In a chemical reaction, a by-product is a secondary product formed in addition to the main product. In polymerization, by-products can be formed through side reactions or termination steps. These by-products can sometimes affect the properties of the final polymer or require removal through purification processes.

在化学反应中，副产物是除主要产物外形成的次要产物。在聚合反应中，副产物可以通过副反应或终止步骤形成。这些副产物有时会影响最终聚合物的性能，或者需要通过纯化工艺去除。