Curing agents

More information about crosslinkers can be found under the product list!

More about crosslinkers

The crosslinked structure of polyester and vinyl ester resins is formed by radical chain polymerization. The initial step in polymerization is the initiation of a chain reaction, which involves the formation of free radicals that can grow from the monomer or other substance (initiator). Radical formation can be created by physical or chemical methods. The most common methods are:

• Thermal
• Redox chemical reaction
• Radiation process

Of the given methods, the use of the second type (redox chemical reaction) is the most typical, where in the redox reaction the oxidizing agent is the initiator and the reducing agent is mostly a variable metal or tertiary amine. In the composite industry, a solvent solution of 1-12% of a cobalt compound (Co-stearate, Co-naphthoate, Co-octoate) is most often used as the variable valence metal. The solvent is usually i-propanol or a mixture of toluene and i-butyl acetate.

In summary, cobalt as an activator promotes the decomposition of the initiator (peroxide) into radicals at room temperature, which causes the cleavage and radical formation of the monomeric units and the unsaturated dicarboxylic acids –C = C–. The radicals then form a high molecular weight crosslinked structure called a polymer during a chain reaction.

Such a chemical reaction occurs in both unsaturated polyester and vinyl ester, where its rate can be controlled by changing the type of activator and initiator and adding it.