Nucleation of crystallizable polymers is quantified through an efficie
ncy scale obtained and calculated using differential scanning calorime
try (DSC). This scale, defined in self-nucleation experiments, is a si
mple, convenient and reliable calorimetric efficiency scale. Typical n
ucleating agents for isotactic polypropylene are evaluated; they rate
at best at 60 to = 70% on this efficiency scale.