Determination of Melting-, Boiling-, Glass Transition Temperatures

Thermal analysis is a powerful technique to measure the relationship between the physical properties of substances and temperature. It is mainly used to study physical changes (glass transition, melting, boiling, and adsorption, etc.) and chemical changes (dehydration, decomposition, oxidation, and reduction, etc.). Thermal analysis not only provides thermodynamic parameters, but also kinetic data with certain reference value. Therefore, thermal analysis is an important analysis method in the theoretical research of thermodynamics and kinetics, providing valuable information on the research and selection of materials.

Melting Temperature

The melting temperature (T_m) refers to the temperature at which the material transforms from a solid crystal to a liquid amorphous state when the temperature is raised. The melting peak can be used to study the crystallinity, purity and crystal form of the polymer.

Boiling Temperatures

Boiling is a phenomenon of violent vaporization that occurs simultaneously inside and on the surface of a liquid at a certain temperature. The boiling temperature is at which the saturated vapor pressure of the liquid is equal to the external pressure. The boiling temperature changes with the change of external pressure, the pressure is low, the boiling temperature is also low.

Glass Transition Temperature

The glass transition temperature (T_g) is one of the most important thermophysical properties of amorphous polymers. It refers to the transition temperature from the glass state to the high elastic state of the amorphous phase in an amorphous polymer or a partially crystalline polymer.

Application of Our Services

• Study the thermal oxidation, thermal degradation and thermal crosslinking of polymers.
• Study the compatibility of multiphase systems, etc.

Figure 1. (a) Predicted melt pool temperature contours after scanning the 5th track, (b) melt pool width of various scanning speeds, (c) melt pool depth of various scanning speeds, (d) comparison of the predicted melt pool dimensions as function of scanning speed and (e) comparison of the melting depth of simulation and experiment. (Hussein, A.; et al. 2013)

At Alfa Chemistry, we use various thermochemical calculation software to simulate and determine the T_m, boiling temperature and T_g using molecular dynamic (MD) simulation. Our simulation process are as follows:

Melting Temperature Simulation

Step1. Input the ingredients and the atmosphere conditions.

Step2. Build a structure: Melt it at a temperature higher than the T_m to obtain a liquid structure.

Step3. Construct an identical structure under the same conditions, and relax below the T_m to obtain a solid structure.

Step4. Compliment the liquid structure in Step2 with the temperature used in Step3 to get a supercooled liquid structure.

Step5. Combine the two models in Step3 and Step4, and relax briefly to eliminate the stress.

Step6. After the structure in Step5 is resolved, the equilibrium temperature is determined as the T_m when the system is stable.

Step7. Output the equilibrium calculation results at the multiphase transition temperature.

Step8. Export system properties (such as T_m, pressure, etc.), and species properties.

Boiling Temperatures Determination

• Create a new blank document.
• Find and select the substance in the Selection of Components.
• Select the physical property method 'NRTL' on the Global tab page in Method. Set parameters in the menu tree.
• Enter the Pure Analysis page and select the physical properties to be calculated. The boiling temperature is a thermodynamic property, so the thermodynamics properties are selected.
• Check the result, when the saturated vapor pressure is equal to the outside atmospheric pressure, it is the boiling temperature of the substance under the outside atmospheric pressure.

Figure 2. Molecular dynamics simulations for T_g predictions of polyhydroxyalkanoate biopolymers. (Bejagam, K. K.; et al. 2020)

Glass Transition Temperatures Calculation

1. The software Gromacs is used to simulate the T_g of polymers.

2. Cool down the structure from a higher temperature (1000 K).

3. After 8 ns of equilibrium, the simulation of cooling process starts.

4. The simulation rate is 10 K/ns, and the data obtained from the balance process is used for the density calculation.

5. Determine the T_g value based on density.

Our determination of melting-, boiling-, glass transition temperatures services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!

References

• Hussein, A.; et al. Finite element simulation of the temperature and stress fields in single layers built without-support in selective laser melting. Materials & Design. 2013, 52: 638-647.
• Bejagam, K. K.; et al. Molecular dynamics simulations for glass transition temperature predictions of polyhydroxyalkanoate biopolymers. Physical Chemistry Chemical Physics. 2020, 22.