Thermal behavior of isotactic polypropylene in different content of β-nucleating agent

The effects of non-isothermal and isothermal crystallization on the formation of alpha- and beta-phase in isotactic polypropylene (iPP) with different content of beta-nucleating agent are investigated by differential scanning calorimetry (DSC). On non-isothermal crystallization, the content of beta-phase and regularity of its crystals are depended on both cooling rate and the content of beta-nucleating agent. The faster cooling rate is, the lower of melting peak temperature (T-mp) and crystallization peak temperature (T-cp) of alpha- and beta-phase are. The enthalpy of fusion (a dagger H) of beta-phase increases with cooling rate in a certain range for the sample with 0.1 wt% beta-nucleating agent (G(1)) and decreases for that with 0.3 wt% beta-nucleating agent (G(3)). On isothermal crystallization, the enthalpy of fusion of beta-phase in G(1) is higher than in G(3) which is related to the efficiency of nucleation in different concentration of nucleating center in two samples.