Altek® H520-B is a prepromoted, thixotropic, general purpose low reactive orthophthalic polyester resin. The low exotherm of Altek H520-B allows for the application of thick laminate sections that can cure at one time without the generation of excessive heat. Altek H520-B provides good chemical bonding between laminate application if proper application procedures are followed. When used with the proper glass reinforcement content, AOC's Altek H520-B produces a composite with superior mechanical properties that can assist in the reduction of cracking. Resin color changes from blue to neutral after addition of peroxide. This color change provides a visual assurange to the fabricator that the peroxide has been mixed with the resin.