About Polypropylene. Polypropylene (a.k.a. PP, Polypropene) stands as a thermoplastic polymer comprising 10,000 to 20,000 monomer units, making it a notable contender in the realm of polymer production. In fact, it ranks as the second most widely manufactured commodity plastic, surpassed only by polyethylene. In a qualitative approach, PP is a colorless, translucent to transparent solid with a glossy surface. PP is a versatile, durable, and extremely rugged material. The properties and texture of PP may vary based on the specific manufacturing process employed during its creation. It is known to have good tensile strength despite its lightweight nature. PP has great elasticity, fatigue resistance, and water resistance, along with a higher melting point compared to many other plastics available in the market. Its chemical resistance proves favorable, displaying a good resistance to chemicals, greater scratch resistance when compared to other polyolefins, and good environmental stress cracking resistance. Additionally, PP lends itself well to processes such as injection molding and extrusion and exhibits a low moisture absorption rate.

As a thermoplastic, PP is capable of melting and flowing (in a reversible physical transformation) when subjected to increases in temperature and pressure, subsequently assuming a predetermined shape upon the cessation of these specific conditions. Based on its exceptional mechanical and thermal properties, PP finds suitability across a broad spectrum of applications, encompassing fibers, injection molding, thermoforming, film production, and blow molding. The strength and adaptability of PP can be attributed to a network of interlocking crystallites that facilitate the creation of sturdy and resilient objects. The continuous advancement in both manufacturing processes and catalyst technology has led to the development of three major types of PP resins: homopolymers, random copolymers, and impact (or block) copolymers. Such copolymers are obtained by copolymerization of propylene with ethylene or higher olefins. Each type of PP resin is characterized by distinct chemical formulas, exemplifying their unique compositions and properties.

Regarding the polymerization of propylene, it is important to mention that the way each propylene monomer unit links to the other generates polymers with distinct characteristics. Those structural chains can be summarized as follow: * Atactic. The pendant methyl groups are attached in a random manner on the polymer backbone chain. At room temperature, atactic polypropylene is a waxy and tacky solid. * Isotactic. All the methyl groups are on the same side of the winding spiral chain molecule. Isotactic polypropylene has higher stiffness and a wider spectrum of applications. * Syndiotactic. The pendant methyl groups are attached in an alternating pattern on the polymer backbone chain. It is soft and clear, in addition to having a good gloss.

PP stands as a non-reactive substance, exhibiting stability even under ambient conditions. It maintains its structural integrity without decomposition in the presence of atmospheric air, effectively refraining from emitting any noxious gases or hazardous byproducts. However, it is essential to note that PP has the potential to react with potent oxidizing agents; therefore, caution must be exercised to prevent its proximity to such materials. When considering extended storage periods, PP should be stored in a cool environment that offers proper ventilation. In terms of handling, storage, and transportation, no additional special precautions are necessary, underscoring the convenient and straightforward nature of dealing with this material.

PP production consists in the polymerization of propylene, in such a way that different PP manufacturing routes are related to different sources of the propylene used. The most typical PP production routes are based on propylene co-product from ethylene manufacturing (via steam cracking processes) and propylene by-product of petroleum refining. Raw materials and the respective production processes employed in the manufacturing of Polypropylene are listed below.

The uses and applications of Polypropylene may vary according to its specification. The main forms of Polypropylene are homopolymer polypropylene; polypropylene impact copolymer; and polypropylene random copolymer. In addition to the differences in molecular structure, this polymer has different possible applications depending on the form in which it is produced and commercialized: non-woven fiber, fiber, injection, raffia.