scholarly journals Structure Evolution of Epoxidized Natural Rubber (ENR) in the Melt State by Time-Resolved Mechanical Spectroscopy

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 946
Author(s):  
Rossella Arrigo ◽  
Leno Mascia ◽  
Jane Clarke ◽  
Giulio Malucelli
Keyword(s):  
Natural Rubber ◽  
Rheological Behavior ◽  
Structural Changes ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Epoxidized Natural Rubber ◽  
Structure Evolution ◽  
Gradual Transition ◽  
Mechanical Spectroscopy ◽  
Time Resolved

In this work, time-resolved mechanical spectroscopy (TRMS) was used to accurately characterize the rheological behavior of an epoxidized natural rubber (ENR) containing 25 mol% of epoxy groups. Conventional rheological tests are not suitable to characterize with accuracy the frequency-dependent linear viscoelastic behavior of materials, such as ENR, in a transient configurational state. For this reason, TRMS was used to determine the true rheological behavior of ENR, as well as to gain some insights into the changes of its macromolecular architecture under the dynamic conditions experienced during the measurements. The constructed master curves for the moduli revealed a gradual transition of the ENR rheological state from liquid-like to solid-like through the formation of an “elastic gel” throughout the bulk of the polymer. Furthermore, the evolution of the stress relaxation modulus revealed a slow relaxation mechanism, resulting from thermally activated reactions in the molten state attributed to the formation of crosslinks. Finally, the crosslink density evolution was estimated from the TRMS data and compared with results derived from equilibrium solvent-swelling measurements. These demonstrated the accuracy of the TRMS data in the prediction of the structural changes that can take place in polymers during processing.

scholarly journals Effect of SiO2 Particles on the Relaxation Dynamics of Epoxidized Natural Rubber (ENR) in the Melt State by Time-Resolved Mechanical Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 276
Author(s):  
Rossella Arrigo ◽  
Leno Mascia ◽  
Jane Clarke ◽  
Giulio Malucelli
Keyword(s):  
Natural Rubber ◽  
Rheological Behavior ◽  
Loss Modulus ◽  
Chain Scission ◽  
Epoxidized Natural Rubber ◽  
Simultaneous Occurrence ◽  
Relaxation Dynamics ◽  
Mechanical Spectroscopy ◽  
Time Resolved ◽  
Two Parameters

The rheological behavior of an epoxidized natural rubber (ENR) nanocomposite containing 10 wt.% of silica particles was examined by time-resolved mechanical spectroscopy (TRMS), exploiting the unique capability of this technique for monitoring the time-dependent characteristics of unstable polymer melts. The resulting storage modulus curve has revealed a progressive evolution of the elastic component of the composite, associated with slower relaxations of the ENR macromolecular chains. Two major events were identified and quantified: one is associated with the absorption of the epoxidized rubber macromolecules onto the silica surface, which imposes further restrictions on the motions of the chains within the polymer phase; the second is related to gelation and the subsequent changes in rheological behavior resulting from the simultaneous occurrence cross-linking and chain scission reactions within the ENR matrix. These were quantified using two parameters related to changes in the storage and loss modulus components.

Solvent Dependence of Structural Dynamics and Spin-flip Processes in 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (ortho-3CzBN)

2020 ◽  
Author(s):  
Masaki Saigo ◽  
Kiyoshi Miyata ◽  
Hajime Nakanotani ◽  
Chihaya Adachi ◽  
Ken Onda
Keyword(s):  
Dft Calculations ◽  
Excited States ◽  
Structural Changes ◽  
Photophysical Properties ◽  
Delayed Fluorescence ◽  
Time Resolved ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Solvent Dependence ◽  
Acetonitrile Solutions

We have investigated the solvent-dependence of structural changes along with intersystem crossing of a thermally activated delayed fluorescence (TADF) molecule, 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (o-3CzBN), in toluene, tetrahydrofuran, and acetonitrile solutions using time-resolved infrared (TR-IR) spectroscopy and DFT calculations. We found that the geometries of the S1 and T1 states are very similar in all solvents though the photophysical properties mostly depend on the solvent. In addition, the time-dependent DFT calculations based on these geometries suggested that the thermally activated delayed fluorescence process of o-3CzBN is governed more by the higher-lying excited states than by the structural changes in the excited states.<br>

Preparation coated of urea beads from banana peel bioplastic and epoxidized natural rubber 50

2020 ◽  
Author(s):  
H. K. Abdulkadir ◽  
S. A. Abdul Shukor ◽  
R. Hamzah ◽  
N. Z. Noriman ◽  
Omar S. Dahham ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Epoxidized Natural Rubber ◽  
Banana Peel
Sign in / Sign up

Export Citation Format

Share Document