Study Of Non-isothermal Crystallization Kinetics Research Articles

Study of Nonisothermal Crystallization Kinetics of Unstretched and Uniaxially Stretched Electroactive PVDF Composite Films

AbstractIncorporation of graphene‐based fillers such as graphene oxide (GO) and reduced graphene oxide (rGO) into polyvinylidene fluoride (PVDF) followed by uniaxial stretching can significantly improve their electroactive phase content as well as the dielectric properties. In this study, the nonisothermal crystallization kinetics of unstretched and uniaxially stretched PVDF‐GO and PVDF‐rGO composite films are investigated through differential scanning calorimetry (DSC) at different cooling rates. Avrami‐modified Jeziorney's model is used to understand their crystallization behavior which leads to the nucleation of electroactive crystalline phases in PVDF. Avrami's exponent “n” values in the range of 2–4 are obtained for nonisothermal crystallization of PVDF in different samples which reveal both two‐ and three‐dimensional growth of spherulites in the crystalline region. Kissinger's method is used to calculate the activation energy of crystallization and the results reveal accelerated crystallization of PVDF after addition of GO and rGO fillers followed by uniaxial stretching.

Crystallization kinetics and photoluminescence studies on SiO2‐ZnGa2O4:Cr3+ glass ceramics

AbstractSiO2‐ZnGa2O4:Cr3+ glass ceramics were prepared by a sol‐gel method. The influence of TiO2 addition on the crystallization behavior and photoluminescence properties were investigated in detail. The nonisothermal crystallization kinetic studies based on Kissinger, Ozawa, and Matusita models were performed on the SiO2‐ZnGa2O4:Cr3+ glasses with different amount of TiO2. The introducing of TiO2 component as nucleant in the glasses can significantly reduce the crystallization activation energy. The results of the crystallization kinetic calculation and scanning electronic microscope observations indicated that the crystallization of ZnGa2O4:Cr3+ from the glass possessed a surface nucleation and growth mechanism. Near infrared emission of the glass ceramics was obtained under the excitation at 414 nm. The crystal field parameters around Cr3+ and excited state dynamics of Cr3+ were studied in detailed.

Functionality of Cellulose Nanofiber as Bio-Based Nucleating Agent and Nano-Reinforcement Material to Enhance Crystallization and Mechanical Properties of Polylactic Acid Nanocomposite.

Polylactic acid (PLA), a potential alternative material for single use plastics, generally portrays a slow crystallization rate during melt-processing. The use of a nanomaterial such as cellulose nanofibers (CNF) may affect the crystallization rate by acting as a nucleating agent. CNF at a certain wt.% has been evidenced as a good reinforcement material for PLA; nevertheless, there is a lack of information on the correlation between the amount of CNF in PLA that promotes its functionality as reinforcement material, and its effect on PLA nucleation for improving the crystallization rate. This work investigated the nucleation effect of PLA incorporated with CNF at different fiber loading (1–6 wt.%) through an isothermal and non-isothermal crystallization kinetics study using differential scanning calorimetry (DSC) analysis. Mechanical properties of the PLA/CNF nanocomposites were also investigated. PLA/CNF3 exhibited the highest crystallization onset temperature and enthalpy among all the PLA/CNF nanocomposites. PLA/CNF3 also had the highest crystallinity of 44.2% with an almost 95% increment compared to neat PLA. The highest crystallization rate of 0.716 min–1 was achieved when PLA/CNF3 was isothermally melt crystallized at 100 °C. The crystallization rate was 65-fold higher as compared to the neat PLA (0.011 min–1). At CNF content higher than 3 wt.%, the crystallization rate decreased, suggesting the occurrence of agglomeration at higher CNF loading as evidenced by the FESEM micrographs. In contrast to the tensile properties, the highest tensile strength and Young’s modulus were recorded by PLA/CNF4 at 76.1 MPa and 3.3 GPa, respectively. These values were, however, not much different compared to PLA/CNF3 (74.1 MPa and 3.3 GPa), suggesting that CNF at 3 wt.% can be used to improve both the crystallization rate and the mechanical properties. Results obtained from this study revealed the dual function of CNF in PLA nanocomposite, namely as nucleating agent and reinforcement material. Being an organic and biodegradable material, CNF has an increased advantage for use in PLA as compared to non-biodegradable material and is foreseen to enhance the potential use of PLA in single use plastics applications.

Non-Isothermal Crystallization and Degradation Kinetic Studies of Synthesized Mo-TG end Capped Poly(ε-Caprolactone)

The molybdenum thioglycolate (Mo-TG) end capped poly(e-caprolactone) (PCL) was prepared in the presence of novel Mo-TG nanohybrid initiator by ring opening polymerization (ROP) technique. The structural analysis was carried out by FTIR, 1H and 13C NMR techniques for the synthesized PCL. The particle size of the end capped Mo-TG nano hybrid in the PCL matrix was analysed by HRTEM. The morphology, surface roughness and average surface roughness of the polymer sample were investigated by AFM. The geometry of the nucleated crystals of PCL was examined using polarized optical microscopy (POM). The crystallization and thermal history of the sample under non-isothermal condition were assessed by DSC and TGA. The morphology of the nucleated crystals was analysed theoretically with the help of kinetic models for Mo-TG end capped PCL under non-isothermal crystallization condition. The kinetic parameters associated with crystallization and degradation processes of PCL were also determined using various kinetic models.

Nonisothermal crystallization kinetic studies on melt processed poly(ethylene terephthalate)/polylactic acid blends containing graphene oxide and exfoliated graphite nanoplatelets

ABSTRACTNonisothermal crystallization kinetics of poly(ethylene terephthalate)/polylactic acid (PET/PLA) (90/10 and 75/25 wt %/wt %) blend prepared by a melt mixing process in the presence of graphene oxide (GO) and exfoliated graphite nanoplatelets (xGnP) were investigated. The transmission electron microscope (TEM) results revealed that both the GO and xGnP were not inclined to the PLA phase, and the distribution of GO in the blend matrix was better than that of xGnP. The scanning electron microscope (SEM) results demonstrated that both the fillers showed compatibilizing effect and refined the morphology of PLA dispersed phase. The crystallinity and crystallization behavior of samples were studied by X‐ray diffraction (XRD) and multiple cooling rate Differential scanning calorimetry (DSC), respectively. The results showed that the degree of crystallinity and crystallization rate of PET was reduced by blending with PLA. Inclusion of the fillers to the blend further reduced the crystallinity while the crystallization rate was increased. Analysis based on Hoffman‐Lauritzen theory revealed that, compared to xGnP, the GO as a better nucleating agent could more effectively reduce lamella thickness and surface folding free energy of the nanocomposites. Crystallization kinetic studies by Jeziorny model revealed two levels of primary and secondary crystallization mechanisms for all samples. Moreover, activation energy of crystallization of the GO‐containing nanocomposites was lower than that of xGnP‐based systems. All the theoretical treatment and experimental results confirm that, compared to xGnP, the GO is more suitable filler and has stronger effect on enhancing the crystallization kinetic of the PET/PLA blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47569.HIGHLIGHTS Studied crystallization kinetics of PET/PLA blend containing xGnP and GO nanoplatelets Compared the role of xGnP and GO in crystallization kinetics of the system Analyzed the crystallization kinetics of the system by various models Determined the surface folding free energy of the developed systems GO‐based systems exhibited lower crystallization activation energy than that of the xGnP‐based systems

Thermal degradation and crystallization kinetics studies on synthesized calcium mercaptosuccinate end-capped poly(ε-caprolactone) nanocomposite

The calcium mercaptosuccinate (Ca-MS) functionalized poly(e-caprolactone) (PCL) was successfully synthesized by ring-opening polymerization (ROP) method at 160 °C for 2 h under nitrogen atmosphere with mild stirring in the presence of stannous octoate (SO) as ROP catalyst. The synthesized Ca-MS functionalized PCL was characterized by FTIR spectroscopy, NMR spectroscopy, atomic force microscopy, HRTEM and polarized optical microscopy (POM) like analytical techniques. The microstructure of Ca-MS nucleated PCL crystals was analysed by POM. The thermal properties of Ca-MS functionalized PCL were examined using differential scanning calorimetry and thermogravimetric analysis techniques. The non-isothermal crystallization and degradation kinetic studies were carried out to assess the crystallinity as well as the energy of activation (Ea) of Ca-MS functionalized PCL. The FTIR spectrum showed a peak at 1720 cm−1 corresponding to the carbonyl stretching of PCL. The 1H-NMR spectrum showed an alkoxy proton signal at 4.1 ppm. The non-isothermal crystallization kinetic study showed the 3D crystal growth with the Ea value of 142.4 kJ/mol.

Non-isothermal crystallization kinetics and degradation kinetics studies on barium thioglycolate end-capped poly(ε-caprolactone)

The poly(e-caprolactone) (PCL) was synthesized by ring-opening polymerization at 160 °C under nitrogen atmosphere for 2 h by bulk polymerization method in the presence of barium thioglycolate (Ba-TG) as an initiator and stannous octoate as a catalyst. The monomer-to-initiator ratio was maintained at 400. The Ba-TG end-capped PCL was characterized by various analytical tools like FTIR spectroscopy, NMR spectroscopy, AFM, DSC, TGA, POM and HRTEM. The non-isothermal crystallization kinetic study was executed with the help of DSC in order to determine the rate at which nucleation formation and spherulitic growth take place. The thermal degradation kinetic studies were performed with the help of TGA to know the degradation rate as well as energy of activation (Ea) using different non-isothermal kinetic models. The main aim of the present investigation is to determine the role of chain end-capping agent (Ba-TG) on the crystallization and degradation process of PCL. It was found that the Ba-TG induced the 3D spherulitic crystal growth of PCL.

An efficient organic additive to control the crystallization rate of aliphatic polyketone: A non-isothermal crystallization kinetics study

Three types of organic compounds—two carboxylic acids and an anhydride, were used as additives for polyketone (PK). The effect of the additive structure and their feed ratios on the melting temperature, crystallization temperature, and crystallization rate of PK were studied. We found that the crystallization temperature could be reduced significantly by introducing a small quantity of organic additive, in particular, an anhydride. On addition of 1 phr of anhydride, the crystallization temperature was reduced by 10.7 °C. Therefore, the non-isothermal crystallization kinetics of aliphatic PK/anhydride blends with various feed ratios was investigated using DSC. The results were analyzed by various theoretical models, such as Avrami, Ozawa and combined Avrami-Ozawa models.

Electroactive phase nucleation and non-isothermal crystallization kinetics study in [DEMM][TFSI] ionic liquid incorporated P(VDF-HFP) co-polymer membranes

The electroactive phase nucleation and subsequent non-isothermal crystallization kinetics of different extents of aliphatic quaternary ammonium-based ionic liquid (IL) N,N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis(trifluoromethylsulfonyl) imide ([DEMM][TFSI]) incorporated poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) co-polymer membranes have been explored using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Different macroscopic models are used to assess the overall non-isothermal crystallization parameters of the membranes. The effective activation energy (E X ) of the crystallization process of the membranes is estimated by the differential isoconversional methods of Friedman. The analysis of DSC responses, infrared spectra, and X-ray diffractograms of the different IL incorporated polymer membranes reveal that a possible interaction between the ions of the IL and disordered dipoles of the co-polymer in the melt state, essentially delays the overall crystallization process and preferentially yield different electroactive (all trans or trans-gauche) chain conformations at different cooling rates of crystallization. The proportional variation of effective activation energy and the value of the Hoffman–Lauritzen crystal growth parameters, adopting the method proposed by Vyazovkin, with the IL content also support the same.

Enhanced nonisothermal and isothermal cold crystallization kinetics of biodegradable poly(l‐lactide) by trisilanolisobutyl‐polyhedral oligomeric silsesquioxanes in their nanocomposites

ABSTRACTIn this work, the nonisothermal and isothermal cold crystallization behaviors of poly(l‐lactide) (PLLA)/trisilanolisobutyl‐polyhedral oligomeric silsesquioxanes (tsib‐POSS) nanocomposites with low tsib‐POSS contents were fully investigated. For all the samples, the variations of heating rate and the tsib‐POSS loading may influence the nonisothermal cold crystallization of PLLA. During the nonisothermal crystallization kinetics study, the Ozawa equation failed to fit the nonisothermal crystallization process of PLLA, while the Tobin equation could fit it well. For the isothermal crystallization kinetics study, the crystallization rates of all the samples increased with increasing crystallization temperature. The cold crystallization activation energy of PLLA was increased with 1 wt % tsib‐POSS. Moreover, the addition of tsib‐POSS and the increment of tsib‐POSS loading could increase the crystallization rate of PLLA, indicating the nucleating agent effect of tsib‐POSS. However, the crystallization mechanism and crystal structure of PLLA remained unchanged in the nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43896.

Thermal studies on benzamide and benzanilide grafted LDPE

Low density polyethylene (LDPE) was melt grafted with two different functionalities namely amide and anilide in an inert atmosphere at 160 °C under different experimental conditions by thermolysis method and the order of the functionalization reaction was determined. The % grafting was determined by FTIR spectroscopy quantitatively based on the relative intensity (FTIR-RI) method. It is observed that while increasing the mass% of DCP, the corrected peak area of carbonyl and C–H out-of-plane bending vibrations was increased linearly. Here, the benzamide system showed higher % functionalization than benzanilide system. DSC and TG characterized the thermal properties of the functionalized LDPE. TG studies concluded that the thermal stability of functionalized polymer was increased for both systems. A plausible reaction mechanism was used to explain the experimental results obtained. Non-isothermal crystallization kinetic study was carried out for the both benzamide and benzanilide grafted LDPE.

Morphology, Crystallization and Dynamical Mechanical Behavior of iPP/Nano-CaCO3 Composites

This article describes our study of crystallization behavior of nano-CaCO3-filled polypropylene under nonisothermal from the melt by differential scanning calorimetry (DSC). Morphology observation indicated with increasing CaCO3 content the aggregates increased. Nano-CaCO3 acted as nucleating site during nonisothermal crystallization in all iPP/nano-CaCO3 composites. For nonisothermal crystallization kinetic studies, the result indicated that the Jeziorny and Ozawa approach cannot adequately describe the nonisothermal crystallization kinetic of iPP composite. In addition, Mo equation was employed to describe the nonisothermal crystallization kinetic process with satisfied results. Dynamic mechanical analysis indicated with increasing CaCO3 content the glass transition decreased slightly.

Comparative study of non-isothermal crystallization kinetics between Fe80P13C7 bulk metallic glass and melt-spun glassy ribbon

Differential scanning calorimetry was used to investigate the thermal behavior and non-isothermal crystallization kinetics of Fe80P13C7 glassy alloy in the forms of both bulk rod and the melt-spun ribbon. The apparent activation energy E of the first crystallization event for the ribbon and bulk samples are determined to be 432±17kJ/mol and 529±26kJ/mol, respectively, by Kissinger method, and 421±17kJ/mol and 514±26kJ/mol, respectively, by Ozawa method. It is proposed that larger the apparent activation energy E in the bulk sample may be ascribed to less amount of free volume in the supercooled liquid state of the bulk sample. The crystallization kinetics of the first crystallization event in the bulk and ribbon samples has been studied by non-isothermal approach and the local Avrami exponent for the first crystallization peak is evolved to reveal the crystallization mechanism. The local Avrami exponent of the bulk sample is less than 1.5 in the whole process for the first crystallization event, which means the crystallization mechanism of diffusion-controlled growth of pre-existing nuclei. While the local Avrami exponent for the ribbon sample is in the range of 1.5–2.5 in most cases, which means the crystallization mechanism is diffusion-controlled growth of the initial crystal type, at the same time, along with the nucleation rate decreases with time. The difference in the local Avrami exponent for the first crystallization event between the bulk and ribbon sample indicates that there are higher degree of short-range order in the bulk sample than that in the ribbon sample in the supercooled liquid state. These results distinctly indicate that the difference of crystallization behavior for the first crystallization event between the bulk and ribbon samples of Fe80P13C7 glassy alloy results from the difference nature in their supercooled liquid states which is related to the as-prepared state of samples.

A study of non-isothermal primary crystallization kinetics and soft magnetic property of Co65Fe4Ni2Si15B14 amorphous alloy

The non-isothermal primary crystallization kinetics and soft magnetic properties of Co65Fe4Ni2Si15B14 amorphous alloy have been investigated using differential scanning calorimeter (DSC), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). It is found that the apparent crystallization activation energy Ec is not the same as the calculation methods of Kissinger and Doyle–Ozawa, and is 471.68 and 461.50kJ/mol, respectively. At the steady crystallization stage, the local crystallization energy decreases gradually, and the thermal stability of the residual amorphous matrix becomes weak finally. This is ascribed to the diffusion of boron atoms at elevated temperatures. As a result, this primary crystallization mechanism can be explained by JMA nucleation-and-growth model and normal grain growth kinetic mode. During crystallization, some of nanocrystals such as Co–B intermetallics, Co2Si, Fe23B6 and NiB precipitate from amorphous matrix after annealing at 773K. This leads to soft magnetic properties being improved finally.

Nonisothermal crystallization kinetics of low‐density polyethylene inside percolating network of ZnO nanoparticles

AbstractThe nonisothermal crystallization of low‐density polyethylene inside percolating network of ZnO nanoparticles (LDPE/60 vol % ZnO) was investigated via differential scanning calorimetry (DSC), and compared to that of LDPE bulk (pristine LDPE and LDPE/1.15 vol % ZnO). The results revealed that crystallization behavior of LDPE inside ZnO percolating network was quite different from that of LDPE bulk. The former showed ∼ 4°C higher crystallization onset temperatures contrasting to the latter, demonstrating nucleation effect of ZnO on LDPE crystallization. On the other hand, much longer half‐crystallization times were observed for the former, illustrating that crystallization of LDPE is retarded by the continuous ZnO network to some extent. Moreover, LDPE embedded inside ZnO network has by far larger crystallization activation energy and smaller specific free energy of the folding surface in contrast to LDPE bulk. Finally, nonisothermal crystallization kinetics study illustrated that both modified Avrami and Liu methods could be used to describe satisfactorily nonisothermal crystallization kinetics for all the samples investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Functionalization of Multiwalled Carbon Nanotubes by Poly (Ethlylene Glycol) and Non-Isothermal Crystallization Kinetic Study

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.

Nonisothermal crystallization kinetics study of LDPE/MWCNT nanocomposites: Effect of aspect ratio and surface modification

AbstractIn this article, the effect of aspect ratio and chemical modification of multiwall carbon nanotubes (MWCNT) on the nonisothermal crystallization kinetics of LDPE/MWCNT nanocomposites was studied. Nine different samples were prepared using different MWCNT to study both effects. The cooling rate (R) was varied in the range 2–10°C/min. In this article, the effect of CNT loading, surface modification, and aspect ratio were studied. For the same MWCNT concentration, aspect ratio and COOH modification had weak influence on both the peak crystallization temperature and the crystallization onset temperature. However, the crystallization onset temperature was significantly affected by the amount of MWCNT. The rate parameters in the modified Avrami method and Mo method [F(T)] of analyses show a very good fit of data. The Vyazovkin and Sbirrazzuoli method of analysis, which is based on Hoffman–Lauritzen theory for secondary crystallization, was also used. Temperature dependency of activation energy was obtained for 30–75% relative crystallinity of the produced nanocomposites. Activation energy based on calculations of Hoffman‐Lauritzen theory showed a decrease with the increase in the concentration of MWCNT and crystallization temperature. A proposed model of the form E = a exp (‐bXT) which relates the activation energy, E, to relative crystallinity, X, and crystallization temperature, T, was able to fit the whole set of data. Incorporation of MWCNT in nanocomposites lowers the activation energy; hence enhances the initial crystallization process as suggested by the different methods of data analyses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Optical–electrical hybrid operation with amorphous Ge1Sb4Te7 phase change thin films

Based on study of non-isothermal crystallization kinetics and orthogonal test of pulsed-laser crystallization parameters of Ge1Sb4Te7, minimum nanosecond laser pulse duration (threshold) for crystallization recording was used for optical–electrical hybrid operation. The crystallized bits arrays were optically recorded with minimum pulse duration of 40 ns and electrically read out with maximum current signal contrast of ∼20 times.

The effect of fluoride ions on the structure and crystallization kinetics of La 2O 3-containing diopside based oxyfluoride glasses

Oxyfluoride glasses in the system CaO–MgO–BaO–SiO 2–Al 2O 3–La 2O 3–CaF 2 were obtained by adding CaF 2 (3–8 wt%) to a parent diopside based glass composition, Ca 0.8Ba 0.1MgAl 0.1La 0.1Si 1.9O 6. The characterization of the glasses has been made by density, dilatometry and FTIR measurements. Non-isothermal crystallization kinetic studies in conjunction with XRD and SEM have been employed in order to investigate the effects of fluoride ion additions on crystallization behaviour and mechanism of glasses.

The application of differential thermal analysis to the study of isothermal and non-isothermal crystallization kinetics of coal fly ash based glasses

The crystallization kinetics of glasses obtained from coal fly ash was investigated by both isothermal and non-isothermal methods using differential thermal analysis (DTA) data. In DTA experiments, glass samples having coarse (800–1000 μm) and fine (<180 μm) particle sizes were used and the results were compared. The Avrami exponent (n) was calculated by means of Johnson–Mehl–Avrami (JMA) and Ozawa equations. Calculated kinetic parameters indicated that the appropriate crystallization mechanisms were bulk and surface crystallization for coarse and fine particles, respectively. Isothermal and non-isothermal DTA experiments showed that the crystallization activation energies of coarse glasses are changed in the range of 444–578 kJ/mol, while the crystallization activation energies of fine glasses are changed in the range of 610–662 kJ/mol. It was found that crystallization activation energies of fine glasses are higher than those of the coarse glasses. Results showed that isothermal and non-isothermal crystallization kinetics of glasses produced from coal fly ash is in agreement within the experimental error.