Parameters Of Non-isothermal Crystallization Research Articles

Non-isothermal crystallization behavior of Ag nanoparticles modified expanded graphite/paraffin composite phase change material

The thermal conductivity enhancement fillers and supporting material have significant influence on the crystallization process of phase change materials (PCMs) in composite PCMs. In this work, the non-isothermal crystallization behavior of Ag nanoparticles modified expanded graphite/paraffin (AEP) composited PCMs was studied to analyze the effect of expanded graphite (EG) and Ag nanoparticles on the crystallization process of paraffin wax (PW). The results showed that non-isothermal crystallization parameters of t1/2 and F(T) and activation energy of 0-AEP was lower than those of PW, indicating that the crystal growth and nucleation of PW were accelerated by EG. After Ag nanoparticles were modified, the t1/2 and F(T) and the activation energy of AEP were increased which were higher than that of 0-AEP but still lower than that of pure PW, revealing that the crystal growth and nucleation of PW were restricted by the surface interaction between Ag and PW. The non-isothermal crystallization analysis results provide a valuable reference for deeply understanding phase change behavior and kinetics of the CPCMs.

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.

Nonisothermal Crystallization Kinetics of Poly(lactic acid) Nucleated with a Multiamide Nucleating Agent

Addition of a commercial available multiamide compound (N,N′,N′′-tricyclohexyl-1,3,5- benzenetricarboxylamide, defined here as TMC) into ecofriendly poly(lactic acid) (PLA) can accelerate the crystallization rate of the material remarkably and broaden its applications. In this paper, the nonisothermal crystallization behavior of biodegradable PLA nucleated by 0.3 wt.% of TMC was investigated by differential scanning calorimetry (DSC). The modified Avrami, Tobin, Ozawa, and Mo models were applied to describe the kinetics of the crystallization process. Various parameters of nonisothermal crystallization, such as the crystallization half-time and crystallization rate constant, reflected that TMC significantly accelerated the crystallization process. The activation energy values of the neat PLA and PLA/TMC blend, determined by the Kissinger method, increased with the addition of TMC. The study should be helpful for understanding the relationship between processing and properties of this material.

Study on crystallization performance of polyethylene terephthalate/polybutylene terephthalate alloys

Abstract Polyethylene terephthalate (PET) is a kind of high performance engineering plastic. However, the application of pure PET is subject to limitation because of its slow crystallization rate. In order to overcome this difficulty, thermoplastic resins are often added into PET matrix by a compounding technique. Polybutylene terephthalate (PBT) possesses many advantages such as a high degree of crystallinity and rapid molding, thus, is very suitable to adjust the crystallization behaviors of PET. In this work, the crystallization behaviors of PET/PBT alloys were studied by a differential scanning calorimeter (DSC) and thermal platform polarizing microscope. The obtained results indicate that the content of PBT could tune the melting and crystallization behaviors of the alloy. The parameters of non-isothermal crystallization of the alloys for blends were analyzed by the Jeziorny and Kissinger methods. The non-isothermal crystallization process for PET, PBT and PET/PBT alloys fit the Jeziorny model well at the early stage, but there is a certain small deviation at the later stage, indicating that the nucleation mechanism of PET/PBT alloy is complicated. In addition, the crystallization rate accelerates with an increase in cooling rate. The alloys show the best crystallization performance when the content of PBT is 10 wt%, and their crystallization activation energy reaches up to -201.78 kJ/mol.

Kinetics of crystallization in selenium molybdate glass

In this work we have studied isothermal and non-isothermal crystallization kinetics in Ag2O modified selenium molybdate glass employing differential scanning calorimetry. Activation energies for crystallization and glass transition were estimated following Ozawa and Kissinger methods. The value of the Avrami exponent was determined from the experimental results and was related to the nature of crystal nucleation and growth. The Matusita model was employed to extract non-isothermal crystallization parameters. The applicability of the Johnson–Mehl–Avrami (JMA) model to both isothermal and non-isothermal cases was tested. We showed that the JMA model gave the best description of isothermal crystallization, whereas the Sestak–Berggren (SB) model described the non-isothermal transformation kinetics adequately.

Calculation of non-isothermal crystallization parameters for the Cu 15(As 2Se 3) 85 metal-chalcogenide glass

This work analyzes the possibility of using an alternating series development in deriving the relations allowing the determination of the parameters of non-isothermal crystallization. When this series development is applied onto the process of non-isothermal glass crystallization it suffices to take only the first term of the series. Linear fitting yields a relation from which one can determine the Avrami parameter n, dependent on the crystallization mechanism, and the activation energy. By an analogous procedure, taking the first two terms of the developed series, one obtains the Matusita equation. Both of these relations hold also when the temperature T is only somewhat higher than the initial T o , and not only when T > > T o . Experimental measurements by differential scanning calorimetry method and the application of the relations derived, as well as of other standard methods for calculating parameters of non-isothermal crystallization, were performed for the chalcogenide glass Cu 15(As 2Se 3) 85.

Nonisothermal crystallization behavior of highly exfoliated polypropylene/clay nanocomposites prepared by in situ polymerization

AbstractPolypropylene/clay nanocomposites (PPCNs) were prepared via an in situ polymerization method with a Ziegler–Natta/clay compound catalyst in which the MgCl2/TiCl4 catalyst was embedded in the clay galleries. The wide‐angle X‐ray diffraction and transmission electron microscopy results showed that the clay particles were highly exfoliated in the polypropylene (PP) matrix. The nonisothermal crystallization kinetics of these PPCNs were investigated by differential scanning calorimetry at various cooling rates. The nucleation activity were calculated by Dobreva's method to demonstrate that the highly dispersed silicate layers acted as effective nucleating agents. The Avrami, Jeziorny, Ozawa, and Mo methods were used to describe the nonisothermal crystallization behavior of the PP and PPCNs. Various parameters of nonisothermal crystallization, such as the crystallization half‐time, crystallization rate constant, and the kinetic parameter F(t), reflected that the highly exfoliated silicate layers significantly accelerated the crystallization process because of its outstanding nucleation effect. The activation energy values of the PP and PPCNs determined by the Kissinger method increased with the addition of the nanosilicate layers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Crystallization behavior of carbon black‐filled polypropylene and polypropylene/epoxy composites

AbstractThe crystallization behavior of polypropylene (PP)/carbon black (CB) and PP/epoxy/CB composites was studied with differential scanning calorimetry (DSC). The effects of compatibilizer MAH‐g‐PP and dynamic cure on the crystallization behavior are investigated. The nonisothermal crystallization parameters analysis showed that CB particles in the PP/CB composites and the dispersed epoxy particles in the PP/epoxy composites could act as nucleating agents, accelerating the crystallization of the composites. Morphological studies indicated that the incorporation of CB into PP/epoxy resulted in its preferential localization in the epoxy resin phase, changing the spherical epoxy particles into elongated structure, and thus reduced the nucleation effect of epoxy particles. Addition of MAH‐g‐PP significantly decreased the average diameter of epoxy particles in the PP/epoxy and PP/epoxy/CB composites, promoting the crystallization of PP more effectively. The isothermal crystallization kinetics and thermodynamics of the PP/CB and PP/epoxy/CB composites were studied with the Avrami equation and Hoffman theory, respectively. The Avrami exponent and the crystallization rate of the PP/CB composites were higher than those of PP, and the free energy of chain folding for PP crystallization decreased with increasing CB content. Addition of MAH‐g‐PP into the PP/epoxy and PP/epoxy/CB composites increased the crystallization rate of the composites and decreased the chain folding energy significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 104–118, 2006

Mutual influence of LDPE and PP in their blends during crystallization

An indication for the mutual influence of LDPE and PP was the change of the morphology parameters of PE and PP at different ratios of the polymers in blends. That influence depends on the blend composition and is different for PE and PP. It is especially interesting in the blend PE75/PP25 where the influence between PE and PP shows dependence also on the sample geometry. Melting parameters, non-isothermal crystallization parameters - crystallization peak temperature Tc, crystallization begin temperature Tonset, half-width w1/2 of the crystallization peak, degree of crystallinity α and crystallization rate coefficient CRC, as well as the isothermal kinetics parameters showed dependence on the blend composition. It was established that PE is more stable then PP concerning the mutual influence of both polymers on their crystallization. It was established that PE affects the crystal nucleation of PP and causes a decreasing of PP spherulite size.

Nonisothermal Crystallization Behavior of Poly(ethylene terephthalate)-Nylon 6 Blends

Nonisothermal crystallization behavior of blends of poly(ethylene terephthalate) (PET)-nylon 6 has been investigated. Component polymers in the blends exhibited separate crystallization and melting peaks. Nonisothermal crystallization parameters, like rate of crystallization, has changed for both the component polymers, whereas the degree of crystallinity has increased for PET with increasing amount of nylon 6 in the blends and decreased for nylon 6 with increasing amount of PET in blends. Thus blending seems to have improved crystallization parameters.

Assessing polymer crystallizability from nonisothermal crystallization behavior

AbstractCrystallization of polymers plays an important role in polymer processing because the structure developed during crystallization influences the mechanical and physical properties of the polymer product. The crystallization of polymers takes place under nonisothermal crystallization is essential for optimizing the processing conditions to obtain a product with desired properties. A simple approach based upon analysis of the nonisothermal crystallization behavior of a polymer to characterize the inherent crystallizability of the polymer and its sensitivity to processing conditions is reported. The polymers used in the present investigation include various grades of polyethylenes and polypropylenes. It is shown that a simple graphical analysis of the nonisothermal crystallization parameters can be used to quantify the inherent crystallizability of polymers and sensitivity of its structure development to changes in the cooling rates. © 1993 John Wiley & Sons, Inc.