English: Thermal transitions in (A) amorphous and (B) semicrystalline polymers, represented as traces from differential scanning calorimetry (DSC). Heat flow (exotherm down) is on the y-axis, and temperature is on the x-axis. As the temperature increases, both amorphous and semicrystalline polymers go through the glass transition (Tg). As the temperature continues to increase, amorphous polymers (A) experience increasingly rapid molecular motions but do not exhibit other phase transitions. However, semicrystalline polymers (B) undergo crystallization and melting transitions (at temperatures Tc and Tm, respectively).