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There is significant overlap between the application of these two chemistries. Acrylates generally have superior adhesion, cure speed and impact resistance. Epoxies quickly establish tack free surfaces, have reasonable adhesion to a variety of substrates and would maintain their properties to high temperatures. The end-user is encouraged to think in terms of the process issues for the the production line. Reliance on a partnership with the chemical and curing equipment vendor(s) will select the best chemistry for the situation, rather than forcing a particular chemistry into an application. UV cationic curing epoxies require time and/or heat to cure and develop their properties after UV exposure. However, this potential advantage does not translate into faster cure speed to establish fixture of parts or hardening of a coating. Also, there is no indication that this conveys depth of cure that is comparable to acrylates. Epoxies are versatile products, adhering well to many substrates. Epoxies show better resistance to water than acrylates as measured on a percentage basis. However, because of the higher initial adhesion (tensile) values of acrylates, the final advantage does not fall to either class. Epoxies have the potential to be severely inhibited by exposure to moisture before cure. This may demand an increased level of workplace and processing controls for epoxies versus acrylates. Epoxies are much more difficult to cure to clear, colorless products. This translates to a smaller process window with respect to exposure dose and time than acrylates. The above test matrices are extremely valuable screening devices for CS&A choices. Obviously other possible factors are often involved, such as flexibility, impact, dispense practicality, etc. |
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UV curing of acrylate resins versus cationic epoxies in ADHESIVES AGE, Vol. 39, N° 4 (04/1996)
