molecular relaxation

molecular relaxation

[mə′lek·yə·lər ‚rē‚lak′sā·shən]
(physical chemistry)
Transition of a molecule from an excited energy level to another excited level of lower energy or to the ground state.
References in periodicals archive ?
Therefore, the mechanism of slow molecular relaxation could reasonably explain the long-term behavior.
This complicated phenomenon is one of the motivations for starting this study, to investigate molecular relaxation changes occurring in a polymer during weathering as an explanation to supplement chemical degradation for these observations.
For example, it allows the measurement of [T.sub.g] when a reaction or molecular relaxation is going on and separates decomposition from crosslinking.
"Molded EPS patterns shrink with time due to molecular relaxation of the stresses in the cell walls and equilibration of the gas composition in each cell with the surrounding air," according to the authors.
The calculated flow front velocities and fill-times for mould A (Table 3) are useful for evaluating models for residual molecular orientation in terms of the time available for molecular relaxation post injection.
It is common to observe that polymers become harder during exposure while simultaneously crosslink density is diminishing which is counter to expectations of polymer networks, unless other explanations are invoked, such as molecular relaxation, increase in hydrogen bonding or loss of dangling polymer chain ends.
Third Prize: "Molecular Relaxation Phenomena During Accelerated Weathering of a Polyurethane Coating" -- Dilhan Fernando, Xiaodong Shi, and Stuart G.
Shrinkage results from the gas composition in each cell coming into equilibrium with the surrounding air and from molecular relaxation.
Hot drawing in the solid state is emphasized since it offers the possibility to produce high-strength fibers from high-MFI resins due to the significantly slower molecular relaxation in the solid state compared to the molten state.
This is because of the molecular relaxation occurred at relatively high pretreatment temperature.
Relatively fast molecular relaxation in the melt or solution state hinders orientation of macromolecules by adopting the entropically favorable random coil conformation.
In the glassy state the molecular relaxation engages cooperative movements in larger scales than the liquid-like state [13].

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