The large spherulite size, heterogeneous nucleation and constant spherulite growth rate of POM suggests a straightforward two dimensional Avrami analysis, with two adjustable parameters, to(T) and K(T), to be appropriate to thin samples in the DSC. For T > 147 degrees C, spherulite densities inferred from results for the rate parameter K(T) and microscopical measurements of spherulite growth rates are consistent with observed spherulite sizes. The KO values may also be used to model non-isothermal crystallization in the same temperature range (dT/dt < 10 k/minute). Whilst K(T) shows little dependence on molecular weight, samples containing 30 wt% TPU crystallize more slowly owing to a reduced nucleation density.