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ATG Gelcoat Gun Operations Manual

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Catalyst - Methyl Ethyl Ketone Peroxide (MEKP)

MEKP is among the more hazardous materials found in commercial channels. The safe handling
of the “unstable (reactive)” chemicals presents a definite challenge to the plastics industry. The
highly reactive property which makes MEKP valuable to the plastics industry in producing the

curing reaction of polyester resins also produces the hazards which require great care and caution
in its storage, transportation, handling, processing and disposal. MEKP is a single chemical.
Various polymeric forms may exist which are more or less hazardous with respect to each other.
These differences may arise not only from different molecular structures (all are, nevertheless,
called “MEKP”) and from possible trace impurities left from the manufacture of the chemicals, but
may also arise by contamination of MEKP with other materials in its storage or use. Even a small

amount of contamination with acetone, for instance, may produce an extremely shock-sensitive
and explosive compound.

WARNING

Contamination with promoters, materials containing promoters (such as

laminate sandings), or with any readily oxidizing material (such as brass

or iron) will cause exothermic redox reactions which can be explosive in

nature. Heat applied to MEKP or heat buildup from contamination

reactions can cause the material to reach its Self-Accelerating

Decomposition Temperature (SADT).

Researchers have reported measuring pressure rates-of-rise well over 100,000 psi per second when

certain MEKP’s reach their SADT. For comparison, the highest-pressure rate-of-rise listed in
NFPA Bulletin NO.68, “Explosion Venting”, is 12,000 psi per second for an explosion of 12%
acetylene and air. The maximum value listed for a hydrogen explosion is 10,000 psi per second.
Some forms of MEKP, if allowed to reach their SADT, will burst even an open topped container.
This suggests that it is not possible to design a relief valve to vent this order of magnitude of

pressure rate-of-rise. The user should be aware that any closed container, be it a pressure vessel,
surge chamber, or pressure accumulator, could explode under certain conditions. There is no
engineering substitute for care by the user in handling organic peroxide catalysts. If, at any time,
the pressure relieve valve on top of the catalyst tank should vent, the area should be evacuated at
once and the fire department called. The venting could be the first indication of a heat, and

therefore, pressure build-up that could eventually lead to an explosion. Moreover, if a catalyst
tank is sufficiently full when the pressure relief valve vents, some catalyst may spray out, which
could cause eye injury. For this reason, and many others, anyone whose job puts them in an area
where this vented spray might go, should always wear full eye protection even when laminating
operations are not taking place.
Safety in handling MEKP depends to a great extent on employee education, proper safety

instructions, and safe use of the chemicals and equipment. Workers should be thoroughly
informed of the hazards that may result from improper handling of MEKP, especially regarding
contamination, heat, friction and impact. They should be thoroughly instructed regarding the
proper action to be taken in the storage, use, and disposal of MEKP and other hazardous
materials used in the laminating operation. In addition, users should make every effort to:



Store MEKP in a cool, dry place in original containers away from direct sunlight and away
from other chemicals.



Keep MEKP away from heat, sparks, and open flames.



Prevent contamination or MEKP with other materials, including polyester over spray and
sandings, polymerization accelerators and promoters, brass, aluminum, and non-stainless
steels.