What are PVC lubricants and what are they used for?
It may be generally agreed that this particular topic is one of the most complex in the world of PVC. This group of additives covers several aspects to consider, and what is presented in the literature often differs significantly from reality when formulating.
As we've mentioned in other articles, PVC requires additives to become a functional plastic. Some of these additives fall into several categories. plasticizers, thermal stabilizers, lubricants, among others.
When we talk about a lubrication system, we usually refer to a group of additives that affect the rheology of a non-Newtonian flow plastic when it is being processed.
During the transformation process, commonly in extrusion, factors such as torque, compression, temperature, and the viscosity of the formulated melt play a major role in the fusion of the polymer. In PVC, this term refers to when the material has been properly processed, exhibits a good surface finish, and its physical and mechanical properties have reached an optimal point. Failure to achieve this usually results in a non-conforming product for the end user.
Concepts related to PVC lubrication
Achieving proper fusion is very complex, as the lubrication system designed by the formulator must consider 
both formulation aspects and the type of transformation process. Formulating a rigid, opaque formula intended for pipe extrusion is not the same as injection-molding semi-rigid parts for blenders.
Another factor involved here is flowability, which the production manager will want to consider to maintain productivity on their production lines and ensure proper process control with minimal downtime. An overly lubricated formula will have high flowability and often melting problems because the material, instead of being worked, will slip inside the equipment. Conversely, an under-lubricated material can stick to the equipment and burn, generating significant waste or spoilage.
PVC lubricants are divided into three categories based on their polarity with PVC: internal, external, and internal/external. Internal lubricants promote proper fusion without the need to increase the melt temperature by reducing friction and enhancing flow. External lubricants typically delay fusion but help prevent the polymer from sticking to the equipment and improve surface finish. The last category provides an intermediate effect between the two.
Polarity should be understood as the compatibility of PVC with certain materials based on their molecular structure and adsorption capacity. Internal lubricants are typically short carbon chains, fatty acid oils, fatty acid esters, or glycerin, which are excellent for preserving transparency. External lubricants are usually hydrocarbons or high-molecular-weight waxes that merely coat the PVC molecule and, as mentioned, delay fusion. Other types of lubricants include stearates, amides, stearic acid, paraffin waxes, and others.
The formulator should remember that the key to a proper lubrication system lies not only in selecting the correct ingredients and their types, but also in understanding their interaction with each other and with the rest of the additives used. It is important to note that PVC additives, such as thermal stabilizers and plasticizers, have a significant effect on lubrication.
There are PVC lubricants that, in addition to their effect during processing, serve a secondary function. Some examples include release agents, antiblocking agents, and antistatic additives.
The PVC lubricants Depending on their nature, they can be liquid, powder, or flakes. There is a preference for one over another based on your company's handling and feeding system.
If you need assistance with this, our technical team at Chemical Additives can advise you and offer our available lubricants. Also, if you don't require PVC formulation and prefer a compound, you can purchase it through our sister company. Chemical Compounds.
Chemical Additives SA de CV.