hardened PDMS cylinder on the glass of a stereomicroscope light

Polydimethylsiloxane (PDMS) is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological (or flow) properties. It is optically clear, and is generally considered to be inert, non-toxic and non-flammable. PDMS has been assigned CAS number 63148-62-9, and is occasionally called dimethicone. It is one of several types of silicone oil. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... Polymer is a generic term used to describe a very long molecule consisting of structural units and repeating units connected by covalent chemical bonds. ... Rheology is the study of the deformation and flow of matter. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences and alloys. ... Silicones, or polysiloxanes, are inorganic polymers consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. ...

Chemistry

The chemical formula for PDMS is (CH₃)₃SiO[SiO(CH₃)₂]_nSi(CH₃)₃, where n is the number of repeating monomer [SiO(CH₃)₂] units. Industrial synthesis can begin from dimethylchlorosilane and water by the following net reaction: A chemical formula (also called molecular formula) is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. ... Water (from the Old English word wæter; c. ...

 n[Si(CH3)2Cl2] + n[H2O] → [SiO(CH3)2]n + 2n[HCl] 

This also produces hydrochloric acid, which is generally released as a gas. For medical uses, a process was developed where the chlorine atoms in the silane precursor were replaced with acetate groups, so that the reaction product of the final curing process is nontoxic acetic acid (vinegar). As a side effect, the curing process is also much slower in this case. This is the chemistry used in consumer applications, such as silicone caulk and adhesives. The chemical substance hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride (HCl) gas. ... Flash point 43 Â°C R-phrases , S-phrases , , , US Permissible exposure limit (PEL) 10 ppm Supplementary data page Structure & properties n, εr, etc. ... For a description of caulking in computer game creation, refer to caulking (computer games) Caulking is a process used in the sealing of the seams in wooden boats and making them watertight. ... An adhesive is a compound that adheres or bonds two items together. ...

Silane precursors with more acid-forming groups and fewer methyl groups, such as methyltrichlorosilane, can be used to introduce branches or cross-links in the polymer chain. Ideally, each molecule of such a compound becomes a branch point. This can be used to produce hard silicone resins. Similarly, precursors with three methyl groups can be used to limit molecular weight, since each such molecule has only one reactive site and so forms the end of a siloxane chain. Vulcanization is an example of cross-linking. ... Silicone resins is a type of silicone material which is formed by branched, and cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non reactive substituent, usually Me or Ph, and X is a functional group H, OH, Cl or OR. These groups are further condensed...

The polymer is manufactured in multiple viscosities, ranging from a thin pourable liquid (when n is very low), to a thick rubbery semi-solid (when n is very high). PDMS molecules have quite flexible polymer backbones (or chains) due to their siloxane linkages, which are analogous to the ether linkages used to impart rubberiness to polyurethanes. Such flexible chains become loosely entangled when molecular weight is high, which results in PDMS having an unusually high level of viscoelasticity. The pitch drop experiment at the University of Queensland. ... A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl groups. ... A polyurethane is any polymer consisting of a chain of organic units joined by urethane links. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... A viscoelastic material is one in which: hysteresis is seen in the stress-strain curve. ...

Mechanical properties

Viscoelasticity means that at long flow times (or high temperatures), PDMS acts like a viscous liquid, similar to honey. However at short flow times (or low temperatures) it acts like an elastic solid, similar to rubber. In other words, if you leave some PDMS on a surface overnight (long flow time), it will flow to cover the surface and mold to any surface imperfections. However if you roll the same PDMS into a sphere and throw it onto the same surface (short flow time), it will bounce like a rubber ball. Viscosity is a measure of the resistance of a fluid to deformation under shear stress. ... A liquid will assume the shape of its container. ... This article is in need of attention from an expert on the subject. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ...

Although the viscoelastic properties of PDMS can be intuitively observed using the simple experiment described above, they can be more accurately measured using dynamic mechanical analysis. This involves using a specialized instrument to determine the material's flow characteristics over a wide range of temperatures, flow rates, and deformations. Because of PDMS's chemical stability, it is often used a calibration fluid for this type of experiment. Dynamic mechanical analysis (DMA) or dynamic mechanical thermal analysis (DMTA) is a technique used to study and characterize materials. ...

Uses

Many people are indirectly familiar with PDMS because it is the primary component in Silly Putty, to which PDMS imparts its characteristic viscoelastic properties. The rubbery, vinegary-smelling silicone caulks, adhesives, and aquarium sealants are also well-known. PDMS is also used as a component in silicone grease and other silicone based lubricants, as well as in defoaming agents, damping fluids, heat transfer fluids, cosmetics and other applications. PDMS has also been used as a filler fluid in breast implants, although this practice has decreased somewhat, due to safety concerns. It continues to be used in knuckle replacement implants, with good results. It has been suggested that Thinking Putty be merged into this article or section. ... A lubricant (colloquially, lube, although this usually refers to personal lubricants) is a substance (usually a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... This article is in the process of being merged into Heat, and may be outdated. ... Closeup of a womans eye while wearing makeup Cosmetics or makeup are substances to enhance the beauty of the human body, apart from simple cleaning. ... Breast implant diagram Silicone gel-filled breast implants Saline-filled breast implants A breast implant is a prosthesis used in cosmetic surgery to enlarge the size of a womans breasts (known as breast augmentation) or to reconstruct the breast (for example, after a mastectomy, or during male-to-female...

Activated dimethicone, a mixture of polydimethylsiloxanes and silicon dioxide (sometimes called simethicone), is used in over-the-counter preparations as an anti-foaming agent and carminative. R-phrases   S-phrases   Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Simethicone, is an oral antifoaming agent used to reduce bloating, discomfort and pain caused by excess gas in the stomach or intestinal tract. ... An antifoaming agent is a food ingredient intended to curb effusion or effervescence in preparation or serving. ... A carminative, also known as carminativum ( plural: carminativa), is a medicinal drug with antispasmodic activity that is used against cramps of the digestive tract in combination with flatulence. ...

As a food additive, it has the E number E900 and is used as an anti-foaming agent and an anti-caking agent. Food additives are substances added to food to preserve it or improve its flavor and appearance. ... For the mathematical constant see: E (mathematical constant). ... An antifoaming agent is a food ingredient intended to curb effusion or effervescence in preparation or serving. ... Anticaking agents are used in such things as table salt to keep the product from forming lumps, making it better for packaging, transport and for the consumer. ...