How to choose EVA foam lubricant

    Do you need to add lubricant to EVA foam? Yes. The EVA foaming process is inseparable from the lubricant. The purpose of using the lubricant is to make the EVA foam extrusion process simple.

    There are two types of EVA foam lubricants: internal lubricant and external lubricant.

    The difference between the internal lubricant and the external lubricant in the use effect is: the external lubricant is used to reduce the melt and metal parts. The internal lubricant changes the rheological behavior and viscosity of the melt by changing the intermolecular friction, and has the function of improving the fluidity and uniformity of the melt.

    The key to the distinction between the two EVA foam lubricants is the compatibility between the polymer and the lubricant. The inner lubricant has greater compatibility, while the outer lubricant has less compatibility. However, compatibility tends to improve as temperature and pressure increase. At this time, what was originally an external lubricant can become an internal lubricant, so there is no strict boundary between the two. In many cases, a lubricant often plays the role of internal and external lubrication at the same time, but a certain kind of lubrication is the main one.

    One factor that should be paid attention to in the EVA low-foaming extrusion molding process is that the melt should flow smoothly through the cavity to form a smooth surface that is not easy to break. Lubricant affects the surface finish of the cavity and the mixing and distribution of foaming gas, thereby affecting the cells of EVA foam.

     In the extrusion formula of EVA foam, these three kinds of lubricants often need to be present at the same time. The author has done a lot of tests on this. Lubrication has a great influence on the quality of extruded products, the energy consumption of the extrusion process, and the length of the mold cleaning cycle. Extruding products of the same quality has a difference of 30-100% in energy consumption and a difference of 1 to 5 times in the cleaning cycle. It can be seen that the lubricant plays a very important role in the extrusion process of EVA low foam cotton products.