Initiators for polymerising unsaturated polyester resins are usually employed in inhibited form. Dibenzoyl peroxide. for example, is used in the form of a 50 % paste in plasticiser, whilst cyclohexanone peroxide is used in solution form. This decreases the decomposition rate in radical formation, but this can be increased by incorporating accelerators such as diethyl aniline. An amount of 0.5 (of the 10 % solution supplied) will give a pot life of about 4 hours at 20 °C if the initiator is dibenzoyl peroxide (2 %).
The reactivity of the accelerator also depends upon the alkylation type of such aromatic amines. If dimethyl aniline is used, for example. the pot life will be only 50 minutes under the same conditions, whilst with dimethyl-p-toluidine it drops to at mere 15 minutes. Another important point to watch is that an unsaturated polyester resin which has been accelerated with diethyl aniline tends relatively easily to yellow.