Examples include flame retardants, thermal stabilizers, and UV stabilizers. As with other materials, the CTE is defined as the change in length per unit length per unit rise in temperature. Polymer material CTE's are in general much higher than those of metals. Therefore, when metal inserts are placed in a molded part, it is important to verify that with temperature excursions the maximum tensile strength of the plastic is not exceeded. A load placed on a polymer material will result in an initial deformation, but with the load remaining over time, permanent deformation will occur.
Creep data is difficult to find, but is often expressed in terms of a creep modulus.
Fillers Fillers are materials added to plastics whose intent is to modify the physical nature of the plastic without significantly modifying its mechanical properties. The T G can loosely be defined as a temperature point where a polymer experiences a significant change in properties. Typically, a large change in Young's Modulus is experienced. Amorphous polymers are structural below T G . This stage of going from stiff to flowing is over a wide temperature range.