IMDG Code 38-16 – Update 2 – Polymerizing Substances and Special Provision 386

Second in this series is changes to ‘Polymerizing Substances and Special Provision 386’.

What is polymerization and what dangers are involved when a substance undergo polymerization?

Monomers (small molecules) joining together to form polymer (large molecule) under a chemical reaction is called polymerization. This reaction may produce intense heat and pressure which may result in fire, explosion of closed containers or tanks. Chemical to chemical the triggering reason for polymerization may differ and may include heat, sunlight, contact with another chemical, light etc.

 Some of the accidents due to Polymerization

Jan 31, 2006

  • Reason:       Runaway chemical reaction involving acrylic polymers
  • Location:     Morganton, NC
  • Result:        1 suffered, fatal burn injury, 14 other injuries, two seriously injured, entire facility destroyed, 1/3rd of a mile radius glass windows broke, two churches and a house was destroyed
  • For more information click here

 Aug 28, 2005

  • Reason:       Styrene monomer escaping from Rail tank
  • Location:     Cincinnati, Ohio    
  • Reason:       A safety valve at the top of the tank had opened
  • Result:        The population within a radius of 0.5 miles around the tank was evacuated. A curfew with a radius of 1 mile was imposed. The Lunken regional airport was temporarily closed. Two policemen were hospitalized and later released after they had inhaled the gas.
  • For more information click here

August 14, 1994

  • Reason:        Explosion and fire at a butadiene cylinder exposed to the sunshine
  • Location:      Yokkaichi, Mie, Japan
  • Reason:       500 kg butadiene cylinder ruptured during use.
  • Result:         8.3 square meters of a building in which a fire occurred burned down. Three hoppers and two exhaust gas deodorizers partially burned. The windows of 32 buildings in the factory site and 85 nearby housing units were damage
  • For more information click here

New Provisions in IMDG Code 38-16

New provisions added to IMDG Code 38th amendment to prevent dangerous polymerization states Chemically unstable substances shall not be accepted for transport unless the necessary precautions have been taken to prevent the possibility of a dangerous decomposition or polymerization under normal conditions of transport”.

Above condition assigned to gasses, flammable liquids, toxic substances and corrosive substances  are listed under sections

  • 2.2.4 Gases not accepted for transport
  • 2.3.5 Flammable Liquid Substances not accepted for transport
  • Toxic Substances not accepted for transport
  • 2.8.3 Corrosive Substances not accepted for transport

What does special provision 386 require for substances liable to polymerize?

  • When chemical stabilization is employed, the person offering the packaging, IBC or tank for transport shall ensure that the level of stabilization is sufficient to prevent the substance in the packaging, IBC or tank from dangerous polymerization at a bulk mean temperature of 50°C, or, in the case of a portable tank, 45°C.
  • Where chemical stabilization becomes ineffective at lower temperatures within the anticipated duration of transport, temperature control is required.
  • In making this determination factors to be taken into consideration include, but are not limited to, the capacity and geometry of the packaging, IBC or tank and the effect of any insulation present, the temperature of the substance when offered for transport, the duration of the journey and the ambient temperature conditions typically encountered in the journey (considering also the season of year), the effectiveness and other properties of the stabilizer employed, applicable operational controls imposed by regulation (e.g. requirements to protect from sources of heat, including other cargo transported at a temperature above ambient) and any other relevant factors.”

Existing UN Numbers for which SP 386 is assigned

1010, 1051, 1060, 1081, 1082, 1085, 1086, 1087, 1092, 1093, 1143, 1167, 1185, 1218, 1246, 1247, 1251, 1301, 1302, 1303, 1304, 1545, 1589, 1614, 1724, 1829, 1860, 1917, 1919, 1921, 1991, 2055, 2200, 2218, 2227, 2251, 2277, 2283, 2348, 2352, 2383, 2396, 2452, 2521, 2527, 2531, 2607, 2618, 2838, 3022, 3073 and 3079.

New UN Numbers added to Polymerization Substances Solids and Liquids

3531, 3532, 3533, 3534

For Class 4.1 Polymerizing substances and mixtures refer to section of IMDG Code


Further reading

IMDG Code 38-16 – Update 1 – Classification



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