Segmental Dynamics in Poly(3-hydroxybutyrate-co- 4-hydroxybutyrate)s above the Glass Transition Temperature: 13C Nuclear Magnetic Relaxation in the Amorphous Phase

1996 ◽  
Vol 29 (7) ◽  
pp. 2479-2486 ◽  
Author(s):  
A. Spyros ◽  
R. H. Marchessault
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Phase ◽  
Magnetic Relaxation ◽  
Nuclear Magnetic Relaxation ◽  
Segmental Dynamics ◽  
Nuclear Magnetic

scholarly journals Modelling the Mechanical and Strain Recovery Behaviour of Partially Crystalline PLA

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1342 ◽  
Author(s):  
John Sweeney ◽  
Paul Spencer ◽  
Karthik Nair ◽  
Phil Coates
Keyword(s):  
Finite Element ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Stress Relaxation ◽  
Shape Memory ◽  
Yield Stress ◽  
Amorphous Phase ◽  
Strain Recovery ◽  
Stress Strain

This is a study of the modelling and prediction of strain recovery in a polylactide. Strain recovery near the glass transition temperature is the underlying mechanism for the shape memory in an amorphous polymer. The investigation is aimed at modelling such shape memory behaviour. A PLA-based copolymer is subjected to stress–strain, stress relaxation and strain recovery experiments at large strain at 60 °C just below its glass transition temperature. The material is 13% crystalline. Using published data on the mechanical properties of the crystals, finite element modelling was used to determine the effect of the crystal phase on the overall mechanical behaviour of the material, which was found to be significant. The finite element models were also used to relate the stress–strain results to the yield stress of the amorphous phase. This yield stress was found to possess strain rate dependence consistent with an Eyring process. Stress relaxation experiments were also interpreted in terms of the Eyring process, and a two-process Eyring-based model was defined that was capable of modelling strain recovery behaviour. This was essentially a model of the amorphous phase. It was shown to be capable of useful predictions of strain recovery.

13C Nuclear Magnetic Relaxation Study of Segmental Dynamics of Hyaluronan in Aqueous Solutions

2005 ◽  
Vol 6 (3) ◽  
pp. 1397-1404 ◽  
Author(s):  
Photis Dais ◽  
Emmanuel Tylianakis ◽  
John Kanetakis ◽  
Francois R. Taravel
Keyword(s):  
Aqueous Solutions ◽  
Magnetic Relaxation ◽  
Nuclear Magnetic Relaxation ◽  
Segmental Dynamics ◽  
Relaxation Study ◽  
Nuclear Magnetic

Effects of counterion size and backbone rigidity on the dynamics of ionic polymer melts and glasses

2017 ◽  
Vol 19 (40) ◽  
pp. 27442-27451 ◽  
Author(s):  
Yao Fu ◽  
Vera Bocharova ◽  
Mengze Ma ◽  
Alexei P. Sokolov ◽  
Bobby G. Sumpter ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Melts ◽  
Static Dielectric Constant ◽  
Segmental Dynamics ◽  
Ionic Polymer ◽  
Segmental Relaxation

Backbone rigidity, counterion size and the static dielectric constant affect the glass transition temperature, segmental relaxation time and decoupling between counterion and segmental dynamics in significant manners.

Isothermal Crystallization of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy Near the Glass Transition Temperature

2004 ◽  
Vol 449-452 ◽  
pp. 933-936 ◽  
Author(s):  
Zhuang Qi Hu ◽  
Q.S. Zhang ◽  
Hai Feng Zhang ◽  
B.Z. Ding ◽  
Z.M. Rao
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Alloy ◽  
Amorphous Phase ◽  
Isothermal Crystallization ◽  
Metastable Phases ◽  
Bulk Amorphous Alloy ◽  
Thermal Stability Of

Isothermal crystallization of Zr55Al10Ni5Cu30bulk amorphous alloy near the glass transition temperature has been investigated. The microstructures and thermal stability of the annealed amorphous alloy were examined by HRTEM, XRD and DSC. The amorphous phase in the Zr55Al10Ni5Cu30bulk amorphous alloy crystallized at 420°C through the following processes of amorphous →amorphous with clusters + metastable phases→metastable phases.

Fast Dynamics in Glass-Forming Polymers Revisited

1996 ◽  
Vol 455 ◽  
Author(s):  
J. Colmenero ◽  
A. Arbe ◽  
C. Mijangos ◽  
H. Reinecke
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Supercooled Liquid ◽  
Time Range ◽  
Time Behavior ◽  
Exponential Behavior ◽  
Segmental Dynamics ◽  
Glass Forming ◽  
Short Time

ABSTRACTThe so called “fast-dynamics” of glass-forming systems as observed by time of flight (TOF) neutron scattering techniques is revisited. TOF-results corresponding to several glass-forming polymers with different chemical microstructure and glass-transition temperature are presented together with the theoretical framework proposed by us to interpret these results. The main conclusion is that the TOF-data can be explained in terms of quasiharmonic vibrations and the particular short time behavior of the segmental dynamics. The segmental dynamics display in the very short time range (t ≈ 2 ps) a crossover from a simple exponential behavior towards a non-exponential regime. The first exponential decay, which is controlled by C-C rotational barriers, can be understood as a trace of the behavior of the system in absence of the effects (correlations, cooperativity, memory effects…) which characterize the dense supercooled liquid like state against the normal liquid state. The non-exponential regime at t > 2 ps corresponds to what is usually understood as α and β relaxations. Some implications of these results are also discussed.

Sign in / Sign up

Export Citation Format

Share Document