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Octamethylcyclotetrasiloxane
Octamethylcyclotetrasiloxane, also called D4, is an organosilicon compound and one of a number of cyclic siloxanes (cyclomethicones). It is a colorless viscous liquid with a high boiling point. It has historically been used on a large scale in personal care products including cosmetics, hair conditioners and emollients (moisturising creams), Global production in 1993 was 136,000 tons, however it is now facing significant pressure from regulators. It is a substance of very high concern In the EU, where it was classified as a PBT and effectively banned in personal care products in 2018. The US EPA began reevaluating its risks in 2020. Replacements include branched-chain alkanes (isoparaffins). Production and polymerization Commercially D4 is produced from dimethyldichlorosilane. Hydrolysis of the dichloride produces a mixture of cyclic dimethylsiloxanes and polydimethylsiloxane. From this mixture, the cyclic siloxanes including D4 can be removed by distillation. In the presence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decamethylcyclopentasiloxane
Decamethylcyclopentasiloxane, also known as D5 and D5, is an organosilicon compound with the formula . It is a colorless and odorless liquid that is slightly volatile. It is used in various cosmetic products. It also is used as a dry cleaning solvent and has been marketed as an "eco-friendly" and "green" alternative to perchloroethylene in the 2000s, under the tradename GreenEarth. Decamethylcyclopentasiloxane is persistent in nature and possibly bioaccumulative. Decamethylcyclopentasiloxane is considered non-toxic but its long-term health effects are unknown. Use The compound is classified as a cyclomethicone. Such fluids are commonly used in cosmetics, such as deodorants, sunblocks, hair sprays and skin care products. It is becoming more common in hair conditioners, as it makes the hair easier to brush without breakage. It is also used as part of silicone-based personal lubricants. D5 is considered an emollient. In Canada, among the volume used in consumer products approxim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siloxane
In organosilicon chemistry, a siloxane is an organic compound containing a functional group of two silicon atoms bound to an oxygen atom: . The parent siloxanes include the oligomeric and polymeric hydrides with the formulae and . Siloxanes also include branched compounds, the defining feature of which is that each pair of silicon centres is separated by one oxygen atom. The siloxane functional group forms the backbone of silicones , the premier example of which is polydimethylsiloxane (PDMS). The functional group (where the three Rs may be different) is called siloxy. Siloxanes are manmade and have many commercial and industrial applications because of the compounds’ hydrophobicity, low thermal conductivity, and high flexibility. Structure Siloxanes generally adopt structures expected for linked tetrahedral ("''sp''3-like") centers. The Si−O bond length is 1.64 Å (vs Si–C distance of 1.92 Å) and the Si-O-Si angle is rather open at 142.5°. By ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexamethylcyclotrisiloxane
Hexamethylcyclotrisiloxane, also known as D3 and D3, is the organosilicon compound with the formula . It is a colorless or white volatile solid. It finds limited use in organic chemistry. The larger tetrameric and pentameric siloxanes, respectively octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, are of significant industrial interest, whereas 1,000–10,000 tonnes per year of the trimer is manufactured and/or imported in the European Economic Area. Structure and reactions Hexamethylcyclotrisiloxane adopts a planar structure and is considered strained. It reacts with organolithium reagents to give, after hydrolysis, dimethylsilanols: : : Safety and environmental considerations The LD50 for the related pentamer (D5) is >50 g/kg in rats. See also * Octamethylcyclotetrasiloxane (D4) * Decamethylcyclopentasiloxane Decamethylcyclopentasiloxane, also known as D5 and D5, is an organosilicon compound with the formula . It is a colorless and odorless liquid that is sli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrakis(trimethylsilyloxy)silane
Tetrakis(trimethylsilyloxy)silane (TTMS) is an organosilicon compound with the formula Si[OSi(CH3)3]4. This colourless liquid is used as a reagent in organic synthesis. Application TTMS can be used for thin film coating with a nanostructured silicon dioxide prepared by plasma-enhanced chemical vapor deposition (PECVD) at atmospheric pressure. See also * Hexamethylcyclotrisiloxane * Polymethylhydrosiloxane References {{Reflist External linksSilicone End Cap Plugs Trimethylsilyl compounds Siloxanes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parts Per Billion
In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are * parts-per-million - ppm, * parts-per-billion - ppb, * parts-per-trillion - ppt, * parts-per-quadrillion - ppq, This notation is not part of the International System of Units - SI system and its meaning is ambiguous. Applications Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Therefor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ECHA
The European Chemicals Agency (ECHA; ) is an agency of the European Union working for the safe use of chemicals. It manages the technical and administrative aspects of the implementation of the European Union regulation called Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). ECHA is the driving force among regulatory authorities in implementing the EU's chemicals legislation. ECHA has to ascertain that companies comply with the legislation, advances the safe use of chemicals, provides information on chemicals and addresses chemicals of concern. It is located in Helsinki, Finland and is operational since 2007. ECHA is an independent and mature regulatory agency established by REACH. It is not a subsidiary entity of the European Commission. The agency is headed by Executive Director Sharon McGuinness. Establishment The ECHA was created by European Union regulation dating from 18 December 2006 to manage the then-new legislation to regulate the man ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Union
The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The union has a total area of and an estimated population of over 449million as of 2024. The EU is often described as a ''sui generis'' political entity combining characteristics of both a federation and a confederation. Containing 5.5% of the world population in 2023, EU member states generated a nominal gross domestic product (GDP) of around €17.935 trillion in 2024, accounting for approximately one sixth of global economic output. Its cornerstone, the European Union Customs Union, Customs Union, paved the way to establishing European Single Market, an internal single market based on standardised European Union law, legal framework and legislation that applies in all member states in those matters, and only those matters, where the states ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science Of The Total Environment
Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which study the physical world, and the social sciences, which study individuals and societies. While referred to as the formal sciences, the study of logic, mathematics, and theoretical computer science are typically regarded as separate because they rely on deductive reasoning instead of the scientific method as their main methodology. Meanwhile, applied sciences are disciplines that use scientific knowledge for practical purposes, such as engineering and medicine. The history of science spans the majority of the historical record, with the earliest identifiable predecessors to modern science dating to the Bronze Age in Egypt and Mesopotamia (). Their contributions to mathematics, astronomy, and medicine entered and shaped the Greek natural phi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landfill Gases
Landfill gas is a mix of different gases created by the action of microorganisms within a landfill as they decompose organic waste, including for example, food waste and paper waste. Landfill gas is approximately forty to sixty percent methane, with the remainder being mostly carbon dioxide. Trace amounts of other volatile organic compounds (VOCs) comprise the remainder (<1%). These trace gases include a large array of species, mainly simple s.Hans-Jürgen Ehrig, Hans-Joachim Schneider and Volkmar Gossow "Waste, 7. Deposition" in Ullmann's Encyclopedia of Industrial Chemistry, 2011, Wiley-VCH, Weinheim. Landfill gases have an influence on . The major components are [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ring Strain
In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are substantially smaller than the idealized value of approximately 109°. Because of their high strain, the heat of combustion for these small rings is elevated. Ring strain results from a combination of angle strain, conformational strain or Pitzer strain (torsional eclipsing interactions), and transannular strain, also known as van der Waals strain or Prelog strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane. Ring strain energy can be attributed to the energy required for the distortion of bond and bond angles in order to close a ring. Ring strain energy is believed to be the cause of accelerated rates in altering ring reactions. Its interactions with traditional bond energi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environment Agency
The Environment Agency (EA) is a non-departmental public body, established in 1996 and sponsored by the United Kingdom government's Department for Environment, Food and Rural Affairs, with responsibilities relating to the protection and enhancement of the environment (biophysical), environment in England (and until 2013 also Wales). Based in Bristol, the Environment Agency is responsible for flood management, waste management, regulating land and water pollution, and conservation. Roles and responsibilities Purpose The Environment Agency's stated purpose is, "to protect or enhance the environment, taken as a whole" so as to promote "the objective of achieving sustainable development" (taken from the Environment Act 1995, section 4). Protection of the environment relates to threats such as flood and pollution. The vision statement, vision of the agency is of "a rich, healthy and diverse environment for present and future generations". Scope The Environment Agency's remit c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
