ADR Class 5.2

Organic peroxides are subject to exothermic decomposition at normal or elevated temperatures. Decomposition may be due to heat, impurities, rubbing or shock. Decomposition may result in the release of flammable or noxious vapors or gases. For certain organic peroxides, temperature regulation is necessary; under confined conditions they can undergo explosive decomposition.

The explosive characteristic can be limited by the introduction of diluents or by using suitable containers/packaging. Organic peroxides cause serious eye damage to the cornea, even after brief contact or corrosive to the skin. It has the particularity of self-igniting by itself, if the appropriate circumstances are met, without the need to mix with combustible and/or flammable materials, since P.O. itself is flammable organic matter, apart from its oxidizing nature.

Any material is considered to be of Class 5.2 when the organic peroxide preparation complies with the following:

• Contain more than 1% active oxygen and a maximum of 1% hydrogen peroxide.
• Contain more than 0.5% maximum of active oxygen and 7% maximum of hydrogen peroxide.

Organic peroxides are classified into seven types ranging from A to G. Type A is not acceptable for transport as the packaging in which the test is produced is unsatisfactory. Type G is exempt from the provisions of this chapter for organic peroxides. The classification ranging from B to F is given by the maximum quantity of material allowed per package according to packing instruction IBC520 for IBC’s and P520 for packages with the packing methods described in OP1 to OP8 for the latter. Those Organic Peroxides which are allowed to be transported in tanks according to chapter 4.2 (portable tanks) and 4.3 (ADR tanks) are listed in 4.2.5.2 under the transport instruction for portable tanks T23.

The collective headings need to be specified:

• The type ranging from B to F of the organic peroxide.
• The physical state of matter.
• Temperature regulation if it presents TDAA (the minimum temperature at which matter undergoes thermal decomposition, explosive, etc.).

The mixtures of organic peroxides can be assimilated to that of the most dangerous peroxide of the composition and transported under the conditions foreseen by the latter. Two stable P.O.’s mixed together may result in an unstable mixture so it will be necessary to determine the TDAA and the regulation and critical temperature calculated according to provision 2.2.52.1.16.

Organic peroxides already classified whose transport is authorized according to the list of organic peroxides already classified can be transported in packaging, IBCs and portable tanks. Those not on this list must be authorized for transport by the competent authority.

The competent authority of the country of origin shall carry out the classification of the organic peroxides not listed in 2.2.52.4 or in 4.1.4.2 P502 or in 4.2.5.2 T23 portable tank transport instruction, in order to finally assign a collective heading as well as the declaration of approval indicating the classification and the applicable conditions of carriage dictated by the Contracting Party, either the country of origin or the consignee.

To ensure the safety of organic peroxides, desensitizers are added, desensitizing them in such a way that in case of leakage the peroxide is not concentrated. Diluents can be liquid or solid organic materials, solid inorganic materials or water.

Type A diluents are organic liquids that are compatible with organic peroxide and have a boiling point of at least 150°C.

Type B diluents are organic liquids compatible with organic peroxides with a boiling point below 150 but equal to 60ºC and a flash point of at least 5ºC.

Type B diluents can be used to desensitize all P.O. as long as their boiling point is 60ºC higher than the TDAA of the P.O. in a package for a maximum weight of 50Kg.

The total or partial substitution of a diluent A or B by another diluent with different properties requires an evaluation of the preparations on the basis of the classification for class 5.2. Solid organic and inorganic materials can be used for desensitizing provided they are compatible, without altering the thermal stability and hazard class of the preparation.

Water may be used for desensitizing whenever indicated in list 2.2.52.4 or by decision of the competent authority with the indication with water or dispersion with water.

Solid organic and inorganic materials can be used for desensitizing as long as they are compatible with the P.O. without altering the thermal stability or hazardousness of the preparation.