Epoxy resins, additives Hardeners

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

These materials have a very good biocompatibility, in addition to an inert and bioactive behavior. The main problem with these carbon materials is their easy wear, which results in the release of black, sharp-edged particles. This may induce either a tattoo effect or the frequent appearance of granuloma as a foreign body reaction with inflammatory cells. This reaction is neither chemical nor physiological, but is a physical and mechanical effect (Oppenheimer effect). The problem has been resolved by the addition of epoxy resins to harden the carbon... 

Comparing the phase diagrams of AC 540 modified DGEBA epoxy resin and hardener HHPA showed that the oxidized homopolymer with an acid functionality of 2.0 (AC 5120) was more miscible in epoxy resin and the RVP grafted AC 5120 had comparable miscibility as that of AC 5120. Similarly, ethylene acrylic acid-vinyl acetate terpolymer (AC 1450) was less miscible in epoxy resin compared to AC 5120 due to less chemical interaction with epoxy resin. Thus, the miscibility of the blends was reduced by the addition of HHPA to various blend systems. 

Although epoxy resin and hardener may be used in unmodified form in adhesive systems, most systems will consist of components that have been modified by incorporation of various additives to achieve specific effects. Formulators will add catalysts or blend hardeners to obtain a specific usable life of the mix and to control the curing temperature. Reactive diluents may be added to modify viscosity or flexibility. Fillers impart improved compression strength and reduce shrinkage and cost. Solvents may be used to reduce viscosity or improve adhesion. Various additives may be added, usually at a low percentage, to reduce aeration, improve adhesion to difficult surfaces, or minimize settlement of fillers. Depending on the application, particular properties such as flame retardency. 

It seems that the addition of epoxy resin improves wet strength for some MDF cements. It was reported that epoxy resin can harden in the presence of hydroxide ions (OIT) from the cement [19] and as consequence, an epoxy network may form, which may decrease degradation. 

NFPA Health 3, Flammability 1, Reactivity 0 Uses Curing agent for cast PU elastomers, food-contact PU resins epoxy resin curing/hardening agent corrosion inhibitor intermediate for paints, dyes, polymers isocyanate resins polyamides determination of tungsten and sulfates curing system additive for bisphenol A-ep-ichlorohydrin epoxies for food contact antioxidant in food-contact rubber articles for repeated use... 

Synonyms MN-dimethyl-i,3-propanediamine N,N-dimethyl-i,3-diaminopropane 3-(dimethylamino)-propylamine dimethylamino-propylamine i-amino-3-dimethylaminopropane N,JV-dimethyl-N-(3-aminopropyl)amine 3-(dimethylamine)propylamine N,N-dimethyl-i,3-propylenediamine 3-(N,N-dimethylamino)propylamine 3-aminopropyldimethylamine DMPA Uses intermediate substance in the synthesis of alkylamidopropyldimethylamines/alkylamidobetaines found as an impurity in cosmetic surfactants present in e.g. shampoos hardener of epoxy resins additive in fuel, dyes, pesticides and binding agents in the production of ion-exchangers A... 

The versatility of epoxy-resin systems arises from the many combinations of epoxy resins and hardeners, each of which gives a different cure profile and results in a different molecular structure in the resulting polymer. Compared with other adhesive systems such as cyanoacrylates or anaerobics, epoxies are not very sensitive to impurities. This gives tremendous scope for modification of their properties by additives, modifiers, fillers, rubber tougheners,... 

A variety of materials has been proposed to modify the properties of asphaltic binders to enhance the properties of the mix (112), including fillers and fibers to reinforce the asphalt—aggregate mixture (114), sulfur to strengthen or harden the binder (115,116), polymers (98,117—121), mbber (122), epoxy—resin composites (123), antistripping agents (124), metal complexes (125,126), and lime (127,128). AH of these additives serve to improve the properties of the binder and, ultimately, the properties of the asphalt—aggregate mix. 

The higher molecular-weight soHd epoxy resins are used in formulations that usually consist of a resin, hardener, reinforcing filler, pigments, flow control agents, and other modifiers. In addition to using conventional hardeners in these formulations, epoxy resins can also be hardened with other resins, ie, acryhcs or polyesters. 

In addition to electrical uses, epoxy casting resins are utilized in the manufacture of tools, ie, contact and match molds, stretch blocks, vacuum-forrning tools, and foundry patterns, as weU as bench tops and kitchen sinks. Systems consist of a gel-coat formulation designed to form a thin coating over the pattern which provides a perfect reproduction of the pattern detail. This is backed by a heavily filled epoxy system which also incorporates fiber reinforcements to give the tool its strength. For moderate temperature service, a Hquid bisphenol A epoxy resin with an aHphatic amine is used. For higher temperature service, a modified system based on an epoxy phenol novolak and an aromatic diamine hardener may be used. 

Materials used for insulating sheaths should be inert and easy to machine they are generally plastics or casting epoxy resins. Epoxy resins are easier to handle because of their moulding ability but they are not chemically inert to certain species, including many non-aqueous solvents. Additionally, care must be taken when preparing the epoxy resins that air bubbles do not appear in the mixture prior treatment of the adhesive and hardener mixture under vacuum for a short while reduces the problem. 

A formulation used in USA is 54.7 parts epoxy resin, 10.3 parts aromatic amine, and 30.0 parts BJO phenolic microsphere. It has an apparent density of 336 kg/m3 and is viable for two hours. The mixture is hardened at 71 °C for 2 hours or at 82 °C for 1 hour 88). Recently, Prigozhin and Krasnikova 89) successfully applied simplex planning to the formulation of EDS materials with good properties. In addition to glass and phenolic microspheres, polystrene18), carbon38 40>, and mineral microspheres 18,59) have also been used. 

Many epoxy adhesives are capable of being B-staged. A B-staged resin is one in which a limited reaction between the resin and hardener has taken place so that the product is in a semicured but solid state. In the B-staged state, the polymeric adhesive is still fusible and soluble. On additional heat curing, the adhesive will progress from the B stage to a completely cured state. This will usually be accompanied by moderate flow. 

Among the variety of polymer thermosets, epoxies enjoy the most widespread use and are certainly the most studied. They are usually synthesized from oligomeric, end-functional epoxy resins and multifunctional curing agents or hardeners . In addition, catalysts sometimes are employed to speed the crosslinking reactions or allow them to take place at lower temperatures. 

Generally these compositions contain an epoxy-novolac, a hardener, a catalyst, silica fillers, and an internal lubricant/mold release compound. Brom-inated epoxies and antimony trioxide are included to provide the required flame retardant characteristics. Other, unspecified additives are used to promote adhesion or to reduce corrosion rates. Because of their superior thermal capabilities and electrical properties, epoxidized novolacs are preferred over epoxy homopolymers. Near stoichiometric amounts of hardeners such as novolacs (Equation 1), anhydrides, and primary amines can be used to cure the resins in the presence of a catalyst. The linkages which are formed include ethers, esters, or secondary amines, respectively. 

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