Styrene
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| Styrene | |
|---|---|
| Image:Styrol(Delokalisierung).png | |
| General | |
| Systematic name | Phenylethene |
| Other names | Vinyl benzene, cinnamene, styrol |
| Molecular formula | C8H8 |
| SMILES | c1ccccc1C=C |
| Molar mass | 104.15 g/mol |
| Appearance | colourless oily liquid |
| CAS number | [100-42-5] |
| Properties | |
| Density and phase | 0.9 g/cm3 |
| Solubility in water | < 1% |
| Melting point | -30 °C (243.15 K) |
| Boiling point | 145 °C (418.15 K) |
| Acidity (pKa) | ? |
| Basicity (pKb) | ? |
| Chiral rotation [α]D | ? ° |
| Viscosity | ? cP at ? °C |
| Structure | |
| Molecular shape | ? |
| Coordination geometry | ? |
| Crystal structure | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | MSDS |
| Main hazards | flammable |
| Flash point | 31 °C |
| R/S statement | R: 10-36 S: 38-20-23 |
| RTECS number | ? |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | ? |
| Other cations | ? |
| Related ? | ? |
| Related compounds | ? |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
Styrene (also vinyl benzene, ethenylbenzene, phenethylene or phenylethene, cinnamene, diarex HF 77, styrolene, styrol, styropol) is an organic compound which is an aromatic hydrocarbon having the chemical formula C8H8. At room temperature and pressure, styrene is a liquid. The chemical structure is shown at right. It is colourless, oily, toxic, flammable, and occurs in very small amounts in some plants, but is produced in industrial quantities from petroleum. The production of styrene in the United States was increased dramatically during the 1940's to supply the war needs for synthetic rubber. Because the styrene molecule has a vinyl group with a double bond, it can readily undergo polymerization. It is used as a monomer to make plastics such as polystyrene, ABS, styrene-butadiene (SBS) rubber, styrene-butadiene latex, SIS (styrene-isoprene-styrene), S-EB-S (styrene-ethylene/butylene-styrene), styrene-divinylbenzene (S-DVB), and unsaturated polyesters. It evaporates easily and has a sweet smell. It often contains other chemicals that can result in a sharp, unpleasant smell.
Styrene dissolves in many organic liquids but does not dissolve significantly in water. Millions of tonnes per day are produced to make products such as rubber, plastic, insulation, fiberglass, pipes, automobile parts, food containers, and carpet backing.
Most of these products contain styrene linked together in a long chain (polystyrene) as well as unlinked styrene. Low levels of styrene also occur naturally in a variety of foods such as fruits, vegetables, nuts, beverages, and meats.
Production
Styrene is most commonly produced by the catalytic dehydrogenation of ethylbenzene. Ethylbenzene is mixed in the gas phase with 10–15 times its volume in high-temperature steam, and passed over a solid catalyst bed. Most ethylbenzene dehydrogenation catalysts are based on iron(III) oxide, promoted by several percent potassium oxide or potassium carbonate. On this catalyst, an endothermic, reversible chemical reaction takes place.
| Image:Ctk-ethylbenzene.png | Image:Ctk-arrow-eq.png | Image:Ctk-styrene.png | Image:Ctk-plus.png | Image:Ctk-h2.png |
Steam serves several roles in this reaction. It is the source of heat for powering the endothermic reaction. It limits carbon deposition (coking) inside the reactor, which would otherwise degrade the catalyst's performance. It also dilutes the concentration of the reactant and products in the reaction mixture, shifting the position of chemical equilibrium towards products. A typical styrene plant operates several reactors in series, injecting fresh steam into the reaction mixture between each reactor. Each steam injection reheats the reaction mixture and shifts the position of chemical equilibrium further towards the products, making higher conversion possible. Typical per-pass conversions are on the order of 65%. The separation of styrene from the remaining ethylbenzene requires tall distillation towers, because styrene and ethylbenzene have similar boiling points (145 °C for styrene, 136 °C for ethylbenzene). Improving conversion and so reducing the amount of ethylbenzene that must be separated is the chief impetus for researching alternative routes to styrene.
Health effects
Breathing high levels of styrene for a short time can result in nervous system effects such as depression, concentration problems, muscle weakness, tiredness, and nausea, and possibly eye, nose, and throat irritation.
Animals breathing styrene vapour in short-term studies damaged their nasal lining. Long-term exposure damaged the liver. There is no information on human health effects of breathing low levels for a long time, but effects are likely to be similar.
There is some available information on the human health effects from eating or touching styrene. Animal studies show that ingestion of high levels of styrene over several weeks can cause damage to the liver, kidneys, brain, and lungs. When styrene was applied to the skin of rabbits, it caused irritation.
There is no information available as to whether breathing, ingesting, or touching styrene affects foetal development (teratogenic) or human reproduction. In animal studies, short-term exposure to very high levels resulted in some reproductive and developmental effects.
The International Agency for Research on Cancer (IARC) has determined that styrene is potentially carcinogenic to humans. Several studies of workers have shown that breathing styrene may result in developing leukemia. There is no information on the carcinogenicity of styrene in people who either swallow it or get it on their skin. Studies in animals that breathed or ate styrene suggest that it is mildly carcinogenic.
