Hey everyone. So now let's take a look at the thermal properties of polymers. With this, we're going to talk about 2 temperatures. We have our glass transition temperature which we're going to say represents T_g. And this is just the temperature above which the polymer transitions from hard to soft and moldable.

Then we have our crystalline melting temperature, which we're going to say is T_m. This is the temperature at which a polymer turns into a viscous liquid. If we take a look at this image, we have a water bottle at different phases. And we're increasing the temperature as we go from left to right. Before we reach our T_g temperature, we're going to be in its hard phase.

But once we pass the T_g, we see that the bottle starts to bend and become soft and moldable. And if we would increase the temperature even more past the T_m, we would see that the bottle starts to look like it's melting. That's because it's resembling a viscous liquid. Now, we're going to say here as our degree of crystallinity increases, so do our T_g and T_m.

Because remember, if you increase your crystallinity, you're increasing the overall strength of your polymer, which means you have to increase the temperature that much more to go from hard to soft moldable, to go from matte to a viscous liquid. Alright. So, just keep in mind when we're talking about thermal properties, we're talking about these two temperatures which can affect the composition and the way we see a given polymer.