Glass Transition Dynamics of Poly(L-lactic acid) during Isothermal Crystallisation Monitored by Real-Time Dielectric Relaxation Spectroscopy Measurements

2005 ◽  
Vol 26 (17) ◽  
pp. 1423-1427 ◽  
Author(s):  
Madalena Dionísio ◽  
María Teresa Viciosa ◽  
Yaming Wang ◽  
João F. Mano
Keyword(s):  
Lactic Acid ◽  
Glass Transition ◽  
Dielectric Relaxation ◽  
Real Time ◽  
Dielectric Relaxation Spectroscopy ◽  
Transition Dynamics ◽  
Isothermal Crystallisation

scholarly journals Using Dielectric Relaxation Spectroscopy to Characterize the Glass Transition and Onset of Crystallinity of Skim-Milk Powder

2018 ◽  
Author(s):  
Martin G. Buehler
Keyword(s):  
Glass Transition ◽  
Shelf Life ◽  
Dielectric Relaxation ◽  
Loss Tangent ◽  
Milk Powder ◽  
Skim Milk ◽  
Skim Milk Powder ◽  
Dielectric Relaxation Spectroscopy ◽  
Scanning Calorimetry ◽  
Boundary Curves

This paper describes the dielectric relaxation spectroscopy (DRS) method for obtaining glass transition temperature and the onset of crystallinity of skim milk powder (SMP). The methodology consists of exposing SMP samples to numerous constant temperatures, T, and water activities, aw, and measuring the relaxation time. Measurements are based on changes in the loss-tangent height at its peak frequency. Glass transition times are identified at peaks in the loss-tangent height versus time curve and the onset of crystallinity times are identified when the loss-tangent height collapses. The analysis leads to two boundary curves: glass transition Tg, aw curve and the onset of crystallinity Tc, aw curve. They separate the SMP stable (long shelf life) and unstable (short shelf life) regions. Two curve fitting algorithms were developed for (a) aw2, tg curve where tg is the time to glass transition and aw2, tc curve where time tc is the time to onset of crystallinity and (b) Tg, aw and Tc, aw boundary curves. Finally, the DRS data are compared to differential scanning calorimetry (DSC) results.

Crystallization of Poly(l-lactic acid) Probed with Dielectric Relaxation Spectroscopy

2006 ◽  
Vol 39 (19) ◽  
pp. 6513-6520 ◽  
Author(s):  
Ana Rita Brás ◽  
María Teresa Viciosa ◽  
Yaming Wang ◽  
Madalena Dionísio ◽  
João F. Mano
Keyword(s):  
Lactic Acid ◽  
Dielectric Relaxation ◽  
Dielectric Relaxation Spectroscopy

scholarly journals Effect of soft segment molecular weight on the glass transition, crystallinity, molecular mobility and segmental dynamics of poly(ethylene oxide) based poly(urethane–urea) copolymers

RSC Advances ◽  
2017 ◽  
Vol 7 (65) ◽  
pp. 40745-40754 ◽  
Author(s):  
Oguzhan Oguz ◽  
Stefanos A. Koutsoumpis ◽  
Eren Simsek ◽  
Emel Yilgor ◽  
Iskender Yilgor ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Ethylene Oxide ◽  
Dielectric Relaxation ◽  
Molecular Mobility ◽  
Soft Segment ◽  
Dielectric Relaxation Spectroscopy ◽  
Segmental Dynamics ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

The effect of poly(ethylene oxide) (PEO) soft segment molecular weight (Mn= 2000, 4600, 8000 g mol−1) molecular mobility and segmental dynamics of a series of polyurethane–urea copolymers (PU) was investigated by dielectric relaxation spectroscopy.

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