hat is the glass transistional temperature (Tg) in the context of polymeric materials?What effect does crystallinity have on Tg ? Draw a stress/strain graph and draw twocurves; one for a plastic below its Tg and one for when it is above Tg.

The glass transition temperature (Tg) is a critical property of polymeric materials. It is the temperature at which a polymer transitions from a hard, glassy material to a soft, rubbery material. Below the Tg, the polymer chains are frozen and the material behaves like a brittle glass, while above the Tg, the chains can move freely and the material behaves like a flexible rubber.

Crystallinity has a significant effect on Tg. In general, increasing the degree of crystallinity in a polymer will increase its Tg. This is because the crystalline regions in a polymer are more ordered and have stronger intermolecular forces than the amorphous regions, so more energy (in the form of heat) is required to allow the polymer chains to move freely.

A stress/strain graph is a plot of the applied stress (force per unit area) on the y-axis versus the resulting strain (deformation) on the x-axis. For a plastic below its Tg, the curve would start at the origin and rise steeply, indicating that the material is stiff and brittle. There would be a small amount of deformation (strain) before the material fractures.

For a plastic above its Tg, the curve would also start at the origin but rise more gradually, indicating that the material is soft and flexible. There would be a large amount of deformation before the material fractures. The area under the curve, which represents the energy absorbed by the material before fracture, would be much larger for the plastic above its Tg than for the plastic below its Tg.