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Topic Review
Chemical Depolymerization Methods of Poly(ethylene terephthalate)
The significant amount of waste generated by poly(ethylene terephthalate) (PET) requires the development of a recycling process chain in which chemical recycling plays an important role. On the one hand, it allows the depolymerization of degraded plastics that do not meet the quality requirements to be used in mechanical recycling, and on the other hand, provides an opportunity to process cheap waste and obtain products with greater added value. It can be widely used in the recycling of both packaging plastics and textiles, or other waste generated with PET.
  • 755
  • 12 Oct 2023
Topic Review
Chemical Derivatization in Flow Analysis
Chemical derivatization involves modification of the analyte for improving selectivity and/or sensitivity. It is particularly attractive in flow analysis in view of its highly reproducible reagent addition(s) and controlled timing. Then, measurements without attaining the steady state, kinetic discrimination, exploitation of unstable reagents and/or products, as well as strategies compliant with Green Analytical Chemistry, have been efficiently exploited. Flow-based chemical derivatization has been accomplished by different approaches, involving e.g. flow and manifold programming, solid-phase reagents, and strategies for sample insertion and reagent addition, as well as to increase sample residence time.
  • 719
  • 08 Mar 2022
Topic Review
Chemical Enzymology of Monoamine Oxidase
Monoamine oxidase (E.C. 1.4.3.4) enzymes MAO A and MAO B are FAD-containing proteins located on the outer face of the mitochondrial inner membrane, retained there by hydrophobic interactions and a transmembrane helix. The redox co-factor (FAD) is covalently attached to a cysteine and buried deep inside the protein behind an aromatic cage that aligns substrates towards the flavin. MAO metabolizes neurotransmitters such as dopamine and serotonin in the nervous system so is a target for drugs to modify amine levels. MAO also metabolizes a wide range of biogenic amines in all tissues. Current accumulated evidence, particularly from theoretical modelling, supports hydride transfer as the chemical mechanism. The long active site cavity accommodates a wide chemical variety of small molecules designed as inhibitors, including coumarins, chromones, triazoles, and more. Inactivators that bind covalently to MAO include hydrazines, cyclopropylamines and propargylamines. This entry is an extract adapted from a review outlining the remaining uncertainties in the understanding of this key drug target.
  • 1.1K
  • 19 Oct 2021
Topic Review
Chemical Explosive
The vast majority of explosives are chemical explosives. Explosives usually have less potential energy than fuels, but their high rate of energy release produces a great blast pressure. TNT has a detonation velocity of 6,940 m/s compared to 1,680 m/s for the detonation of a pentane-air mixture, and the 0.34-m/s stoichiometric flame speed of gasoline combustion in air. The properties of the explosive indicate the class into which it falls. In some cases explosives can be made to fall into either class by the conditions under which they are initiated. In sufficiently large quantities, almost all low explosives can undergo a Deflagration to Detonation Transition (DDT). For convenience, low and high explosives may be differentiated by the shipping and storage classes.
  • 786
  • 01 Nov 2022
Topic Review
Chemical Industry in China
The chemical industry in China is one of China's main manufacturing industries. It valued at around $1.44 trillion in 2014, and China is currently the largest chemicals manufacturing economy in the world. The chemical industry is central to modern China's economy. It uses special methods to alter the structure, composition or synthesis of substances to produce new products, such as steel, plastic, and ethyl. Chemical industry provides building materials for China's infrastructure, including subway, high-speed train, and highway. Prior to 1978, most of the product was produced by the state-owned business, and the share in product outputted by state-owned business had decreased in 2002. The Chinese chemical industry is also one of the world's largest producers of both controlled and non-controlled precursor chemicals used in the Global illicit drug trade, particularly in the Golden Triangle as well as Latin America.
  • 1.5K
  • 26 Oct 2022
Topic Review
Chemical looping
Chemical looping technology in general, is the rising star in chemical technologies, which is capable of low CO2 emissions with applications in the production of heat, fuels, chemicals, and electricity. This entry discusses the technology in general, gives an overview of some pilot scale plants and the different chemical looping processes with focus on the production of heat and chemicals, highlights the importance of the development of oxygen carrier materials with suitable properties, 2.11.0.0 2.11.0.0
  • 3.1K
  • 02 Nov 2020
Topic Review
Chemical Properties of Calcium Phosphate
 Calcium phosphate (CaP)-based biomaterials have superior properties and have been widely used for bone defect repair, due to their similarities to the inorganic components of human bones. The biological performance of CaPs, as a determining factor for their applications, are dependent on their physicochemical properties. Hydroxyapatite (HAP) as the most thermally stable crystalline phase of CaP is mostly used in the form of ceramics or composites scaffolds with polymers. Nanostructured CaPs with large surface areas are suitable for drug/gene delivery systems. CaP is not only a family of natural minerals, but also includes biominerals in humans, which are the main inorganic component of hard tissue (bone and teeth).
  • 1.2K
  • 27 Oct 2022
Topic Review
Chemical Recycling for Plastic Waste
Plastics play an integral role in shaping our modern society and are ubiquitous in our daily lives. Their superior material characteristics, performance, and low production cost make them desirable for vast consumer and industrial applications. Chemical or feedstock recycling refers to any reprocessing technology directly affecting the formulation of polymeric waste or the polymer itself.  The recycling plastic waste through chemical means are explored.
  • 366
  • 23 May 2023
Topic Review
Chemical Rings
The epoxidized group, also known as the oxirane group, can be considered as one of the most crucial rings in chemistry. Due to the high ring strain and the polarization of the C–O bond in this three-membered ring, several reactions can be carried out. One can see such a functional group as a crucial intermediate in fuels, polymers, materials, fine chemistry, etc. 
  • 853
  • 30 Aug 2021
Topic Review
Chemical Safety
Chemicals as elements, compounds, mixtures, solutions and emulsions are very widely used and transported in the modern industrial society. Of necessity, they are also used in schools, universities and other training facilities to educate pupils in their safe use and handling and also are commonly used in domestic situations for cleaning, gardening and DIY. However, there are chemicals that should not mix or get in contact with others, as they can produce byproducts that may be toxic, carcinogenic, explosive etc, or can be dangerous themselves. To avoid disasters and mishaps, maintaining safety is considered paramount, especially by chemists. Chemical safety includes all those policies, procedures and practices designed to minimise the risk of exposure to potentially hazardous chemicals. This includes the risks of exposure to persons handling the chemicals, to the surrounding environment, and to the communities and ecosystems within that environment. The hazardous nature of many chemicals may be increased when mixed with other chemicals, heated or handled inappropriately. In a chemically safe environment, users are able to take appropriate actions in case of accidents although many incidents of exposure to chemical hazards occur outside of a controlled environments such as manufacturing plants or laboratories. It is estimated that 1.6 million human deaths occur each year from contact with hazardous chemicals. and that in 2016, 45 million disability-adjusted life-years were lost, a significant increase from 2012.
  • 754
  • 21 Nov 2022
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