Nonisothermal Crystallization Kinetics of Ethylene Vinyl Alcohol Copolymer with Poly(oxypropylene)diamine Intercalated Montmorrilonite

Films of ethylene vinyl alcohol copolymer (EVOH) and EVOH containing poly(oxypropylene)diamine intercalated montmorrilonite were prepared by solution casting. The nanostructures and viscosity were characterized by small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and rheological testing. The nonisothermal crystallization kinetics of the samples were investigated by the Ozawa's and Mo's methods and the crystallization activation energy by Kissinger's model. The SAXS and TEM analysis demonstrated that the nanoplatelets, with an intercalated structure, were dispersed in the EVOH matrix. The rheological tests showed that the incorporation of the modified clay could increase the viscosity of the composite system. The Mo's method more successfully described the nonisothermal ctystallization behavior of neat EVOH and its nanocomposites as compared with the Ozawa's method. Adding the nanoclays had a heterogeneous nucleation effect to accelerate the crystallization of EVOH despite hindering the macromolecular chains movement.     

Nonisothermal Crystallization Behavior of Polypropylene-C60 Nanocomposites

The nonisothermal crystallization behavior of polypropylene (PP) and PP-fullerene (C₆₀) nanocomposites was studied by differential scanning calorimetry (DSC). The kinetic models based on the Jeziorny, Ozawa, and Mo methods were used to analyze the nonisothermal crystallization process. The onset crystallization temperature (T_c), half-time for the crystallization (t_1/2), kinetic parameter (F(T)) by the Mo method and activation energy (ΔE) estimated by the Kissinger method showed that C₆₀ accelerates the crystallization of PP, implying a nucleating role of C₆₀. Furthermore, due to the reduced viscosity of PP by adding 5% C₆₀, the parameters of crystallization kinetics for the PP-5%C₆₀ nanocomposites changed remarkably relative to that of neat PP and when lower contents of C₆₀ were added to PP.     

Study on the Nonisothermal Crystallization Kinetics of Poly(Vinylidene Fluoride)/Tributyl Citrate Blends Via Thermally Induced Phase Separation

The nonisothermal crystallization kinetics of poly (vinylidene fluoride) (PVDF) in PVDF/tributyl citrate (TBC) blends having undergone thermally induced phase separation were investigated through differential scanning calorimetry measurements. Ozawa theory, Mo's method and Kissinger model were used to analyze the kinetics of the nonisothermal crystallization process. The Ozawa theory failed to describe the crystallization behavior of PVDF in the PVDF/TBC blends, whereas the Mo model was able to describe the nonisothermal crystallization process fairly well. The crystallization activation energy was determined by the Kissinger method, and was in the range of 90–165 kJ/mol.     

Nonisothermal Crystallization Kinetics of Nylon 66/Montmorillonite Nanocomposites

Polyamide 66(PA66)/montmorillonite nanocomposites were prepared via direct melt compounding. The nonisothermal crystallization of PA66 and PA66/MMT nanocomposites were investigated by differential scanning calorimetry. The results show that MMT platelets play a competing role in the crystallization process of nylon 66. On the one hand, they can act as a nucleator for the PA66 matrix, accelerating the crystallization rate; on the other hand, they retard the crystal/spherulite growth, especially for nanocomposites with higher MMT content. The analysis results using Jeziorny and Mo equations verify the dual actions of the nucleation and the obstruction of crystallization of MMT in the PA66 matrix. Kissinger's method was used to obtain the activation energy of the crystallization process; the results confirm that the incorporation of MMT causes the above actions.     

Influence of Hollow Glass Microspheres Modified by a Rare-Earth/Titanium Coupling Agent on the Nonisothermal Crystallization of Polypropylene

Hollow glass microspheres (HGMs) were surface modified by a rare-earth/titanium coupling agent. Then polypropylene/HGMs composites were prepared by the method of melt blending. The nonisothermal crystallization of the polypropylene (PP) and its composites were investigated by differential scanning calorimetry. The results showed the modified HGMs caused a decrease in the peak crystallization temperature and onset crystallization temperature. Further analysis of the nonisothermal crystallization kinetics, by using the Jeziorny and Mo equations, showed that the crystallization rate rose with increasing cooling rate. Moreover, the presence of the modified HGMs slightly increased the crystallization rates of PP.     

Non‐isothermal Melt Crystallization Kinetics for Poly(ethylene 2,6‐naphthalate) (PEN)/Montmorillonite Nanocomposites Prepared by Melt Intercalation

The nonisothermal crystallization behaviors for poly(ethylene 2,6‐naphthalate) (PEN) and poly(ethylene 2,6‐naphthalate) (PEN)/montmorillonite nanocomposites prepared by melt intercalation were investigated using differential scanning calorimetry (DSC). The Jeziorny, Ozawa, Ziabicki, and Kissinger models were used to analyze the experimental data. Both the Jeziorny and the Ozawa models were found to describe the nonisothermal crystallization processes of PEN and PEN/montmorillonite nanocomposites fairly well. The results obtained from the Jeziorny and the Ozawa analysis show that the montmorillonite nanoparticles dispersed into PEN matrix act as heterogeneous nuclei for PEN and enhance its crystallization rate, accelerating the crystallization, but a high‐loading of montmorillonites restrain the crystal growth of PEN. The analysis results from the Ziabicki and the Kissinger models further verify the dual actions stated above of the montmorillonite nanoparticles in PEN matrix.     

Nonisothermal Crystallization Kinetics of Poly(Vinylidene Fluoride) in a Poly(Vinylidene Fluoride)/Poly(Methyl Methacrylate)/Dipropylene Glycol Dibenzoate System via Thermally Induced Phase Separation

The nonisothermal crystallization kinetics of poly(vinylidene fluoride) (PVDF) in PVDF/polymethyl methacrylate (PMMA)/dipropylene glycol dibenzoate (DPGDB) blends, where DPGDB served as a diluent, via solid–liquid (S-L) phase separation during a thermally induced phase separation process was investigated through differential scanning calorimetry (DSC) measurements. It was found that the Ozawa model could only describe the nonisothermal crystallization behavior of PVDF/PMMA/DPGDB system to some extent. The influence of the cooling rate and PMMA/PVDF weight ratio in the PVDF/PMMA/DPGDB system on the crystallization mechanism was also examined based on the Avrami–Jeziorny method and Mo method. Primary crystallization and secondary crystallization were observed in the Avrami–Jeziorny analysis. The analysis by the Avrami–Jeziorny and Mo models indicated that the increase of PMMA/PVDF weight ratio decreased the crystallization rate during the primary crystallization stage. The results showed that the Mo method could well explain the kinetics of the primary PVDF crystallization. The Avrami–Jeziorny method, however, could not well describe the nonisothermal crystallization process of PVDF in the primary crystallization stage. The activation energy, determined by the Kissinger method, was not suitable to reflect the PVDF crystallization process in the PVDF/PMMA/DPGDB system.     

Synthesis and Non-isothermal Crystallization Behavior of PET/Surface-treated TiO 2 Nanocomposites

Poly(ethylene terephthalate) (PET)/TiO ₂ nanocomposites were prepared by melt-blending PET and surface-treated TiO ₂ . The crystallization behavior and the non-isothermal crystallization kinetics of these composites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo's methods were applied to describe the kinetics of the non-isothermal crystallization process. It was found that the PET matrix with incorporated surface-treated TiO ₂ particles has lower crystallization temperature and melting point than that with incorporated pure nano-TiO ₂ particles. Unlike plain TiO ₂ , surface-treated TiO ₂ particles showed less effect on the degree of crystallization of the PET matrix.     

Nonisothermal Crystallization Behavior of Polypropylene Grafted Silane and Styrene Using γ-Ray Irradiation

Polypropylene grafted silane and styrene (named PP-g-Si/St in this article) was successfully prepared by radical graft polymerization initiated by γ-ray irradiation. The influence of total absorbed dose on the graft ratio of vinyltrimethoxysilane onto PP and the melt flow rate (MFR) of the PP-g-Si/St product were studied. The effect of graft ratios of vinyltrimethoxysilane on the melting point and nonisothermal crystallization kinetics of PP-g-Si/St was investigated by the method of differential scanning calorimetry (DSC). With increasing vinyltrimethoxysilane and styrene (used as viscosity modifier and free radical source) grafted on PP, the melting point of PP-g-Si/St became lower. Several different analysis methods, including those of Avrami, Jeziorny, and Mo and colleagues, were employed to describe the nonisothermal crystallization process of the grafted samples. The results indicate that the peak temperature of crystallization of PP-g-Si/St sample was lower than that of virgin PP. Crystallization kinetics revealed that the rates of nucleation and growth were affected differently by the graft ratio of vinyltrimethoxysilane onto PP. The activation energy was calculated on the basis of the method of Kissinger, and the values were 253.6 and 215.7 kJ/mol for virgin PP and PP-g-Si/St, respectively.     

Crystallization Behavior of Rare‐earth Doped Luminous Pigment/Polyamide 6 Composites

The crystallization behavior of well‐dispersed rare‐earth doped luminous pigment/polyamide 6 (PA6) composites prepared through in situ polymerization was investigated by DSC. The rare‐earth doped luminous pigments could accelerate the forming of γ form crystals and also had a great effect on the crystallinity and crystallization rate of PA6 composites. The Ozawa, Jeziorny, and Mo methods were used to analyze the non‐isothermal crystallization kinetics. It was found that the Ozawa method was unsuitable for non‐isothermal crystallization of PA6 composites. The results of Jeziorny analysis showed that the crystallization rates of PA6 composites increased when the luminous pigment content was larger than 5 wt.%. Mo's analysis also showed that the presence of the pigment shortened the crystallization time and accelerated the crystallization rate. Polarized optical microscopy showed that the spherulites became smaller with increasing of the luminous pigment amount due to the heterogeneous nucleation.     

Synthesis of Polypropylene/Attapulgite Nanocomposites and Their Crystallization Behavior Studied by Step-Scan DSC

Attapulgite (AT) was modified by grafting with butyl acrylate (BA) via polymerizations initiated by Gamma radiation. Polypropylene (PP)/AT nanocomposites were synthesized via melt extrusion in a twin-screw extruder. Fourier transform infrared (FTIR) spectroscopy and thermogravimetry (TG) were used to assess the structure of the hybrid materials and the dispersion of AT was verified by transmission electron microscopy (TEM). The crystallization kinetics of PP/AT nanocomposites were investigated by differential scanning calorimetry (DSC) and analyzed by using the Avrami method. The isothermal crystallization kinetics showed that the addition of AT increased both the crystallization rate and the isothermal Avrami exponent of PP. Step-scan differential scanning calorimetry (SDSC) was used to study the influence of AT on the crystallization and subsequent melting behavior. The results revealed that PP and PP/AT nanocomposites experienced multiple melting and secondary crystallization processes during heating. The melting behaviors of PP and PP/AT nanocomposites varied with the variation of crystallization temperature and AT content.     

Morphology,Nonisothermal Crystallization Behavior and Mechanical Properties of Polypropylene Modified by Ionomers

The morphology and nonisothermal crystallization behavior of polypropylene modified by ionomers based on ethylene copolymers (Surlyn 8920 and 9320) were investigated by using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The crystallization rate of polypropylene was accelerated by the ionomers which initiated heterogeneous nucleation of the polypropylene. At low ionomers content (0.25 wt%), Surlyn 8920, neutralized by sodium, was more efficient to enhance the crystallization rate of polypropylene than Surlyn 9320 (neutralized by zinc). The crystallization process of polypropylene modified by the ionomers was analyzed by different kinetics models. The study showed that the Mo approach was applicable for this system, whereas the Avrami, Jeziorny, and Ozawa methods were not. Furthermore, the notched impact strength of polypropylene modified by the ionomers was increased without any reduction of tensile strength and flexural modulus.     

Effects of Montmorillonite on the Nonisothermal Crystallization Behavior of the Poly(trimethylene terephthalate)/Polypropylene/Montmorillonite Nanocomposites

Organic montmorillonite (MMT) reinforced poly(trimethylene terephthalate) (PTT)/ polypropylene (PP) nanocomposites were prepared by melt blending. The effects of MMT on the nonisothermal crystallization of the matrix polymers were investigated using differential scanning colorimetry (DSC) and analyzed by the Avrami equation. The DSC results indicated that the effects of MMT on the crystallization processes of the two polymers exhibited great disparity. The PTT's crystallization was accelerated significantly by MMT no matter whether PTT was the continuous phase or not, but the thermal nucleation mode and three-dimensional growth mechanism remained unchanged. However, in the presence of MMT, the PP's crystallization was slightly retarded with PP as the dispersed phase, and was influenced little with PTT as the dispersed phase. When the MMT content was increased from 2_wt% to 7_wt%, the crystallization of the PTT phase was slightly accelerated, whereas the crystallization of the PP phase was severely retarded, especially at lower temperatures. Moreover, the nucleation mechanism for the PP's crystallization changed from a thermal mode to an athermal one. In the polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilized PTT/PP blends, with the addition of 2_wt% MMT during melt blending, the T _c (PTT) shifted 7.8°C to lower temperature and had a broadened exotherm, whereas the T _c (PP) shifted 17.1°C to higher temperature, with a narrowed exotherm. TEM analysis confirmed that part of the PP-g-MAH was combined with MMT during blending.     

Preparation and Characterization of Linear Low Density Polyethylene/Carbon Nanotube Nanocomposites

Linear low‐density polyethylene (LLDPE)/multiwalled carbon nanotube (MWNT) nanocomposites were prepared via melt blending. The morphology and degree of dispersion of nanotubes in the polyethylene matrix were investigated using scanning electron microscopy (SEM). Both individual and agglomerates of MWNTs were evident. The rheological behavior and mechanical and electrical properties of the nanocomposites were studied using a capillary rheometer, tensile tester, and Tera ohm‐meter, respectively. Both polyethylene and its nanocomposites showed non‐Newtonian behavior in almost the whole range of shear rate. Addition of carbon nanotubes increased shear stress and shear viscosity. It was also found that the materials experience a fluid‐solid transition below 1 wt% MWNT. Flow activation energy for the nanocomposites was calculated using an Arrhenius type equation. With increasing nanotube content, the activation energy of flow increases. A decrease of about 7 orders of magnitude was obtained in surface and volume resistivity upon addition of 5 wt% MWNT. In addition, a difference between electrical and rheological percolation thresholds was observed. The results confirm the expected nucleant effect of nanotubes on the crystallization process of polyethylene. A slight increase in Young's modulus was also observed with increasing MWNT content.     

Nonisothermal Crystallization Behaviors of Flame-Retardant Copolyester/Montmorillonite Nanocomposites

In order to obtain poly(ethylene terephthalate) (PET) engineering plastics with good flame retardancy, heat resistance, and mechanical properties, a novel phosphorus-containing copolyester (PET-co-DDP)/organo-montmorillonite (OMMT 1%) nanocomposite (PET-co-DDP/OMMT) was prepared by in situ intercalating polymerization. Nonisothermal crystallization kinetics and nanoscale morphology of this composite have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Based on the results of the nonisothermal crystallization kinetics, the flame-retardant copolyester PET-co-DDP has a lower crystallization rate than pure PET, while PET-co-DDP/OMMT nanocomposite has a higher crystallization rate than pure PET. Based on the Augis and Bennett method, the activation energies for nonisothermal crystallization of pure PET, PET-co-DDP, and PET-co-DDP/OMMT nanocomposite were evaluated as 101, 138, and 76 kJ mol^?1, respectively. All the evidence shows that PET-co-DDP strongly influences the crystallization behavior because of its irregular chain structure, while the addition of nanoscale OMMT to this copolymer can significantly enhance the crystallization rate owing to its remarkable nucleating effect. An understanding of the above crystalline behaviors will be beneficial in preparing PET engineering plastics with good overall comprehensive performance.     

Non‐Isothermal Crystallization Kinetics of PA6/Attapulgite Composites Prepared by Melt Compounding

The non‐isothermal crystallization behaviors of neat polyamide 6 (PA6) and PA6/attapulgite (ATB) composites were examined using differential scanning calorimetry. The results show that ATB acts as a nucleator for PA6 matrix, accelerating the crystallization, and simultaneously obstructs the crystallization especially for the composites with higher ATB content. The analysis results using the Jeziorny and Liu equations verify the dual actions of the nucleation and the obstruction of crystallization of the ATB in the PA6 matrix. Kissinger's method is employed to obtain the activation energy of the crystallization processes; the results further indicate that the addition of ATB may also cause the above actions. It is speculated that there is a very complicated crystallization mechanism in the PA6/ATB composites based on the analysis of Avrami exponents obtained by the Jeziorny model.     

Synthesis and characterization of “mulberry”-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/multiwalled carbon nanotube nanocomposites

Nanocomposites composed of multi-wall carbon nanotubes (MWNTs) and Fe₃O₄ nanoparticles were fabricated using solvothermal method. Transmission and scanning electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction measurements confirmed that these mulberry-like Fe₃O₄ microparticles which were combined with the MWNTs in a random pattern are constructed with tiny nanocrystallites (12 nm in average diameter). The magnetic properties of the Fe₃O₄/MWNTs nanocomposites were measured using a vibrating sample magnetometer. Results showed that the Fe₃O₄/MWNTs nanocomposites exhibited superparamagnetism at room temperature and possessed a lower saturation magnetization (around 27.6 emu/g) than that of the pure Fe₃O₄ nanoparticles (around 33.7 emu/g). The Fe₃O₄/MWNTs nanocomposites have potential applications in engineering and medicine.     

Effect of Organoclay Platelets on Crystallization of PTT/EPDM-g-MA Blends: Nonisothermal Melt Crystallization Kinetics

PTT/EPDM-g-MA (80/20 w/w) nanocomposites were prepared by melt mixing of poly(trimethylene terephthalate) (PTT), ethylene-propylene-diene copolymer grafted with maleic anhydride (EPDM-g-MA), and organoclay. The blend nanocomposites show typical sea-island morphologies. The nonisothermal crystallization kinetics of pure PTT and 80/20 (w/w) PTT/EPDM-g-MA blends with various amounts of the clay were extensively studied by differential scanning calorimetry (DSC). The Avrami, Ozawa, and Mo methods were used to describe the nonisothermal crystallization process of pure PTT and 80/20 (w/w) PTT/EPDM-g-MA blends with various amounts of the clay. Avrami analysis results show that the crystallization rates of 80/20 (w/w) PTT/EPDM-g-MA blends with the clay were faster than those of pure PTT or PTT/EPDM-g-MA blends without clay, which indicates that the clay particles promote crystallization effectively, in agreement with the Mo analysis results. Ozawa analysis can describe the nonisothermal crystallization of pure PTT very well but was rather inapplicable to the 80/20 (w/w) PTT/EPDM-g-MA blends with various amounts of the clay.     

Thermal and Structural Behaviors of Polypropylene Nanocomposites Reinforced with Single-Walled Carbon Nanotubes by Melt Processing Method

In this work, polypropylene (PP) matrix reinforced with several single-walled carbon nanotubes (SWNTs) concentrations were prepared by a melt-mixing method. The effect of SWNTs on the thermal degradation behavior of polypropylene was studied by thermal gravimetric analysis. The results revealed that adding the SWNTs into the PP can increase the decomposition temperature. The results obtained from differential scanning calorimetry showed that incorporating SWNTs reduced the crystallinity but increased the crystallization temperature of the PP. The mechanical measurements showed that the tensile modulus of the nanocomposite was greatly enhanced to 882 MPa, compared to 485 MPa for pristine PP. For wide-angle X-ray diffraction tests, two cooling methods were used. The addition of SWNTs to the polymer in slow-cooled samples resulted in partial crystallization in the γ -form, while SWNTs had no effect in water-cooled samples, the sample crystallizing in the α -form. Scanning electron microscopy observations on the fracture surface of the nanocomposites showed the dispersion of the SWNTs in the nanocomposites.