Epoxy resins reactive diluents

AroCy . [Bhtme-Poulenc] Dicyanate monomers and jHepolymeis co-reacts with and cutes epoxy resins reactive diluent for adhesives, pepiegs laminating resin. 

Apart from epoxy resins, reactive diluents and epi-chlorohydrin, other compounds containing at least one epoxy group in their molecules are also potential causes of contact allergy. Examples of these epoxy compounds include glycidyl methacrylate (Matura et al. 1995 Fig. 6), epoxy propane [CAS 75-56-9] (Steinkraus and Hausen 1994 Morris et al. 1998), 2,3-epoxypropyl trimethyl ammonium chloride (EPTMAC) [CAS 3033-77-0] (Estlander et al. 1997) and trans-y (4-methoxyphenyl)glycidate (Buisson et al. 1991). 

Diluents have much lower vapor pressures and generally do not evaporate at ambient conditions. However, they do have a finite vapor pressure, and given the right set of conditions (time, temperature, and pressure) they will vaporize. Two distinct classes of diluents are used with epoxy resins nonreactive diluents and reactive diluents. Reactive diluents will enter into the crosslinking reaction with the primary resin, and nonreactive diluents will not. Nonreactive diluents primarily act as low-molecular-weight plasticizers for the epoxy composition. 

Skin. Most epoxy resins are not acutely irritating to the skin. However, they are capable of causing skin sensitization. Susceptibility to skin irritation and sensitization varies from person to person. The epoxy resins are considered to be milder skin sensitizers than amine-type curing agents or epoxy functional reactive diluents. 

Although DGEBA resins provide the backbone of most epoxy formulations, they may be blended with other types to achieve modifications. Epoxy novolacs, having higher functionality, increase the cross-linking density, which improves heat resistance but decreases impact resistance. Incorporation of epoxidized oils increases flexibility at the expense of heat and chemical resistance. Low-viscosity polyfunctional epoxies based on polyols or polyhydric phenols reduce viscosity and can increase functionality without impairing cured properties. Monofunctional reactive diluents will also decrease viscosity and form part of the polymer backbone, to impart a measure of flexibility without the possibility of migration. Properties of commercially available epoxy resins and diluents from various suppliers are listed in Table 1. 

Synonyms Coconut fatty acid glycidyl ester Uses Dispersant for inorg. fillers surf.-treating agent paint modifier textiles stabilizer syn. resins reactive diluent for epoxy resins Trade Names BlemmerDFA... 

Uses Comonomer for alkyd and acrylic resins reactive diluent for epoxy resins resin modifier for coatings applies. produces resins with reduced VOC contenL exc. color and gloss retention, high hardness, exc. exterior durability Manuf/Dislrib. Aldrich... 

Glycidyl and Vinyl Esters. Glycidyl neodecanoate [26761-45-5] sold commercially as GLYDEXXN-10 (Exxon) or as CarduraElO (Shell), is prepared by the reaction of neodecanoic acid and epichl orohydrin under alkaline conditions, followed by purification. Physical properties of the commercially available material are given in Table 3. The material is a mobile Hquid monomer with a mild odor and is used primarily in coatings. Eor example, it is used as an intermediate for the production of a range of alkyd resins (qv) and acryHcs, and as a reactive diluent for epoxy resins (qv). 

Modified Bismaleimides. Bismaleknide resins may be further modified and blended with other thermoset resins or reactive diluents to achieve either specific end-use properties or processibiUty. Thermoset resins that can be used for modification are unsaturated polyesters, vinylesters, cyanate esters, and epoxies. 

Monofunctional aliphatic glycidyl ethers, eg, based on / -butanol or mixed Cg—alcohols, are used exclusively as reactive diluents to reduce viscosities of epoxy resin systems. Some loss of desirable cured properties results from the lowered functionality of the systems. 

Modified liquid epoxy resins liquid epoxy resins with added reactive diluents or solvents mild to moderate irritants moderate to strong sensitizers low volatility, exposure unlikely unless heated, sprayed, or spread over large unventilated surfaces low toxicity... 

Uses. Reactive diluent in epoxy resin systems stabilizer of chlorinated compounds manufacture of rubber... 

Uses. Reactive diluent for epoxy resins stabilizer for organic compounds chemical intermediate for synthesis of ethers and esters... 

Uses. As a chemical intermediate and as a reactive diluent for diepoxides and epoxy resins. 

Production of glycidol and its broad applications as an intermediate, as a reactive diluent in epoxy resins and as a stabilizer and a sterilant may result in its release into the environment through various waste streams (Ivashkiv Dunham, 1973 Kaplan et al, 1982 Nomeir et al, 1995 Department of Health and Human Services, 1999). 

Glycidol is an epoxide used as a chemical intermediate in the production of functional epoxides, glycidyl urethanes, pharmaceuticals and other products. It is also used as a reactive diluent in epoxy resin systems and as a sterilant. Occupational exposure may occur during its production and use. No data were available on environmental exposure to glycidol. 

Secondary ingredients in epoxy adhesives include reactive diluents to adjust viscosity mineral fillers to lower cost, adjust viscosity, or modify the coefficient of thermal expansion and fibrous fillers to improve thixotropy and cohesive strength. Epoxy resins are often modified with other resins to enhance certain properties that are necessary for the application. Often these modifications take the form of additions of elastomeric resins to improve toughness or peel strength. 

An ingredient added to an adhesive to reduce the concentration of base resin or binder is called a diluent. Diluents are principally used to lower the viscosity and modify the processing conditions of some adhesives. The degree of viscosity reduction caused by various diluent additions to a conventional epoxy adhesive is shown in Fig. 1.5. Diluents do not evaporate as does a solvent, but they become part of the final adhesive. Reactive diluents react with the resin base during cure, so that the final adhesive characteristics are determined by the reaction product of the binder and diluent. Nonreactive diluents do not react with the resin or curing agent and, therefore, more seriously weaken the final properties. Coal and pine tar are common nonreactive diluents. 

FIGURE 1.5 Viscosity reduction of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin by reactive diluents.31... 

The aliphatic epoxy resins formed from reaction with hydrogen peroxide or peracetic acid include epoxidized polybutadiene, epoxidized soya or linseed oil, and epoxidized polyglycols. The resulting products have too low a functionality for use as base polymers. They are almost always used in combination with other epoxy resins to improve properties such as cure rate, flexibility, and heat deflection temperature. Therefore, these resins are often considered to be reactive diluents and flexibilizers. 

The polyglycol diepoxies are used primarily as flexibilizers and reactive diluents. Commercial products are available where n varies from 2 to 7. Generally, these are used in the range of 10 to 30 percent by weight with DGEBA or epoxy novolac resins to improve flexibility without a significant loss in physical properties. 

Of course, in the case of both curing agents and catalysts, suitable adjustments will have to be made for the presence of nonreactive fillers and modifiers. Such ingredients can be liquids such as a solvent, a hydrocarbon resin, or a plasticizer. Since they do not contribute any epoxide functionality, they should not be considered when one is determining stoichiometry. However, if the additives have epoxy functionality, such as in the case of reactive diluents, the stoichiometric calculations will have to take these materials into consideration, by calculating ratios similarly as with an epoxy resin. 

The higher-MW semisolid (EEW of 225 to 280) and solid epoxy resins (EEW > 450) may be blended into lower-MW resins to improve flexibility and decrease reactivity. They also improve adhesion due to the higher concentration of hydroxyl groups along the molecular chain. Ten percent of a higher-MW epoxy resin blended into a conventional liquid epoxy resin (EEW of 190) can significantly improve flexibihty, but a reactive diluent frequently needs to be added to the formulation to counteract the increased viscosity caused by the addition. 

Glycidyl ethers of aliphatic polyols based on polyglycol, glycerin, and other polyols are flexible epoxy resins. They are used as reactive diluents and flexibihzers for solvent-free epoxy resin formulations. Epoxy-polyglycol resins that are produced from the reaction of epichlorohydrin and polyester polyols based on ethylene or propylene oxide are the most common of these types of flexible epoxy resins. Examples of typical commercial aliphatic epoxy resins are shown in App. C. 

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