To obtain wollastonite-filled β-iPP composites, the wollastonite with β-nucleating surface (β-wollastonite) was prepared through chemical reaction between wollastonite with α-nucleating surface (α-wollastonite) and pimelic acid. The formation of calcium pimelate on the surface of wollastonite was proved using Fourier transform infrared spectrometry and scanning electron microscopy. The crystallization behavior, melting characteristics, non-isothermal crystallization kinetics, and crystalline morphologies of α- and β-wollastonite-filled iPP composites were studied by differential scanning calorimetry and polarizing optical microscopy. It is found that the crystallization peak temperatures of β-wollastonite-filled iPP composites were higher than that of α-wollastonite-filled iPP composites, which indicated that wollastonite with β-nucleating surface has stronger heterogeneous nucleation than that of wollastonite with α-nucleating surface. Although the crystallization temperatures of iPP and iPP composites decreased with increasing cooling rates, α-wollastonite-filled iPP composites mainly crystallized in α-spherulite and β-wollastonite-filled iPP composites formed β-spherulite. In addition, the spherulite size of β-wollastonite-filled iPP composites was smaller than that of α-wollastonite-filled iPP composites. Jeziorny and Mo methods were applicable to study the non-isothermal crystallization kinetics of wollastonite-filled iPP composites. The activation energy (?E) and the nucleation efficiency (EN) of non-isothermal crystallization were calculated by Kissinger method and the equation proposed by Fillon, respectively. The β-wollastonite-filled iPP composites exhibited higher crystallization rate, activation energy, and EN than that of α-wollastonite-filled iPP composites. 相似文献
Kaolin-filled polypropylene (PP) composites generally form α-crystal due to the effect of kaolin with α-nucleation. The transition from α- to β-nucleation of kaolin has been investigated, and a novel kaolin with β-nucleation (β-kaolin) and kaolin-filled PP composites with high β-crystal content were prepared first. The DSC and WAXD results indicated that the β-kaolin exhibits stronger β-nucleating ability than CaPA as β-nucleating agent for PP crystallization. It is found that the β-crystal content has been influenced little by filler contents in β-kaolin-filled PP composites. Mechanical properties and spherulitic morphology of filled PP composites was characterized. The synergistic effect of filler and β-crystal significantly improved impact strength of kaolin-filled PP composites.
Standard high resolution 13C NMR spectra of PA10T, PA6T, PA106, and PA66 were obtained by a nonacidic solvent mixture of HFIP and CDCl3. Several chemical shifts were found extremely sensitive to the polyamide type. According to the standard spectra, semi-aromatic copolyamides comprising PA10T, PA6T, PA106, and PA66 units could be distinguished. The ratio of each polyamide component in the copolyamide was determined through the integration of the methylene carbon peak associated with the amine group. 13C NMR analysis results were consistent with the theoretical values and copolyamide hydrolysis test results, making 13C NMR analysis quite reliable on the quick composition analysis of semi-aromatic copolyamides. Based on this technique, several commercial semi-aromatic copolyamides were further examined and their compositions were easily determined. 相似文献
The processability of ultrahigh molecular weight polyethylene (UHMWPE) improved by oligomer-modified calcium carbonate (CaCO3) was observed in our previous work. In order to understand the effect of oligomer-modified CaCO3 on the crystallization of UHMWPE, the non-isothermal crystallization behavior and crystallization kinetics of UHMWPE composites filled by oligomer-modified CaCO3 was studied by differential scanning calorimetry in this work. Jeziorny and Mo methods were used to describe the non-isothermal crystallization kinetics of UHMWPE composites.
The effect of modified filler content and cooling rate on the crystallization temperature and crystallization rate was discussed. The heterogeneous nucleation of modified CaCO3 slightly increases the crystallization temperature of UHMWPE. The crystallization enthalpy of UHMWPE composites is significantly higher than that of UHMWPE. The crystallization rate of UHMWPE composites depends on the filler contents and cooling rate.
β-nucleated PP/PET blends were prepared using nano-CaCO3 supported β-nucleating agent (β-NA), PP as matrix, and PET as dispersion phase. The effects of preparation methods, PET content, and melting temperature
on the non-isothermal crystallization behavior and the melting characteristic and polymorphic composition of PP in the blends
were investigated by differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). The results indicated
that the PP crystallized predominantly in β-modification in the presence of β-NA. However, efficiency of β-NA for PP crystallization decreased with addition of PET and increasing PET contents. The β-nucleation of β-NA for PP crystallization in the blends was dependant on the preparation methods. The high β-nucleation and high β-PP content were obtained for PP/PET blend prepared at the temperature of 265 °C and added the β-NA into the blend at the temperature of 180 °C. However, the addition of β-PP or β-NA into blends at 265 °C decreased the β-nucleation, and no β-PP was formed because the β-NA mainly dispersed on the PET dispersion phase or at the interface between PP and PET. 相似文献