PP - Polypropylene
Polypropylene is a thermoplastic polymer with a low specific gravity, high stiffness, relatively high temperature resistance, and good resistance to chemicals and fatigue.
During the invention of isotactic polypropylene by Giulio Natta of Montedison in 1954, Natta discovered that propylene could be polymerized with Ziegler-Natta catalyst to a new crystalline, stereoregular fraction.
Polypropylene can be produced in three forms: isotactic, syndiotactic and atactic.
Polypropylene (PP) is one of the numerous derivatives of propylene CH3-CH=CH2. Depending on the type of polymerization and catalyst used, the polymers may present an orderly and disorderly configuration. When polymers have a regular arrangement of their atoms, like in isotactic polypropylene, it is easy for them to pack together into crystals. But if there is no order, packing cannot occur. In fact there are various types of polypropylene with different applications depending on the arrangement of the macromolecules; their characteristics are influenced therefore not only by the molecular weight but also by the presence of branching along the molecular chain.
Polypropylene is a plastic which is pliable; it can be shaped and molded easily. As it becomes easier to mold and shape when hot, we call it thermoplastic. Polypropylene, in fact assumes plastic state when heated and returns to a rigid state when cooled. This characteristic makes it possible to manufacture articles by injection, extrusion, blown-extrusion and vaccum forming. Polypropylene is never used in its pure state. Additives are added to the plastic in order to obtain the mechanical characteristics needed for the articles to be manufactured. Polypropylene (PP) is commercially available in three different varieties vis: Homopolymers, Impact and Random Copolymers.
The melting of polypropylene occurs as a range, so a melting point is determined by finding the highest temperature of a differential scanning calorimetry chart. Perfectly isotactic PP has a melting point of 171 °C (340 °F).
Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F).
Propylene was first polymerized to a crystalline isotactic polymer by Giulio Natta as well as by the German chemist Karl Rehn in March 1954.
This pioneering discovery led to large-scale commercial production of isotactic polypropylene by the Italian firm Montecatini from 1957 onwards under the trademark “MOPLEN”.
Later on, other European and American and Japanese companies commenced production under various commercial trade-marks.
LyondellBasell, Sinopec Group, SABIC, PetroChina Group, Braskem Group, Reliance Industries Ltd, IPIC Group, Total PC, ExxonMobil, Formosa Plastics are some of the leading producers of polypropylene in the world.
Global Polypropylene (PP) capacity was 63.7 MMT in 2011 against demand of 52 MMT. The capacity is expected to increase to 75 MMT in 2016 with demand reaching 66 MMT. ExxonMobil, Formosa, Borealis, Saudi Amarco, Westlake, Ineos, Chevron Phillips, Dow, Equistar, Oxychem, Formosa, Shell, Nova, Braskem, Williams, Borouge, and CPC Corp. - Taiwan are some of the companies which announced polypropylene capacity expansion plans starting 2012 to 2017.
In India the total PP capacity is expected to reach 4970 KTA by 2016-17 and Reliance Industries Ltd capacity is projected to be around 2900 KTA in 2016-17.
OPAL would be ramping up its capacity in the coming months. They are currently operating the polypropylene unit at 50 per cent capacity. But in about four months, the plant is expected to operate at 100 per cent of its capacity of 340 KTA.
IOCL is expected to add 700 KTA PP capacities by 2017-18.
Growth in global PP consumption will be driven mainly by a combination of rapid economic development of the numerous emerging economies in Asia-Pacific (led by India and China), Central Europe, and the Middle East along with steady growth in mature economies such as North America and West Europe. As the emerging economies move toward more consumer-based economies, plastics usage in general is forecast to increase. Government incentives to provide investments in export-oriented plastics converting capacities in many of these countries (Middle East) will also help fuel PP demand growth.
Northeast Asia, Southeast Asia, and the Indian Subcontinent will be the major engines of demand growth. Therefore, economic performance and major shifts in consumption patterns in those regions will be of utmost importance to global markets. In 2015, these regions combined to make up 57% of all global demand and that share increases to 61% by 2020 and 64% by 2025, owing to large populations in markets that continue to develop.
In 2015, globally PP's largest application globally continued to be injection molding at 33.1% of total demand. Injection molding applications cover many major segments such as household containers like storage totes, thin wall injection molding (TWIM) for cups, rigid packaging products for food, and automotive products. Film and sheet, at 24.1% of total demand, is the second-largest segment; it is most commonly recognized by its major components, BOPP (biaxial-oriented PP) film used for snack-food packaging, and packaging sheet for thermoforming.
Another key factor for PP resin growth is its competitiveness versus other resins or alternative packaging such as paper and glass. Across most regions, PP is forecast to remain very competitive versus polyethylene (PE) grades. Particularly in China, where much of the growth is coming from, PP prices are forecast to be favorable versus PE as a result of the large increases expected for capacity through the end of 2016.
Polypropylene can be processed by virtually all thermoplastic-processing methods. Most typically PP Products are manufactured by: Extrusion Blow Moulding, Injection Moulding, and General Purpose Extrusion. Expanded Polypropylene (EPP) may be moulded in a specialist process.
PP Applications include Buckets, bowls, crates, toys, medical components, washing machine drums, battery cases, bottle caps. Elastomer modified for bumpers, etc.
Talc filled for additional stiffness at elevated temperatures - jug kettles, etc. OPP films for packaging (e.g. crisps, biscuits, etc.). Fibres for carpets, sports clothing.