Mechanical properties of polymers can be improved by incorporating nanoparticles

however

there are few works about the influence of nanoparticles on the crystallization mechanism of polymers．To develop an understanding of the important role of nanoparticles in polymer crystallization

the current paper introduced different surface modifications for calcium carbonate nanoparticles

and studied their effects on the crystallization behavior of isotactic polypropylene (iPP) by DSC measurement．The CaCO3 particles used are 40 nm in diameter

and their surfaces were treated by stearic-coating

PS-grafting

and PBA-grafting methods

respectively．The isothermal crystallization results show that the addition of both neat and modified nono-CaCO3 into PP has an obvious nucleating effect on the crystallization of iPP

resulting in lower supercooling degree

higher rate of nucleation and overall rate of crystallization

and higher crystallinity．Even through grafted PBA and PS belong to amorphous polymers

their evident nucleating effects indicate some regular structure forming on the particles surface．However

the grafted PBA exhibits different effect from PS because of its distinct molecular polarity and stiffness．On the other hand

the non-isothermaI crystallization results show that the addition of these nano-CaCO3 reduced the rate of nucleation and overall rate of crystallization of iPP

which is related with the slower formation procedure of β-form crystallites of iPP．The melting behavior and WAXD results revealed that all of these nano-CaCO3 have a strong promoting effect on the nucleation and crystallization of β-form crystallites of iPP

especially for the systems containing modified fillers

implying that this promoting effect was strongly dependent on the surface modifications of the nano-CaCO3 particles．