Temperature gradients of various molten polymers during the cooling process were examined using a cooling jacket apparatus coupled with a novel temperature sensor. The temperature gradients appeared to be influenced by the heat transfer between the cooling medium and the polymer, the melt temperature, and crystallization temperature of the polymers. The results were then compared with theoretically generated data. The simple theoretical model yields a good comparison with the experimental data at the center of the duct but the accuracy is more limited at other radial positions.