relaxation
Meaning
The time-dependent reorganization of the atomic or molecular structure in a non-equilibrium material toward its equilibrium state describes a fundamental thermodynamic aging process. This structural relaxation occurs in glasses, polymers, and amorphous metals below their glass transition temperature. It leads to continuous changes in physical properties such as density, enthalpy, and mechanical stiffness over time.
Kinetics Description
Non-linear behavior characterizes this structural reorganization because the relaxation rate depends on both temperature and the instantaneous state of the structure. As structural relaxation proceeds, the material becomes denser, which restricts molecular movement and slows down further relaxation. This self-retarding effect means that the system approaches equilibrium at a decreasing rate.
It requires multi-parameter models to accurately predict the long-term behavior of these amorphous networks. Understanding this non-linear pathway is essential for designing high-precision optical lenses where refractive index drift cannot be tolerated.
Operational Change
Material properties will drift during storage or operation, affecting the product performance. Polymer components can become more brittle and prone to cracking due to structural relaxation. This aging must be factored into the lifetime prediction of plastics.
Temperature Influence
Annealing the material near its transition temperature can accelerate this process to stabilize the structure. Higher temperatures increase molecular mobility, allowing the material to reach its equilibrium density much faster. This pre-treatment prevents further drift during the subsequent service life of the product.