A glass transition temperature (Tg) describes the point at which a thermoset polymer changes its physical structure to a crystalline state and is an average of the temperature range those changes occurred. The actual glass transition temperature range depends upon the molecular structure of the material, the testing method, sample preparation, the cure schedule, and the degree of cure.
Glass epoxy tubes and sheets have been used for many years in outdoor applications such as railroad track insulators and oil refinery insulators. They act as electrical insulation preventing electrolytic and galvanic corrosion and are constantly exposed to UV radiation. Convolute & filament wound glass epoxies have also been used for decades as antenna protection and are frequently the body of sonobuoys dropped into the ocean for sonar underwater research or submarine detection.
Lamitex® G30 is known for excellent thermal resistance, good chemical resistance, and superior mechanical properties. For instance, our G30 was tested to have flexural strengths of up to 67,267 psi. These properties are maintained during continuous use to temperatures from cryogenic to 450 °F (232 °C) and intermittently, as high as 900 °F (482 °C). Material specs for the downhole drilling industry refer to this as "MSTOT" or “Maximum Short Term Operating Temperature.” Polyimides are also inherently resistant to flame combustion and do not usually need to be mixed with flame-retardants, which at times can affect the mechanical properties of a thermoset laminate. Polyimide laminates have a flexural strength half-life at 480 °F (249 °C) of 400 hours.