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1.
The non-isothermal crystallization kinetics of pure poly(ethylene terephthalate) (PET), PET/mica and PET/TiO2-coated mica composites were investigated by differential scanning calorimetry with different theoretical models, including the modified Avrami method, Ozawa method and Mo method. The activation energies of non-isothermal crystallization were calculated by Kissinger method and Flynn–Wall–Ozawa method. The results show that the modified Avrami equation and Ozawa theory fail to describe the non-isothermal crystallization behavior of all composites, while the Mo model fits the experiment data fair well. It is also found that the mica and TiO2-coated mica could act as heterogeneous nucleating agent and accelerate the crystallization rates of PET, and the effect of TiO2-coated mica is stronger than that of mica. The result is further reinforced by calculating the effective activation energy of the non-isothermal crystallization process for all composites using the Kissinger method and the Flynn–Wall–Ozawa method.  相似文献   

2.
Titanium dioxide (TiO2) nanoparticles were pretreated with excessive toluene‐2,4‐diisocyanate (TDI) to synthesize TDI‐functionalized TiO2 (TiO2‐NCO), and then polymeric nanocomposites consisting of polyamide 6 (PA6) and functionalized‐TiO2 nanoparticles were prepared via a melt compounding method. The interfacial interaction between TiO2 nanoparticles and polymeric matrix has been greatly improved due to the isocyanate ( NCO) groups at the surface of the functionalized‐TiO2 nanoparticles reacted with amino groups ( NH2) or carboxyl ( COOH) groups of PA6 during the melt compounding and resulted in higher tensile and impact strength than that of pure PA6. The nonisothermal crystallization kinetics of PA6/functionalized TiO2 nanocomposites was investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization DSC data were analyzed by the modified‐Avrami (Jeziorny) methods. The results showed that the functionalized‐TiO2 nanoparticles in the PA6 matrix acted as effective nucleation agents. The crystallization rate of the nanocomposites obtained was faster than that of the pure PA6. Thus, the presence of functionalized‐TiO2 nanoparticles influenced the mechanism of nucleation and accelerated the growth of PA6 crystallites. POLYM. COMPOS., 35:294–300, 2014. © 2013 Society of Plastics Engineers  相似文献   

3.
D. Olmos  P.D. Castrillo 《Polymer》2009,50(7):1732-550
The influence of high energy ball milling process, HEBM, and the presence of TiO2 nanoparticles on the non-isothermal crystallization and fusion behavior of the HDPE were investigated. HEBM was used to homogeneously disperse TiO2 nanoparticles into a high density polyethylene, HDPE. Differential scanning calorimetry was used to analyze their non-isothermal crystallization and fusion behavior while, with X-ray diffraction the crystalline structures were determined. Atomic force microscopy was used to study the influence of the presence of nanoparticles on the final morphology of the polymer. It has been demonstrated that HEBM is a good method to prepare nanocomposites of well dispersed TiO2 nanoparticles within an HDPE matrix. When nanoparticles are absent the HEBM induces reduction of crystallinity of the polymer although a double crystallization process was observed; however, when nanoparticles are present, in addition of being favored the appearance of a metastable monoclinic phase, the fraction of crystals increases as milling time increases. AFM clearly showed how well dispersed were the TiO2 nanoparticles within the HDPE and how they are localized exactly between the lamellas. This result is the first clear visual evidence confirming that well dispersed nanoparticles actually do not act as nucleating agents in semicrystalline polymers. It was also shown that a 2% by weight of well dispersed TiO2 nanoparticles within the HDPE matrix induces a more homogeneous crystallization leading to denser spherulites with thicker lamellae.  相似文献   

4.
The study of the non‐isothermal crystallization behavior of poly(trimethylene terephthalate) (PTT)/TiO2 nanocomposites using untreated and surface‐treated TiO2 has been carried out with different theoretical models. The PTT/untreated TiO2 and surface‐treated TiO2 nanocomposites were prepared employing batch mixing technique with an aim to investigate the influence of the TiO2 dispersion on the crystallization behavior. The nucleation efficiency of the TiO2 nanoparticles has been demonstrated with the use of Avrami and Jeziorny models. Test results indicated that the PTT matrix with surface‐treated TiO2 particles has higher crystallization temperature and melting point than those with untreated PTT/TiO2 nanocomposites. Unlike untreated TiO2, surface‐treated TiO2 particles also showed less effect on the degree of crystallization of the PTT matrix. The TiO2 nanoparticles act as a nucleating agent in the PTT matrix by reducing the t½ of the crystallization time, thus making it easy to form crystals. © 2012 Society of Plastics Engineers  相似文献   

5.
Poly(ethylene terephthalate) (PET)/Barite nanocomposites were prepared by direct melt compounding. The nonisothermal melt crystallization kinetics of pure PET and PET/Barite nanocomposites, containing unmodified Barite and surface‐modified Barite (SABarite), was investigated by differential scanning calorimetry (DSC) under different cooling rates. With the addition of barite nanoparticles, the crystallization peak became wider and shifted to higher temperature and the crystallization rate increased. Several analysis methods were used to describe the nonisothermal crystallization behavior of pure PET and its nanocomposites. The Jeziorny modification of the Avrami analysis was only valid for describing the early stage of crystallization but was not able to describe the later stage of PET crystallization. Also, the Ozawa method failed to describe the nonisothermal crystallization behavior of PET. A combined Avrami and Ozawa equation, developed by Liu, was used to more accurately model the nonisothermal crystallization kinetics of PET. The crystallization activation energies calculated by Kissinger, Takhor, and Augis‐Bennett models were comparable. The results reveal that the different interfacial interactions between matrix and nanoparticles are responsible for the disparate effect on the crystallization ability of PET. POLYM. COMPOS., 31:1504–1514, 2010. © 2009 Society of Plastics Engineers  相似文献   

6.
Non-isothermal crystallization kinetics of polypropylene (PP)/methylacryloypropy polyhedral oligomeric silsesquioxanes (MAP-POSS) nanocomposites (PP/MAP-POSS) were investigated by DSC at various cooling rates. Jeziorny and Mo method were used to study the non-isothermal crystallization kinetics. The results show that the Jeziorny and Mo method are all successful in describing the non-isothermal crystallization kinetics of PP/MAP-POSS nanocomposites. The MAP-POSS can act a role of heterogeneous nucleation and increase the crystallization rate constant Z c and decrease crystallization half time t 1/2, and the spherulite crystal size decreases, the inter-spherulitic action or crosslinking structure each other appear at the appropriate content. The DSC peak temperature T p increase about 5 °C, t 1/2 reduce 0.21 min at 6 % content of MAP-POSS and heating rate of 10 °C/min. The MAP-POSS can also increase the mechanical property of PP/MAP-POSS nanocomposites, the tensile strength and impact strength increase from 12.97 to 19.93 MPa and from 33.2 to 52.6 kJ/m2, respectively, at 4 % content of MAP-POSS. But the spherulitic crystal becomes larger and boundaries become clearer again; the macrophase separation will occur and mechanical properties decrease when more and more MAP-POSS was added. The nanocomposite has the best mechanical property at 4 % content of MAP-POSS.  相似文献   

7.
Poly(ethylene terephthalate) (PET)/SiO2 nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO2 nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO2 nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO2 nanoparticles exhibited strong nucleating effects. It was found that SiO2 nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006  相似文献   

8.
Poly(ethylene sebacate) (PESeb) and PESeb/silica nanocomposites (PESeb/SiO2) were prepared by in situ polymerization from the direct esterification of ethylene glycol with sebacic acid in the presence of proper amounts of silica nanoparticles. The non-isothermal crystallization behavior of PESeb/SiO2 nanocomposites has been studied using different theoretical equations such as Avrami, Ozawa and combined Avrami and Ozawa equations. It is found that the addition of nanoparticles of SiO2 influenced the mechanism of nucleation and the growth of PESeb crystallites. Also, the nanocomposites show a higher Avrami value than the neat PESeb, implying a more complex crystallization configuration. Moreover, the combined Avrami and Ozawa equation can successfully describe the crystallization model under the non-isothermal crystallization. The crystallization activation energies, E a, calculated from “Kissinger’s equation” have shown that the synthesized PESeb/SiO2 nanocomposites have lower energy than the neat PESeb, reflecting the much lower energy barrier for the rapid heterogeneous nucleation.  相似文献   

9.
The nonisothermal crystallization kinetics of polyoxymethylene (POM), polyoxymethylene/Na–montmorillonite (POM/Na–MMT), and polyoxymethylene/organic–montmorillonite (POM/organ–MMT) nanocomposites were investigated by differential scanning calorimetry at various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the nonisothermal crystallization process of POM/Na–MMT and POM/organ–MMT nanocomposites. The difference in the values of the exponent n between POM and POM/montmorillonite nanocomposites suggests that the nonisothermal crystallization of POM/Na–MMT and POM/organ–MMT nanocomposites corresponds to a tridimensional growth with heterogeneous nucleation. The values of half‐time and the parameter Zc, which characterizes the kinetics of nonisothermal crystallization, show that the crystallization rate of either POM/Na–MMT or POM/organ–MMT nanocomposite is faster than that of virgin POM at a given cooling rate. The activation energies were evaluated by the Kissinger method and were 387.0, 330.3, and 328.6 kJ/mol for the nonisothermal crystallization of POM, POM/Na–MMT nanocomposite, and POM/organ–MMT nanocomposite, respectively. POM/montmorillonite nanocomposite can be as easily fabricated as the original polyoxymethylene, considering that the addition of montmorillonite, either Na–montmorillonite or organ–montmorillonite, may accelerate the overall nonisothermal crystallization process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2281–2289, 2001  相似文献   

10.
The aim of this study was to investigate the crystallization behavior and UV‐protection property of polyethylene terephthalate (PET)‐ZnO nanocomposits. PET‐ZnO nanocomposites containing 0.5–3.0 wt % of ZnO were successfully synthesized by in situ polymerization. The Fourier transformed infrared (FTIR) spectroscopy indicated the silane coupling agent was anchored onto the surface of ZnO. Scanning electron microscope (SEM) images showed ZnO particles were dispersed homogeneously in PET matrix with amount of 0.5–1.0 wt %. Differential scanning calorimetry (DSC) results exhibited that the incorporation of ZnO into PET resulted in increase of the melting transition temperature (Tm) and crystallization temperature (Tc) of PET‐ZnO nanocomposites. The crystallization behavior of PET and PET‐ZnO nanocomposites was strongly affected by cooling rate. ZnO nanoparticles can act as an efficient nucleating agent to facilitate PET crystallization. UV–vis spectrophotometry showed that UV‐ray transmittance of PET‐ZnO nanocomposites decreased remarkably and reached the minimum value of 14.3% with 1.5 wt % of ZnO, compared with pure PET whose UV‐ray transmittance was 84.5%. PET‐ZnO nanocomposites exhibited better UV‐protection property than pure PET, especially in the range of UVA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

11.
Nonisothermal melt crystallization kinetics of syndiotactic polypropylene (sPP)/alumina nanocomposites were investigated via differential scanning calorimetry. The addition of alumina nanoparticles significantly increases the number of nuclei and promotes the crystallization rate of sPP. Nonisothermal melt crystallization kinetics was analyzed by fitting the experimental data to a Nakamura model using Matlab. The average values of Avrami exponent n are 1.7 for both sPP and sPP/Al2O3 nanocomposites during slow cooling, which implies a two‐dimensional growth is the predominant mechanism of crystallization following a heterogeneous nucleation. The two nanocomposites give n values equal to 2.3 during faster cooling, indicating that the main growth type taking place for sPP/alumina nanocomposites is also the two‐dimensional growth. The subsequent melting behavior shows that the presence of alumina nanoparticles changed both the cold crystallization and the recrystallization of sPP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

12.
Poly(?‐caprolactone) (PCL)/titanium dioxide (TiO2) nanocomposites were prepared by in situ polymerization of ?‐caprolactone in the presence of modified‐TiO2 nanoparticles as initiators. The molecular weight of PCL matrix was dependent on the amount of the TiO2 fillers. The incorporation of TiO2 did not significantly affect the crystalline structure of PCL. Moreover, a tendency of the nanoparticles to form aggregates was observed, especially at higher fillers contents. The analysis of the crystallization process showed that the addition of TiO2 nanoparticles accelerated the crystallization rate of PCL, and the crystallization rates increased by increasing the filler content. The crystallization activation energy dependence on the filler content observed here is probably the consequence of the two competing factors. The tendency of activation energy obtained by nonisothermal crystallization is similar to that of isothermal crystallization. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers  相似文献   

13.
Photodegradable styrene–butadiene rubber (SBR)/TiO2 nanocomposites were prepared by a colloidal route through the simple mixing of a commercial polymer latex and synthetic anatase nanoparticles. Stable colloids of pure anatase TiO2 nanoparticles with an average diameter of 7 nm were prepared by a solvothermal route from the hydrolysis of titanium alkoxide by hydrogen peroxide in the presence of oleic acid. The photocatalytic degradation of the SBR–TiO2 nanocomposites was carried out in ambient air at room temperature under a UV lamp and was monitored by Fourier transform infrared and UV–visible spectroscopies and differential scanning calorimetry. The results show that the SBR–TiO2 nanocomposites were photocatalytically degraded under UV light, which indicate that the butadiene chains in the nanocomposite were oxidized during UV irradiation. Thermal analysis measurements indicated that crosslinking reactions occurred. The presence of anatase TiO2 nanoparticles was found to accelerate the photocatalytic process, and the degradation mechanism was similar to that of the pure SBR polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

14.
A study of the nucleation effect of TiO2 in poly(trimethylene terephthalate)/TiO2 nanocomposite has been carried out using different theoretical models. The models were applied and developed with the aim to describe and better understand the influence of the TiO2 dispersion on crystallization characteristics of PTT. The PTT/TiO2 nanocomposites with untreated and surface‐treated TiO2 were prepared by the melt mixing method. The nucleation efficiency of the TiO2 nanoparticles has been analyzed with the use of the Avrami model and Mo's method. It was found that the PTT matrix incorporated with surface‐treated TiO2 particles has a higher crystallization temperature and melting point than that incorporated with untreated TiO2 particles. As per the models, unlike untreated TiO2, surface‐treated TiO2 particles had a lesser effect on the degree of crystallization of the PTT matrix. The TiO2 nanoparticles act as a nucleating agent in the PTT matrix thereby reducing t½ of the crystallization and leading to easier crystallization of the polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

15.
Nanocomposites based on neodymium‐doped titanium dioxide (Nd‐TiO2)/poly(n‐butyl methacrylate) (PBMA) have been prepared by an in situ polymerization of butyl methacrylate monomer with varying concentrations of Nd‐TiO2 nanoparticles. The resulting nanocomposites have been analyzed by ultraviolet (UV)–Visible spectroscopy, Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis, and impedance analyzer (TGA). The results of UV and FTIR spectroscopy have indicated the interaction of nanoparticles with the PBMA matrix. Spherically shaped nanoparticles with an average size of 10–25 nm have been revealed in the TEM and their homogeneous dispersion, and interaction of polymer matrix has been confirmed by SEM and XRD studies. The thermal stability and glass transition temperature of the composites were significantly enhanced by the addition of nanoparticles. The AC conductivity and dielectric properties of nanocomposites have been found to be higher than pure PBMA, and the maximum electrical properties have been observed for 7 wt% composite. The reinforcing nature of the nanoparticles in PBMA has been reflected in the improvement in tensile strength measurements. The result indicated that the tensile strength of nanocomposites have greatly enhanced by the addition of Nd‐TiO2 nanoparticles whereas the elongation at break decreases with the loading of nanofillers. To understand the mechanism of reinforcement, tensile strength values have been correlated with various theoretical modeling. The research has been found to be promising in the development of novel materials with enhanced tensile strength, dielectric constant, and thermal properties, which may find potential applications in energy storage and nanoelectronic devices. J. VINYL ADDIT. TECHNOL., 25:9–18, 2019. © 2018 Society of Plastics Engineers  相似文献   

16.
The crystallization of polyethylene terephthalate (PET) and its effect on the electrical behavior of nanocomposites of PET and carbon nanotubes (CNTs) was studied. A series of nanocomposites composed of polyethylene terephthalate/carbon nanotubes (PET/CNTs) containing 0, 1 and 2% wt/wt carbon nanotubes were prepared by melt extrusion. The morphology developed by the nanocomposites during non-isothermal crystallization at different cooling rates was evaluated using various experimental techniques. Thermal analysis showed an increase in the crystallization temperature of the nanocomposites, which was associated with the nucleation ability of the CNTs, and confined growth that resulted in a 3D-to-1D reduction in the crystallite geometry of the nanocomposites. X-ray diffraction indicated that the crystal structure of the nanocomposites was not affected by the presence of carbon nanotubes or the cooling rate. However, the crystallinity of PET and the nanocomposites increased as the cooling rate decreased. The electrical conductivity of the materials as a function of the cooling rate, at a constant CNT content, showed a marked (two orders of magnitude) increase in passing from the amorphous state to the crystalline state. The results of theoretical calculations indicated self-assembly between the surface of the nanotubes and the aromatic ring of PET; it was proposed that the stacking of aromatic rings on the surface of the nanotubes has an effect on the rearrangement of electric charge.  相似文献   

17.
This work reports an in situ WAXS and SAXS investigation, under X‐ray synchrotron source radiation, on the structural evolution during solid‐state uniaxial deformation of poly(ethylene terephthalate) (PET) nanocomposites with 0.3 wt % of 3D nanoparticles [nanotitanium dioxide (TiO2) and nanosilica (SiO2)]. Good dispersion and average agglomerate sizes of nanoparticles of about 80 nm for both nanocomposites were revealed by transmission electron microscopic characterization. The influence of the nanofillers on the deformation‐induced phase's formation and their evolution along the stretching process were compared with respect to the neat PET. WAXS results indicated that the structural evolution of all samples passes through three main stages, with evolution of amorphous phase into mesophase, a rapid increase of molecular orientation, and the formation of a periodical mesophase (PM). The incorporation of the nanofillers promoted a higher fraction, and an earlier formation, of PM during stretching when compared with pure PET. Furthermore, the presence of TiO2 nanoparticles in the PET matrix resulted in the earliest formation and the highest amount of PM and the retardation of crack growth and bigger voids when compared with PET/SiO2 nanocomposite. A multiscale structural evolution mechanism is proposed to interpret these results. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39752.  相似文献   

18.
Monomer casting polyamide 6(MCPA6)/toluene 2,4-diisocyanate functionalized multi-walled carbon nanotubes (MWNTs-NCO) nanocomposites were prepared via in situ anionic ring opening polymerization, and the non-isothermal crystallization behavior of the nanocomposites were investigated by differential scanning calorimetry with various cooling rates. The commonly used Avrami, Ozawa, Mo, and Urbanovici–Segal models were employed to analyze the non-isothermal crystallization data and the validity of the models on the process of MCPA6 and its nanocomposites was discussed, where Mo and Urbanovici–Segal models could well describe the non-isothermal crystallization process for the samples. The results revealed that MWNTs could accelerate the crystallization process of MCPA6, attributing to the nucleating effect of the nanofillers. Finally, the effective energy barrier for non-isothermal crystallization was evaluated as a function of the relative crystallinity by applying an isoconversional method.  相似文献   

19.
Nanostructural TiO2/modified multi-wall carbon nanotubes photocatalysts were prepared by hydrolysis of Ti(iso-OC3H7)4 providing chemical bonding of anatase TiO2 nanoparticles onto oxidized- or amino-functionalized multi-wall carbon nanotubes (MWCNT). The processes of functionalization of the MWCNT and the deposition of TiO2 influence the photocatalytic activity of the synthesized nanocomposites. The phase composition, crystallite size, and the structural and surface properties of the obtained TiO2/modified-MWCNT nanocomposite were analyzed from XRD, FEG-SEM, TEM/HRTEM and FTIR data, as well low temperature N2 adsorption. In the photocatalytic study, the TiO2/oxidized-MWCNT catalyst showed the highest and the TiO2/amino functionalized-MWCNT catalysts somewhat lower degradation rates, indicating that the enhancement of photocatalysis was supported by the more effective electron transfer properties of the oxygen- than amino-containing functional groups, which support the efficient charge transportation and separation of the photogenerated electron-hole pairs.  相似文献   

20.
In this study, the effects of the surface chemical modification of titanium dioxide (TiO2) nanoparticles and their addition into polyamide 11 (PA11) on the mechanical, dynamic‐mechanical, and tribological properties of PA11/TiO2 nanocomposites were investigated. To improve the interfacial adhesion between the nanoparticles and the polymeric matrix, the surface of TiO2 nanoparticles was modified with 3‐aminopropyl trimethoxysilane (ATPMS). Nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermogravimetric analysis (TG) were used to evaluate the efficiency of the surface chemical modification of TiO2 nanoxide. PA11/TiO2 nanocomposites with 2 and 4 wt% of TiO2 were prepared in an internal mixer. The interfacial adhesion between the matrix and the TiO2 was evaluated by dynamic‐mechanical analysis (DMA), and the dispersion of nanoparticles was analyzed by scanning electron microscopy (SEM). The NMR spectrum of the modified TiO2 exhibited peaks in the region between −55 ppm and −70 ppm, indicating disubstituted and trisubstituted chemical structures between alkoxysilano structures and TiO2. Nanocomposites with modified TiO2 exhibited the lowest tan δ peak values, which provide evidence that the chemical modification of the TiO2 facilitated energy dissipation at the interface of TiO2 with the PA11 matrix. Surface modification of the TiO2 nanoparticles with ATPMS caused a greater reduction of the mass loss by abrasion when compared with nonmodified PA11/TiO2 nanocomposites; this reduction reached approximately 70% in comparison with the mass loss of neat PA11. POLYM. COMPOS., 37:1415–1424, 2016. © 2014 Society of Plastics Engineers  相似文献   

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