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Tribology of Polymer and their Composites
Published in Ahmed Abdelbary, Extreme Tribology, 2020
Thermal degradation of polymers is a molecular deterioration occurring at high temperatures. The components of the long chain of an overheated polymer can begin to separate and react with one another to change the properties of the polymer. This generally involves changes in the molecular weight of the polymer. Typical property changes include ductility reduction, chalking, color changes, cracking and general reduction in most other desirable physical properties (Madorsicy and Straus, 1959).
A review on viscosity retention of PAM solution for polymer flooding technology
Published in Petroleum Science and Technology, 2022
Juan Du, Chunhong Lv, Xitang Lan, Jifeng Song, Pingli Liu, Xiang Chen, Qiang Wang, Jinming Liu, Guixian Guo
Thermogravimetric analysis is often used to determine the kinetic parameters such as activation energy and reaction order for thermal degradation of polymers (Zhang et al. 2017). Mu-hoe Yang et al. used thermogravimetric analysis to conduct experiments on polyacrylamide solid powder at four heating rates of 5, 10, 20 and 40 °C/min in a nitrogen atmosphere in the range of 100–900 °C, and continuously recorded the changes in temperature and weight of samples, as well as the difference in weight. The results show that thermal degradation can be divided into two different stages, and the first stage is the first-order reaction with PAM weight loss rate of about 10% and activation energy of 32.8 kcal/mol, and the second stage is the second-order reaction with PAM weight loss rate of about 80% and activation energy of 45.6 kcal/mol (Yang 1998).
Novel methacrylate copolymers functionalized with fluoroarylamide; copolymerization kinetics, thermal stability and antimicrobial properties
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Kinetic of thermal degradation of solids has been investigated from thermogravimetric (TG) thermograms at linear rates of temperature rise in a number of studies. Thermogravimetry is widely used as a method to investigate the thermal degradation of polymers and to determine the kinetic parameters. The thermal stability and degradation depend on the composition [5, 19].
Structure of graphene and its disorders: a review
Published in Science and Technology of Advanced Materials, 2018
Gao Yang, Lihua Li, Wing Bun Lee, Man Cheung Ng
Thermal annealing of graphene in certain environment allows the removal of lattice defects and the restoration of graphitic structure. For e.g. surface contamination by polymer residues in graphene transfer step can be partially reduced by annealing at vacuum or reducing environment, as mentioned in Section 3.6. The sensitivity of electronic structure of graphene to the removal of polymer residue can be harnessed to tailor the properties of graphene. Generally, thermal degradation of polymers like PMMA is a complex radical chain reaction [341], which proceeds in three steps [342], as seen in Figure 18(b). Lin et al. [329] employed TEM in combination with Raman spectroscopy to study the thermal decomposition of PMMA (see Figure 18(a)). The decomposition temperature was lower for PMMA facing the air (PMMA–A) but higher for PMMA facing the graphene (PMMA–G). Experimental results reveal that the interaction between the thermally generated free carbons radicals on the graphene sheet and the polymer chains leads to the sp3-hybridization of carbons when annealing over a long period or at a high-temperature of 200 °C, due to the random scission of polymer chains. The rehybridization alters graphene’s band structure near the Fermi level (see Figure 18(f)), and the reduced Fermi velocity is responsible for the 2D blue-shift after annealing (see Figure 18(c,d)). Further, it is evidenced from Figure 18(e) that suspended graphene seems to be more sensitive to temperature than SiO2 supported graphene, and the 2D blue-shift is more significant at higher temperature. In the annealing treatment of rGO [330], a smaller amount of free radicals was created when rGO was annealed at low-temperature. As the annealing temperature was increased from 500 to 1000 °C, the amount of oxygen groups on the graphene surface decreased. As a result, the adjacent rGO layers got increasingly closer to each other, leading to the improvement of electrical conductivity between layers [343]. Conductivity measurement confirmed that the conductivity was lower when less free radicals were distributed in a two-dimensional ordered phase. Therefore, thermal annealing can reduce the oxidation level of rGO in a controlled manner for obtaining desired defects, conductivity, capacitance and surface reactivity. It is also found that thermal annealing in the presence of a hydrocarbon gas makes the high-conductive rGO accessible by defect healing [344].