PVC Resin vs PVC Pellets

PVC Resin vs PVC Pellets: Many market players often use the term.PVC resinto describe PVC compound in pellet form because this description is used for other plastic resins. In this article, we would like to explain the differences, advantages, and disadvantages between these concepts and our recommendations regarding them. Of course, the main difference is obvious: PVC compound is in pellet form and PVC resin is in powder form.

PVC Resin

Unlike other plastics, PVC resin is a white powder that cannot be processed on its own as it requires the help of other chemical additives to provide certain processing properties and also for the lifespan of the finished product. In the value chain of other commodity plastics, one goes from polymerization to the transformer and finally to the end user, where the former determines the formula and main final characteristics of the product. In contrast, with PVCthere is an intermediate step where the formulator must make custom products for the transformer and end user, where it must extrude and subsequently make PVC pellet.

Although there are intermediate processes in other commodity plastics to add general additives like pigments or UV protectors, the base resin does not undergo a high degree of modification of the properties that the manufacturer determined from the polymerization stage. This makes PVC resin so useful and turns it into the most versatile plastic on the market.

Main Properties of PVC Resin

Usually, SMEs only pay attention to the molecular weight or K value of the PVC resin in powder form as a basis for formulation. Moreover, assuming that all resins are identical, even if only the brand is changed and a K value is maintained, could not be more false, as PVC resin manufacturers have their own formulas and process conditions. In this section, we present the main properties to consider.

K Value – This property is closely linked to the normal distribution of molecular weights formed during polymerization, always reporting a range within which the manufacturer considers most of the chains to be. This is not a fixed value, but a reference that allows us to know for which applications it is more suitable to use a certain grade of PVC resin.

Inherent Viscosity – This is another reference similar to the K value that allows us to see the viscoelastic behavior of the molten mass during processing. This will guide us in understanding the fluidity of the material and how easy it will be to melt the PVC resin in our equipment.

Absorption Capacity – Usually, the higher the K value, the greater the absorption capacity, although this is not the only thing that determines this property of the resin. During polymerization, certain additives are added that improve this characteristic of the resin. This property is crucial for the adsorption of plasticizers and mixing process times, as it often takes too long to dry the PVC resin.

Yellowing of Resin – Depending on the manufacturer, they add a certain amount of stabilizers and antioxidants that delay the yellowing of the PVC resin from the polymerization and filtration process. An economical PVC resin will have limitations in its use in crystal and transparent applications precisely because of this characteristic.

Impurities –the PVC resins may present agglomerations and infusible gels where it limits their use in very thin plastic films and printing. These impurities can cause many processing problems and generate waste, which is why it is preferred to avoid these types of grades. 

Particle Size – The particle size helps with the correct fluidity, absorption, and dispersion of additives during the mixing and extrusion process. Quality control with sieves allows us to know how reproducible the PVC resin.

Although it is always healthy and strategic to have two suppliers for a certain input in any company, in the case of PVC resin it is recommended to perform an exhaustive validation process that ensures that we are talking about the same grade, counterpart, and that the behavior is similar. If you need more information about PVC resinour sister company Chemical Additives de Méxicooffers information on this subject and all the additives required for its formulation.

PVC pellet

The PVC pelletcontrary to PVC resins the term for a material that is already formulated, plasticized, melted, pigmented, and has gone through a previous extrusion process. Its benefits are several, such as avoiding the need to develop formulation knowledge, investing in infrastructure and technology to make a consistently high-quality product, and the easy handling that allows us to maintain a cleaner work area. 

Many companies believe that formulating and manufacturing PVC pellet s an easy task, but it is not. The mixing process is a dirty task where, if your company is focused on another activity that generates more value, it is recommended to leave it to the experts. Cross-contaminations, charges with agglomerations, operational errors, are some of the examples that can be costly for your company. Beyond the mixing process, the second phase of extrusion also has its peculiarities that are only learned by going through the process.

Customers often face the question of what is more convenient, buying PVC pellets or PVC resin to formulate. The answer is extremely complex as there are many hidden costs that companies do not consider and that go beyond buying machinery and raw materials; developing human talent and learning formulation is an intangible cost for any company. Therefore, it is very difficult to make a direct comparison, although it is known that obtaining PVC pellet facilitates many quality problems in the finished product. This additional pelletizing process that gives work and fusion to the already formulated PVC resin greatly helps customers with handling and the final finish of their finished pieces.

PVC Pellet Size – Depending on your process and, above all, if you add pigment or color concentrates, a smaller PVC pellet will help with better dispersion in the customer transformer's process.

Burr and Lumps – The burr in PVC pellets ideally should be eliminated or reported as not all PVC transformation equipment exerts sufficient mechanical work and friction to break down the impurities present in this input.

Shape – The shape of the PVC pellet goes hand in hand with the type of PVC compoundWe consider that beyond geometry, size will continue to be the most determining factor for better processing and handling of this material.

We hope that in this article the reader has been able to understand the differences between PVC pellets and PVC resintheir benefits and disadvantages to consider before making a purchase decision. Chemical Compounds we manufacture rigid PVC compounds, semi-rigid PVC and Flexible PVC for all types of industry, always complying with the high standards of those organizations that regulate our market. Ask our expert technicians.