Simply put, polyvinyl is a general term referring to a compound (resin) that results from a merger of a diversity of vinyl monomers. As such, there exist polyvinyl compounds of chloride, alcohol and acetate. These elements that constitute a polyvinyl compound are responsible for the different characteristics exhibited by the same. To this end, their applications are specific to the characteristics they exhibit. For instance, polyvinyl chloride (PVC) is typically a thermoplastic compound hence; it finds application in the manufacture of packaging and construction materials. Ideally, the material is easy to modify and use; it is affordable too. On the other hand, polyvinyl acetate (PVAc) is transparent in nature, and it is applicable in the manufacture of glues as well as adhesives. Moreover, it is responsible for the glossy appearance of textile and paper materials when applied as a coating material. With regards to polyvinyl alcohol (PVA), its characteristic that renders it odorless and tasteless is what makes it an influential compound in food industry. It is powdery in nature and serves “as a binding/coating agent” (Thornton, 2002). Furthermore, it serves as a moisture barrier.
With respect to the synthesis of polyvinyl, this paper will approach this subject on three fronts that include the manufacture of PVC, polyvinyl alcohol and polyvinyl acetate. In view of PVC, this is a compound that encompasses both salt and oil in its lattice. The salt (chloride) and the oil (ethylene) are the elements that form the precursor compound (monomer polyvinyl chloride (MVC)) that undergoes polymerization to form PVC resin. This reaction, which occurs in a reactor, commences when a monomer (MVC) is mixed with water in the presence of an initiator (dioctanoyl peroxide). The mixture results into droplet-like compounds that eventually disintegrate sparking a chain reaction that form the PVC. To this, to enhance the stability of the finished product on exposure to UV or light, additives (anti-oxidants) are added. Moreover, other additives that include plasticizers, fillers and compatibilizers among others are added to give the PVC its desirable characteristics. Vitally, since this reaction is exothermic, it is necessary that cooling of the vessel is done in the due course to keep the temperatures low (Titow, 1984). The reaction below is a manifestation of whatever transpires- MVC undergoes polymerization to form PVC. This reaction results in the formation of compounds with molecular weights that range, roughly, between 45,000 and 64,000.
The post-treatment of the compound includes degassing which aids in expelling an embedded monomer in the polymer slurry, and centrifugation that flushes out water from the same.
PVAc is chemically represented as (C4H6O2) n. This polymer results from a reaction that happens when a monomer of vinyl acetate and water mix. This compound appears like a milkfish emulsion that polymerizes to form PVAc.
PVA is a peculiar type of polymer that is a consequence of a unique process other than polymerization. Principally, PVAc is reacted with an alcohol in the presence of an alkaline catalyst to form the compound (PVA). In the course of the reaction (alcoholysis), the acetate group is substituted by the hydroxyl group i.e.
The excellent properties of PVC are what make it applicable to different fields. For instance, the compound exhibits excellent electric cum insulation characteristics that span over an extensive temperature range. This compound, unlike other polyvinyl, is durable (Rahman, 2004). Moreover, it is cheap, recyclable, and easy to work on. Importantly, the compound displays excellent resistivity characteristics to UV degradation. Nonetheless, this compound displays its fair share of disadvantages, for example, it has a restricted temperature for use (700C) beyond which temperature rapidly shoots to 800C. Moreover, toxic elements, for instance, plasticizers e.g. phthalates, which are normally added, could leach out. Finally, its durability is disadvantageous when it comes to the ultimate disposal of the same; it is non-biodegradable (Manas and Salil, 2006).
References
Manas, C., & Salil, R. (2006). Plastics technology handbook. Arizona: University of Phoenix Press.
Rahman, S. (2004). “Thermoplastics at Work: A Comprehensive Review of Municipal PVC Piping Products.” Underground Construction, 1, 56–61.
Thornton, J. (2002). Environmental Impacts of polyvinyl Chloride Building Materials. Oxford: Oxford University Press.
Titow, W. (1984). Pvc Technology. London: Elsevier Applied Science Publishers.