润滑剂的功能

The function of lubricants

1.增加熔融指数

1. increase melting index

聚合物熔体的熔融指数是表征其加工流动性的重要参数。一般随着温度升高﹐熔融指数增加﹐熔体的流动速率增加。

Melt index of polymer melt is an important parameter to characterize its processing fluidity. Generally, as the temperature increases, the melt index increases and the melt flow rate increases.

由于受材料热稳定性等因素的限制,加工温度不可能无限度的升高。而且靠提高加工温度降低熔体黏度还会增加能耗。

Due to the thermal stability of materials, the machining temperature can not be increased indefinitely. Moreover, increasing the processing temperature and reducing the viscosity of the melt will increase energy consumption.

这时，添加适量的内润滑剂能够改变树脂熔体的流变行为﹐有效的增加熔融指数，达到降低熔体黏度﹐提高熔体流动性之目的。

At this time, adding a proper amount of internal lubricant can change the rheological behavior of the resin melt, effectively increase the melting index, reduce the viscosity of the melt and improve the melt fluidity.

2.减小内生热

2. reduction of endogenous heat

内生热即聚合物流动过程内部磨擦产生的热。在高速加工成型工艺中﹐高剪切使大量的机械能转化为热能﹐熔体黏度越大﹐剪切力越强﹐因此产生的内生热越多。

Endogenous heat is the heat generated by internal friction in the process of polymer flow. In the process of high speed machining, high shear makes a large amount of mechanical energy converted into thermal energy. The greater the viscosity of the melt, the stronger the shear force, the more endogenous heat is produced.

内生热的不良后果会导致聚合物熔体局部过热﹑使其热稳定性下降。添加内润滑剂可以有效的降低熔体黏度，有效减小内生热。

The adverse consequences of endogenous heat will lead to partial overheating and thermal stability of polymer melts. The addition of internal lubricants can effectively reduce the viscosity of the melt and effectively reduce the internal heat.

可能带来的不良后果是低熔融黏度可能使注塑成型等加工难以进行﹐这种情况下，我们应该选择能够赋予树脂内部结构单元足够高的润滑性 ﹐同时又对聚合物溶剂化作用极小的润滑剂。

The possible adverse effect is that the low melting viscosity may make the injection molding difficult to proceed. In this case, we should choose a lubricant that can give the internal structural unit of the resin a high enough lubricity and a small solvent to the polymer.

这样就就可以通过减少树脂内部界面的磨擦生热或将产生的内生热尽快散逸而提高加工稳定性﹐也避免了熔融黏度的降低和制品热变形温度下降等问题。

In this way, the processing stability can be improved by reducing the friction heat of the internal interface of the resin or releasing the generated heat as soon as possible, and the reduction of the melting viscosity and the decrease of the thermal deformation temperature of the products are also avoided.

3.脱模作用

3. demoulding effect

聚合物加工后期，制品成型。这时需要比较容易的从磨具上脱落下来，以提高加工效率和产品的质量。

At the later stage of the polymer processing, the products are formed. At this time, it is easier to peel off the abrasive tools so as to improve the processing efficiency and product quality.

这时可以添加具有脱模作用的润滑剂。脱模作用的润滑剂一般为外润滑剂﹐多是极性化合物﹐它们与树脂兼容性有限﹐能够从熔体迁移到表面﹐极性基团与金属表面具有一定的亲和性。这样在熔体和金属表面之间形成一层相对稳定﹑互为隔离的分子层﹐因此抑制聚合物熔体与加工机械表面之间的粘着。

Lubricants with demoulding effect can be added at this time. The lubricants for demoulding are usually external lubricants, most of which are polar compounds. They have limited compatibility with the resin and can migrate from the melt to the surface. The polar groups have a certain affinity with the metal surface. In this way, a relatively stable and isolated layer of molecular layer is formed between the melt and the metal surface, thus inhibiting the adhesion between the polymer melt and the machined surface.