Plasticizers

 Plasticizers

Plasticizers have been used as polymer additives since the nineteenth century; however, the humankind has known the plasticizing effect of water for thousands of years. As a matter of fact, the first clay figure found in Europe dates back to 24,000 BC, making pottery most likely the first human activity involving plasticizers. The Council of the International Union of Pure and Applied Chemistry (IUPAC) defined a plasticizer as a substance or material incorporated in a material (usually plastic or elastomer) to increase its flexibility, workability or distensibility. By this definition, a plasticizer may reduce the melt viscosity, lower the temperature of a second-order transition or lower the elastic modulus of the product. Poly(vinyl chloride) (PVC) is the third most widely produced synthetic plastic polymer, after polyethylene and polypropylene (PP). Unmodified PVC is mainly employed in the construction industry (e. g. pipes, door and window components, etc.) where its natural rigidity is needed. However, the addition of organic molecules, known as plasticizers, can provide increased flexibility, extensibility, and processability [10]. In 2014, the global plastic market involved 8.4 MTons of plasticizers, of which 80–90 % was employed in the PVC industry. The physical action of plasticizers produces a reduction of Young’s modulus, density, melt viscosity and glass transition temperature of the polymer, while they enhance the final product flexibility, deformation at break and toughness [11, 12]. For this reason, flexible PVC can be used in many applications where it can replace rubber and polyolefins, such as electrical cable insulation, inflatable products, packaging, etc. The mechanism of plasticization involves the formation of secondary bonds between plasticizer and polymer chains, where they act like “spacers,” increasing the distance of neighbour chains, hindering their interaction and increasing their mobility