Diluents monofunctional

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. 

Low-viscosity diglycidyl ether resins of undisclosed composition" have been marketed in the United States and in Britain. The materials are stated to be totally difunctional, i.e. free from monofunctional reactive diluents. The cured resins have properties very similar to those of the standard diglycidyl ether resins. 

In order to increase the flexibility, and usually, in consequence, the toughness of the resins, plasticisers and flexibilisers may be added. Non-reactive plasticisers such as the conventional phthalates and phosphates have proved unsuccessful. Monofunctional materials, which in some cases also act as reactive diluents, have been used but are not of great importance. 

The results for the formulations containing isobutyl vinyl ether are shown in Figure 2. Due to the vinyl ether double bond to maleate double bond ratio constraint, the compositions used for this study are located in one comer of the triangular graph. It was unfortunate that compositions containing little or no DVE-3 were incompatible and could not be evaluated. Viscosities were not measured on these formulations. Cure dose increases as the amount of monofunctional diluent increases. Pencil hardness increased as the vinyl ether double bond to maleate double bond ratio increased. These results indicate that substitution of a monofunctional maleate or vinyl ether diluent results in reduced cure speed and pencil hardness. 

Maleate/vinyl ether formulations based on a model unsaturated polyester prepared from maleic anhydride and 1,5-pentane diol and triethylene glycol divinyl ether were studied. At molecular weights of less than about 10,000 the cured films were extremely brittle. When the equivalent weight of the unsaturated polyester was increased by replacing some of the maleic anhydride with succinic anhydride, measurable values for film elongation could be obtained but the cure speed was definitely slower. When either diethyl maleate or isobutyl vinyl ether were added as monofunctional diluents the cure dose needed to obtain 200 MEKDR was increased and the flexibility measured by pencil hardness increased as the amount of diluent was increased. A urethane vinyl ether was synthesized and used to replace DVE-3 and films with increased elongation were obtained at equivalent at dosages as low as 1 J/cm2. 

Other products that may be epoxidized in this way include dihydric and trihydric phenols, aliphatic polyols such as glycerol, and simple alcohols such as butanol or alyl alcohol. These products, especially the monofunctional glycidyl ethers, are used at relatively low percentages to reduce the viscosity of formulations containing DGEBA resins. In this way, they act as reactive diluents. 

The monofunctional epoxy diluents are essentially chain stoppers since they inhibit crosslinks from forming. The extent to which the cured properties are affected is directly dependent on the concentration of the diluent added to the epoxy resin. The general effect is to reduce viscosity and improve the impact and thermal shock resistance while slightly reducing the thermal resistance. The thermal expansion of the cured resin is increased, as it is also with nonreactive diluents. This can lead to internal stress on the bond line depending on the thermal expansion of the substrate material. 

Monofunctional epoxy diluents are used primarily with DGEBA epoxy blends. The most common monofunctional diluents are butyl glycidyl ether and phenyl glycidyl ether. The effect of butyl glycidyl ether and other reactive diluents on the viscosity of epoxy resin is shown in Fig. 6.3. Because the monofunctional diluents reduce crosslink density, they are used at relatively low levels to avoid degrading heat and chemical resistance or other properties of the adhesive. 

Monofunctional epoxy diluents are long-chain molecules that have one functional group that can react with the epoxy system. The linkage prevents the diluent from migrating out of the cured epoxy during aging. The long chains force the molecules in the cured structure to... 

In adhesive formulations, glycidyl ethers are the most common monofunctional diluent. These include butyl glycidyl ether and allyl glycidyl ether. Other effective monofunctional... 

FIGURE 8.3 Commercial epoxy-containing monofunctional reactive diluents. 

Monomers are usually low-MW, monofunctional materials that chemically incorporate into the cured coating rather than volatilize into the atmosphere, as is common with solvent diluents. Monomer diluents are chosen on the basis of providing good solvency, effectively reducing the viscosity of the oligomer without excessively retarding the cure rate. Certain diluents will contribute to the physical properties of the adhesive. However, generally they provide soft, thermoplastic films because of their linear and uncrosslinked nature. 

Measurement of conversions of various formulations at various EB doses can be used to rank the reactivity of the formulation. A particularly useful procedure has been to prepare a standard mixture of an acrylate resin with various reactive diluent monomers in order to compare the volatility and reactivity of new monomers. For these studies, a mixture of 40 weight % of a Bis-phenol A epoxy dlacrylate resin with 60% of the test liquid monomer has proved convenient. A viscosity measurement of the mixture also provides information on the relative viscosity reducing ability of the test monomer. Illustrative examples of these measurements are shown in Table I and Figure 1. Mote from these examples that a monofunctional monomer, Monomer B, can be used to provide the low volatility and high reactivity typical of the multifunctional monomers, while also serving to reduce the crosslinking. Many other available monofunctional monomers are found to be either more volatile or less reactive than Monomer B. 

TABLE 14.3. Select Examples of Monofunctional Epoxy Diluents... 

Materials used were the standard commercially available grades. "CARDOLITE" Brand NC-513 is 3M s monofunctional epoxy reactive diluent CR-100, 3M s flow control agent DC-200, Dow-Corning antifoam Cab-O-Sil, Cabot fumed silica Epon 1001-X-75, Shell solid epoxy resin as 75% solution in xylene Tint-Ayd( ) EP-30-01, Daniels predispersed titanium dioxide liquid epoxy resin, standard bis-phenol-A diglycidyl ether of epoxide equivalent weight 190 grams/equivalent. 

Polymerization of V at its melting point (about 75°C) was too rapid to permit adding and mixing of the catalyst. Addition of a reactive monofunctional liquid diluent such as perfluorobutylphenyl isocyanate allowed the resulting isocyanate solution to be cooled to 40°C the catalyst was then added and mixed before appreciable polymeriza-... 

Five-membered cyclic carbonates are easily available as a result of the insertion of gaseous carbon dioxide into an oxirane ring (see review [12.]). Recent work in the field of new methods for preparing cyclic carbonates is dedicated primarily to the development of new catalytic systems and the synthesis of monofunctional compounds from epoxides and carbon dioxide (see, for example, reviews [13-16]). Monocyclic carbonates are used in a wide spectrum of applications solvents, components of liquid electrolytes, reactive diluents, chemical intermediates, and so on. It should be noted that this preparation also solves the problem of chemical fixation and utilization of C02. 

In view of the functionality thus created, it is interesting to consider possible applications for the epoxldlzed oils mentioned as epoxy monomers per se. Indeed, some epoxldlzed oils are commonly used as reactive diluents for other epoxy prepolymers in order to reduce cost or Improve processability (10,11) examples claimed in reference 11 Include epoxldlzed linseed, butylated linseed, soybean, and tall oils. However, although some fundfimental studies of the effects of monofunctional reactive diluents on the viscoelastic and other properties of epoxy resins have been published (see, for example, reference 12), little or no analogous Information on the effects of multifunctional reactive diluents appears to exist. At the same time, some reactive additives such as polyols (13), poly(ether esters) (14) and carboxy-terminated elastomers (15) have been used to provide an elastomeric toughening phase for epoxies. 

Diluent A is a monofunctional acrylate containing a urethane group. 

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. 

Interfacial polymerization will tolerate the presence of impurities in the reactants that simply dilute the material and thereby produce nonequivalence of reactants. These diluents might be water or inert contaminants in the acid chloride. Reactive monofunctional species are harmful in either phase. To maximize molecular weight, it is essential to use high purity monomers. Molecular weight control can be achieved, if desired, with appropriate use of monofunctional reagents. Examples of impurities interfering with the interfacial polyamidation of MPDI are half hydrolyzed acid chloride, monoamide, partially oxidized amines, and reactive surfactants. 

Uses Diluent for UV/EB-curable lacquers and pigmented coatings for paper, wood, vinyl flooring, flexible vinyl Features Reactive monofunctional... 

Uses Diluent for PVC, other plastics, films Features Reactive monofunctional provides film flexibility, toughness, adhesion, nonyellowing chats. 

The simplest UV-curable ink or coating formulations may consist of only three components. In practice, however, a typical industrial formulation contains a much greater number of ingredients. The three essential components are (1) a UV-reactive prepolymer which provides the bulk of the desired properties, (2) a diluent system composed of multifunctional acrylate esters (and at times monofunctional acrylic esters) and (3) a photoinitiator system. The most commonly used multifunctional acrylate in an UV-curable ink or coating formulation is an acrylic acid ester of either pentaerythritol (PETA), trimethyl-olpropane (TMPTA) or hexanediol (HDDA). 

The polyamide-imide achieved at the end of this process is a high-molecular-weight, fully imidized polymer in solvent with no condensation by-products, since the carbon dioxide gas is easily removed. This convenient form makes it especially beneficial for the manufacturer where the primary end use is wire enamel or another coating application. The solution viscosity is thus controlled by stoichiometry, monofunctional reagents, and polymer solids. The typical polymer sohds level is 35 to 45% and it may be diluted further by the supplier or customer with diluents. 

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