What Is Styrene?
Styrene is an aromatic hydrocarbon with the formula C6H5CH=CH2.
It is also known as styrene, phenylethylene, styrene, and cinnamene. It is highly flammable and toxic and should be handled with care.
Uses of Styrene
Styrene is mainly used as a raw material for synthetic resins. It is used in the production of synthetic resins such as polystyrene (PS), ABS resin, AS resin, and unsaturated polyester. Styrene can also be used as a monomer for polymerization, as it easily polymerizes into polystyrene in the presence of heat and catalysts.
In particular, polystyrene resin has a very wide range of applications, including packaging materials for electrical appliances, kitchenware, containers, plastic models, automobiles, various parts of household appliances, and food trays, due to its low cost and good moldability. Depending on the application, polystyrene may be used by itself or in expanded polystyrene (styrene foam).
In addition, styrene is used not only as a raw material for manufacturing styrene butadiene rubber, polystyrene, synthetic resin paints, and FRP, but also for building materials such as adhesives, glues, and heat insulators, as well as dry oils, polyester resins, and ion exchange resins.
Properties of Styrene
A colorless liquid with aromatic properties, it is lighter than water with a specific gravity of 0.9044 and floats on water because it is insoluble in water. It has a flash point of 32°C, a melting point of -30.63°C, a boiling point of 145.2°C, and a refractive index of 1.5439. It is soluble in alcohols and ethers.
Styrene has a structure in which one hydrogen atom of benzene is replaced by a vinyl group. Because of the vinyl group, it is extremely reactive and easily polymerized by heating, light, peroxides, etc. to form polystyrene, which gradually increases in viscosity from a liquid state to a colorless solid state.
The vapor density is 3.6, which is heavier than that of air, and it easily stays in low places to form explosive gas mixtures. When temperatures rise due to sunlight or other factors, it can polymerize, posing a fire or explosion hazard. Therefore, it is recommended to store in a cool and dark place with good ventilation.
Other Information on Styrene
1. Production Method of Styrene
Dehydrogenation Method
Styrene is synthesized by dehydrogenating the raw material ethylbenzene at high temperature. The process is carried out under reduced pressure at 550°C or higher using a catalyst consisting mainly of iron oxide. Since this reaction is reversible, Styrene is synthesized by removing the hydrogen produced by the oxidation of ethylbenzene to allow the reaction to proceed.
Another method to synthesize Styrene is to oxidize the hydrogen produced in the reaction, thereby lowering the partial pressure of hydrogen and increasing the temperature in the system due to the heat of reaction, thereby allowing the reaction to proceed.
Halcon Method
This method was developed by Halcon International, Inc. in the U.S. and can synthesize Styrene and propylene oxide from ethylbenzene and propylene. In this method, ethylbenzene is air-oxidized to ethylbenzene hydroperoxide, which reacts with propylene under reaction conditions of 2 to 7 MPa and 100 to 130°C to produce propylene oxide and methylbenzyl alcohol.
Styrene is obtained by catalytic dehydration of the resulting methylbenzyl alcohol using a titanium oxide catalyst. The yield of propylene oxide and Styrene is high, and it is considered an advantageous method for simultaneous synthesis of these two substances.
2. Safety of Styrene
Styrene is a flammable liquid and has been reported to be a self-reactive chemical. It is also a fire and explosion hazard that can polymerize under the influence of heat, light, oxidants, oxygen, and peroxides.
Harmful by inhalation and may cause skin and eye irritation. Caution should also be exercised with regard to permissible concentrations in the work environment, as long-term or repeated exposure may cause central nervous system and liver damage.
The Ministry of the Environment’s Initial Environmental Risk Assessment suggests that there may be health effects if Styrene is inhaled through respiration. When handling, it is recommended that appropriate protective equipment such as protective gloves, impervious protective front coverings, safety glasses or safety goggles, and gas masks for organic gases be used.