autoacceleration

thumb|Course of a redox-initiated methyl methacrylate substance polymerization with clearly visible Trommsdorff-Norrish-effect / autoacceleration

In polymer chemistry, autoacceleration (gel effect) is a dangerous reaction behavior that can occur in free-radical polymerization systems. It is due to the localized increases in viscosity of the polymerizing system that slow termination reactions. The removal of reaction obstacles therefore causes a rapid increase in the overall rate of reaction, leading to possible reaction runaway and altering the characteristics of the polymers produced. It is also known as the Trommsdorff–Norrish effect after German chemist Johann Trommsdorff and British chemist Ronald G.W. Norrish.