Methacrylate reactive diluents

Another approach to high soHds alkyd coatings is the partial replacement of solvent in a conventional long-oil alkyd with a reactive diluent. Eor example, dicyclopentenyloxyethyl methacrylate [70191-60-9J, mixed amides from the condensation of acrylamide (qv) (2-propeneamide)... 

Because of its low price, compatibility, low viscosity and ease of use styrene is the preferred reactive diluent in general purpose resins. Methyl methacrylate is sometimes used, but as it does not copolymerise alone with most unsaturated polyesters, usually in conjunction with styrene in resins for translucent sheeting. Vinyl toluene and diallyl phthalate are also occasionally employed. The use of many other monomers is described in the literature. 

The acrylate or methacrylate functional PIBs have also been used in UV-curable solventless coatings formulation in the presence of reactive diluents (multifunctional acrylate or methacrylate esters) and a UV-sensitizer [104]. The products were transparent, flexible films, with very little extractables, in which hard polyacrylate or polymethacrylate domains were dispersed in the soft PIB matrix. Tensile strength and ultimate elongation have also been obtained. 

These same rules apply to other resins such as the family of unsaturated polyesters. In these, the reactive diluents dilute the ester groups. A reduction in ester group concentration can be achieved by using more rigid skeletal structures and employing only terminal ester groups (vinyl ester resins) or urethane links (vinyl urethanes, urethane methacrylates). The chemical resistance of these resins is summarized in Table 3.6. 

Chem. Descrip. Ethoxylated, nonyl phenol methacrylate Uses Monomer for adhesives (pressure-sensitive, laminating) functional intermediate in metal coatings, fiber optics, inks, stereo lithography, and optical illusions reactive diluent for radiation and peroxide cure applies. Features Good pigment/tiller wetting good tackitier compat. 

Chem. Descrip. Alkyl methacrylate polymer in hydrocarbon oil Uses Vise, index improver for formulation of high vise, index hydraulic fluids emulsifier, dispersant for emulsion polymerization reactive diluent for adhesives and coatings... 

Uses Reactive diluent for radiation and peroxide-cured adhesives, electronics, photopolymers, cosmetics PPG-5 methacrylate CAS 39420-45-6 (generic)... 

To illustrate their effectiveness as anaerobic adhesives several combinations of the adduct, with or without added filler, reactive diluents, or peroxide, were screened using nut/bolt combinations. The results in terms of breakaway torque are listed in Table 2. The strengths obtained, although none of the systems were optimized, demonstrated the use of the methacrylated polyester compounds as anaerobic curing or thermal curing adhesives. 

Radiation curable adhesives can be based on raw materials that are not greatly different from those used in acrylic adhesives (first, second, and third generations), epoxy adhesives, urethane adhesives, and anaerobic adhesives. The formulation approach, however, is somewhat different. Very important is that no solvents are used to thin the resins a monomer reactive diluent is used instead. The monomer must be matched with the resin to give the desired set of properties with respect to adhesion, substrate, flexibility or stiffness, cure behavior, and durability of the cured product. Most of the radiation curable adhesives have an acrylate (or methacrylate) basis many of the acrylics are modified. 

Under the assumption of bimolecular termination, the reaction diffusion parameter R (equation (4.2)) was determined for the bulk photopolymerization of multifunctional (meth)acrylates [I, 3, 6, 17, 481. It was found that for methacrylates at the plateau level, R was in the order of 2 1 moP [6] and for acrylates R was 3-5 1 moP [I7J. In general, reduction of network cross-linking density by co-polymerization with a difunctional reactive diluent (2-hydroxyethyl methacrylate (HEMA), octyl methacrylate) [3] increased the values of R due to increased mobility of the polymerization system until a plateau is reached. The addition of an inert diluent (polyethylene glycol 400 (PEG 400) [3, 6] or hydrogenated monomers [25. 53]) to a flexible monomer of low viscosity did not change R,... 

Contact sensitizers from a patient s own materials, such as formaldehyde, isothiazolinones, nickel, chromium, cobalt, colophony (in the form of resin acids), epoxy resin oligomers, reactive diluents, acrylates, methacrylates, polyamines and di-isocyanates, can be analyzed. In fact, any product can be analyzed, but it is not a routine task for laboratories and may be very expensive. There are two main reasons for chemical analyses. First, on patch testing, the patient is found to be allergic to a specific chemical, and the causative product(s) are analyzed for the chemical. Second, the patient s own material has caused an allergic test reaction, but MSDS or other information from the manufacturer did not reveal the causative chemical. In this case, it may be reasonable to analyze the material... 

Tetrahydrofurfural methacrylate and isobornyl acrylate were the main components in the analysed two-component glues. Ethylhexyl methacrylate and 2-hydroxyethyl methacrylate (2-HEMA) were present as reactive diluents. High concentrations of two sen-sitisers, HEMA (26%) and isobornyl acrylate (24%), were present, although undeclared. Undeclared epoxy resin (6%) had been added to two glues. 

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). 

Anaerobic acrylic sealants or cyanoacrylates are known sensitizers, while the modified acrylic structural adhesives that cure in air more rarely cause allergy. Tosti et al. (1993) reported of three carpenters, each of whom became sensitized to wood paints and glues with butyl acrylate, 2-ethoxyethyl methacrylate, or a phth-late. Epoxy resin compounds are another commonly used group of adhesives, which contain resins (generally included in patch-test screening batteries), hardeners, and reactive diluents, as well as many other potentially harmful ingredients, such as tar, fillers, colorants, and other plastics. 

The monomers which are most widely used in photopolymerization processes to form networks are acrylates. The reason is that they polymerize fast. Methacrylates generally polymerize more slowly but, due to the stiffer main chain, yield harder products. By copolymerization of monoacrylates (/=2) with di-(/=4) or triacrylates (/=6), crosslinked networks are formed. In order to avoid the presence of free monomer in the cured product, monoacrylates are sometimes omitted. The acrylic esters of the lower mono-, di- or trialcohols or the lower ethylene or propylene glycols are liquids of low viscosity and, especially with the lower alcohols, of repellent odor. They are often used in coating formulations as reactive diluents for the more viscous oligomers. 

The terra acrylate resins refers to acrylate-functional polymers. This means that the reactive group, which can be either an acrylate or a methacrylate functionality (Scheme 16.25), is still present in the polymer. (This is also the distinction from acrylics, which are polymers prepared from acrylate monomers and in which the acrylate functionality is no longer present.) These polymers are generally dissolved in a reactive diluent or in a diluent mixture. Depending upon the application these resins are cured with a peroxide initiator or with the combination of light and a photoinitiator, the so-called UV curing [11] see Section 16.8.5. When curing occurs with a peroxide, the peroxide is mixed with the resin and the mixture is then cast into on a mold. 

The reactive diluent is required for tuning the resin formulation to the application viscosity. The nature of the diluent is partly dependent on the structure of the resin. In the case of methacrylate-functional resins, methacrylate-functional diluents are mostly used, whereas in the case of acrylate-functional resins, acrylate-functional diluents are commonly applied. 

The composite resin industry is the main exception with respect to the selective choice of reactive diluents. Within this industry, styrene is used as well as reactive diluent (known in combination with unsaturated polyesters). Methacrylates are then often referred to as - chemically erroneously - vinyl esters. 

Unsaturated polyesters (see Section 16.7) can be used in UV curing as well, but only in combination with a special reactive diluent system, which is based on vinyl ethers. Kinetic analysis has revealed that in that specific case the fumarate forms a charge transfer complex with the vinyl ether and a homopolymerization of this charge-transfer complex takes place as depicted in Scheme 16.34. An advantage of a charge-transfer complex radical polymerization is that it is less susceptible toward oxygen inhibition than methacrylate systems. This is illustrated by the fact that the first commercial UV powder system, in which the powder is sprayed (much oxygen), melted, and then UV-cured, was based on a fumarate-vinyl ether system. 

Reactive diluent is a very important component of unsaturated polyester resins. It should act as a solvent for unsaturated polyester resins as well as copolymerize with unsaturated bonds in the polymer backbone. Styrene is the most commonly used diluent due to good solvency, low cost, low viscosity and good reactivity. Apart from styrene, other monomers such as vinyl toluene, methyl methacrylate and a-methyl styrene as well as some polyfunctional diluents such as 1,6-hexanediol diacrylate, diallyl phthalate, divinyl benzene, and trimethylolpropane triacrylate are used. 

As pointed out in the introduction, unsaturated polyester resins are commonly combined with reactive diluent monomers (Table 12.3). Styrene is most frequently used for this purpose.However, monomers such as methyl methacrylate, diallyl phthalate, " triallyl cyanurate, " vinyl toluene,a -methylstyrene, p-t rt-butylstyrene, and chlorostyrene have also been studied (Table 12.3), showing varying degrees of utility. 

Solid monomer-solid initiator systems were tried with a variety of monomers and initiators. Two types of monomer systems were used 1) monomers whose melting points were lower than the adiabatic reaction temperature. Acrylamide worked well but n-octadecyl acrylate did not because it was not sufficiently reactive 2) High melting point monomers with a reactive diluent in which the monomer could dissolve at high temperature. Zinc dimethacrylate/acrylamide or zinc dimethacrylate/methacrylic acid both supported frontal propagation with BPO initiator. 

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