is there is any graph which shows phase transformation of plastic after heating then cooling.
There isn't a phase transformation in plastic like there is in metals. When you heat treat plastic you are just annealing it. In other words the polymer chains are stretched and frozen during the molding process (or any process that melts and solidifies the material) and this creates stresses that when a chemical attack happens the plastic with fracture. When you anneal plastic your allowing stretched polymers to relax. Sometimes this will also cause your perfect part that is under great stress to become warped in its relaxed state. This can be resolved using fixtures when annealing the plastic. To anneal a plastic you need to take the plastic to about 20F below the ASTM D648 @ 66PSI and hold it there for approximately 1/2 hour at that temp. This is difficult if the plastic is very thick (4 blocks of plastic and you want to machine it.) If plasticis not annealed it is similar to having a 1 ton chain with a 1990 lbs hanging on the end of it. All you need is a small force added or a stress concentrator such as oxidation reaction to attach it and the thing will snap in front of you and you can hear and watch it happen. To view the stresses in plastic you can mold the plastic out of a clear polymer and then using 2 polarized sheets and a backlight the stress in the plastic will bend the light and you will see the coloration. These iso bars of color show the location of the stresses (which are typically at corners, gates and at the knit lines. people.rit.edu/andpph/text-polari...
confusing issue. browse with search engines like google. that could actually help!
