Publish Time: 2022-05-09 Origin: Site
Polyvinyl chloride is a versatile synthetic material that is widely used in various industries. It is important to understand how is PVC manufactured for different industry people. Because, it will help them to seek insight into its production.
In this article, you will get knowledge of the step-by-step process behind the manufacturing of PVC. It includes the techniques, different stages, and so on.
The process of producing Vinyl Chloride Monomer from the chlorination of ethylene and pyrolysis of the resulting ethylene dichloride in a cracking unit. Moreover, polymerization of the VCM leads to the creation of PVC, which has a glass transition temperature of 70-80 ℃.
There are two mostly used and well-known methods to manufacture PVC for commercial purposes. The methods are given below:
Suspension PVC (S-PVC).
Bulk or Emulsion (E-PVC).
The suspension or S-PVC is a well-known process globally. Because in this way we can produce high-grade PVC using the latest technology.
In pressure-tight reactors or high-performance reactors, polymerization initiators, and other additives are introduced with the monomer. After that, the mixture in the reaction vessel is diluted continuously to ensure that the PVC resin particles remain suspended and maintain a consistent size.
The average size of particles in typical suspension polymerized PVC falls within the range of 100-150 μm. Although, they can vary between 50-250 μm. Moreover, these specific particle sizes are crucial for achieving desired properties in PVC products.
Suspension PVC grades are carefully formulated to meet a wide range of requirements. For instance, some grades are designed to have high plasticizer absorption, making them suitable for flexible PVC products. On the other hand, some grades are engineered with characteristics like high bulk density and excellent powder flow, which are essential for rigid extrusion processes.
It is noteworthy that suspension polymerization represents a significant portion, approximately 80% of global PVC production. This method is widely employed due to its effectiveness in achieving the desired particle sizes and meeting diverse application requirements in the PVC industry.
In this Emulsion process, we utilize surfactants that are commonly known as soaps. Generally, it is used to disperse the vinyl chloride monomer within water. The soap acts as a protective agent which are allowing the monomer to be trapped inside micelles. Furthermore, polymerization occurs with the aid of initiators that are soluble in water.
The result of primary particles in suspension polymerized PVC is solid spheres with smooth surfaces. Though, these particles tend to cluster together and form aggregates that have irregular shapes. On average, these aggregates have a particle size ranging from 40 to 50 μm, with individual sizes varying from 0.1 to 100 μm.
Most importantly, surfactants play a great role in this process as they enable the successful dispersion of the vinyl chloride monomer in water. After that, the surfactants form micelles that encapsulate the monomer and provide protection during polymerization. Moreover, the water-soluble initiators facilitate the polymerization reaction, contributing to the formation of PVC.
Lastly, the primary particles formed in this method possess a uniform and solid structure. Also, it appears as smooth-surfaced spheres. However, due to their propensity to aggregate, the overall particle structure becomes irregular. In fact, these aggregates with their varying sizes significantly influence the properties of the resulting PVC product. As a result, E-PVC resins are used in many applications, for instance, coating, dipping, or spreading.
Here are some key points of the suspension PVC and Emulsion PVC process:
Suspension PVC (S-PVC) Process | Bulk or Emulsion (E-PVC) Process |
Minimize the costs of the flexible PVC formulation. | Maximum the costs of the flexible PVC formulation. |
| After obtaining PVC particles, they are combined with plasticizers and formed into pellets, which are subsequently utilized in various processing methods. For instance, extrusion, calendaring, and injection molding. | Plasticizers are added to the obtained PVC powder to create a paste, which is then applied in coatings, dipping, and spraying applications. |
The processing equipment generally comes with a high cost. | The cost of processing equipment can vary, and it may or may not be expensive. |
To conclude, it can be said that manufacturing PVC is not a generalized process. It is very crucial to learn properly about this versatile material. Because the knowledge about the PVC production process provides valuable insights into its various applications and benefits as well.
Wants to know in depth from the industry experts that would be better suited for your application then contact our experts today!
References:
https://www.researchgate.net/publication/312002659_PolyVinyl_Chloride
https://www.mdpi.com/2073-4360/14/15/3035