Papers by Keyword: Nonisothermal Crystallization

Abstract: Abstract.In this paper, the nonisothermal crystallization kinetics was investigated by differential scanning calorimetry for the poly(m-xylylene adipamide) (MXD6) which were prepared by polymerization in reactor. The Avrami theory modified by Jeziorny and Z.S. Mo equation were used to describe the nonisothermal crystallization kinetics. The analysis based on the Avrami theory modified by Jeziorny shows that the Avrami exponent n of MXD6 ranges from 2.3 to 3.3, Moreover, both Avrami exponent (n) were around 3.0, which probably suggests a thermal nucleation and a three-dimensional crystal growth. The good linearity of the plots indicates the successful application of Z.S. Mo method in this case.

Abstract: Abstract. Poly(ethylene terephthalate)(PET)/poly(trimethylene terephthalate) (PTT) and PET/PTT /montmorillonite(MMT) nanocomposites were prepared by melt blending through a co-rotating twin screw extruder. Their morphology was characterized by Scanning Electron Microscope(SEM). And the nonisothermal crystallization behavior was studied by Differential Scanning Calorimetry(DSC). The results indicated that MMT dispersed homogeneously in the PTT matrix; the crystallization onset temperature(Tonset) and the crystallization peak temperature(Tp) in crystallization exotherms of PET/ PTT/MMT nanocomposites shifted to higher temperature as MMT content increased, which proved MMT acted as heterogeneous nucleating agent, and the crystallization behavior became imperfect as the cooling rate increased.

Abstract: Multi-walled carbon nanotubes (MWNT) were successfully chemically modified (MWNT-COOH) and reacted with polyethylene glycol (PEG) to prepare nanocomposites. As- prepared kinds of functionalized MWNT (MWNT-g-PEG) were characterized with FTIR, TGA and TEM. Nonisothermal crystallization kinetics of MWNT-g-PEG composites was investigated by differential scanning calorimeter (DSC). The kinetics was analyzed using the Ozawa and Avrami equation modified by Jeziorny. The results showed that the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the modified Avrami analysis could explain the behavior of MWNT-g-PEG nanocomposite only. It is observed that the presence of MWNT hindered the mobility of PEG chains and decreased the overall crystallization rate. It was found that the crystallization behavior of MWNT-g-PEG nanocomposite was strongly affected by the incorporation of MWNT. The data for the nonisothermal crystallization could be analyzed properly by the Avrami equation modified by Jeziorny. The results showed that the presence of MWNT decreased the overall nonisothermal crystallization rate of the PEG chains which were grafted onto the MWNT due to MWNT might act as physical hindrances retarding the mobility of PEG chains and decreased the crystallinity.

Abstract: The influence of compatibilizer and dispersant on the nonisothermal crystallization behavior of HDPE/UHMWPE/HA is investigated here by differential scanning calorimetry (DSC). It has been analyzed by Jeziorny method. For different composites, the Jeziorny plots shows the linear portion. The small deviations from linearity only appear at higher relative crystallinity because of the secondary crystallization. The value of Avrami parameter n is between 2.7 and 3.5. At the same temperature, Z_c and S_i become bigger after adding compatibilier and dispersant while tmax is decreasing. The activation energy of crystallization also have been studied by Kissinger equation. The result shows that the addition of compatibilizer and dispersant can decrease the activation energy. In addition, the compatibilizer and dispersant also improve the mechanical properties of composites.

Abstract: The crystallization behavior of semi-crystalline plastics plays a vital role in the development of properties of plastics. The present study examines the effect of addition of 1-5% nano talc filler particles on the nucleation behavior and crystal morphology. Differential Scanning Calorimetry was used to study the dynamic crystallization kinetics of PEEK with different loadings of nano talc filler. The crystalline morphology and non-isothermal kinetics were investigated. Crystallization behaviour was studied using Avrami equation. It is found that the addition of nano-talc enhances the rate of nucleation; however, the growth rate of the crystals reduces.

Abstract: Nonisothermal crystallization behaviors of PVA and poly (vinyl alcohol) and Silica (PVA/SiO2) nanocomposites prepared via a self-assembly monolayer (SAM) technique are investigated in this study. Differential scanning calorimetry (DSC) is used to measure the crystallization temperature and enthalpy of PVA and nanocomposites in nitrogen at various cooling rate. The results show that the degree of crystallinity of PVA and nanocomposites decreases when the SiO2 content increases but increases with an increasing cooling rate. The peak crystallization temperature decreases with an increasing cooling rate.