Example: In a polymerization, auto-acceleration may be due to a variety of causes. An example of auto-acceleration in a polymerization is the Norrish–Trommsdorf effect (gel effect) which leads to a significant increase in the rate of radical polymerization with monomer conversion. The effect is due to the rate of termination decreasing with increasing viscosity of the system, causing an increase in the concentration of propagating radicals.