Melt Crystallization Kinetics Research Articles

The effect of tetra‐needle‐like zinc oxide whisker as additive on the crystallization kinetics of polybutylene adipate terephthalate/polylactic acid blend

AbstractHerein, we investigate the effect of the addition of tetra‐needle‐like zinc oxide whisker (T‐ZnOw), a novel reinforcing additive, on the melt crystallization behavior of biodegradable polybutylene adipate terephthalate (PBAT)/polylactic acid (PLA) polymer blends. PBAT and PLA were blended in a Haake mixer at a fixed weight ratio of 70/30, and the contents of T‐ZnOw varied from 0 to 7 wt%. The melt thermal properties and crystallization behavior of PBAT/PLA blends and PBAT/PLA/T‐ZnOw composites were studied using differential scanning calorimetry. The kinetics of melt crystallization have been quantitatively explained using a range of mathematical formalisms. The Avrami equation is adopted to analyze the isothermal crystallization process and kinetics of PBAT/PLA/T‐ZnOw composites. For its nonisothermal crystallization process and kinetics, the Ozawa equation cannot describe the entire process, while the Jeziomy‐modified Avrami equation can only describe the initial stage of its nonisothermal crystallization. Using Mo‐analysis, the impact of T‐ZnOw contents on the composite's nonisothermal crystallization kinetic has been thoroughly examined. Given that the PBAT/PLA blend system's crystal formation may be inhibited by T‐ZnOw, the observation demonstrates that T‐ZnOw only marginally alters this process. The work is of significant scientific value and adds a new concept to the development of sustainable thin film for packaging.Highlights T‐ZnOw is used as a novel additive for PBAT/PLA polymer blends. The crystallization of PBAT/PLA/T‐ZnOw composite systems is thoroughly examined. T‐ZnOw marginally reduces the kinetics of the crystallization process of PBAT/PLA blends. PBAT/PLA/T‐ZnOw composites follow volume nucleation with mixed 2D/1D growth. The nonisothermal crystallization of PBAT/PLA/T‐ZnOw composites is validated by Mo‐analysis.

Eco-friendly zinc-metal-organic framework as a nucleating agent for poly (lactic acid)

Eco-friendly poly(L-lactic acid) (PLA) can be made more versatile, and its crystallization rate is accelerated by adding Zinc-based metal-organic framework (Zn-MOF) particles. Using differential scanning calorimetry (DSC), the non-isothermal melt crystallization behavior of biodegradable PLA nucleated by 0.3 to 3 wt% of Zn-MOF was examined. The non-isothermal melt crystallization kinetics parameters were determined using a modified Avrami model and Mo approach. Zn-MOF dramatically accelerated the crystallization process, as evidenced by several non-isothermal crystallization metrics, including the crystallization half-time and crystallization rate constant. The melt crystallization temperatures of the PLA-Zn-MOF composites, with contents of 0.7 and 1 wt%, were increased by 21 °C compared to the neat PLA. Using the Friedman isoconversional kinetic method, the neat PLA and PLA-Zn-MOF composites' effective activation energy values, ∆E, were determined. The ∆E values of PLA-Zn-MOF from 0.3 to 1 wt% Zn-MOF composites were lower than that of neat PLA. Moreover, polarized optical microscopy revealed the formation of numerous small-sized PLA spherulites upon Zn-MOF addition. The results indicate that the Zn-MOF (at concentrations of 0.7 to 1.0 wt%) can be used as an efficient nucleating agent for PLA, where it increases the melt crystallization temperature, nucleation density, and crystallinity without changing the crystalline structure, while also significantly reduces the effective activation energy and the size of spherulites. Additionally, scanning electron microscopy confirms good dispersion of Zn-MOF (0.3 to 1 wt%) within the PLA matrix.

Design of Crystal Growth Dimensionality in Synthetic Wax: The Kinetics of Nonisothermal Crystallization Processes.

The demand for the development of multifunctional materials in emerging technologies has stimulated intensive research on the control of crystallization processes in numerous scientific and engineering fields. In this article, we examine the kinetics of nonisothermal melt crystallization in synthetic wax using differential scanning calorimetry (DSC) supported by polarized optical microscopy (POM) to describe crystallization modes in a multicomponent molecular system. We detected the macroscopic growth of three crystal phases and the formation of two crystal phases as a transformation from a disordered crystal mesophase into an ordered crystal. To characterize individual crystal phase formation, we examine the activation energy evaluated by isoconversional analysis and utilize the Ozawa and Mo methods to determine the kinetic details of the crystal growth from the isotropic phase. Our investigation reveals the possibility of the design of crystal growth dimensionality as three-dimensional spherulitic-like, two-dimensional rodlike, and one-dimensional needle-shaped crystal forms of shorter n-alkanes by controlling the solidification pathway of long-chain n-alkanes and the interplay of the thermodynamic and kinetic mechanisms of crystallization.

Kinetika Kristalisasi Campuran Minyak Sawit Bebas Asam Lemak Trans untuk Produksi Margarin

Non-trans-fat (NTF) margarine was produced by substituting partially-hydrogenated palm oil in margarine oil blend with fully-hydrogenated palm oil. Three types of NTF oil blends were used in this study. To obtain an NTF oil blend with similar physical properties to the reference oil blend, which contain partially-hydrogenated oil, the melting properties and crystallization kinetics were evaluated. The iodine value of raw material oil was measured, and the oil was mixed to form the margarine oil blends. Fatty acid composition (FAC) and solid fat content (SFC) of the oil blends were examined. Melting properties of the oil blends were determined based on SFC analysis, while crystallization kinetics were determined using Avrami model. The results showed that there was no trans fatty acids detected in the NTF oil blends. The rate of crystallization constant (k) of the Avrami index of reference oil and NTF-1 oil blend were 0.1413 ± 0.0047 and 0.1369 ± 0.0016 min-n, respectively, whilst their Avrami exponent (n) were 0.93 ± 0.02 and 0.94 ± 0.01, respectively. There was no significant difference on these Avrami indexes, and therefore NTF-1 oil blend could be selected as an alternative oil blend for margarine production.

Crystallization kinetics in the chiral compound showing the vitrification of the smectic CA* phase for moderate cooling rates

ABSTRACT The crystallization of the 3F5FPhF6 compound from the liquid crystalline antiferroelectric smectic CA* phase is investigated in various conditions using differential scanning calorimetry and polarizing optical microscopy. The kinetics of isothermal melt and cold crystallization is studied on the basis of the Avrami model. The kinetics of non-isothermal cold crystallization is analysed using the Ozawa model and the activation energy is determined by the Augis-Bennett, Friedman’s differential isoconversional and Matusita methods. The border temperature between the diffusion-controlled crystallization and thermodynamically-controlled crystallization is estimated. The high fragility index of 105 is determined from the α-process in the smectic CA* phase by the broadband dielectric spectroscopy. The metastable, conformationally disordered crystal phase, forming only via cold crystallization, is reported.

Crystallization and fusion kinetics of Poly(butylene terephthalate)/Titanium Dioxide

In this paper, the crystallization, fusion, and activation energy (Ea) of PBT/TiO2 were thoroughly evaluated using DSC. Increasing the rates shifted the peaks of melt crystallization to lower temperatures while the fusions were almost unaffected. TiO2 hindered the melt crystallization of PBT and lower crystallization rates, i.e., CMAX and K’ were acquired, in general, the crystallinity degree (Xc) was 4% higher in PBT/TiO2 which is in the marginal error. Pseudo-Avrami and Mo models were applied to evaluate the melt crystallization kinetics; both fitted the melt crystallization quite well; deviations were observed at the beginning and the crystallization end most due to the nucleation and spherulites impingement during the secondary crystallization. Ea was evaluated using the Friedman model, considering the values of Ea less energy has to be removed from PBT/TiO2 when compared to PBT, specifically at 1% of TiO2.

Phase Sequence, Kinetics of Crystallization and Molecular Dynamics of the Chiral Liquid Crystalline Compound Forming a Hexatic Smectic Glass

The vitrification of the antiferroelectric hexatic smectic XA* phase and cold crystallization are reported for (S)-4′-(1-methylheptylcarbonyl)biphenyl-4-yl 4-[5-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]benzoate. The kinetics of isothermal cold crystallization and melt crystallization are investigated, revealing that both are controlled mainly by diffusion, as indicated by decrease in the characteristic crystallization time with increasing temperature of crystallization, with an activation energy of 114 kJ/mol. A weak relaxation process is detected in a crystal phase, with an activation energy of 38 kJ/mol, implying the conformationally disordered crystal phase. The estimated fragility parameter of the investigated glass former is equal to 94.5, which indicates rather high fragility.

Effect of Two Crystalline Forms on the Multiple Melting and Crystallization Kinetics of Thermoplastic Polyurethane

Exploring the origin of multiple melting of thermoplastic polyurethane (TPU) is of great significance for comprehending the mechanism for its phase transition. Herein, the effects of two crystal forms (Form-I and Form-II) and crystal form transition on the melting behaviors and crystallization kinetics of TPU are reported. As the function of the crystallization temperature (Tc), Form-II and Form-I develop at Tc ≥ 130 °C and Tc ≤ 130 °C, respectively, which leads to distinct differential scanning calorimetry (DSC) melting curves of TPU. It is found that the repeated melting–recrystallization occurs during the melting of Form-I, which includes the crystal form transition of Form-I to Form-II, resulting in four melting peaks in the DSC heating curves of Form-I. The results reveal that the mesophase (Form-I) could transform into the stable crystal form (Form-II) through melting–recrystallization upon heating in TPU, and TPU has the ability to continuously reorganize the ordered structure upon heating. Meanwhile, the intervention of Form-I significantly increases the overall isothermal crystallization rates, and the motion ability of TPU molecular chains is the crucial factor affecting the generation of Form-I.

Comparing non-isothermal melt and cold crystallization behavior and kinetics of poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) copolyesters

Comparing non-isothermal melt and cold crystallization behavior and kinetics of poly(ethylene 2,5-furandicarboxylate-co-ethylene terephthalate) copolyesters

Crystallization Behavior and Morphology of Biodegradable Poly(ε-caprolactone)/Reduced Graphene Oxide Scaffolds.

Morphology, thermal properties and the non-isothermal melt crystallization kinetics of biodegradable poly(ε-caprolactone) (PCL)/reduced graphene oxide (rGO) scaffolds are studied with differential scanning calorimetry (DSC) at various cooling rates (5, 10, 15 and 20 °C/min). Thermally induced phase separation was used to manufacture the scaffolds (TIPS). The micrographs show a more homogeneous and defined morphology with larger pores and thicker pore walls. The melting temperature (Tm), melting enthalpy (ΔHm), crystallization enthalpy (ΔHc) and degree of crystallinity (Xc) increased with the addition of rGO, suggesting larger and more perfect crystalline structures. The degree of crystallinity increased with the presence of rGO. The crystallization peak shifted to higher temperatures as the rGO concentration increased independently of the cooling rates. The peak shifted to lower temperatures as the cooling rate increased with the same rGO composition. The values of t1/2 (time needed to reach 50% crystallization) were lower for scaffolds with rGO. The values of the crystallization rate coefficient were higher when the porous support contained rGO, which indicates that their crystallization systems are faster. The activation energy obtained with the Kissinger method decreased with the presence of rGO. The results indicate that reduced graphene oxide acts as a nucleating agent in the non-isothermal melt crystallization process. The addition of small quantities of rGO changes their thermal properties with which they can be modified for application in the field of tissue engineering.

Poly(l-lactic acid) nucleation by alkylated carbon black

Biodegradable polymers are raising an increasing interest as alternative to oil-based materials. Among available biodegradable polymers, the most promising is possibly poly(l-lactic acid) (PLLA), which can be produced from renewable resources at reasonable costs. However, PLLA has some processing limitations, mainly associated with slow melt crystallization kinetics. In this work, an attempt is made to overcome these PLLA limitations, by using different kinds of carbon-based nanofillers. PLLA compounds were prepared in a twin screw extruder and characterized mainly by gel permeation chromatography, rotational rheometry and differential scanning calorimetry. Alkylated carbon black (aCB) in PLLA compounds not only induces high melt thermal stabilization (as also occurs with other carbon based nanofillers) but also acts as a nucleating agent, thus reducing crystallization times. aCB nucleation of PLLA is possibly due to the well known tendency of hydrocarbon tails to form ordered local aggregates, when bounded to solid structural layers.

Fully biodegradable Poly(butylene succinate-co-1,2-decylene succinate)/Cellulose nanocrystals composites with significantly enhanced crystallization and mechanical property*

Poly (butylene succinate-co-1,2-decylene succinate) (PBDS) is a promising biodegradable polyester with n-octyl being the side group (Polymer 2021, 213, 123197). The toughness of PBDS is significantly higher than that of linear poly (butylene succinate) (PBS), while the tensile strength and crystallization rate of PBDS are remarkably lower than those of PBS. In this research, fully biodegradable PBDS/cellulose nanocrystals (CNC) composites were prepared at low CNC loadings with the aim of improving the crystallization and mechanical properties. The surface morphology study suggested CNC achieved an even distribution in PBDS. As an efficient heterogeneous nucleating agent, CNC obviously enhanced the nonisothermal melt crystallization behavior and isothermal melt crystallization kinetics of PBDS, as evidenced by the upward shift of melt crystallization temperature and shorter crystallization half-time. Both the nucleation activity and nucleation efficiency of CNC were quantitively evaluated, which were 0.40 and 44.9%, respectively, at a CNC loading of 2 wt%. CNC did not change the crystallization mechanism and crystal structure of PBDS. The mechanical properties study indicated that the tensile mechanical properties (Young's modulus and tensile strength from the tensile test) and storage modulus (from dynamic mechanical analysis) of PBDS were obviously enhanced by CNC, indicating the reinforcement effect.

Crystal structures, crystallization and II–I transition behaviors of iPB-1 in iPB-1/UHMWPE blends. Part 1. Crystal structures and crystallization behaviors

Blending with UHMWPE inhibits the overall melt crystallization kinetics of iPB-1 due to its spherulite nucleation density decrease in spite of the observed spherulite growth enhancement. It may provide a model system for II–I transition study.

Insight into cold- and melt crystallization phenomena of a smectogenic liquid crystal

This paper describes the insight into the different nature of cold- and melt crystallization kinetics of a smectogenic liquid crystal.

Crystallization Kinetics of Poly(lactic acid)–Graphene Nanoscroll Nanocomposites: Role of Tubular, Planar, and Scrolled Carbon Nanoparticles

Graphene nanoscrolls (GNS) are 1D carbon-based nanoparticles. In this study, they were investigated as a heterogeneous nucleating agent in the poly(lactic acid) (PLA) matrix. The isothermal and non-isothermal melting behavior and crystallization kinetics of PLA-GNS nanocomposites were investigated using a differential scanning calorimeter (DSC). Low GNS content not only accelerated the crystallization rate, but also the degree of crystallinity of PLA. The Avrami model was used to fit raw experimental data, and to evaluate the crystallization kinetics for both isothermal and non-isothermal runs through the nucleation and growth rate. Additionally, the effect of the dimensionality and structure of the nanoparticle on the crystallization behavior and kinetics of PLA is discussed. GNS, having a similar fundamental unit as CNT and GNP, were observed to possess superior mechanical properties when analyzed by the nanoindentation technique. The scrolled architecture of GNS facilitated a better interface and increased energy absorption with PLA compared to CNTs and GNPs, resulting in superior mechanical properties.

Enhancing the crystallization of biodegradable poly(ε-caprolactone) using a polyvinyl alcohol fiber favoring nucleation

In this study, biodegradable poly(ε-caprolactone) (PCL)/polyvinyl alcohol (PVA) fiber composites were prepared using melt processing techniques with different PVA fiber contents. The effect of PVA fiber on the non-isothermal and isothermal melt crystallization kinetics of PCL/PVA fiber composites was studied by using differential scanning calorimetry. Non-isothermal crystallization peak temperatures were enhanced significantly, as exemplified by about 20 K increase for the composite loaded with 5 wt% PVA fiber at a cooling rate of 20 K/min compared to that of neat PCL. The crystallization half-time decreased from 1.67 min for neat PCL to 0.80 min for composite with 5 wt% PVA fiber at a cooling rate of 5 K/min. PVA fiber was also found to dramatically accelerate the isothermal crystallization rate of PCL/PVA fiber composites. The crystallization half-time of composite containing 5 wt% PVA fiber was reduced by more than 10 times compared with neat PCL. Moreover, dynamic mechanical analysis results showed that PVA fiber had a strengthening effect on the PCL.

Analysis of the rheological property and crystallization behavior of polylactic acid (Ingeo™ Biopolymer 4032D) at different process temperatures

Abstract The aim of this study was to determine the rheological property and crystallization behavior of polylactic acid (PLA) with improved heat resistance (Ingeo™ Biopolymer 4032D) through investigation of the melt viscosity and crystallization kinetics of PLA at different process temperatures. The viscosity was measured using a rotational rheometer under conditions of shear rates of 0.01, 0.1, and 1/s. The obtained rheological data show that the viscosity tended to decrease slightly as the shear rate increases and decrease sharply as the temperature increases from 180°C to 210°C. To investigate the effect of the process temperature on the crystallization kinetics and final crystallinity of PLA, thermal analysis using isothermal differential scanning calorimetry (DSC) were also performed. The Avrami equation was successfully applied for the isothermal crystallization kinetics model. From crystallization temperature of 85°C to 120°C, we found that the Ingeo™ Biopolymer 4032D PLA had the fastest crystallization rate (t 1/2: 26.0 min) and the largest crystallinity (47.4%) at 100°C.

The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites.

In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.

Isothermal melt crystallization kinetics study of cellulose nanocrystals nucleated biodegradable Poly(ethylene succinate)

The isothermal melt crystallization kinetics of fully biodegradable poly(ethylene succinate) (PES)/cellulose nanocrystals (CNC) composites was studied in this research. Due to the efficient nucleating agent effect, the crystallization rate of PES was remarkably enhanced by low loadings of CNC; consequently, the composites displayed shorter crystallization half-time and greater nucleation density than neat PES. Through the self-nucleation and nonisothermal melt crystallization studies, the nucleation efficiency values of CNC were quantitively evaluated in PES/CNC composites. Despite CNC loading, the nucleation efficiency exceeded 50%. With increasing the CNC loading from 0.25 to 1 wt%, both the crystallization rate of the composites and the nucleation efficiency of CNC at different loadings first increased, reached a maximum, and then decreased, displaying the CNC loading dependence. Such dependence was attributed to the different dispersion states of CNC in the composites.

The features of the structural state and phase composition of the surface layer of aluminum alloy Al-Mg-Cu-Zn-Zr irradiated by the high current electron beam

The structural and phase changes in the surface layer of the 1933 aluminum alloy caused by the irradiation of a high-current relativistic electron beam are studied. The impact of the electron beam leads to the formation of a remelted surface layer with surface relief and microcracks. The structural phase state of this layer is determined by the complex impact of the electron beam and the kinetics of melt crystallization under ultrafast cooling. Via X-ray diffraction studies and the results of energy dispersive X-ray microanalysis it became possible to make a conclusion that submicron sizes of magnesium oxide are present in the remelted layer. MgO inclusions are distributed homogeneously in the remelted layer. The presence of MgO inclusions leads to hardening of the surface layer of the alloy. The nature of formation of MgO during the impact of a pulsed electron beam are discussed