Effect Of Illite On Crystallization From The Melt Of Isotactic Polypropylene And Poly(Vinylidene Fluoride)

Illite based nanocomposites of isotactic polypropylene(iPP)and poly(vinylidene fluoride)(PVDF)were prepared by melt and solution blending,respectively.The crystallization behavior,crystal structure and crystalline morphology of nanocomposites were investigated by Differential Scanning Calorimeter(DSC)/Polarizing Optical Microscope(POM)/Transmission Electron Microscope(TEM)/Atomic Force Microscope(AFM)/X-ray Photoelectron Spectroscopy(XPS)/Wide-angle X-ray Diffraction(WAXD)and Infrared Spectroscopy(IR).And the influence of different structures on related mechanical properties of the nanocomposites was studied.The main results are summarized as follows.It was found that the pristine illite could facilitate the nucleation of iPP in its a-form obviously.Both the crystallinity and crystallization rate of iPP increase with the content of illite increase.1 wt%illite leads to an increment of iPP crystallinity from 33%to 50%.Moreover,the modulus and tensile strength of 99/1 iPP/illite composite of 1 wt%increase from 1.4 GPa to 1.9 GPa and from 30.5 MPa to 37.1 MPa,respectively.The above-mentioned influences of illite on iPP depend on its content and dispersion in iPP matrix.The calcium pimelate(CaHA)modified illite,i.e.,CaHA-illite,exhibits β-iPP nucleation ability to iPP.For comparison,blends of iPP with CaHA,CaHA/N2H4-illite,CaHA/CTAB-illite,HA/Ca2+-illite-1 and HA/Ca2+-illite-2 were also studied.The results show that the CaHA-illite exhibits the highest nucleation ability on β-iPP.During isothermal crystallization process as high as 93%β-iPP crystals can be obtained with the existence of CaHA-illite.Due to the high crystallinity and crystal fraction of β-iPP,the iPP/CaHA-illite exhibits the best mechanical properties with increments of 36%and 163%in tensile modulus and maximum strain compared with the pure iPP,respectively.For PVDF/illite nanocomposites,the results show that unmodified illite does not affect the crystallization of PVDF.On the other hand,the modified illite promotes the y-phase crystallization of PVDF.Therefore,the effect of modified illite on y-phase PVDF crystallization at different crystallization temperatures was studied in detail.The modified illite can effectively boost the nucleation of γ-phase due to the electrostatic interaction between PVDF and modified illite.A 2 wt%modified illite can generate pure γ-phase regardless of crystallization conditions.For the samples with modified illite less than 2 wt%,increasing the crystallization temperature or the content of modified illite facilitates the formation of more y-phase.Moreover,the effect of PVDF blending with poly(butylene succinate)(PBS)on y-PVDF was discussed in this work,providing a reference to obtain 100%y phase in processing.The technique of preparing pure γ-phase PVDF materials with modified illite may exhibit a huge application in the fabrication of cheap pyro-or piezoelectric devices.