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 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 Combined thermal analysis of plant oils

2021 ◽  
Author(s):  
Kinga Tamási ◽  
Kálmán Marossy
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Low Temperature ◽  
Glassy State ◽  
Mechanical Analysis ◽  
Plant Oils ◽  
Scanning Calorimetry ◽  
Natural Plant ◽  
The Moment ◽  
Current Reversal

AbstractThe paper deals with the study of seven selected natural plant oils. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermally stimulated discharge (TSD) methods were used. It has been found that most of the oils tested are in a glassy state at low temperature and have multiple transitions in the low temperature range. DSC shows complex melting-like processes or glass transition. For both DMA and TSD, the scaffold supportive method was used and found as a suitable one. DMA and TSD proved more sensitive than DSC and revealed at least two transitions between − 120 and − 40 °C. In the case of three oils (argan, avocado and sunflower), current reversal was observed by TSD; this symptom cannot be fully explained at the moment.

Physical aging of atactic polystyrene as seen by dielectric relaxational and low-frequency vibrational Raman spectroscopies

2005 ◽  
Vol 351 (33-36) ◽  
pp. 2593-2598 ◽  
Author(s):  
A. Wypych ◽  
E. Duval ◽  
G. Boiteux ◽  
J. Ulanski ◽  
L. David ◽  
...  
Keyword(s):  
Physical Aging ◽  
Low Frequency ◽  
Atactic Polystyrene

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.

Formation of active centres and generation of chains on low temperature photosensitized polymerization of acrylonitrile in the glassy state

1988 ◽  
Vol 30 (5) ◽  
pp. 1006-1013
Author(s):  
L.N. Aleksandrova ◽  
M.I. Gorilovskii ◽  
O.B. Mikova ◽  
G.N. Gerasimov ◽  
A.D. Abkin (dec.)
Keyword(s):  
Low Temperature ◽  
Glassy State ◽  
Active Centres

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
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