China 
Africa 
Explore chapters and articles related to this topic
Dielectric Analysis of Different Natural and Synthetic Polymer Types
Published in Jose James, K.P. Pramoda, Sabu Thomas, Polymers and Multicomponent Polymeric Systems, 2019
Hugo Salazar, Pedro M. Martins, C.M. Costa, S. Lanceros-Méndez
Polymers can be classified as polar or apolar (Figure 10.1) due to their chemical structure [8]. Apolar polymers are efficient isolating materials, and they show dielectric loss values around 10−4–10−3 and a quasi-constant dielectric permittivity of 2.5–3, even with changes of frequency and temperature. This type of polymers is usually composed of carbon and hydrogen atoms symmetrically disposed all along a carbon chain. Polyethylene and poly(tetrafluoroethylene) are two examples of apolar polymers. In contrast, polar polymers are usually composed of molecules with electronegative atoms, like oxygen, nitrogen, fluoride, or chloride, which provide dipoles to the polymer structure. They are characterized by higher dielectric constant and loss factor, about 3.5–10 and 10−2–10−1, respectively. Examples of polar polymers are proteins, and their polar character depends on their lateral amino acid chain.
Introduction
Published in Xianguo Li, Principles of Fuel Cells, 2005
Various families of hydrocarbon exist as shown in Table 1.3, and they differ according to their molecular structures. The cyclanes and aromatics have a closed ring-like structure for their carbon chain. The cyclanes, also called cycloparaffins, cycloalkanes, or naphthenes, have single carbon–carbon bond (C–C). While the aromatic or benzene family has a building block of six carbon atoms forming a closed ring, each carbon atom has a single and a double bond with its two neighboring carbon atoms (–C=) and the one additional bond for each carbon atom can be attached various side chains, as simple as one hydrogen atom, or as complex as any hydrocarbon group in various structural arrangements. The alkane, alkene, and alkyne families have an open carbon chain structure with the two ends of the carbon chain remaining unconnected. The alkane family has its molecules entirely made up of single carbon–carbon bonds (C–C), whereas alkene and alkyne families consist of one double or one triple carbon–carbon bonds (i.e., C=C or C≡C), respectively, with the rest of carbon atoms connected in a single bond. The simplest species in the alkane family is methane (CH4) and ethane (C2H6). If one hydrogen atom in the alkane family is replaced by one hydroxyl (—OH) group, it becomes the common alcohol family, for example, methyl alcohol (CH3OH), or methanol, replaces methane (CH4); and ethyl alcohol (C2H5OH), or ethanol, corresponds to ethane (C2H6), and so on. Therefore, alcohols can be generically designated as ROH, where R is the parent hydrocarbon radical in the alkane family.
Constituent Materials
Published in B. T. Åström, Manufacturing of Polymer Composites, 2018
Several hydrocarbon polymers other than PE and PP exist, although they are rarely of interest in composite applications. However, if one includes elements other than carbon and hydrogen, virtually endless other combination possibilities arise. Apart from carbon and hydrogen, the most common elements are oxygen which can form two covalent bonds; nitrogen with three; sulfur with two, four, or six; fluorine with one; chlorine with one; and silicone with four. As long as only carbon makes up the polymer backbone, one talks of carbon-chain polymers, whereas polymers having some non-carbon backbone atoms are referred to as heterochain polymers.
Infrared photodissociation spectroscopic and theoretical study of H n C4O+ (n = 1, 2) cation clusters in the gas phase
Published in Molecular Physics, 2021
Wei Li, Jiaye Jin, Xiaonan Wu, Xunlei Ding, Guanjun Wang
The simulated spectra (red) of [HC4O·CO]+ cations (a and b) and HC4O+ core cation (c) are compared with the experimental spectrum (black) shown in Figure 2. The experimental spectrum has six peaks which centre at 1526, 1890, 2188, 2230, 3062 and 3200 cm−1 listed in Table 1. Apparently, the simulated spectra of (a) the linear CO tagging complex and (b) the T-shape CO tagging complex match the experimental result well. The peaks in the 3062 and 3200 cm−1 regions are attributed to terminal CH stretching vibrations for the [HC4O·CO]+ cation, which indicate that the weakly tagged CO group has two different tagging sites. The 2188 cm−1 can be appropriated for terminal CO stretching vibration of the HC4O+ core ions. The peak in 2230 cm−1 can be attributed to tagging CO stretching vibration of the complex [HC4O·CO]+ cation. The peaks in the 1526 and 1890 cm−1 region can be attributed to the CC asymmetrical and symmetrical stretching vibrations of the C4 chains. The comparison indicates that the HC4O+ core ion each involves a terminal CH moiety and a terminal CO subunit, suggesting that it is carbon chain derivative terminated by hydrogen atom and oxygen atom.
Reactive molecular dynamics simulation of oil shale combustion using the ReaxFF reactive force field
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Zhijun Zhang, Hanyu Zhang, Jun Chai, Liang Zhao, Li Zhuang
Due to the oxidation by O2 molecules, O and OH radicals and then the abstraction of H radicals, kerogen combustion process was mainly initialized by thermal decomposition of the structure to produce small fragments. In stage I, the oxygen-attacking position was basically located in sulfoxides, aliphatic amines and carbon atom at the end of the carbon chain. Bond breaking positions are shown in Figure 4. Hydrogen atoms are separated from N (2642), N (2774) and N (2715) by oxygen attacking (Figure 4a,d,f). Two sulfoxides of S (2632) and S (2648) break and transform into S-O radicals at the end of the carbon chain, which promote further decomposition of the carbon chain (Figure 4b,c). Figure 4e shows O (2803) radical attacks carbon atom on carbon chain. In stage I, oxygen attacked the site with high reactivity to break the bond or further increased the reactivity to promote the decomposition reaction. And the results of kinetic calculation revealed that the activation energy values of the combustion increased with the increasing of oxygen content, resulting in the chemical bond break to make the kerogen molecules looser to promote decomposition.
Strategy for repurposing of disposed PPE kits by production of biofuel: Pressing priority amidst COVID-19 pandemic
Published in Biofuels, 2022
Sapna Jain, Bhawna Yadav Lamba, Sanjeev Kumar, Deepanmol Singh
The polymer which is largely used in making of PPE is Polyproylene (PP), a non woven material that can be used once. It is the lightest known downstream petrochemical product obtained by polymerization of monomer propylene. The basic structure of PP is a saturated carbon chain having methyl group attached to alternate carbon atom (Figure 1). The presence of methyl group makes PP different from Polyethylene and imparts hardness to it. The hardness, lightweight (density of 0.90 g/cm3) i.e. high strength to weight ratio makes it suitable for various industrial applications [12].