The effects of non-isothermal and isothermal crystallization on the formation of α- and β-phase in isotactic polypropylene
(iPP) with different content of β-nucleating agent are investigated by differential scanning calorimetry (DSC). On non-isothermal
crystallization, the content of β-phase and regularity of its crystals are depended on both cooling rate and the content of
β-nucleating agent. The faster cooling rate is, the lower of melting peak temperature (Tmp) and crystallization peak temperature (Tcp) of α- and β-phase are. The enthalpy of fusion (∆H) of β-phase increases with cooling rate in a certain range for the sample
with 0.1 wt% β-nucleating agent (G1) and decreases for that with 0.3 wt% β-nucleating agent (G3). On isothermal crystallization, the enthalpy of fusion of β-phase in G1 is higher than in G3 which is related to the efficiency of nucleation in different concentration of nucleating center in two samples.