润滑剂是能够改善塑料加工性能的一种添加剂。按其作用机理可分为外润滑剂和内润滑剂两种。外润滑剂能在加工时增加塑料表面的润滑性，减少塑料与金属表面的黏附力，使其受到机械的剪切力降至最少，从而达到在不损害塑料性能的情况下最容易加工成型的目的。内润滑剂则可以减少聚合物的内摩擦，增加塑料的熔融速率和熔体变形性，降低熔体黏度及改善塑化性能。实际上每一种润滑剂都有可以实现某一要求的作用，总是内外润滑的共同作用，只是在某一方面更突出一些。同一种润滑剂在不同的聚合物中或不同的加工条件下会表现出不同的润滑作用，如高温、高压下，内润滑剂会被挤压出来而成为外润滑剂。

Lubricant is an additive that can improve the processability of plastics. According to its mechanism, it can be divided into two types: external lubricants and internal lubricants. The lubricant can increase the lubricity of the plastic surface during processing, reduce the adhesion of the plastic and the metal surface, and reduce the mechanical shear force to the least, so as to achieve the purpose of processing the most easily without damaging the plastic properties. Internal lubricants can reduce the internal friction of polymers, increase the melting rate and melt deformation of plastics, reduce melt viscosity and improve plasticizing performance. In fact, each lubricant has the function of achieving a certain requirement, which is always the joint function of internal and external lubrication, but it is more prominent in one aspect. The same lubricant can show different lubricants in different polymers and different processing conditions, such as high temperature and high pressure, and the internal lubricants will be squeezed out and become external lubricants.

一般润滑剂的分子结构中，都会有长链的非极性基和极性基两部分，它们在不同的聚合物中的相容性是不一样的，从而显示不同的内、外润滑的作用。

In the molecular structure of the general lubricants, there are two parts of the long chain nonpolar and polar groups, and their compatibility in different polymers is different, thus showing different internal and external lubrication.

通常润滑剂均兼具有内、外润滑剂的功能，不过，不同的润滑剂其内、外润滑性能不同，有的润滑剂内润滑性较差，而外润滑性能较好；有的润滑剂外润滑性较差，而作为内润滑剂性能较好。通常认为，与聚合物相容性好、极性基团极性大的润滑剂多用作内润滑剂；反之，则用作外润滑剂，但也有内润滑及外润滑剂性能均佳的品种。

Usually lubricants both have the functions of both internal and external lubricants. However, different lubricants have different internal and external lubricating properties, some lubricants are poor in lubricity, and the external lubrication performance is better; some lubricants are poor in external lubrication, and the properties of internal lubricants are better. It is generally believed that the lubricants with good compatibility and polar group polarity are mostly used as internal lubricants; conversely, they are used as external lubricants, but also have excellent properties of both internal and external lubricants.