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
La fusión es muy compleja de lograr pues el sistema de lubricación diseñado por el formulador debe considerar 
aspectos tanto de la formulación como el tipo de proceso de transformación. No es lo mismo formular una fórmula rígida opaca destinada para hacer tubería mediante el proceso de extrusión que inyectar piezas semi rígidas de licuadoras.
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.
La polaridad se debe entender como la compatibilidad del PVC con ciertos materiales de acuerdo a su estructura molecular y su capacidad de ser absorbidos por la matriz polimérica. Usualmente los internos son cadenas de carbono cortas, ácidos grasos, ésteres de ácidos grasos o mono- y di-glicéridos (GMS, GMO), que suelen ser excelentes para cuidar la transparencia. Aquellos externos normalmente son hidrocarburos o ceras de alto peso molecular que son
incompatibles con la matriz del PVC y migran a la interfase polímero-metal (barril, husillo, dado), reduciendo la adherencia y por tanto retrasando la fusión. Otros tipos de lubricantes incluyen stearates, amides, stearic acid, paraffin waxes, among 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.