Influence of lithium perchlorate on the properties of polyether networks: specific volume and glass transition temperature

1988 ◽  
Vol 21 (4) ◽  
pp. 1117-1120 ◽  
Author(s):  
Jean Francois Le Nest ◽  
Alessandro Gandini ◽  
Herve Cheradame ◽  
Jean Pierre Cohen-Addad
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Specific Volume ◽  
Lithium Perchlorate

Molecular Dynamics Simulation on Compatibility and the Glass Transition Temperature of HTPB/Plasticizer Blends

2013 ◽  
Vol 718-720 ◽  
pp. 136-140 ◽  
Author(s):  
Lu Xia Yang ◽  
Lin Yu Mei ◽  
Yan Hua Lan ◽  
Li Qiong Liao ◽  
Yi Zheng Fu
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Specific Volume ◽  
Md Simulation ◽  
Dibutyl Phthalate ◽  
Dioctyl Phthalate ◽  
Dynamics Simulation ◽  
Solubility Parameters

By means of full atomistic molecular dynamics (MD) simulation, the solubility parameters for hydroxyl-terminated polybutadiene (HTPB), dioctyl sebacate (DOS), dioctyl adipate (DOA), dibutyl phthalate (DBP), dioctyl phthalate (DOP), nitrated esters nitroglycerine (NG) and diethylene glycol dinitrate (DEGDN) are calculated and the results are in agreement with the literature values. Furthermore, in order to reveal the HTPB/plasticizer blend property, the specific volume vs. temperature curves of the blend systems are simulated by employing MD simulation to obtain the glass transition temperature (Tg). From the specific volume vs. temperature curve, the Tg of HTPB, HTPB/DOS, HTPB/DOA, HTPB/DBP, HTPB/DOP, HTPB/NG and HTPB/DEGDN are 197.54, 176.30, 183.11, 189.27,187.40, 200.03 and 205.31 K, respectively. It should be pointed out that as for HTPB and DOS, DOA, DBP, DOP, the solubility parameters are similar and there is only one glass transition of the blend system, these indicate that these studied blend systems are miscible, but HTPB/NG and HTPB/DEGDN are not miscible.

scholarly journals Model of the DGEBA-EDA Epoxy Polymer: Experiments and Simulation Using Classical Molecular Dynamics

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Andreas Gavrielides ◽  
Thomas Duguet ◽  
Maëlenn Aufray ◽  
Corinne Lacaze-Dufaure
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Specific Volume ◽  
Conversion Degree ◽  
Cross Linking ◽  
Stoichiometric Ratio ◽  
Covalent Bonds ◽  
Conversion Rates

Polyepoxy samples are synthesized from diglycidylether of bisphenol A (DGEBA) and ethylene diamine (EDA) monomers at a stoichiometric ratio of 2 DGEBA : 1 EDA in model conditions in order to promote a high degree of polymerization and a low density of defects and to try to approach the ideal models obtained by simulation. A slow polymerization (>24 h at ambient temperature) and a postcuring achieved in an inert atmosphere lead to a conversion degree of 92±2% and a midpoint glass transition temperature of 391±1 K. In parallel, a model is created with a multistep cross-linking procedure. In this work, all-atom molecular dynamics (MD) simulations are performed with LAMMPS and the GAFF 1.8 force field. In the initial liquid mixture of reactants (600 molecules), proper mixing is demonstrated by the calculation of the partial radial distribution functions (RDF), which show a minimum intermolecular distance of 2.8 Å and similar distributions for EDA-EDA, DGEBA-DGEBA, and DGEBA-EDA molecules in the simulation boxes. Then, in alternation with MD equilibrations, cross-linking is performed on frozen configurations by creating covalent bonds between reactive pairs within a reaction radius of 3 Å. The resulting boxes show conversion rates of 90-93% and densities close to the experimental value. Finally, a cooling ramp from 700 K to 25 K is applied in order to monitor the specific volume and the coefficient of volumetric thermal expansion (CVTE) of the polymer and to derive the glass transition temperature. Experimental thermomechanical analyses (TMA) compares well with simulations for both the specific volume and the CVTE evolutions with temperature. Whereas the uncertainty remains high with the fitting procedure used, we calculate a glass transition temperature of 390±8 K which compares very well with the experimental values (391±1 K from DSC and 380 K from TMA).

Molecular Dynamics Simulations of the Glass Transition Temperature of Amorphous Cellulose

2012 ◽  
Vol 214 ◽  
pp. 7-11 ◽  
Author(s):  
Xiu Mei Zhang ◽  
M.A. Tschopp ◽  
Sheldon Q. Shi ◽  
Jun Cao
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Specific Volume ◽  
Reasonable Agreement ◽  
Reactive Force ◽  
Time Step ◽  
Amorphous Cellulose ◽  
Dynamics Simulations ◽  
Insight Into

Molecular modeling and dynamics simulations were used to generate equation of state properties of amorphous cellulose with the reactive force field ReaxFF which has been extensively parameterized and validated for hydrocarbon in a previous communication. Obtaining specific volume as a function of temperature for amorphous cellulose, the change in slope of the specific volume vs. temperature curves can be used to locate glass transition temperatures (Tg) reliably. With the results, there was reasonable agreement between experimental results and values of density and Tg obtained from the simulations. In addition, the suitable ReaxFF time step was investigated to help conserve the total energy of the system. The results show that the glass transition temperature can be used to verify the equilibration of the amorphous cellulose and to provide insight into the further deformation simulations.

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