Reactive resin

Duromers (cross-linked polymers) based on highly reactive resins with short setting times. 

A second type of uv curing chemistry is used, employing cationic curing as opposed to free-radical polymerization. This technology uses vinyl ethers and epoxy resins for the oligomers, reactive resins, and monomers. The initiators form Lewis acids upon absorption of the uv energy and the acid causes cationic polymerization. Although this chemistry has improved adhesion and flexibility and offers lower viscosity compared to the typical acrylate system, the cationic chemistry is very sensitive to humidity conditions and amine contamination. Both chemistries are used commercially. 

Heat-reactive resins are more compatible than oil-soluble resins with other polar-coating resins, such as amino, epoxy, and poly(vinyl butyral). They are used in interior-can and dmm linings, metal primers, and pipe coatings. The coatings have excellent resistance to solvents, acids, and salts. They can be used over a wide range of temperatures, up to 370°C for short periods of dry heat, and continuously at 150°C. Strong alkaUes should be avoided. 

Substituted heat-reactive resins are most widely used in contact-adhesive appHcations and, to a lesser extent, in coatings (77,78) -butylphenol, cresol, and nonylphenol are most frequendy used. The alkyl group increases compatibiHty with oleoresinous varnishes and alkyds. In combination with these resins, phenoHcs reduce water sensitivity. Common appHcations include baked-on and electrical insulation varnishes, and as modifiers for baking alkyds, rosin, and ester gum systems. Substituted heat-reactive resins are not used for air-dry coatings because of theh soft, tacky nature in the uncured state substituted nonheat-reactive phenoHcs are the modifying resin of choice in this case. 

Substituted nonheat-reactive resins do not form a film and are not reactive by themselves, but are exceUent modifier resins for oleoresinous varnishes and alkyds. Thein high glass-transition temperature and molecular weight provide initial hardness and reduce tack oxygen-initiated cross-linking reactions take place with the unsaturated oils. 

Dicylopentadiene Resins. Dicyclopentadiene (DCPD) can be used as a reactive component in polyester resins in two distinct reactions with maleic anhydride (7). The addition reaction of maleic anhydride in the presence of an equivalent of water produces a dicyclopentadiene acid maleate that can condense with ethylene or diethylene glycol to form low molecular weight, highly reactive resins. These resins, introduced commercially in 1980, have largely displaced OfXv o-phthahc resins in marine apphcations because of beneficial shrinkage properties that reduce surface profile. The inherent low viscosity of these polymers also allows for the use of high levels of fillers, such as alumina tfihydrate, to extend the resin-enhancing, fiame-retardant properties for apphcation in bathtub products (Table 4). 

Reinforcing Resins. Reinforcement and stiffness of a compound can also be achieved with the use of reactive resins. Resins consisting of two-component systems of resorcinol or resorcinol condensation products and a methylene donor such as hexamethoxymethylmel amine (HMMM) or hexamethyltetramine (HMT) are the most popular in tires. These materials can be prereacted and added to the formula, or for more effective results they can react in situ ie, they can be added separately into the formula and react when the tire is vulcanized. 

Under certain condition, however, reactions are still preferably conducted in solution. This is the case e.g., for heterogeneous reactions and for conversions, which deliver complex product mixtures. In the latter case, further conversion of this mixture on the solid support is not desirable. In these instances, the combination of solution chemistry with polymer-assisted conversions can be an advantageous solution. Polymer-assisted synthesis in solution employs the polymer matrix either as a scavenger or for polymeric reagents. In both cases the virtues of solution phase and solid supported chemistry are ideally combined allowing for the preparation of pure products by filtration of the reactive resin. If several reactive polymers are used sequentially, multi-step syntheses can be conducted in a polymer-supported manner in solution as well. As a further advantage, many reactive polymers can be recycled for multiple use. 

M291 Skin Decontamination Kit This kit is used to decontaminate the soldier s hands, face, ears, and neck. Packets in the kit consist of a foil-laminated fiber material containing a reactive resin. It replaces the M258A1 Skin Decontamination Kit. 

Substituted heat-reactive resins, 18 782 Substituted isoquinolines, 21 208 Substituted nickel carbonyl complexes, 17 114... 

Although polyurethanes or other reactive resins can be used in RTM, the most common resins are polyesters and epoxies. The two pumping reservoirs in Figure 7.90, then, contain polyester resin and initiator, or epoxy resin and hardener, respectively. Epoxies require relatively long cycle times. When cycle time is critical, low viscosity vinyl ester, acrylamate, or urethanes can be injected very rapidly into the mold. Even the use of thermoplastics is possible. 

Amides, carbamates, and ureas can be generated by nucleophilic cleavage of resin-bound esters, carbonates, and carbamates, respectively, with amines (Figure 3.20). These reactions only proceed well if sufficiently reactive resin-bound derivatives are used. 

A reactive resin is to be discharged from a reactor to drums (radius 0.3 m, height 0.9 m). In order to obtain a low viscosity allowing a practicable transfer time, the discharge temperature should be above 75 °C. It is known that the heat release rate of the resin is 10Wkg at 180°C and the activation energy of the reaction is 80 kj mob1. 

In a way partly analogous to the above method, if a fibrillar network of bacterial cellulose is interpenetrated with various monomers or reactive resins that are subsequently solidified, the resulting composites may be expected to exhibit a significant reinforcement of the substrate polymers in mechanical and/or thermal performance. This has been suggested recently by Yano et al. [74],... 

Diglycidyl ether of resorcinol-based epoxy resins provide the highest functionality in an aromatic diepoxide. It is one of the most fluid of epoxy resins, with a viscosity of 300 to 500 cP at 25°C. Because of its high functionality, it is a very reactive resin and cures more rapidly than DGEBA epoxies with most conventional curing agents. 

There are two general classes of photoinitiators (1) those that undergo direct photofragmentation on exposure to uv or visible light irradiation and produce active free radical intermediates and (2) those that undergo electron transfer followed by proton transfer to form a free radical species. The choice of photoinitiator is determined by the radiation source, the film thickness, the pigmentation, and the types of base resin employed. Examples of typical photoinitiator systems used to cure reactive resins are shown in Table 14.2. Benzophenone is perhaps one of the most common photoinitiators. 

A considerable number of industrial bioconversions utilize covalently immobilized biocatalysts. Examples include Penicillin acy-lases V and G, aminoacylases, and aspartase. In some cases the biocatalyst is immobilized through cross-linking and in others the catalyst is captured by a reactive resin. Covalent immobilization often leads to extremely stable catalysts with high potential for reuse and... 

The spherical shape has additional drawbacks. Because a sphere has the smallest possible surface area of all geometric shapes, its ability to develop opacity/ hide hide is low. Another difference is in settling behavior. A sphere will settle in a straight line while flakes move back and forth like a leaf. This effect can mainly be observed in reactive resin systems where enough time during the fluid stage is available to result in concentration differences of the aluminum in different sections of the part. 

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