Polypropylene is a thermoplastic that is produced by the polymerization of propene monomers. The chemical formula is (C3H6)n. PP is among the most used plastics today and it can be molded or extruded into many plastic products in which toughness, flexibility, light weight, and heat resistance are required. It is also spun into fibres for employment in industrial and household textiles.
Types of polypropylene
Homopolymers: It is a general purpose grade. It contains polypropene monomers in semi crystalline form. They have high melting points, excellent stiffness, superior scratch resistance, and good chemical resistance against most inorganic acids, alkalis, and salts. In addition, homopolymers provide strong resistance to environmental stress cracking when in contact with alcohols, esters, detergents or polar hydrocarbons.
They are further divided into random and block copolymers.
Random copolymers: It is produced by polymerizing ethene and propene. Ethene units (6%) are incorporated randomly into the chains.
Block copolymers: It has more ethene content (5 – 15%) than the random copolymers and the co-monomer units are arranged in a regular pattern. This makes the polymer tougher and less brittle than the random copolymers.
Impact copolymer: A propylene homopolymer containing a co-mixed propylene random copolymer phase which has an ethene content of 45-65%.
Manufacturing Process: Polypropylene is synthesized by the polymerization of propene using the Ziegler Natta catalyst or metallocene catalyst.
Flexible Packaging: PP films’ excellent optical clarity and low moisture-vapor transmission make it suitable for use in food packaging. Other markets shrink-film overwrap, electronic industry films, graphic arts applications, disposable diaper tabs and closures, etc. PP Film is available either as Cast Film or bi-axially orientated PP (BOPP).
Rigid Packaging: PP is blow molded to produce crates, bottles, and pots. PP thin walled containers are commonly used for food packaging.
Consumer Goods: Polypropylene is used in several household products and consumer goods applications including translucent parts, housewares, furniture, appliances, luggage, toys etc.
Automotive: Due to its low cost, outstanding mechanical properties and moldability, polypropylene is widely used in automotive parts. Main applications include battery cases and trays, bumpers, fender liners, interior trim, instrumental panels and door trims.
Fibers and Fabrics: PP fiber is utilized in a host of applications including raffia/slit-film, tape, strapping, bulk continuous filament, staple fibers, spun bond and continuous filament. PP rope and twine are very strong and moisture resistant very suitable for marine applications.
Medical: Polypropylene is used in various medical applications due to high chemical and bacterial resistance. Also, the medical grade PP exhibits good resistance to steam sterilization. Disposable syringes is the most common medical application of polypropylene. Other applications include Medical vials, diagnostic devices, petri dishes, intravenous bottles, specimen bottles, food trays, pans, pill containers, etc.
Industrial: Polypropylene sheets are widely used in industrial sector to produce acid and chemical tanks, sheets, pipes, Returnable Transport Packaging (RTP), etc. because of its properties like high tensile strength, resistance to high temperatures and corrosion resistance.