Differential scanning calorimetry (DSC), polarized optical microscopy, and X-ray diffraction methods were used to investigate the isothermal crystallization behavior and crystalline structure of poly(e-caprolactone) (PCL)/multiwalled carbon nanotube (MWNT) composites. PCL/MWNT composites were prepared via the mixing of a PCL polymer solution with carboxylic groups containing multiwalled carbon nanotubes (c-MWNTs). Both Raman and Fourier transform infrared spectra indicated that carboxylic acid groups formed at both ends and on the sidewalls of the MWNTs. A transmission electron microscopy micrograph showed that c-MWNTs were well separated and uniformly distributed in the PCL matrix. DSC isothermal results revealed that introducing c-MWNTs into the PCL structure caused strongly heterogeneous nucleation induced by a change in the crystal growth process. The activation energy of PCL drastically decreased with the presence of 0.25 wt % c-MWNT in PCL/ c-MWNT composites and then increased with increasing MWNT content. The result indicated that the addition of c-MWNT to PCL induced heterogeneous nucleation (lower total activation energy) at a lower c-MWNT content and then reduced the transportation ability of polymer chains during crystallization processes at a higher MWNT content (higher total activation energy). A correlation between the crystallization kinetics, melting behavior, and crystalline structure of PCL/c-MWNT composites was also discussed. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: [598][599][600][601][602][603][604][605][606] 2006

X-ray diffraction methods and DSC thermal analysis have been used to investigate the structural change of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of s-caprolactam and then exfoliaton of the layered saponite or montmorillonite by subsequent polymerization. Both X-ray diffraction data and DSC results indicate the presence of polymorphism in nylon 6 and in nylon 6/clay nanocomposites. This polymorphic behavior is dependent on the cooling rate of nylon 6/clay nanocomposites from melt and the content of saponite or montmorillonite in nylon 6/&y nanocompasites. The quenching from the melt induces the crystallization into the y crystalline form. The addition of clay increases the crystallization rate of the Q crystalline form at lower saponite content and promotes the heterophase nucleation of y crystalline form at higher saponite or montmorillonite content. The effect of thermal treatment on the crystalline structure of nylon 6/clay nanocomposites in the range between Tg and Tm is also discussed.

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Differential scanning calorimeter (DSC) and polarized optical microscopy (POM) have been used to investigate the isothermal and nonisothermal crystallization behavior of poly(-caprolactone) (PCL)/multi-walled carbon nanotube (MWNT) composites. PCL/MWNT composites have been prepared by mixing the PCL polymer with carboxylic groups containing multi-walled carbon nanotubes (c-MWNTs) in tetrahydrofuran solution. Raman spectrum of c-MWNT indicated the possible presence of carboxylic acid groups at both ends and on the sidewalls of the MWNTs. The TEM micrograph showed that the c-MWNT is well separated and uniformly dispersed in the PCL matrix. DSC isothermal results showed that the introduction of c-MWNT into the PCL initiates strongly heterogeneous nucleation, which induced a change of the crystal growth process. The activation energy of PCL significantly decreases by adding 0.25 wt% c-MWNT into PCL/c-MWNT composites and then increases as c-MWNT content increases. The result demonstrates that the addition of c-MWNT into PCL induces the heterogeneous nucleation at lower c-MWNT content and then inhibits the polymer chain transportation ability during crystallization at higher c-MWNT content. In this study, we have also studied the nonisothermal crystallization kinetics and melting behavior of PCL/c-MWNT composites at various cooling rates. The correlation among isothermal and nonisothermal crystallization kinetics and melting behavior of PCL/c-MWNT composites can be also discussed. POLYM. ENG. SCI., 46: 1309 -1317, 2006.

This work describes the thermal stability and magnetic properties of polyvinylidene fluoride (PVDF)/magnetite nanocomposites fabricated using the solution mixing technique. The image of transmission electron microscopy for PVDF/magnetite nanocomposites reveals that the 13 nm magnetite nanoparticles are well distributed in PVDF matrix. The electroactive β-phase and piezoelectric responses of PVDF/magnetite nanocomposites are increased as the loading of magnetite nanoparticles increases. The piezoelectric responses of PVDF/magnetite films are extensively increased about five times in magnitude with applied strength of electrical field at 35 MV/m. The magnetic properties of PVDF/magnetite nanocomposites exhibit supermagnetism with saturation magnetization in the range of 1.6 × 10−3–3.1 × 10−3 emu/g, which increases as the amount of magnetite nanoparticles increases. The incorporation of 2 wt % magnetite nanoparticles into the PVDF matrix improves the thermal stability about 25 °C as compared to that of PVDF. The effect of magnetite particles on the isothermal degradation behavior of PVDF is also investigated.