Diluent epoxy resin

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). 

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. Diluent for epoxy resins stabilizer of chlorinated organic compounds... 

Solvents used as nonreactive diluents include acetone, cellosolve, methyl ethyl ketone, methyl isobutyl ketone, methylene chloride, 1,1,1-trichloroethane, toluene, and xylene. Skin and eye irritation and, in higher concentrations, CNS depression and respiratory irritation may result ftom exposure to these solvents as diluents for epoxy resin... 

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. 

BMI/amine Michael adduct resins may be further modified and blended with other thermosets or reactive diluents to achieve either specific end-use properties or processability. Epoxy resins are very suitable for the modification of BMI/primary amine adducts, because the secondary amine functionality in the aspartimide structure is a curative for the epoxy group. 

Finally, it is possible to fill a small shallow hole the size of the electrode required with carbon paste. These pastes are made from particles of graphite and a suitable hydrophobic diluent such as Nujol [103], silicone rubber [104], paraffin [105], epoxy resin [106], Teflon [107], or Kel-F... 

Similar to unsaturated polyesters, they are copolymerized with diluents such as styrene using similar free-radical initiators. They differ from polyesters in that the unsaturation is at the end of the molecule and not along the polymer chains. Their burning behavior falls between that of polyester and epoxy resins (LOI = 20-23 vol%, Table 2.4). 

Electrodes made with carbon or graphite paste mixed with a hydro-phobic diluent such as Nujol, paraffin, silicone rubber, epoxy resin, Teflon, or Kel-F, have also been used. Comparative studies between the various types of carbon paste electrode have been carried out11. 

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. 

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. 

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 viscosity of the epoxy resin is only one factor in determining the final viscosity of the formulated system. Some curing agents and resinous modifiers produce little effect on mixed viscosity however, others can have a significant effect by either increasing or decreasing viscosity. Fillers, in general, increase viscosity in direct relationship to their concentration in the system. Diluents can be used to decrease viscosity. 

The viscosity of an epoxy resin is dependent primarily on its molecular weight (MW). Low-MW resins typically have a viscosity in excess of 6000 cP, and conventional DGEBA epoxy resins (EEW = 190) have a viscosity around 12,000 cP. Therefore, for applications requiring relatively low viscosity, it is necessary to include other types of epoxy resin or to use diluents to achieve the desired properties. 

Similarly, lower-molecular-weight diluents may be added to reduce viscosity. Viscosity reduction is often necessary to allow for easier compounding of the ingredients into the formulation or to provide specific application properties. Accelerators are also frequently added to speed the cure rate of epoxy resins at or below room temperature. 

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. 

Commercial products are available where n varies from 2 to 7. The flexible epoxy resins based on polyglycol also make excellent reactive diluents because they have a viscosity of 100 cP at 25°C. Table 4.4 shows the effect of two polyglycol diepoxides on the physical properties of a cured epoxy system. Another type of flexible epoxy resin is derived from dimerized unsaturated fatty acid, cashew nut oils, and other vegetable oils. Other flexible epoxy resins can be made with thiols, aliphatic acids, and hydroxyl-terminated compounds. Applications where flexible epoxy resins are valued include... 

Solvents and diluents are used to lower the viscosity of epoxy resins systems either to permit easy compounding with other ingredients or to aid in application of the adhesive onto a substrate. Both solvents and diluents are low-molecular-weight liquid compounds that are chemically and physically compatible with epoxy resins and their curing agents. They differ primarily by their vapor pressure. 

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. 

Epoxy adhesive formulations demand a great variety of solvents and diluents with a wide range of evaporation rates, solvent strengths, and dispersion powers. These variations are required due to (1) the many types of epoxy resins, curing agents, and possible organic additives that can be used within a formulation and (2) the many different possible methods that can be used to apply the epoxy to the substrate (brush, spray, trowel, etc.). 

The effect of solvent type on the curing rate of epoxy reactions has been well defined. Hydroxyl compounds, such as alcohols, act as catalysts and accelerate curing. However, these solvents are not serious competitors with amines for reacting with the epoxy ring. Water, functioning as a hydroxyl compound, also accelerates the reaction, even more than alcohols. Aprotic solvents, such as aromatic hydrocarbons or mineral spirits, have no effect on the amine-epoxy resin and behave as inert diluents. Carbonyl solvents, such as acetone and methyl ethyl ketone, retard the reaction. 

Diluents are higher-MW components than solvents that are also added to the epoxy adhesive formulation to lower the viscosity and modify processing conditions. The primary function of a diluent in an epoxy resin formulation is to reduce its viscosity to make it easier to compound with fillers, to improve filler loading capacity, or to improve application properties. Solvents, certain curing agents, and flexibilized epoxy resins can also lower the viscosity of epoxy adhesive formulations, but this is not their primary function. The effect of various diluents on the initial viscosity of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin is illustrated in Fig. 6.3. 

FIGURE 6.3 Effect of various diluents on the viscosity of a standard DGEBA liquid epoxy resin.6... 

---