In the cracking of dicyclopentadiene why is it necessary to distill the product very slowly

By cracking the material by using a slow addition and distilling at a low temperature then it will prevent polymerization of the formed monomer.

It is an example of Dirls-Alder mixture reaction. Cyclopentadiene its work is to polymerize readily. It is termed as an organic compound which has formula C5H6. It is colorless in color and strong unpleasant odor. In a cyclic diene, it dimerizes.