A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More specialized polyolefins include polyisobutylene and polymethylpentene. They are all colorless or white oils or solids. Many copolymers are known, such as polybutene, which derives from a mixture of different butene isomers. The name of each polyolefin indicates the olefin from which it is prepared; for example, polyethylene is derived from ethylene, and polymethylpentene is derived from 4-methyl-1-pentene. Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer. Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds (polybutadiene and polyisoprene) and are usually not considered polyolefins. Polyolefins are the foundations of many chemical industries.[1]
Polyolefin properties range from liquidlike to rigid solids, and are primarily determined by their molecular weight and degree of crystallinity. Polyolefin degrees of crystallinity range from 0% (liquidlike) to 60% or higher (rigid plastics). Crystallinity is primarily governed by the lengths of polymer's crystallizable sequences established during polymerization.[2] Examples include adding a small percentage of comonomer like 1-hexene or 1-octene during the polymerization of ethylene,[3] or occasional irregular insertions ("stereo" or "regio" defects) during the polymerization of isotacticpropylene.[4] The polymer's ability to crystallize to high degrees decreases with increasing content of defects.
Low degrees of crystallinity (0–20%) are associated with liquidlike-to-elastomeric properties. Intermediate degrees of crystallinity (20–50%) are associated with ductile thermoplastics, and degrees of crystallity over 50% are associated with rigid and sometimes brittle plastics.[5]
Polyolefin surfaces are not effectively joined together by solvent welding because they have excellent chemical resistance and are unaffected by common solvents. They can be adhesively bonded after surface treatment (they inherently have very low surface energies and don't wet-out well (the process of being covered and filled with resin)), and by some superglues (cyanoacrylates) and reactive (meth)acrylate glues.[6] They are extremely inert chemically but exhibit decreased strength at lower and higher temperatures.[7] As a result of this, thermal welding is a common bonding technique.
Practically all polyolefins that are of any practical or commercial importance are poly-alpha-olefin (or poly-α-olefin or polyalphaolefin, sometimes abbreviated as PAO), a polymer made by polymerizing an alpha-olefin. An alpha-olefin (or α-olefin) is an alkene where the carbon-carbon double bond starts at the α-carbon atom, i.e. the double bond is between the #1 and #2 carbons in the molecule. Alpha-olefins such as 1-hexene may be used as co-monomers to give an alkyl branched polymer (see chemical structure below), although 1-decene is most commonly used for lubricant base stocks.[8]
1-hexene, an example of an alpha-olefin
Many poly-alpha-olefins have flexible alkyl branching groups on every other carbon of their polymer backbone chain. These alkyl groups, which can shape themselves in numerous conformations, make it very difficult for the polymer molecules to align themselves up side-by-side in an orderly way. This results in lower contact surface area between the molecules and decreases the intermolecular interactions between molecules.[9] Therefore, many poly-alpha-olefins do not crystallize or solidify easily and are able to remain oily, viscous liquids even at lower temperatures.[10] Low molecular weight poly-alpha-olefins are useful as synthetic lubricants such as synthetic motor oils for vehicles and can be used over a wide temperature range.[8][10]
Even polyethylenescopolymerized with a small amount of alpha-olefins (such as 1-hexene, 1-octene, or longer) are more flexible than simple straight-chain high-density polyethylene, which has no branching.[7] The methyl branch groups on a polypropylene polymer are not long enough to make typical commercial polypropylene more flexible than polyethylene.
Usesedit
Polyethylene:
HDPE: used for film (wrapping of goods), blow molding (e.g. bottles), injection molding (e.g., toys, screw caps), extrusion coating (e.g., coating on milk cartons), piping for distributing water and gas, insulation for telephone cables. Wire and cable insulation.
Polypropylene: injection molding, fibers, and film. Compared to polyethylene, polypropylene is stiffer but less prone to breaking. It is less dense but shows more chemical resistance.[11]
Synthetic base oil (by far the most used one): industrial and automotive lubricants.[12]
^Alizadeh et al., Macromolecules 32 (1999) 6221-6235
^Bond, Eric Bryan; Spruiell, Joseph E.; Lin, J. S. (1 November 1999). "A WAXD/SAXS/DSC study on the melting behavior of Ziegler-Natta and metallocene catalyzed isotactic polypropylene". Journal of Polymer Science Part B: Polymer Physics. 37 (21): 3050–3064. Bibcode:1999JPoSB..37.3050B. doi:10.1002/(SICI)1099-0488(19991101)37:21<3050::AID-POLB14>3.0.CO;2-L.
^A. J. Kinloch, R. J. Young, The Fracture Behaviour of Polymers, Chapman & Hall, 1995. pp. 338-369. ISBN0 412 54070 3
^"Properties and Applications of Polyolefin Bonding" "[1] Master Bond Inc." Retrieved on June 24, 2013
^ abJames Lindsay White, David D. Choi (2005). Polyolefins: Processing, Structure Development, And Properties. Munich: Hanser Verlag. ISBN1569903697.[page needed]
^ abR. M. Mortier, M. F. Fox and S. T. Orszulik, ed. (2010). Chemistry and Technology of Lubricants (3rd ed.). Netherlands: Springer. ISBN978-1402086618.[page needed]
^"Properties of Alkanes 2013-01-07 at the Wayback Machine." Retrieved on June 24, 2013
^ abL. R. Rudnick and R. L. Shubkin, ed. (1999). Synthetic Lubricants and High-performance Functional Fluids (2nd ed.). New York: Marcel Dekker. ISBN0-8247-0194-1.[page needed]
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MSDS (Material Safety Data Sheet)
April 10, 2024
polyolefin, polyolefin, type, polymer, with, general, formula, ch2chr, where, alkyl, group, they, usually, derived, from, small, simple, olefins, alkenes, dominant, commercial, sense, polyethylene, polypropylene, more, specialized, polyolefins, include, polyis. A polyolefin is a type of polymer with the general formula CH2CHR n where R is an alkyl group They are usually derived from a small set of simple olefins alkenes Dominant in a commercial sense are polyethylene and polypropylene More specialized polyolefins include polyisobutylene and polymethylpentene They are all colorless or white oils or solids Many copolymers are known such as polybutene which derives from a mixture of different butene isomers The name of each polyolefin indicates the olefin from which it is prepared for example polyethylene is derived from ethylene and polymethylpentene is derived from 4 methyl 1 pentene Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds polybutadiene and polyisoprene and are usually not considered polyolefins Polyolefins are the foundations of many chemical industries 1 Contents 1 Industrial polyolefins 2 Properties 3 Uses 4 References 5 External linksIndustrial polyolefins editMost polyolefin are made by treating the monomer with metal containing catalysts The reaction is highly exothermic Traditionally Ziegler Natta catalysts are used Named after the Nobelists Karl Ziegler and Giulio Natta these catalysts are prepared by treating titanium chlorides with organoaluminium compounds such as triethylaluminium In some cases the catalyst is insoluble and is used as a slurry In the case of polyethylene chromium containing Phillips catalysts are used often Kaminsky catalysts are yet another family of catalysts that are amenable to systematic changes to modify the tacticity of the polymer especially applicable to polypropylene Thermoplastic polyolefins low density polyethylene LDPE linear low density polyethylene LLDPE very low density polyethylene VLDPE ultra low density polyethylene ULDPE medium density polyethylene MDPE polypropylene PP polymethylpentene PMP polybutene 1 PB 1 ethylene octene copolymers stereo block PP olefin block copolymers propylene butane copolymers Polyolefin elastomers POE polyisobutylene PIB poly a olefin s ethylene propylene rubber EPR ethylene propylene diene monomer M class rubber EPDM rubber Properties editPolyolefin properties range from liquidlike to rigid solids and are primarily determined by their molecular weight and degree of crystallinity Polyolefin degrees of crystallinity range from 0 liquidlike to 60 or higher rigid plastics Crystallinity is primarily governed by the lengths of polymer s crystallizable sequences established during polymerization 2 Examples include adding a small percentage of comonomer like 1 hexene or 1 octene during the polymerization of ethylene 3 or occasional irregular insertions stereo or regio defects during the polymerization of isotactic propylene 4 The polymer s ability to crystallize to high degrees decreases with increasing content of defects Low degrees of crystallinity 0 20 are associated with liquidlike to elastomeric properties Intermediate degrees of crystallinity 20 50 are associated with ductile thermoplastics and degrees of crystallity over 50 are associated with rigid and sometimes brittle plastics 5 Polyolefin surfaces are not effectively joined together by solvent welding because they have excellent chemical resistance and are unaffected by common solvents They can be adhesively bonded after surface treatment they inherently have very low surface energies and don t wet out well the process of being covered and filled with resin and by some superglues cyanoacrylates and reactive meth acrylate glues 6 They are extremely inert chemically but exhibit decreased strength at lower and higher temperatures 7 As a result of this thermal welding is a common bonding technique Practically all polyolefins that are of any practical or commercial importance are poly alpha olefin or poly a olefin or polyalphaolefin sometimes abbreviated as PAO a polymer made by polymerizing an alpha olefin An alpha olefin or a olefin is an alkene where the carbon carbon double bond starts at the a carbon atom i e the double bond is between the 1 and 2 carbons in the molecule Alpha olefins such as 1 hexene may be used as co monomers to give an alkyl branched polymer see chemical structure below although 1 decene is most commonly used for lubricant base stocks 8 nbsp 1 hexene an example of an alpha olefinMany poly alpha olefins have flexible alkyl branching groups on every other carbon of their polymer backbone chain These alkyl groups which can shape themselves in numerous conformations make it very difficult for the polymer molecules to align themselves up side by side in an orderly way This results in lower contact surface area between the molecules and decreases the intermolecular interactions between molecules 9 Therefore many poly alpha olefins do not crystallize or solidify easily and are able to remain oily viscous liquids even at lower temperatures 10 Low molecular weight poly alpha olefins are useful as synthetic lubricants such as synthetic motor oils for vehicles and can be used over a wide temperature range 8 10 Even polyethylenes copolymerized with a small amount of alpha olefins such as 1 hexene 1 octene or longer are more flexible than simple straight chain high density polyethylene which has no branching 7 The methyl branch groups on a polypropylene polymer are not long enough to make typical commercial polypropylene more flexible than polyethylene Uses editPolyethylene HDPE used for film wrapping of goods blow molding e g bottles injection molding e g toys screw caps extrusion coating e g coating on milk cartons piping for distributing water and gas insulation for telephone cables Wire and cable insulation LDPE mainly 70 used for film 1 Polypropylene injection molding fibers and film Compared to polyethylene polypropylene is stiffer but less prone to breaking It is less dense but shows more chemical resistance 11 Synthetic base oil by far the most used one industrial and automotive lubricants 12 References edit a b Whiteley Kenneth S Heggs T Geoffrey Koch Hartmut Mawer Ralph L Immel Wolfgang 2000 Polyolefins Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a21 487 ISBN 978 3527306732 Tashiro Stein Hsu Macromolecules 25 1992 1801 1810 Alizadeh et al Macromolecules 32 1999 6221 6235 Bond Eric Bryan Spruiell Joseph E Lin J S 1 November 1999 A WAXD SAXS DSC study on the melting behavior of Ziegler Natta and metallocene catalyzed isotactic polypropylene Journal of Polymer Science Part B Polymer Physics 37 21 3050 3064 Bibcode 1999JPoSB 37 3050B doi 10 1002 SICI 1099 0488 19991101 37 21 lt 3050 AID POLB14 gt 3 0 CO 2 L A J Kinloch R J Young The Fracture Behaviour of Polymers Chapman amp Hall 1995 pp 338 369 ISBN 0 412 54070 3 Properties and Applications of Polyolefin Bonding 1 Master Bond Inc Retrieved on June 24 2013 a b James Lindsay White David D Choi 2005 Polyolefins Processing Structure Development And Properties Munich Hanser Verlag ISBN 1569903697 page needed a b R M Mortier M F Fox and S T Orszulik ed 2010 Chemistry and Technology of Lubricants 3rd ed Netherlands Springer ISBN 978 1402086618 page needed Properties of Alkanes Archived 2013 01 07 at the Wayback Machine Retrieved on June 24 2013 a b L R Rudnick and R L Shubkin ed 1999 Synthetic Lubricants and High performance Functional Fluids 2nd ed New York Marcel Dekker ISBN 0 8247 0194 1 page needed Comparison of PE and PP Polyalphaolefin PAO Lubricants Explained www machinerylubrication com Retrieved 2022 06 26 External links edit nbsp Wikimedia Commons has media related to Polyolefins MSDS Material Safety Data Sheet Retrieved from https en wikipedia org w index php title Polyolefin amp oldid 1214656193, wikipedia, wiki, book, books, library,
