Epoxy acrylate photocured

Ariga (45) disclosed developments with CTBN-modified epoxy acrylates which when prepared with other lower molecular weight dicarboxylic acids and select carboxyl-terminated oligopolyesters serve as novel oligomers for photocurable coatings. These systems have low uncured viscosity. In the cured state they possess excellent scratch and crosshatch adhesion, good direct and reverse impacts (duPont impact tester) and pass bending diameters of 2 mm. 

Table 8 examines simple photocurable models based on epoxy-acrylate oligomers. Two recipes represent two modification approaches (a) Synthesized CTBN-modified... 

In a study of polymerization kinetics of photocurable compounds based on an epoxy acrylate oligomer and three analogous diacrylate monomers... 

Glass fiber reinforced composites based on epoxy-acrylate modified UPRs were studied [228]. The authors showed that UPRs, endcapped with acrylate groups and diluted with reactive multifunctional acrylic and allylic monomers in the presence of a photoinitiator, can be photocrosslinked with UV radiation as glass fiber laminates in a rapid process. It was found that the physical properties of the photo-crosslinked laminates are well correlated with the molecular weight of the polyester, the amount of multifunctional monomer added, and the glass fiber content. A greater improvement of the tensile and flexural properties of the photocured products was observed for multifunctional acrylate or acrylether monomers added to the UPR (Table 31) than for allylic monomers. 

Other synthetic fibers, as well as natural fibers, were employed in epoxy-based multicomponent systems. Thus, a comparative study between polymeric fibers reinforced epoxy resins and natural fibers reinforced ones, all obtained by UV curing, was performed [186]. Isotactic PP (iPP) fibers modified with 20 wt% EVA and hemp fibers were employed, while the matrices used were epoxy acrylate and epoxy methacrylate. Data indicated that relatively regular distribution of fibers was achieved the addition of fibers caused an increase in Shore hardness of the epoxy methacrylate based composites the epoxy acrylated composites showed a decrease in hardness when EVA-modified iPP fibers were used, whereas hemp fibers caused an opposite effect. Even more, the iPP fibers reinforced photocurable composites displayed a brittle to ductile fracture transition. 

Stereolithography (SLA) is an additive method and uses a liquid-based systan. The liquid polymer is photocured layer by layer. The liquid polymers are (UV) ultraviolet-curable photopolymer (thermoset) resins such as epoxy, acrylates, and vinyl ethers. The system is illustrated in Figure 15.7. A tub (vat) is filled with the liquid resin. A platform supports the model as it is built. The platform is first raised to just below the liquid surface at a depth of the first layer to be cured. Then a computer-controlled laser is focused so that it solidifies the first layer to the required depth as it is moved in the x, y directions within the 2D area of the first slice. Subsequently, the platform is lowered a distance equal to the second layer thickness to be cured and the process is continued. Layer thicknesses as small as 0.025 mm (0.001 in.) up to 0.5 mm (0.020 in.) can be cured in this manner. 3D Systems is the company that supplies its patented SLA equipment to a worldwide market. 

Several studies have concentrated on the photocrosslinking of epoxy-based resins. Using differential scanning calorimetry the photocuring of epoxy and acrylic prepolymers has been disturbed by the... 

Epoxy resins have been cured using a tris(ethyl acetoacetato) aluminium complex and tris (4-chloro-phenyl) (a-nitrobenzoy-loxy) silane.Resins produced by this catalyst mixture were found to have desirable electrical characteristics. N-vinyl-2-pyrrolidone is claimed to be a much superior resin than several acrylate diluents for photocured coatings... 

Photopolymer systems are photocurable resins incorporating reactive liquid monomers, photoinitiators, chemical modihers and hhers. Typically stereolithography utilizes UV radiation, so UV-curable systems are used. Free-radical-photopolymerizable acrylate systems were originally used however, newer cationic epoxy-resin and vinyl ether systems (based on iodinium- or sulfonium-salt cationic initiators) are now being utilized. 

Typical photocurable resins for photolithography, such as acrylates and epoxy-resin... 

A laser beam directs to the photocurable resin which can be classified as an epoxy, vinyl ether, or acrylate. The 3D structure or mold is built on a platform which can be controlled by an XYZ positioner. When one layer is complete, the platform drops lower into the vat of resin, fresh resin washes over the part, and the laser proceeds to build the next layer. The 3D microstructure is built up in this additive process. When all layers are complete, the part is cleaned and post-cured. The major drawback of this technique is the considerable capital investment. Also, only photocurable resins can be used which can be a limitation if a special material is required. 

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