TG (Glass transition temperature) is the point at which rising temperatures cause resin inside the solid base laminate to start to exhibit soft, plastic-like symptoms. This is expressed in degrees Celsius (°C). The temperature at which a polymer changes from a hard and relatively brittle condition to a viscous or rubber condition. This transition generally occurs over a relatively narrow temperature range. Although there is no phase transition, in this temperature region many physical properties (such as hardness, brittleness, thermal expansion and specific heat) undergo significant and rapid changes. Glass transition temperature is also used as a shorthand way of indicating the temperature at which the mechanical and electrical properties of a laminate begin to degrade
