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In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica(SiO_2-WD70) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide immobilized silica(SiO_2-WD70-DOPO) nanoparticles were prepared. Silica, SiO_2-WD70 and SiO_2-WD70-DOPO were incorporated into polypropylene(PP) by melt compounding. Differential scanning calorimetry(DSC), X-ray diffraction(XRD) and polarized optical microscopy(POM) were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant(kn), and half crystallization time(t1/2) were calculated by Avrami equation,while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased kn, decreased t1/2 and the surface free energy(σe) in the order of PP, PP/SiO_2, PP/SiO_2-WD70 and PP/SiO_2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO_2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO_2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO_2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.
In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica (SiO_2-WD70) and 9,10-dihydro-9- oxa-10-phosphaphenanthrene-10-oxide immobilized silica Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized optical microscopy (POM) were employed to investigate the isothermal crystallization behavior of The kinetic constant (kn), and half crystallization time (t1 / 2) were calculated by Avrami equation, while the surface free energy of folding was calculated by Lauritzen- Hoffman theory. The increased kn, decreased t1 / 2 and the surface free energy (σe) in the order of PP, PP / SiO 2, PP / SiO 2-WD70 and PP / SiO 2 -WD70-DOPO nanocomposites were attributed to the surface modification of silica. DOPO addition had no effect on PP crystal structure but accelerated the cr ytopallization rate. POM determined added SiO 2 -WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO_2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.