Polymer activation energy

The activation energy may be considered as an energy barrier that must be overcome before materials break down. After aging, the tensile strength of the material is calculated as follows: where [ 34 ] is decreased value of activation energy and is the aging temperature.

Dividing 6 by 5 and noting that , one can obtain. After some conversions, we have where. Formula 8 allows quantitatively determining the decrease in activation energy during the aging process. In the experimental conditions with the aging temperature of K, where , formula 8 may be converted to. Adding the k T values of all samples from Table 4 to 5 , the decrease of activation energy during heat aging can be calculated as shown in Table 5.

Adding the values for all samples from Table 4 to 10 , can be calculated as shown in Table 6. It is obvious that, in mechanical aging, the CR content is of significant effect on activation energy of the rubber blends. These results are consistent with the swelling behavior discussed previously.

In the complex aging condition, the tensile strength of samples decreases by both factors of heat and dynamic loading. Formula 8 can be converted to. Using 11 with the k c values from Table 4 , for all samples were calculated and presented in Table 7. It can be also concluded that the complex aging values depend on both from heat aging and from mechanical aging.

The decrease of tensile strength in complex aging conditions may be from heat aging, where is higher than about times. When the rubber samples are under both heat and dynamic loading, these factors may act independently. The hardness shore A , tensile strength, elongation at break, permanent compression, and rebound property data, as well as the calculated activation energy data, used to support the findings of this study are included within the article.

This research was funded by the National Subject KC This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors. Read the winning articles. Journal overview. Special Issues. Academic Editor: Gulaim A. Received 07 Jun Revised 23 Sep Accepted 25 Oct Published 17 Nov Abstract Selection of a suitable thermal aging process could render desirable mechanical properties of the rubbers or blended rubbers. Introduction Natural rubber NR , a very important elastomer, has been widely used in wide range of technical and civil applications.

Experimental Section 2. Table 1. Figure 1. Table 2. Figure 2. Table 3. Table 4. The slope of the viscosity curve of each material, , is taken to obtain the viscous flow activation of the polymer melt at different hole diameters of the die and shear rates.

Figure 1 shows the curve of viscous flow activation energy to shear rate for three materials at different hole diameters of the die. D means the hole diameter of die, and means the shear rate. It can be seen that the viscous flow activation energy of the three materials decreases with the shear rate at low shear rates and keeps constant at high shear rates, which indicates that the sensitivity of the viscosity to temperature reduces with the shear rate at low shear rate while keeping constant at high shear rate.

With the increased shear rate, the resistance-increase effect increases, so the viscous flow activation energy is larger. Therefore, the viscous flow activation energy decreases with the shear rate. This result is basically consistent with what were obtained in the literatures [ 20 , 21 ].

It indicates that there is a resistance-increasing effect on the melt flow for PMMA due to the existence of wall slip at the microscopic scale. The smaller the hole diameter of the die, the more obvious the resistance-increasing effect [ 22 ].

The deformation energy storage and dissipation are increased, so the viscous flow activation energy is increased [ 23 ]. It is consistent with the findings of J. Liang [ 13 ], who reported that the deformation energy storage and dissipation decrease with the microchannel diameter. And the difference of the viscous flow activation energy on the PMMA is significantly reduced. The smaller the hole diameter of the die, the more obvious the resistance-reducing effect [ 22 ].

The flow deformation energy storage and dissipation are reduced, so the viscous flow activation energy is reduced. It also can be seen from Figure 2 that the noncrystalline PMMA has the highest viscous flow activation energy due to the molecular chain structure. PP molecular chain structure only contains a side methyl group, -CH3, so the viscous flow activation energy is second. While the molecular backbone structure of HDPE does not contain any side groups, and only few short branches, the molecular chain is more flexible.

The internal rotation is easy to carry out, and the motion unit has a small chain segment, so the viscous flow activation energy is the lowest [ 24 ]. Therefore, in addition to the melt shear rate, the die diameter and molecular chain structure have a significant influence on the viscous flow activation energy. Since the polymer materials in this test are all pseudoplastic non-Newtonian fluids, the shear stress and shear rate are in accordance with the power law function equation [ 12 ]:.

Taking the logarithm on the two sides of the equation as follows: where is shear stress, is consistency coefficient, is non-Newtonian index, and is shear rate. The calculation of the non-Newtonian index considers the influence of both temperature and hole diameter of the die instead of the shear rate [ 13 , 26 ].

After linear regression of the curves, the non-Newtonian index of each polymer melt at both microscales and macroscales was obtained at different temperatures as shown in Figure 3. It can be seen from Figure 3 that the non-Newtonian index of the three materials increases with temperature regardless of the amorphous or crystalline polymer, which indicates that the sensitivity of the viscosity to the shear rate decreases with temperature.

It is due to the fact that the higher the temperature, the more intense the segment movement. The entanglement of the chain is solved by the shear stress; meanwhile, the reestablishment of that is obtained by the thermal motion. Therefore, it partially reduces the effect of shear rate.

The non-Newtonian properties of the melt are attenuated with temperature [ 15 ]. It indicates that the larger the hole diameter of the die, the weaker wall sliding effect at the microscale due to the existence of wall slip and that the non-Newtonian properties of the melt increase with the wall shear stress [ 21 ]. Reasons are analyzed within the macroscopic scale. On the one hand, the influence of wall slip is eliminated.

On the other hand, with the increased hole diameters of the die, the tensile effect in the convergent flow at the inlet is weakened, and the elastic storage energy is reduced.

When the melt flows, the resistance is decreased and the non-Newtonian properties are weakened, resulting in an increase or no change of non-Newtonian index. Liang [ 13 ] also believes that when the external force conditions are constant, the non-Newtonian index of the melt increases with the diameter of the channel.

Therefore, the non-Newtonian index is not only related with melt temperature but also related with feature size. Variations in feature size are bound to cause changes in the melt non-Newtonian index. From the above three polymer melt rheology tests, it can be seen that the viscous flow activation energy of the polymer melt is mainly related to the shear rate, the feature size, and the material type.

And the viscous flow activation energy has a monotonous decreasing trend with the shear rate. Therefore, considering the influence of the above factors, the size-based viscous flow activation energy model SVAE model is developed as follows:. According to the testing data of polymer melt, the regression analysis shows that the relationship among the coefficients A and B and feature size D of the die is a cubic polynomial model. Therefore, the viscous flow activation energy model based on feature size is further developed as shown in.

The parameter values of different materials can be obtained by regression analysis as shown in Table 2. The calculated viscous flow activation energy value by the conventional equation itself has a certain error, and the feature size has little effect on the viscous flow activation energy for the crystalline polymer material.

Makarov, and A. Stalevich, Izv. Stalevich J. Stalevich, A. Makarov, and E. Saidov, Izv. Makarov, Izv. Stalevich and A. Prom-sti [In Russian], 23, No. Pereborova, Fibre Chemistry , No. Download references. The study was financed within the framework of the state assignment of the Ministry of Science and Higher Education of the Russian Federation, Project No.

Klimova, N. You can also search for this author in PubMed Google Scholar. Zhu, Y. High electrochemical stability of a 3D cross-linked network PEO nano-SiO 2 composite polymer electrolyte for lithium metal batteries. A 7 , — Lee, W. Ceramic-salt composite electrolytes from cold sintering. Google Scholar. Yang, X. Determining the limiting factor of the electrochemical stability window for PEO-based solid polymer electrolytes: main chain or terminal —OH group?

Chen, R. Addressing the interface issues in all-solid-state bulk-type lithium ion battery via an all-composite approach. ACS Appl. Interfaces 9 , — Bouchet, R. Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries. Zhou, D. In situ synthesis of a hierarchical all-solid-state electrolyte based on nitrile materials for high-performance lithium-ion batteries. Energy Mater. Jiang, T.

Solvent-free synthesis of thin, flexible, nonflammable garnet-based composite solid electrolyte for all-solid-state lithium batteries. Markvicka, E. An autonomously electrically self-healing liquid metal—elastomer composite for robust soft-matter robotics and electronics.

Pan, C. A liquid-metal—elastomer nanocomposite for stretchable dielectric materials. Kim, H. Ionoelastomer junctions between polymer networks of fixed anions and cations.

Science , — Park, M. Highly stretchable electric circuits from a composite material of silver nanoparticles and elastomeric fibres. Chen, L. Nano Energy 46 , — Wang, F. Progress report on phase separation in polymer solutions.

Seo, M. Reticulated nanoporous polymers by controlled polymerization-induced microphase separation. Schulze, M. High-modulus, high-conductivty nanostructured polymer electrolyte membrane via polymerization-induced phase separation.

Alarco, P. The plastic-crystalline phase of succinonitrile as a universal matrix for solid-state ionic conductors. Choi, K. Thin, deformable, and safety-reinforced plastic crystal polymer electrolytes for high-performance flexible lithium-ion batteries.

White, T. Polymerization kinetics and monomer functionality effects in thiol-ene polymer dispersed liquid crystals. Macromolecules 40 , — Serbutoviez, C. Polymerization-induced phase separation.

Morphology of polymer-dispersed liquid crystal thin films. Macromolecules 29 , — Phillip, W. Diffusion and flow across nanoporous polydicyclopentadiene-based membranes. Interfaces 1 , —