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chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, propertie ...
, cyanate esters are
chemical substance A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...
s in which the
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxi ...
atom of the phenolic OH group is substituted by a
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
group (). The resulting product with a
cyanate Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate. It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Sma ...
group is termed a cyanate
ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glyceride ...
. Cyanate esters based on a bisphenol or novolac derivative are used in the production of resins.


Use in resins

Cyanate esters can be cured and postcured by heating, either alone at elevated temperatures or at lower temperatures in presence of a suitable catalyst. The most common catalysts are transition metal complexes of cobalt, copper, manganese and zinc. The result is a
thermoset In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and ...
material with a very high glass-transition temperature (Tg) of up to 400 °C, and a very low
dielectric constant The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric constant of an insulat ...
, providing excellent long term thermal stability at elevated end use temperatures, very good fire, smoke and toxicity performance and specific suitability for
printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich stru ...
s installed in critical electrical devices. This is also due to its low moisture uptake. This property, together with a higher toughness compared to epoxies, also makes it a valuable material in aerospace applications. For example, the Lynx Mark II
spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ...
is primarily made of carbon/cyanate ester. The chemistry of the cure reaction is a
trimerization In chemistry, a trimer (; ) is a molecule or polyatomic anion formed by combination or association of three molecules or ions of the same substance. In technical jargon, a trimer is a kind of oligomer derived from three identical precursors oft ...
of three CN groups to a
triazine Triazines are a class of nitrogen-containing heterocycles. The parent molecules' molecular formula is . They exist in three isomeric forms, 1,3,5-triazines being common. Structure The triazines have planar six-membered benzene-like ring bu ...
ring. When the monomer contains two cyanate groups the resulting structure is a 3D polymer network.
Thermoset polymer matrix A thermoset polymer matrix is a synthetic polymer reinforcement where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements. They were first developed for structural applications, such as gla ...
properties can be fine tuned by the choice of
substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as '' side ...
s in the bisphenolic compound.
Bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on an industrial ...
and novolac based cyanate esters are the major products;
bisphenol F Bisphenol F (BPF; 4,4′-dihydroxydiphenylmethane) is an organic compound with the chemical formula . It is structurally related to bisphenol A (BPA), a popular precursor for forming plastics, as both belong to the category of molecules known as ...
and bisphenol E are also used. The aromatic ring of the bisphenol can be substituted with an
allyl In organic chemistry, an allyl group is a substituent with the structural formula , where R is the rest of the molecule. It consists of a methylene bridge () attached to a vinyl group (). The name is derived from the scientific name for garlic, ...
ic group for improved toughness of the material. Cyanate esters can also be mixed with bismaleimides to form BT-resins or with epoxy resins to optimize the end use properties.


References

{{DEFAULTSORT:Cyanate Ester Cyanates Functional groups Esters