Polyvinyl chloride

One of the most widely produced synthetic polymers worldwide is polyvinyl chloride (PVC). PVC is the third most produced polymer on a global scale, after polyethylene, which is the most produced, and polypropylene, which is the second most produced. Both stiff and flexible versions of PVC exist. The stiff shape is mostly employed in the production of pipes. It can also be applied to the production of plastic bottles and packaging for non-food items in the bottling industry. However, the hard form can be softened by adding plasticizers to their compounds, extending the range of applications for this flexible polyvinyl chloride (La Mantia 74). Pollution is the main issue with the use of PVC products. The management of plastics after use has continued to be a significant challenge to many countries because they are non-biodegradable. A large number of plastics have always ended up in landfills where they take between 10 to 35 years before they disappear. Some of them find their way into incinerators where they are burnt at high temperatures to deplete them from the environment. When plastics are dumped into the landfill or incinerators, they pose many negative effects on the environment. The combustion of PVC materials in the incinerators leads to the emission of harmful gasses that impact negatively on the lives of human beings and animals. The plastics in the landfills might also interact with either surface water or underground water to form hazardous chemicals (La Mantia 75). The only solution to the pollution caused by wastes from PVC products is to recycle the plastics. Recycling involves recovering the wastes from PVC products such as scraps of bottles and pipes then reprocessing them into useful products. Wastes of PVC can be recycled into new bottles, electric cable insulators, plumbing pipes, and packaging among others. This paper discusses the whole process of recycling polyvinyl chloride from collection point until the last stage where the melted PVC is used to manufacture new products. The paper also exhaustively explains some of the uses of PVC and problems that are associated with its recycling.
Since PVC is made up of thermoplastic materials, it is 100 percent recyclable physically, energetically, and chemically. The process of recycling PVC involves either mechanical or feedstock recycling (Ciacci, Passarini, and Vassura 125). Mechanical recycling involves the physical breakdown of PVC into small pieces that can be processed into new PVC compounds. Feedstock recycling, on the other hand, is a chemical process that involves the breakdown of the polymer into constituent monomers to make new PVC. However, irrespective of the direction it takes, recycling follows conventional procedures. The first step is the collection of PVC waste materials. During the process of recycling, the supply of the used polyvinyl chloride products should be done in large quantities (Ciacci, Passarini, and Vassura 127). It is however very hard to collect PVC on its own because it is always mixed with other plastics in the dustbins and landfills. During collection, different forms of plastics such as plastic containers, bags, plastic packaging, toys, and bottles are obtained from local dump sites. Some people have also ventured into the business of collecting plastics and providing to the recycling companies. Just after collection, the plastics are transported to plastic yards. At the yards, people pack the plastics then carry them to plastic processing units for recycling.
At the processing units, the recycling process begins by sorting and separation of plastics to obtain the polyvinyl chloride. The sorting and separation process depends on the type of polymeric materials that constitute the plastics. During sorting, the personnel at the recycling industries checks on the codes on the containers. Different plastics have different code labeling that would help one to group them into different categories for processing (Janajreh, Alshrah, and Zamzam 13). Plastics are categorized into polyethylene plastics and polymer plastics. The polyethylene plastics are coded HDPE for the class of high-density polymers. The low-density polyethylene the code is LDPE. The polymer plastics are divided into four groups such as polyvinyl chloride, polyethylene terephthalate, polypropylene, and polystyrene. PVC products are labeled V to help identify them among other plastics (Janajreh, Alshrah, and Zamzam 13). At the industries, the recycling mills sort the plastics by checking in the symbols at the bottom. The machines such as screen changing equipment will easily separate the scrap plastics labeled V and group them as PVC products. Hand sorting is the most preferred method because of its high degree of accuracy in identifying PVC wastes. However, manual separation is quite expensive thus not economical to some companies. Recycling companies also carry out sorting to remove any contaminant that may be present in the PVC (Ciacci, Passarini, and Vassura 129).
After sorting and separation, the polyvinyl chloride is cut into small pieces to increase the surface area. The plastic bottles and PVC pipes are ground to reduce them into small sizes. The heavier and lighter pieces are then separated using some special machines. The separation is necessary to ensure that the final product is made up of similar plastics. The small pieces of PVC then undergo through the cleaning process where they are washed with detergents to remove any remaining contaminant (Ciacci, Passarini, and Vassura 131). The next step is to expose the clean pieces of PVC to low heat to allow them to dry up before reaching the melting chambers. At the melting chambers, the dry flakes of PVC are heated and melted down at high and regulated temperatures. The incinerators are the special apparatus used in the melting process. They can reach high temperatures between 900 to 1000 degrees Celsius (Dickinson 356). During heating, the PVC decomposes due to the elimination of hydrogen chloride. There is the formation of double bond followed by unzipping reactions that occur at a very high rate leading to the formation of polyene sequences as shown below.


The melt, which is mainly composed of the polyenes, is processed into granules that are later compressed into tiny nurdles (pellets). The plastics can later be transported in pellet form to plastic manufacturing companies where they are redesigned into new plastic products. In most situations, the recycled plastics do not resemble the initial products.
Polyvinyl chloride is one of the most used plastics across the world. It has numerous uses that make its global consumption exceed 35 million tons per year. The demand for PVC keeps on growing. The average growth rate for the demand of PVC is 5 % per annum, with developed countries registering even higher values (Kye et al. 47). Some of the uses of PVC that lead to the high demand include construction and healthcare applications. In the construction projects, the used to improve the window profile. This is because polyvinyl chloride is light, durable, and versatile. It can be used to provide a variety of colors and as an alternative to wood frames during construction. The windows that are made of PVC have recorded a lifespan of more than 35 years (Kye et al. 48). Other uses of PVC in construction include the manufacture of water and gas pipes. In healthcare systems, the PVC is used to make blood storage that can keep blood safely and for a longer period. The patients' facemasks, flooring of the operating theaters and surgeons' scalpels are always made of PVC. PVC is also used to manufacture insulators for electrical cables because it is flexible and does not harden or crack for over a long time (Dickinson 361).
Some problems are associated with recycling of PVC. The major problem is the high content of chlorine in the raw PVC and elevated levels of dangerous additives that are always added to the polymer to achieve the intended quality (Dickinson 365). In mechanical recycling, no chemical is added thus the additives pose a challenge during recycling. When PVC wastes of different kinds are fed into the recycler, it is tough to predict the output. This is a challenge in enhancing the high quality of the final product. Some gasses are also still released from the incinerators during recycling, and this is a significant source of environmental pollution.

In conclusion, recycling PVC is a complex process that requires much attention to ensuring that the required quality of output is met. Continuous recycling of PVC waste will help to reduce their pollution effects at the landfills or when burnt in open air. Care must be taken to ensure that PVCs do not cause environmental hazards during their collection, sorting, and melting.
































Works Cited
Ciacci, L., F. Passarini, and I. Vassura. "The European PVC cycle: In-use stock and flows." Resources, Conservation and Recycling, no. 4, 2016, pp. 123-137.
Dickinson, Adam. The Polymers. House of Anansi P, 2013.
Janajreh, I., M. Alshrah, and Samih Zamzam. "Mechanical recycling of PVC plastic waste streams from cable industry: A case study." Sustainable Cities and Society, no.18, 2015, pp. 13-20.
Kye, Hyoungsan et al. "A Study On Mechanical Properties For Recycling Of PVC Scraps." Journal Of The Korean Institute Of Resources Recycling, vol. 24, no. 6, 2015, pp. 45-53.
La Mantia, Francesco Paolo. Recycling Of PVC And Mixed Plastic Waste. 1st ed., Ontario, Chemtec Publishing, 2001.