Polypropylene

Polypropylene is classified as a linear hydrocarbon polymer. The chemical formulation is CnH_2n. Polypropylene is considered to be a very versatile type of polymer. It is available as a plastic and a fiber and is adaptable to many different methods of fabrication and application. Polypropylene is abbreviated as PP, while oriented polypropylene is abbreviated as OPP. The latter is commonly used instead of cellophane in product applications. Polypropylene may be seen across a spectrum of product types. These include moldings, fibers, film, foam, and tape. There are also three different types of polypropylene product grades. These comprise a general purpose or homopolymer; a block copolymer that incorporates ethylene and has a higher impact resistance level; and random copolymers with greater flexibility and clarity. Polypropylene is commonly found in automotive interiors, household or durable garden products, or as an industrial medium.

Brief History

Discovery of Polypropylene. The first polypropylene resin was produced by Professor Giulio Natta in Spain in 1954. The product became commercially available in 1957; from this time the use of polypropylene has grown exponentially. Natta began his studies of synthetic rubber production in 1938. In the same year, he began researching how olefins are polymerized and the reactions that occurred kinetically. This progressed into the discovery of new types of polymers. Further research resulted in the realization of a thermoplastic material, made from a specific polymer. Montecatini, an Italian chemical company, took up the manufacturing of the material. The company has marketed this plastic material as Moplen. Meraklon is the name of the synthetic fiber they produce, Merakrin is their monofilament product, and Moplefan is the packing film. Natta was awarded the Nobel Prize in chemistry in 1963.

Polypropene, or as it is known as polypropylene, is produced from propene. Propene is derived from ethane, gas oil, naphtha, and propane gas. Propene goes through a process of polymerization in order to produce the polymer polypropylene. Multiple processes are possible in the manufacturing of polypropylene. The Ziegler-Natta catalyst method facilitates either a bulk process or a gas phase process. The slurry method may also be used. Alternatively, the metallocene catalyst process is carried out.

Polypropylene plastics have a range of uses. Common commercially available PP plastic products include bottles, caps, drink lids, food containers, and straws. Packaging utilized privately or industrially is made from polypropylene. Polypropylene is also used in upholstery, on automotive dashboards, on boat sails, and for large shipping containers. Carpets, crates, pails, films, sewage and drain pipes, electric cables, and toys can all contain polypropylene. Often polypropylene is used instead of glass as a surface. Moreoever, because of its unique properties, it can provide a suitable alternative for cartons, metals, and various other polymer types. Polypropylene is a thermoplastic bearing the lightest density.

Overview

Polypropylene is both versatile and durable. This polymer has a semirigid structure, is tough, and possesses a good fatigue resistance. There is a translucent quality to polypropylene. Other properties include its chemical resistance ability, as well as its good resistance to heat at high temperatures. A further advantage is its integral hinge property. Given its durability and toughness, polypropylene does not crack through stress. When polypropylene resins are manufactured commercially, additives are added to provide protection while it is being processed and to further enhance the product.

Polypropylene is a vinyl polymer. The chemical name for polypropylene is poly (1-methylethylene). The propene molecule has an asymmetric structure. When polymerized, three possible basic chain structures can be formed. This depends on how the methyl groups are positioned. Chemically, polypropylene may be isotactic, syndiotactic, or atactic. When the methyl groups appear on the same side of the chain, this is called isotactic or syndiotactic. A random arrangement of methyl groups appearing on both sides of the chain is termed atactic. The regular structure of the first two allow crystallization into a rigid material to occur, whereas the random atactic chains are not able to crystallize, instead becoming like rubber. The monomer propylene created by Ziegler-Natta polymerization can make polypropylene. This can also be achieved by metallocene catalysis polymerization. Polymerization is the process whereby nomoners, or simple molecules, are combined to form polymers. Research is being conducted regarding the creation of polymers containing both isotactic and atactic polypropylene blocks contained in the same polymer chain, by means of metallocene catalysts.

Although polypropylene and polyethylene are similar polymers, there are a number of varying properties. Most particularly, polypropylene does not melt below a temperature of 160^o C or 320^o F, whereas polyethylene melts at 100^o C or 212^o F.

Polypropylene may be used as a plastic or as a fiber. Because of its heat-resistant property, a plastic polypropylene is useful for containers that are safe for dishwasher or microwave usage. When manufactured as a fiber, consumers can purchase polypropylene-made carpeting that can be laid inside or outdoors. Outdoor fiber carpets made from this polymer are advantageous as polypropylene is waterproof. Moreover, it can be made in many colors, enhancing the aesthetic look. Other polymers that are manufactured as plastic include nylon, polyethylene, polyester, polystyrene, polycarbonate, poly (methyl methacrylate), and PVC. Fibers can be made from polymers such as nylon, polyethylene, polyester, as well as kevlar, nomex, polyacrylonitrile, cellulose, and polyurethanes.

Health concerns have been raised, and scientists are investigating whether potentially harmful chemicals are emitted when polypropylene (PP) plastics are heated. The issue at stake is whether such toxicity is released in commercially available polypropylene products. The danger would be if toxic chemicals could migrate from the plastic and be absorbed by people. Some companies have added an environmentally friendly additive to polypropylene plastics to render them more effectively biodegradable. Polypropylene is recyclable.

Bibliography

Beach, Evan. "Chemicals With Unknown Toxicity Form When Polypropylene Plastic Is Heated." EHN. Environmental Health Sciences, 25 June 2010. Web. 8 June 2016.

"Discovery of Polypropylene and High Density Polyethylene." ACS. American Chemical Society, 2016. Web. 8 June 2016.

"Guilio Natta – Biographical." Nobelprize.org. Nobel Media, 2014. Web. 8 June 2016.

Hindel, Colin. "Polypropylene (PP)." British Plastics Federation. British Plastics Federation, 2016. Web. 8 June 2016.

"Polypropylene (PP)." Bio-Tec. Bio-Tec Environmental, n.d. Web. 8 June 2016.

"Polypropylene." Polymer Science Learning Center. Polymer Science Learning Center, 2016. Web. 8 June 2016.

"Polypropylene (PP)." RTP Co. RTP Company, 2015. Web. 8 June 2016.

"Polypropylene (PP) Plastic." Prospector. UL, 2016. Web. 8 June 2016.

"Poly (propene) (Polypropylene)." The Essential Chemical Industry. CIEC, University of York, 2 Jan. 2014. Web. 8 June 2016.

Spaniol, Jared; Rulander, Jack, & Leo, Mike. "Polypropylene." Spaniol, Rulander, Leo, n.d. Web. 8 June 2016.