Methyl Ethyl Ketone Peroxides

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About methyl ethyl ketone peroxide (MEKP)

MEKP is a catalyst used in the composites industry for polyester and vinyl ester resins. It reacts with the resin to turn it from a liquid to a solid (cure it). MEKP is an organic peroxide. Since these compounds are unstable in their pure form, they are mixed with inert compounds to form the catalysts used in the industry. Due to this mixing, MEKP can be bought in various grades, which can give a range of gel times. Whilst various types of catalysts are available to cure polyester and vinyl ester resins, MEKP is the most widely used in contact moulding for room temperature cure.

MEKP allows polyester and vinyl ester resins to cure by reacting with the promoter in the resin, or with heat. This starts the chemical reaction of the resin with the styrene monomer (present in the resin) allowing crosslinks to form between them. These crosslinks act as braces, joining the components in the liquid resin together. When some of the crosslinks have formed, the resin forms a gel and is said to be “gelled”. When most of the crosslinks have formed, the resin forms a solid and is said to be “cured”.

Since MEKP must start a chemical reaction within the resin it must be a reactive compound. This makes it one of the most hazardous materials in the composites industry, since it can react with other materials causing a fire or with the human body resulting in chemical burns.

Other catalysts used in curing polyester and vinyl ester resins are:

Benzoyl Peroxide (BPO): For use above 80°C or in combination with an amine promoter

Cumene Hydroperoxide (CHP):  For use above 80°C or in combination with promoters

Acetyl Acetone Peroxide (AAP):  Used where fast cure is required

Tertiary butyl peroctoate and tertiary butyl perbenzoate (TBPO and TBPB):  Used in heat curing processes such as pultrusion and hot press moulding.

Cyclohexanone Peroxide (COX): Gives a more gradual cure.

Special Protection Information

Respiratory Protection: Adequate ventilation should be provided. If above NOHSC exposure standard level, use SA approved respiratory protective equipment.
Eye Protection: Use SA approved chemical splash goggles.
Protective Clothing: Wear chemical resistant gloves such as PVC or rubber. Wear full length trousers, long sleeved shirts and safety boots. CONSULT SAFETY EQUIPMENT SUPPLIERS FOR RECOMMENDATIONS

Effects of Exposure

Eyes: Can cause severe irritation. May cause blindness.
Inhalation: Can cause upper respiratory tract irritation.
Skin: Can cause severe irritation. May cause chemical burns.
Swallowing: Can be severely harmful or fatal.

First Aid Procedures

Eyes: Flush with water for at least 15 minutes.
Inhalation: Remove to fresh air. If breathing is difficult, seek immediate medical assistance.
Skin: Wash with soap and water.
Swallowing: Do NOT induce vomiting. If person is conscious, they should drink large quantities of water. Seek medical advice immediately.

Spill or Leak Procedures

Eliminate all sources of ignition and ventilate area. Wearing protective equipment, stop spill at source, dam area and, if possible, pump liquid into salvage tank. Alternatively, absorb spill with vermiculate or sand. Dampen with water. Scoop up using non-sparking tools into clean polyethylene lined, labeled waste container. Do not allow contact with metal. Dispose of waste in accordance with local, state and federal regulations. Seek advice from supplier. Reporting of spills/leaks may be required under EPA and Dangerous Goods regulations.

Fire Extinguishing Procedures

Wear protective equipment including self-contained breathing equipment. Use water from a safe distance, preferably with fog nozzle. Carbon dioxide may be used on small fires. Cool fire exposed containers with water spray.

Storage and Handling Procedures

DG Class 5.2 (Organic Peroxide). Keep MEKP in its original container. Keep in cool place away from flammables, strong oxidizing and reducing agents – in particular, any accelerators such as cobalt 6% or DMA. Avoid contact with all metallic materials.

KEY to abbreviations – CNS: Central Nervous System EPA: Environmental Protection Authority NOHSC: National Occupational Health & Safety Commission (Worksafe Australia) PVC: Polyvinyl chloride SA: Standards Australia

Disclaimer: Facts and information reported on this page are believed by Composites Australia to be accurate at the date of printing. No responsibility is accepted by Composites Australia for the use or misuse of information on this page. Composites Australia accepts no responsibility for damage or injury caused by information or omissions contained on this page.