塑料助剂又叫塑料添加剂，是聚合物（合成树脂）进行成型加工时为改善其加工性能或为改善树脂本身性能所不足而必须添加的一些化合物。例如，为了降低聚氯乙烯树脂的成型温度，使制品柔软而添加的增塑剂；又如为了制备质量轻、抗振、隔热、隔音的泡沫塑料而要添加发泡剂；有些塑料的热分解温度与成型加工温度非常接近，不加入热稳定剂就无法成型。因而，塑料助剂在塑料成型加工中占有特别重要的地位。用于塑料成型加工品的一大类助剂，包括增塑剂、热稳定剂、抗氧剂、光稳定剂、阻燃剂、发泡剂、抗静电剂、防霉剂、着色剂和增白剂（见颜料）、填充剂、偶联剂、润滑剂、脱模剂等。其中着色剂、增白剂和填充剂不是塑料专用化学品，而是泛用的配合材料。
Plastic additives, also known as plastic additives, are some compounds that must be added when polymer (synthetic resin) is processed in order to improve its processing properties or to improve the properties of resin itself. For example, in order to reduce the forming temperature of polyvinyl chloride resin and make the product soft, plasticizers are added; in order to prepare foam plastics with light shijiazhuang.89ix.comhefei.89ix.com zhangjiakou.89ix.comweight, anti-vibration, heat insulation and nanning.89ix.comwuhan.89ix.comtangshan.89ix.comsound insulation, foaming agents are added; in some plastics, the thermal decomposition temperature is very close to the processing temperature, and it is impossible to form without adding thermal stabilizers. Therefore, plastic additives play a particularly important role in plastic forming process. A wide range of additives used in plastic forming products include plasticizers, heat stabilizers, antioxidants, light stabilizers, flame retardants, foaming agents, antistatic agents, mildew inhibitors, colorants and whiteners (see pigments), fillers, coupling agents, lubricants, demoulding agents, etc. Among them, colorants, whiteners and fillers are not special chemicals for plastics, but widely used matching materials.