PP - Polypropylene
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. Infact 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, infact 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 viz: 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 isotacticpolypropylene by the Italian firm Montecatini from 1957 onwardsunder the trademark “MOPLEN”. Later on, other European and American and Japanese companies commenced production trading under various commercial trade-marks.
The process economics for three polypropylene gas-phase processes are presented: (1) the Dow UNIPOL™ polypropylene process, (2) the CB&I Lummus Novolen® polypropylene process, and (3) the LyondellBasell Spherizone™ polypropylene process. LyondellBasell, Sinopec Group, SABIC, PetroChina Group, Braskem Group, Reliance Industries Ltd, IPIC Group, Total PC, ExxonMobile, Formosa Plastics are some of the leading producers of polypropylene in the world. The name plate plant size capacity has risen from 40 MMT in 2006 to 64 MMT in 2011 for polypropylene plants.
Global Polypropylene (PP) capacity was 64.2 MMT in 2011 against demand of 68.1 MMT. The capacity is expected to increase to 77 MMT in 2016 with demand reaching 83 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 4715 KTA by 2016-17 and Reliance Industries Ltd has planned capacity expansion to 2885 KTA by 2016-17 followed by IOC 650 KTA, HPCL 440 KTA, OPAL340 KTA, HPL 340 KTA and BPCL Assam GC 60 KTA.PP price touched its lowest level in last five years in Nov’08 – 725$/MT-SE Asia prices while in May’12 the prices touched 1385$ MT corresponding to Crude 107.31 $/Barrel and Naphtha 886 $/MT.
High propylene prices have significantly reduced the cost advantage polypropylene had enjoyedwhen compared to other polymers, which is limiting growth prospects in lower end applications,such as plastic bottles. The recent high level of volatility in polypropylene prices and tight feedstocksupplies (propylene), particularly in North America, are also adversely affecting consumption.Yet, polypropylene’s excellent properties and versatility will continue to open up new higher valuemarkets, for example in the automotive industry, thereby supporting continuing strong consumptiongrowth in the future.
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.