Additives for FRP Production

The Relationship Between Curing Agents and Accelerators

Curing agent: Also called an initiator, this agent is an unstable peroxide. Its function is to generate free radicals to initiate the resin's curing reaction.

Accelerator: Its function is to significantly reduce the energy required for the curing agent to decompose, allowing the curing agent to decompose rapidly at room temperature to produce free radicals, thereby achieving room-temperature curing of the resin.

Without an accelerator, many curing agents decompose very slowly at room temperature, and the resin may not cure for several days.

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Unsaturated Polyester Resin & Vinyl Ester Resin System Epoxy Resin Systems

This is the most typical scenario for using a "hardener-accelerator" system.

This is the classic and most common combination for room-temperature curing of FRP. Its core characteristic is "add separately, react upon contact."

Important Note:

Never mix hardener and accelerator directly! They are highly reactive chemicals and can cause a violent reaction, even combustion or explosion.

The accelerator must be added to the resin and stirred thoroughly before adding the hardener.

Other Combination Systems

In addition to the classic cobalt-MEKP combination, other systems are used for specific processes:

System Name	Curing Agent	Accelerator	Features and Applications
Cobalt-MEKP System	MEKP	Accelerator E (Cobalt Salt)	Most versatile, used for hand lay-up, spraying, vacuum infusion, etc.
"Amine-BPO" System	BPO (Benzoyl Peroxide)	Accelerator D (Dimethylaniline)	This cures quickly but can cause yellowing. Often used for quick touch-ups or when color is not a concern.
Two-component system	A peroxide	A metal salt + an amine	Premixing the two accelerators into the resin provides faster curing.

Epoxy Resin Systems

Epoxy resins use a different curing mechanism. They don't use the concept of "accelerators," but rather the "curing agent" itself.

However, accelerators are sometimes added to adjust the curing speed.

Primary curing agents: such as polyamides, fatty amines, and anhydrides.

Accelerators: such as tertiary amines and phenols. Their function is to accelerate the reaction rate between the curing agent and the epoxy resin.

For example, adding a small amount of tertiary amine to an anhydride curing agent can significantly reduce the curing temperature or shorten the curing time.

Precise mixing is crucial for epoxy systems. The amounts of curing agent and accelerator must be added strictly according to the ratio specified by the supplier.

Safety First!

● Curing agents (peroxides) are strong oxidizers and are flammable and explosive. They must be kept away from heat, sparks, friction, and impact.

● Accelerators (cobalt salts and amines) are also somewhat toxic and corrosive.

● Always wear personal protective equipment (gloves, goggles, and protective clothing).

● Never mix curing agents and accelerators directly!

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