Curing agents basic

When the epoxide is to be used, a basic curing agent such as a tertiary amine, R3N, is added to cause the individual prepolymer chains to link together. This "cross-linking" of chains is simply a base-catalyzed epoxide... 

The type of epoxy group and its location within the molecule influence reactivity. Some epoxy resin structures prefer to react with acid curing agents, and others with basic curing agents. Certain epoxy structures are extremely reactive with specific catalysts, and others are virtually inactive. Several types of epoxy resins are reactive with almost all classes of curing agents. 

Phenolic Resins. Phenohc resins (qv) are formed by the reaction of phenol [108-95-2] C H O, and formaldehyde [50-00-0] CH2O. If basic conditions and an excess of formaldehyde are used, the result is a resole phenohc resin, which will cure by itself Hberating water. If an acid catalyst and an excess of phenol are used, the result is a novolac phenohc resin, which is not self-curing. Novolac phenohc resins are typically formulated to contain a curing agent which is most often a material known as hexamethylenetetraamine [100-97-0] C H22N4. Phenohc resin adhesives are found in film or solution... 

Accelerated sulphur systems also require the use of an activator comprising a metal oxide, usually zinc oxide, and a fatty acid, commonly stearic acid. For some purposes, for example where a high degree of transparency is required, the activator may be a fatty acid salt such as zinc stearate. Thus a basic curing system has four components sulphur vulcanising agent, accelerator (sometimes combinations of accelerators), metal oxide and fatty acid. In addition, in order to improve the resistance to scorching, a prevulcanisation inhibitor such as A -cyclohexylthiophthalimide may be incorporated without adverse effects on either cure rate or physical properties. 

Two-pack epoxies These were first patented in 1938 but were not in general production until 1947. They have been very widely used over the last decade. Produced from the by-products of the petroleum industry, the basic epoxy resins may be in the form of relatively low-viscosity liquid resins or they may be solid resins of increasing hardness. Both solid and liquid resins can then be reacted with a number of different curing agents. This means that almost any type of film and with any required properties can be made. 

The curing process of epoxies is mainly dependent on the reactivity characteristics, the structure, and the functional group of resin [61,65], The basic chemical reactions, catalyzed by hydroxyl group (OH), between the epoxide group and the curing agent are [194] ... 

A filler should be dry, nonreactive with the uncured resin, and of a neutral or only slightly basic pH. Adsorbed water, which is present in some degree in most fillers, inhibits dispersion. Thus, most fillers must be dried before they are added to the adhesive formulation. The drying process will drive off adsorbed moisture and gases from the surface of the filler. The filler should generally be nonreactive with the base resins or curing agents that... 

Chapters 4 through 10 describe the basic raw materials that are commonly employed in formulating epoxy adhesives. These include the epoxy resins, curing agents and catalysts, solvents and diluents, resinous modifiers, flexibilizers and tougheners, fillers, and adhesion promoters. 

Basic materials were patented as curing agents, but the applications were limited to dentistry. 

Typical fillers silica, calcium carbonate, carbon black, magnesium hydroxide, basic magnesium carbonate, metal oxides (typically MgO) are used as curing agents... 

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