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Styrene Monomer is an organic compound with the chemical formula C6H5CH=CH2.
Styrene Monomer's structure consists of a vinyl group as substituent on benzene.
Styrene Monomer is a colorless, oily liquid, although aged samples can appear yellowish.
CAS: 100-42-5
MF: C8H8
MW: 104.15
EINECS: 202-851-5
Synonyms:
SM;STYROL;STYRENE MONOMER;PHENYLETHYLENE;VINYLBENZENE;FEMA 3233;ETHENYLBENZENE;CINNAMENE
Styrene Monomer evaporates easily and has a sweet smell, although high concentrations have a less pleasant odor.
Styrene Monomer is the precursor to polystyrene and several copolymers, and is typically made from benzene for this purpose.
Approximately 25 million tonnes of Styrene Monomer were produced in 2010, increasing to around 35 million tonnes by 2018.
Styrene Monomer is a certain organic chemical compound having the chemical formula C8H8 and structural formula CH2=CHC6H5, also known as styrol, vinylbenzene, phenylethene,phenylethylene,styrene,styreen and so on.
Styrene Monomer's chemical structure is made up of a benzene ring bonded onto a vinyl group.
At room temperature and pressure, styrene is a clear, colorless liquid.
Styrene Monomer is an important monomer of synthetic rubber, adhesives and plastics, such as styrene sheet.
Styrene Monomer has a characteristic, sweet, balsamic, almost floral odor that is extremely penetrating.
Styrene Monomer occurs naturally in plants.
Styrene Monomer was first isolated from a resin called storax obtained from the inner bark of the Oriental sweet gum tree (Liquidambar orientalis) by Bonastre.
In 1839, the German apothecary Eduard Simon prepared styrene by distilling it from storax and called it styrol.
Simon observed it solidifi ed into a rubbery substance after being stored and believed Styrene Monomer had oxidized into styrol oxide.
Subsequent analysis showed the solid did not contain oxygen and it was renamed metastyrol. Styrene Monomer was the first written record of polymerization in chemistry.
In 1845, the English chemist, John Blyth, and the German chemist, August Wilhelm von Hofmann (1818 1892), observed that styrene was converted to polystyrene by sunlight and that styrene could be polymerized to polystyrene by heating in the absence of oxygen.
Styrene Monomer took another 70 years for the polymerization of styrene to be described by Hermann Staudinger (1881 1965) in the 1920s.
This laid the foundation for the commercial polystyrene industry that developed in the 1930s.
A vinylarene that is benzene carrying a vinyl group.
Styrene Monomer has been isolated from the benzoin resin produced by Styrax species.
A clear colorless to dark liquid with an aromatic odor.
Flash point 90°F. Density 7.6 lb/gal.
Vapors heavier than air and irritating to the eyes and mucous membranes.
Subject to polymerization.
If the polymerization takes place inside a closed container, the container may rupture violently.
Less dense than water and insoluble in water.
Used to make plastics, paints, and synthetic rubber.
Styrene Monomer Chemical Properties
Melting point: -31 °C (lit.)
Boiling point: 145-146 °C (lit.)
Density: 0.906 g/mL at 25 °C
Vapor density: 3.6 (vs air)
Vapor pressure: 12.4 mm Hg ( 37.7 °C)
Refractive index: n20/D 1.546(lit.)
Fp: 88 °F
Storage temp.: Store at <= 20°C.
Solubility: 0.24g/l
Form: Liquid
pka: >14 (Schwarzenbach et al., 1993)
Specific Gravity: 0.909
Color: Colorless
Odor: at 0.10 % in triacetin. sweet balsam floral plastic
Odor Type: balsamic
Biological source: synthetic
Odor Threshold: 0.035ppm
Explosive limit: 1.1-8.9%(V)
Water Solubility: 0.3 g/L (20 ºC)
FreezingPoint: -30.6℃
Sensitive: Air Sensitive
Merck: 14,8860
BRN: 1071236
Henry's Law Constant: (x 10-3 atm?m3/mol): 3.91 at 25 °C (static headspace-GC, Welke et al., 1998)
Exposure limits: TLV-TWA 50 ppm (～212 mg/m3) (ACGIH and NIOSH), 100 ppm (～425 mg/m3) (OSHA and MSHA); ceiling 200 ppm, peak 600 ppm/5 min/3 h (OSHA); STEL 100 ppm （～425 mg/m3) (ACGIH).
Dielectric constant: 2.4300000000000002
Dielectric constant: 2.4（25℃）
Stability: Stable, but may polymerize upon exposure to light. Normally shipped with a dissolved inhibitor. Substances to be avoided include strong acids, aluminium chloride, strong oxidizing agents, copper, copper alloys, metallic salts, polymerization catalysts and accelerators. Flammable - vapour may travel considerable distance to ignition source
InChIKey: PPBRXRYQALVLMV-UHFFFAOYSA-N
LogP: 2.96 at 25℃
CAS DataBase Reference: 100-42-5(CAS DataBase Reference)
NIST Chemistry Reference: Styrene(100-42-5)
IARC: 2A (Vol. 60, 82, 121) 2019
EPA Substance Registry System: Styrene Monomer (100-42-5)
Styrene Monomer is a colorless or yellow, sweet odor liquid with a penetrating odor.
Styrene Monomer is produced during alkylation of benzene with ethylene.
Styrene Monomer is highly reactive and polymerizes rapidly with a violent explosive reaction.
This demands proper handling, transportation, and storage by adding polymerization inhibitors in adequate quantities during these operations.
Styrene monomer has been extensively used in the manufacture of chemical intermediates, filling components, plastics, resins, and stabilizing agents.
Polymerization Reaction
Styrene Monomer is a common vinyl monomer and is the raw material for the synthesis of polystyrene.
In addition to bulk polymers, copolymers can be copolymerized with other monomers, such as acrylates and acrylonitrile.
Styrene Monomer can be polymerized under free radical photoinitiator or thermal initiator, and can also autopolymerize at high temperature.
As vinyl monomer, Styrene Monomer's polymerization reaction activity is lower than acrylate, methacrylate and other high activity monomer, higher than vinyl acetate and other low activity monomer.
In addition, styrene can also be used as a monomer for anionic polymerization, cationic polymerization and coordination polymerization.
Physical properties
Clear, colorless, watery liquid with a penetrating or pungent rubber-like odor.
Becomes yellow to yellowish-brown on exposure to air.
Experimentally determined odor threshold concentrations in air for inhibited and unhibited Styrene Monomer were 0.1 and 0.047 ppmv, respectively.
Experimentally determined detection and recognition odor threshold concentrations were 220–640 μg/m3 (52–150 ppbv) and 64 μg/m3 (15 ppbv), respectively.
At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 65 and 37 μg/L, respectively.
At 25 °C, the lowest concentration at which a taste was detected was 94 μg/L, respectively (Young et al., 1996).
The average least detectable odor threshold concentrations in water at 60 °C and in air at 40 °C were 3.6 and 120 μg/L, respectively.
Uses
Styrene Monomer is an important monomer of synthetic rubber, adhesives and plastics.
Styrene Monomer is used for the synthesis of styrene butadiene rubber and polystyrene resin, polyester glass fiber reinforced plastics and coatings.
Styrene Monomer is used for preparing polystyrene, ion exchange resin, and foam polystyrene.
Styrene Monomer is also used for copolymerization with other monomers to produce various engineering plastics, such as copolymerization of acrylonitrile and butadiene to produce ABS resin, widely used in various household appliances and industries.
Copolymerization with acrylonitrile, obtained SAN is a resin with shock resistance and bright color.
Styrene Monomer produced by copolymerization with butadiene is a thermoplastic rubber, which is widely used as a polyvinyl chloride and acrylic modifier.
Styrene Monomer and SIS thermoplastic elastomers are made with butadiene and isoprene copolymerization, and as a crosslinking monomer, styrene is used in the modification of PVC, polypropylene, and unsaturated polyester.
Styrene Monomer is used as a hard monomer for the production of styrene acrylic emulsion and solvent pressure sensitive adhesive.
Emulsion adhesive and paint can be prepared by copolymerization with vinyl acetate and acrylic ester.
Styrene Monomer is one of the most commonly used vinyl monomers in the scientific field, used in various modified and composite materials.
In addition, a small amount of styrene is also used as perfume and other intermediates.
By chloromethylation of Styrene Monomer, cinnamyl chloride is used as an intermediate for the non anesthetic analgesic strong pain determination, and styrene is also used as an antitussive, expectorant and anticholinergic original medicine in stomach Changning.
Styrene Monomer can be used to synthesize anthraquinones dye intermediates , pesticide emulsifiers, and styrene phosphonic acids ore dressing agent and copper plating brighteners.
Styrene Monomer, is the simplest and by far the most important member of a series of aromatic monomers.
Also known commercially as styrene monomer (SM), styrene is produced in large quantities for polymerization.
Styrene Monomer is a versatile monomer extensively used for the manufacture of plastics, including crystalline polystyrene, rubber-modified impact polystyrene, expandable polystyrene, acrylonitrile– butadiene–styrene copolymer (ABS), styrene–acrylonitrile resins (SAN), styrene–butadiene latex, styrene–butadiene rubber (SBR), and unsaturated polyester resins.
Styrene Monomer polymers and copolymers are usedextensively in making polystyrene plastics, polyesters, protective coatings, resins, andsynthetic rubber (styrene–butadiene rubber)..
Styrene Monomer is a viscous, highly flammable liquid that evaporates easily and polymerizes readily to polystyrene unless a stabilizer is added.
Styrene Monomer is used in multiple industries, especially in reinforced plastics (e.g., fiberglass boats), and is widely used to make plastics and rubber, packaging materials (e.g., packing peanuts ), insulation for buildings, plastic pipes, food containers (e.g., takeout containers), and carpet backing).
Industrial production
From ethylbenzene
The vast majority of Styrene Monomer is produced from ethylbenzene, and almost all ethylbenzene produced worldwide is intended for styrene production.
As such, the two production processes are often highly integrated.
Ethylbenzene is produced via a Friedel–Crafts reaction between benzene and ethene; originally this used aluminum chloride as a catalyst, but in modern production this has been replaced by zeolites.
By dehydrogenation
Around 80% of Styrene Monomer is produced by the dehydrogenation of ethylbenzene.
Styrene Monomer is achieved using superheated steam (up to 600 °C) over an iron(III) oxide catalyst.
The reaction is highly endothermic and reversible, with a typical yield of 88–94%.
The crude ethylbenzene/Styrene Monomer product is then purified by distillation.
As the difference in boiling points between the two compounds is only 9 °C at ambient pressure this necessitates the use of a series of distillation columns.
This is energy intensive and is further complicated by the tendency of styrene to undergo thermally induced polymerisation into polystyrene, requiring the continuous addition of polymerization inhibitor to the system.
Production
In nature, Styrene Monomer is very little in some plants and their fruits (such as cinnamon, coffee beans and peanuts), and there are styrene in coaltar.
Initially, in nineteenth Century, styrene was separated from storesin distillion.
In the laboratory, styrene is usually prepared by decarboxylation of cinnamic acid.
Styrene Monomer is used as raw material for industrial production,can be produced by catalytic dehydrogenation of ethylbenzene.
The most common way to produce Styrene Monomer is to catalyze dehydrogenation of ethylbenzene at 550~600oC.
Ethylbenzene is mixed into its own 10-16 times volume of high temperature water vapor, through solid phase catalytic bed to achieve dehydrogenation.
The main by-products of the reaction are benzene and toluene.
Styrene Monomer process was developed in the 1930s by BASF (Germany) and Dow Chemical (USA).
After continuous improvement, an iron series catalyst was added with a variety of cocatalysts, and selectivity of styrene was up to 95% in 1978.
The catalyst added was mostly alkali metal or alkaline earth metal, such as potassium, vanadium, molybdenum, tungsten, cerium and chromium.
The ethylbenzene dehydrogenation reactor has two types: isothermal and adiabatic.
The isothermal reactor is a tubular reactor, which is seldom used.
Now, an adiabatic reactor is generally used.
The process includes two parts: ethylbenzene dehydrogenation and Styrene Distillation Separation.
At present, the most mature and developed technology of negative pressure adiabatic dehydrogenation is Lummus technology and Fina technology.
The conversion of ethylbenzene in the reactor is about 35% to 40%.
The dehydrogenation solution contains ethylbenzene 55% to 60%, styrene 35% to 40%, and a small amount of benzene, toluene and tar.
Therefore, Styrene Monomer is necessary to fractionate styrene products by distillation.
As the boiling point of ethylbenzene and styrene is relatively close, the number of plates needed for separation is higher, and styrene is highly polymerizable at higher temperature.
In order to reduce the occurrence of polymerization, the addition of hydroquinone or sulfur inhibitor can still be used to reduce pressure. The control tower temperature is not more than 90 oC.
Styrene Monomer is also commercially produced by POSM process. Styrene and propylene oxide are obtained from ethylbenzene and propylene.
In this production route, ethylbenzene is oxidized to the peroxide of ethylbenzene, and then the peroxide is used to oxidize propylene to obtain 1- phenyl ethanol and propylene oxide.
Finally, Styrene Monomer can be obtained after dehydration of 1- phenyl ethanol.
This method is characterized by the production of 0.4t propylene oxide.
Styrene Monomer does not require high temperature such as dehydrogenation, and avoids the problem of producing propylene oxide by chlorohydrin process.
However, the reaction time is complex, the by-products are large, and the technological process is long.
The consumption of ethylbenzene is higher than that of dehydrogenation.
Production Methods
Styrene Monomer is made by dehydrogenation of ethylbenzene at high temperature using metal catalysts: C6H5CH2CH2(g)→ C6H5CH = CH2(g) + H2(g).
This is called the EB/SM (ethylbenzene/styrene monomer) process.
Styrene Monomer can also be made by PO/SM (propylene oxide/styrene monomer) process).
This process starts by oxidizing ethylbenzene (C6H5CH2CH2) to its hydroperoxide (C6H5CH(OOH)CH3), which is then used to oxidize propylene (CH3CH = CH2) to produce propylene oxide (CH3CH2CHO) and phenylethanol (C6H5CH(OH)CH3).
The phenylethanol is then dehydrated to give styrene and water.
Styrene Monomer can also be synthesized by reacting benzene and ethylene or natural gas.
Contact allergens
The presence of Styrene Monomer in packaged foods is due primarily to leaching of monomer from polystyrene containers.
Polystyrene (PS) is widely used in the manufacturing of food contact materials such as trays for meat, cookies, and candies with disposable plates, cups, etc. and about 50 % of the consumption of PS was related to food packaging and food service articles.
During the production process the Styrene Monomer monomer can become occluded in PS products and may migrate out of these materials into food.
The rate of migration of styrene monomer from polystyrene containers depends mainly on the lipophilicity of the food, surface area of the container per volume of food, duration of contact, and food temperature.
Styrene Monomer was found in 24 food contact materials from different categories (extruded polystyrene foam, expandable polystyrene, high-impacted polystyrene) at concentrations ranging from 9.3 to 3100 mg/kg, with a mean concentration of 340 mg/kg.
This concentration is below the USFDA limit for styrene in food packaging materials which are 5000 mg/kg for fatty foods and 10000 mg/kg for aqueous foods.
Moreover, Styrene Monomer dimers and trimers, which are also residual materials produced during polymerisation, have been detected.
Styrene Monomer was found in various foods such as yoghurt, croissants, cookies, raw chicken, and raw beef held in contact with PS packaging (meat trays, cookie trays, and chocolate candy trays) at concentrations ranging from 2.6 ng/g in raw chicken to 163 ng/g in sandwich cookies.
Styrene Monomer is reasonably anticipated to be a human carcinogen.
Several international brands start to phase out polystyrene foam packaging from their products.
