Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Additional information

Alpha-Methylstyrene is an organic, colourless liquid (20°C, 1013 hPa) with an aromatic odor. The melting and boiling points are 249.95K (-23.2°C) and 438.15K at 1013 hPa (ca. 165°C; range: 438.15 -438.55K ), respectively. The density of alpha-methylstyrene is 0.91 g/cm³ at 20°C. According to REACH Regulation (Annex VII, 7.14, column II), the study on granulometry does not need to be done if the substance is marketed or used in a non solid or non granular form. Alpha-methylstyrene is a liquid at standard conditions and is supplied and used in this form. The vapor pressure is stated to be 2.53 hPa at 20°C. The experimentally determined n-octanol/water partition coefficient log Kow is reported to be 3.48 at 25°C. According to the available and reliable data, the water solubility of alpha-methylstyrene is ca. 100 mg/L (range: 100 -116 mg/L) at 25°C. Alpha-methylstyrene is infinitely soluble in acetone, carbon tetrachloride, benzene, diethyl ether, n-heptane and ethanol. The surface tension was found to be 32.4 mN/m at 20°C (pure substance); the surface tension of diluted solutions is not available. According to REACH Regulation (Annex VII, 7.6, column II), the study on surface tension does not need to be done if based on the structure surface active properties are not to be expected. Alpha-methylstyrene does not contain any functional groups indicating surface active properties. The flash point of alpha-methylstyrene determined via the closed cup method is in the range between 40 and 54°C. Alpha-methylstyrene has an ignition temperature of 574°C. According to REACH Regulation (Annex XI, 1.), a study does not need to be done if based on the available data the substance can be classified, labelled and/or the risk of the substance can be assessed. Alpha-methylstyrene is a liquid at room temperature. For liquids the primary value for ease of ignition is the flash point. Moreover, the experience in the use and testing for other REACH endpoints showed that the substance does not ignite spontaneously in air or react violently with water and testing of the flammability according to EC Methods A.12 and A.13 is therefore not scientifically necessary. The flammability limits in air are reported to be in the range between 0.7 and 6.1 vol.-%. According to REACH Regulation (Annex 7.11, column II), the study on explosiveness does not need to be done if based on the structure explosive properties are not to be expected. Alpha-methylstyrene does not contain any chemical groups indicating explosive properties. Furthermore, the calculation of the oxygen balance yielded a value less than -200; based on this explosive properties are not to be expected. According to REACH Regulation (Annex VII, column II), the study on oxidising properties does not need to be done for substances which do not react exothermically with combustible material. The structure of alpha-methylstyrene does not contain functional groups associated with oxidising properties. According to REACH Regulation (Annex IX, column I), the study on the stability in organic solvents and identity of relevant degradation products does only to be done if it is regarded as a substantial property of the substance. Based on the structure it is to be expected that alpha-methylstyrene is stable in organic solvents. The pH of alpha-methylstyrene in water is reported to be 5 -6 at a concentration of 500 mg/L; according to the available data, the water solubility of the substance, however, is ca. 100 mg/L. Therefore this result should be treated with care. According to REACH Regulation (Annex IX, column II), the study on the dissociation constant does not need to be done if this is not possible from a scientific point of view. Alpha-methylstyrene does not contain any chemical groups susceptible to dissociation. The dynamic viscosity is reported to be 0.94 mPa x sec at 20°C..