A Calorimetric Study of the Self-polymerization of a Commercial Monomer: an Incident Investigation Valeria Casson, Giuseppe Maschio* Dipartimento di Principi e Impianti di Ingegneria Chimica “I. Sorgato” Università di Padova, Via F. Marzolo, 9 – 35131 Padova – ITALY; giuseppe.maschio@unipd.it In this work the analysis of an incident in transport of dangerous goods is proposed. The objective of this study is to contribute to the determination of the causes that brought about the self-polymerization of commercial divinylbenzene (DVB 63%) contained in an isothermal container, in order to prevent this incident from happening in the future. Time and conditions during transport/storage of monomers (in particular storage temperature) are very important factors that affect their aptitude of self-polymerization. In particular one hypothesis has been investigated: that the quantity of oxygen in the tanker was insufficient to activate properly the inhibition mechanism. Consequently, the self-polymerization of DVB and the inhibition mechanism of 4-tert-Butylcatechol (TBC) have been studied as a function of temperature and monomer exposure to air with Differential Scanning Calorimetry and Adiabatic Calorimetry techniques. The incident Divinylbenzene is an aromatic monomer used principally for cross-linking styrene in the production of ion exchange resins. Much of this production is located in Europe. In 2006, in Grangemouth docks (Scotland), 24000 litres of DVB 63% contained in a tanker exposed to sunlight self-polymerized. A fracture cause by the movement of the tank, led to the loss of very big amount of monomer, as a dense, white plume of vapours. The firemen sealed off the zone for a range of 500 metres. The residents were not evacuated but were forced to stay at home for 24 hours as a preventive measure, because of the irritating characteristics of the substance for the skin and eyes. The seaport was idle for 36 hours, until the wind had completely dispersed the vapour cloud. No injuries were reported. From available data, it is known that oxygen considerably influences the inhibition properties of TBC, the inhibitor usually added at a level of 900-1200 ppm by weight to commercial DVB to prevent the self-polymerization of the material. The self-polymerization generate a runaway reaction (Burton & Nolan 1987 and Maschio et al. 1992). For this reason, attention has been paid in this study to the effect of atmospheric oxygen exposure and of the storage temperature on the DVB/TBC system.