Physical aging in the glassy state of a thermosetting system vs. extent of cure

1993 ◽  
Vol 47 (3) ◽  
pp. 447-460 ◽  
Author(s):  
Xiaorong Wang ◽  
John K. Gillham
Keyword(s):  
Physical Aging ◽  
Glassy State

scholarly journals Physical Aging Behavior of a Glassy Polyether

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 954
Author(s):  
Xavier Monnier ◽  
Sara Marina ◽  
Xabier Lopez de Pariza ◽  
Haritz Sardón ◽  
Jaime Martin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Narrow Temperature Range ◽  
Glass Forming ◽  
Fast Scanning Calorimetry

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

scholarly journals Effect of low‐temperature physical aging on the dynamic transitions of atactic polystyrene in the glassy state

2019 ◽  
Vol 57 (20) ◽  
pp. 1394-1401 ◽  
Author(s):  
Kalouda Grigoriadi ◽  
Tristan Putzeys ◽  
Michael Wübbenhorst ◽  
Lambèrt C. A. Breemen ◽  
Patrick D. Anderson ◽  
...  
Keyword(s):  
Low Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Atactic Polystyrene ◽  
Dynamic Transitions

scholarly journals Composites Based on Poly(Lactic Acid) (PLA) and SBA-15: Effect of Mesoporous Silica on Thermal Stability and on Isothermal Crystallization from Either Glass or Molten State

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2743
Author(s):  
Tamara M. Díez-Rodríguez ◽  
Enrique Blázquez-Blázquez ◽  
Ernesto Pérez ◽  
María L. Cerrada
Keyword(s):  
Lactic Acid ◽  
Mesoporous Silica ◽  
Isothermal Crystallization ◽  
Physical Aging ◽  
Glassy State ◽  
Poly Lactic Acid ◽  
Molten State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

Several composites based on an L-rich poly(lactic acid) (PLA) with different contents of mesoporous Santa Barbara Amorphous (SBA-15) silica were prepared in order to evaluate the effect of the mesoporous silica on the resultant PLA materials by examining morphological aspects, changes in PLA phases and their transitions, and, primarily, the influence on some final properties. Melt extrusion was chosen for the obtainment of the composites, followed by quenching from the melt to prepare films. Completely amorphous samples were then attained, as deduced from X-ray diffraction and differential scanning calorimetry (DSC) analyses. Thermogravimetric analysis (TGA) results demonstrated that the presence of SBA-15 particles in the PLA matrix did not exert any significant influence on the thermal decomposition of these composites. An important nucleation effect of the silica was found in PLA, especially under isothermal crystallization either from the melt or from its glassy state. As expected, isothermal crystallization from the glass was considerably faster than from the molten state, and these high differences were also responsible for a more considerable nucleating role of SBA-15 when crystallizing from the melt. It is remarkable that the PLA under analysis showed very close temperatures for cold crystallization and its subsequent melting. Moreover, the type of developed polymorphs did not accomplish the common rules previously described in the literature. Thus, all the isothermal experiments led to exclusive formation of the α modification, and the observation of the α’ crystals required the annealing for long times at temperatures below 80 °C, as ascertained by both DSC and X-ray diffraction experiments. Finally, microhardness (MH) measurements indicated a competition between the PLA physical aging and the silica reinforcement effect in the as-processed amorphous films. Physical aging in the neat PLA was much more important than in the PLA matrix that constituted the composites. Accordingly, the MH trend with SBA-15 content was strongly dependent on aging times.

Viscoelastic Relaxation in Glassy Polymers

1986 ◽  
Vol 79 ◽  
Author(s):  
T. S. Chow
Keyword(s):  
Physical Aging ◽  
Glassy State ◽  
Relaxation Times ◽  
Relaxation Modulus ◽  
Time Spectrum ◽  
Shift Factor ◽  
Glassy Polymers ◽  
Viscoelastic Relaxation ◽  
Hole Energy ◽  
Slow Decay

AbstractThe nonequilibrium mechanism controlling the viscoelastic response in the glassy state is analyzed in accordance with our multiple hole energy model. The change in the nonequilibrium glassy state defines the Struik physical aging exponent and determines the motion of the relaxation time spectrum, the transition of the global shift factor and the slow decay of the stress relaxation modulus especially at longer times in the glassy state where the Kohlrausch-Williams-Watts function fails. Although the distribution of relaxation times has its time scales shifted with the aging time, the shape of the spectrum remains very much the same which supports the notion of thermo-aging-rheological simplicity in the glassy and transition states.

Physical aging of glassy state: DSC study of vitrified glycerol systems

Cryobiology ◽  
1991 ◽  
Vol 28 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Zhao Hua Chang ◽  
John G. Baust
Keyword(s):  
Physical Aging ◽  
Glassy State

Physical aging deep in the glassy state of a fully cured polyimide

1992 ◽  
Vol 45 (9) ◽  
pp. 1501-1516 ◽  
Author(s):  
R. A. Venditti ◽  
J. K. Gillham
Keyword(s):  
Physical Aging ◽  
Glassy State

The origin of the faster mechanism of partial enthalpy recovery deep in the glassy state of polymers

2021 ◽  
Author(s):  
Kia L Ngai
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Partial Enthalpy ◽  
Enthalpy Recovery

A novel finding made by Cangialosi and coworkers in physical aging of several polymers way below the glass transition temperature Tg is that equilibrium recovery occurs by reaching a plateau...

Physical Aging of Amorphous Matter: Down to the Nanometric Scale

2006 ◽  
Vol 115 ◽  
pp. 99-112 ◽  
Author(s):  
S. Etienne ◽  
L. David ◽  
E. Duval ◽  
A. Mermet ◽  
A. Wypych ◽  
...  
Keyword(s):  
Liquid Glass ◽  
Characteristic Time ◽  
Degrees Of Freedom ◽  
Physical Aging ◽  
Glassy State ◽  
Relaxation Processes ◽  
Inelastic Light Scattering ◽  
Heterogeneous Nature ◽  
Cooperative Relaxation ◽  
Amorphous Matter

Different degrees of freedom exist in amorphous matter, and are at the origin of relaxation processes (e.g. structural, mechanical). The effect of physical aging of the glassy network on secondary and primary (and cooperative) relaxation is studied. It is shown that if the temperature of aging is below the liquid glass transition temperature and above that of the secondary relaxation, the strength of this last relaxation changes in a non monotonous complex way while the characteristic time of the primary relaxation increases. This feature is explained taking into account the heterogeneous nature of the glassy network. This concept is in agreement with recent inelastic light scattering observations showing that fluctuations of the elastic constants at the nanometric scale are characteristic of the glassy state.

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