Vinyl-Epoxies

Epoxy resins may be blended with certain vinyl polymers to improve the impact strength and peel strength of the adhesive. Polyvinyl acetals, such as polyvinyl butyral and polyvinyl formal, and polyvinyl esters are compatible with DGEBA epoxy resins when added at concentrations of 10 to 20% by weight. The addition improves the resulting impact resistance and peel strength of the cured adhesive. However, temperature and chemical resistance are sacrificed by the addition of the low-glass-transition-temperature vinyl resins. 

The solubility of the vinyl polymer in the epoxy resins will depend on the molecular weight and grade of vinyl used. Polyvinyl esters can be dissolved in liquid epoxy resins that are heated to about 100°C or in melted solid epoxy resins. However, most epoxy-vinyl blends are normally prepared via solvent solution. 

The formulated adhesives are generally available as films or solvent solutions. They are commonly used as laminating adhesives for film or metallic foil because of their high peel strength. A composition consisting of a plasticized polyvinyl chloride copolymer and an epoxy resin can be cured with an aliphatic polyamine, which will crosslink by reacting with both resins. This adhesive possesses excellent adhesion to metals. 

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As stated above, high performance coatings based on epoxies, vinyls or chlorinated rubbers are used almost exclusively on all large ships. A general development in these materials has been the introduction of highly thixotropic types that can be airless sprayed at wet film thicknesses of 300 im or more, that do not run or sag on vertical surfaces. This enables the requisite film thickness to be applied in fewer coats, saving time and reducing application costs. 

Epoxy system curing profile, 10 17-18 Epoxy systems, post-cure for, 10 423 Epoxy vinyl ester composites, 10 452 Epoxy vinyl ester resins, 10 349 Epoxy vinyl esters, 10 383 Eprosartan, 5 187... 

Because of the wide application of these resins to diverse industries and their very different kinetic models and mechanisms of cross-linking and reactions, phenomenological kinetic models for epoxy, vinyl ester, and phenolic resins are presented in the next three subsections. 

Macrocyclization. Trost and Warner17 have effected efficient cyclization to ten-and fifteen-membered rings by use of Pd(0) supported on a polystyrene bearing phosphine ligands. Precursors with an epoxy vinyl terminal group proved particularly suitable. Thus, 1 in the presence of such a Pd(0) catalyst cyclizes to 2 and 3 in 71% yield. The products are isomeric at the double bond, since both are oxidized to the ketone 4. The same catalyst system converted 1 (n = 9) into two macrocyclic isomers in 66% yield. Both cyclizations are concentration dependent. The temperature is also critical, the reaction being particularly clean at 65°. 

FRP materials are made up of the polymer and reinforcing fibers. The polymer is typically a thermoset polymer thermoplastics can be used as well. Some typical thermoset polymers used are epoxy resins, unsaturated polyester resins, epoxy vinyl ester resins, phenolic resins, and high performance aerospace resins such as cyanate esters, polyimides, and bismaleimides. These resins... 

For commodity applications, there are four major classes of resins that are used in FRP applications. They are phenolic resin, epoxy resin, unsaturated polyester resin, and epoxy vinyl ester resins. A more complete description of these types of resins and their many variations can be found in Handbook of Thermoset Plastics. This is not a comprehensive list of resins used in composite manufacture, as commodity materials like polyurethanes and isocyanurate resins are sometimes used as well to make FRP parts. However, these materials are not covered in this chapter owing to their limited use, but, the principals of fire safety that apply for the resins described subsequently apply to these materials as well. 

Epoxy vinyl ester resins are a special class of unsaturated resin. This resin is made by capping an epoxy resin with methacrylic acid and then dissolving in styrene monomer to the desired viscosity. This gives mechanical properties similar to epoxy resins, but the processibility (low viscosity allowing for resin infusion processes) of an unsaturated polyester resin. As with unsaturated vinyl esters, the most common fire retardant vinyl ester resin is based on a resin made from a halogenated system, tetrabromobisphenol A. The level of bromine in the resin and the presence of antimony will determine the fire performance of the resin. These resins are normally used for corrosion resistant equipment or when fire performance and high mechanical properties are required. It is very difficult to get a low smoke value with a brominated vinyl ester resin again due to the fact that bromine... 

Two resins were used to do the first study on laminate construction. The first was a brominated epoxy vinyl ester resin with antimony pentoxide and the second was a brominated unsaturated polyester resin. They were both promoted to cure at room temperature with methyl ethyl ketone peroxide catalyst. The panels were then postcured at 250°F (121°C) for 8 h. Panels were prepared that varied in glass content from 25% to 70% and panel thickness varying from 0.05 in. to 0.25 in. and were tested at the same testing facility. A summary of the FSI test data for the first set of panels tested are shown in Figures 23.1 and 23.2. This graph in Figure 23.1 plots the FSI value versus the panel thickness. This data would indicate that the thickness of the test panel has no effect on the measured... 

The early aerospace adhesives were primarily based on epoxy resin chemistry. However, unique applications requiring high temperatures and fatigue resistance have forced the development of epoxy-phenolic, epoxy-nitrile, epoxy-nylon, and epoxy-vinyl adhesives specifically for this industry. The aerospace industry has led in the development and utilization of these epoxy-hybrid adhesives. 

Epoxy-vinyl Vinyl-epoxy adhesives have moderate strength at temperatures up to 150°C. Oxidation stability is excellent. Vinyl constituents increase the toughness and peel strength. The adhesive is often used for bonding safety glass, aerospace engine structures, and structural panels. 

Soluble thermoplastic polymer additions (e.g., epoxy-nylon and epoxy-vinyl) provide very tough and somewhat flexible systems, but they are limited because of their high viscosity and high raw materials costs. Almost all these systems need to be handled at elevated temperatures or as solvent solutions. They require elevated temperature to achieve wetting and cure. 

Amino Epoxy Vinyl Methacryloxy Novakup series Malvern Minerals... 

Typically tape or film epoxy adhesives are modified with synthetic thermoplastic polymers to improve flexibility in the uncured film and toughness in the cured adhesive. Epoxy resins can also be blended with phenolic resins for higher heat resistance. The most common hybrid systems include epoxy-phenolics, epoxy-nylon, epoxy-nitrile, and epoxy-vinyl hybrids. These hybrid film adhesives are summarized in Table 13.2, and structural properties are shown in Table 13.3. 

Heat cured paste (nitrile-epoxy, nylon-epoxy, vinyl-epoxy)... 

All of the commercial epoxy adhesives presented in App. B bond well to aluminum and to a wide variety of other materials. Sell22 has ranked a number of aluminum adhesives in order of decreasing durability as follows nitrile-phenolics, high-temperature epoxies, elevated-temperature curing epoxies, elevated-temperature curing rubber-modified epoxies, vinyl epoxies, two-part room temperature curing epoxy paste with amine cure, and two-part urethanes. 

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