Crystallization Kinetics Of Poly Research Articles

The crystallization kinetics of poly(ε-caprolactone-co-trimethylene carbonate) (PCLTMC): effects of the molar ratio of CL and TMC

The mode of the Lauritzen–Hoffman theory is shown above. Temperature of Regime II was selected for isothermal crystallization study, and the results showed that the crystallization kinetics of PCLTMC copolymer with high CL content fit the theory.

Effect of fusion temperature on the crystallization kinetics of poly(butylene terephthalate)

A tremendous effect of fusion temperature on the crystallization kinetics of poly(butylene terephthalate) (PBT) was discovered.

The effect of POSS-NH2 and POSS-PEG on the crystallization kinetics of poly (l-lactic acid) by traditional DSC and fast scanning chip calorimetry

The effect of POSS-NH2 and POSS-PEG on the crystallization kinetics of poly (l-lactic acid) by traditional DSC and fast scanning chip calorimetry

Supernucleation Dominates Lignin/Poly(ethylene oxide) Crystallization Kinetics

The effect of lignin nanoparticles (LNPs) on the crystallization kinetics of poly(ethylene oxide) (PEO) is examined. Lignin from spruce and ionic isolation was used to prepare LNPs with a number-averaged diameter of 85 nm (with a relatively large polydispersity) by an ultrasonication method. PEO-based nanocomposites with four different LNP contents (5, 10, 15, and 20 wt %) were prepared and subject to isothermal and nonisothermal crystallization protocols in a series of experiments. Scanning electron microscopy (SEM) images showed well-dispersed LNPs in the crystallized PEO matrix. The incorporation of LNPs exponentially increases nucleation density at moderate loadings, with this trend apparently saturating at higher loadings. However, the spherulitic growth rate decreases monotonically with LNP loading. This is attributed to the substantial PEO/LNP affinity, which impacts chain diffusion and induces supernucleation effect (with efficiencies in the order of 200%), but leads to slower growth rates. The overall crystallization kinetics, measured by the DSC, shows faster nanocomposite crystallization rates relative to the neat PEO at all LNP contents examined. This indicates that the supernucleation effect of LNPs dominates over the decrease in the growth rates, although its influence slightly decreases as the LNP content increases. The strong hydrogen-bonded interactions between the LNPs and the PEO are thus reminiscent of confinement effects found in polymer-grafted NP nanocomposites (e.g., PEO-g-SiO2/PEO) in the brush-controlled regime.

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.

Utilization of microalgae residue and isolated cellulose nanocrystals: A study on crystallization kinetics of poly(ɛ-caprolactone) bio-composites

Exploration of biodegradable materials for conventional application has taken a rising interest across the world. The presented work primarily focused on exploring the effectiveness of isolated CNCs from marine de-oiled green algae biomass residue (Dunaliella tertiolecta) in synthesized poly(ɛ-caprolactone) (PCL). The washed algae biomass residue (WABR) and algae derived CNCs were explored as two different bio-fillers incorporated into PCL for comparison and development of biodegradable and flexible bio-composites with varying bio-filler loading. FTIR, XRD, TGA, UTM, DSC, POM, and SAXS characterized the developed PCL/WABR and PCL/CNC bio-composites. Improved thermal stability was observed in PCL/CNC bio-composites by ~10 °C rise. Besides, increased modulus of 18.38 MPa and tensile strength was obtained in PCL/CNC/1 bio-composites. However, the isothermal kinetics study (at 45 °C) revealed the reduction in the degree of crystallinity of bio-composites, and the axialite formation was visualized via POM. Moreover, CNCs was found as an excellent nucleating agent and effective bio-filler as compared to WABR.

Temperature-modulated fast scanning calorimetry of isothermal crystallization of Poly(butylene terephthalate)

Crystallization kinetics of poly(butylene terephthalate) under high supercooling was examined by Temperature-Modulated Fast Scanning Calorimetry (TM-FSC). By using temperature modulation for isothermal crystallization, we can determine the temperature dependence of crystal growth rate. The positive/negative dependence brings the negative/positive sign of the phase angle of dynamic heat capacity, respectively. The obtained dependence was compared with that of peak time of heat flow on isothermal crystallization. The isothermal peak time is inversely proportional to the crystallization rate and showed a double peak, corresponding to the crystal-growth- and nucleation-dominant temperature ranges. The result of TM-FSC over the entire temperature range including the nucleation-dominant lower temperature range was in agreement with the temperature derivative of the fitting curve of the crystal-growth-dominant higher-temperature peak. Hence, the present analysis confirmed that TM-FSC detected the change in crystal growth rate but not in nucleation rate. The crystal growth rate was practically determined by a mobility factor near the glass transition.

Annealing and crystallization kinetics of poly(lactic acid) pieces obtained by additive manufacturing

AbstractIn this study, we investigated the influence of isothermal treatment of poly(lactic acid) (PLA) 3D printed samples at different crystallization temperatures. In this case, we analyzed the effect of each crystallization temperature on spherulites formation in printed PLA, affecting the final mechanical properties of pieces. For such, the thermomechanical properties, morphological structure, and crystallization kinetics were analyzed before and after thermal treatment. The 3D printed samples were heat treated at 80°C, 90°C, 100°C, 110°C, and 119°C. With annealing, we observed an improvement in the mechanical PLA properties; however, the exothermic crystallization peak was different for the samples. Pieces before annealing were found to have a low crystallinity index (Ic) of 2%–7%, and the pieces after annealing presented a considerable Ic (27%–34%). Annealing temperatures of 100°C, 110°C, and 119°C produced the fastest crystallization kinetics, while annealing temperatures of 80°C and 90°C resulted in the lowest crystallization kinetics for complete crystallization. After annealing, improvement in the flexural strength (34%–47%) and Young's modulus (26%–51%) for all annealed pieces occurred. The appropriate condition was observed at 100°C, which was the onset temperature of crystallization, owing to the combination of the shorter time of crystallization with the increased mechanical properties.

Isothermal Crystallization Kinetics of Poly(ethylene oxide)/Poly(ethylene glycol)-g-silica Nanocomposites.

In this work, the crystallization kinetics of poly(ethylene oxide) (PEO) matrix included with poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO2) nanoparticles and bare SiO2 were systematically investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) method. PEG-g-SiO2 can significantly increase the crystallinity and crystallization temperature of PEO matrix under the non-isothermal crystallization process. Pronounced effects of PEG-g-SiO2 on the crystalline morphology and crystallization rate of PEO were further characterized by employing spherulitic morphological observation and isothermal crystallization kinetics analysis. In contrast to the bare SiO2, PEG-g-SiO2 can be well dispersed in PEO matrix at low P/N (P: Molecular weight of matrix chains, N: Molecular weight of grafted chains), which is a key factor to enhance the primary nucleation rate. In particular, we found that the addition of PEG-g-SiO2 slows the spherulitic growth fronts compared to the neat PEO. It is speculated that the interfacial structure of the grafted PEG plays a key role in the formation of nuclei sites, thus ultimately determines the crystallization behavior of PEO PNCs and enhances the overall crystallization rate of the PEO nanocomposites.

New insights into the memory effect on the crystallization behavior of poly(phenylene sulfide)

In this article, the melt and crystallization kinetics of poly(phenylene sulfide) (PPS) powder was studied by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR) and polarized optical microscopy (POM). It is found that the folded-chain crystals of PPS (melting point at 281 °C) could be erased at about 350 °C, while the equilibrium melting point of extended-chain crystals (melting point at 295 °C) is 370 °C. Although the residual nuclei could be eliminated completely at 370 °C, the spherulite growth rate of PPS during crystallization keeps accelerating with the increasing melting relaxation time, resulting from the transformation of the lamellae and the amorphous cluster to an ordered structure with low entanglement density. Furthermore, due to the restricted chain mobility for the semi-flexible PPS, this unique memory effect would survive in the whole manufacturing process, resulting in the varying results from different researches and the significant influence on the processability and performance of PPS products.

Understanding the effect of chain entanglement state on melt crystallization of the polymer freeze-extracted from solution: The role of critical overlap concentration

Freeze-drying of dilute polymer solution is a widely accepted method to yield disentangled polymer. By this method, it has been pointed out that samples recovered from dilute solution possess a better crystallization ability than the bulk polymer. Here, the important role of the critical overlap concentration c* in polymer solution is firstly stressed to give a more quantitative understanding in the relation between entanglement state and melt crystallization behavior. Crystallization kinetics of poly (lactic acid) freeze-extracted from dichloromethane solution with various concentration below and above c*, as well as the crystalline structure after isothermal crystallization at 110 °C, were investigated by means of differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). Results indicated that crystallization kinetics and lamellar thickness (Lc) show a strong dependence on precursor solution concentration only when the concentration is lower than the critical value (c*), while above c* the crystallization behavior changes a little. Besides, a more rational method to characterize the chain entanglement state in polymer solution and to select concentrations accordingly was suggested, that is, using a dimensionless variable [η]c which is the product of intrinsic viscosity [η] and solution concentration c.

Isothermal Crystallization Kinetics of Poly (3-hydroxybutyrate/ Poly(ethylene-co-vinyl acetate) Blends Enhanced by NH4Cl as a Nucleating Agent

The isothermal crystallization kinetics of poly (3-hydroxybutyrate) (PHB)/NH4Cl composites, PHB/poly(ethylene-co-vinyl acetate), with vinyl acetate contents of 80% (EVA80) blends and PHB/EVA80/1 wt% NH4Cl composites were investigated by using differential scanning calorimetry (DSC). The Avrami approach was applied to estimate the kinetic parameters of the PHB samples under isothermal crystallization conditions. It was found that the values of The Avrami rate constant, of PHB were increased with the incorporation of NH4Cl, declining EVA80 content in the PHB blends, and decreasing crystallization temperature. Moreover, the Avrami exponent, n, remained unchanged in spite of the change in the crystallization temperature, EVA80 content, and presence of NH4Cl. The activation energy, calculated using the Arrhenius equation, for PHB/NH4Cl was much lower than that of pure PHB and PHB/EVA80, suggesting that the NH4Cl induced heterogeneous nucleation. The values for PHB/EVA80/1 wt% NH4Cl increased as the EVA80 content was increased, indicating a retardation effect of EVA80. Furthermore, a modified Lauritzen–Hoffmann treatment (LH) was used to evaluate the nucleation constant, of the PHB samples based on the assumption that U* was 13.8 kJ/mol and the equilibrium melting temperatures were 470 K, intercepts of HL equation, were 25.9 for all PHB samples. The values indicated that the crystallization of PHB in its composites and blends, described here, occurred in regime III. The maximum degradation rate temperatures of the PHB/NH4Cl composites were higher than that of PHB, by 9 oC. No significant change in thermal stability was detected by the addition of EVA80.

Promoted stereocomplex formation and two‐step crystallization kinetics of poly( l ‐lactic acid)/poly( d ‐lactic acid) blends induced by nucleator

Promoted stereocomplex formation and two‐step crystallization kinetics of poly( <scp>l</scp> ‐lactic acid)/poly( <scp>d</scp> ‐lactic acid) blends induced by nucleator

Crystallization kinetics of poly (butylene adipate terephthalate) in biocomposite with coconut fiber

ABSTRACT The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

Enhanced Crystallization Kinetics of PLLA by Ethoxycarbonyl Ionic Liquid Modified Graphene

To investigate the performance of graphene (Gra) modified with ethoxycarbonyl ionic liquid (IL), chain mobility and crystallization kinetics of poly(L-lactic acid) (PLLA), a series of PLLA nanocomposites have been prepared using solution-cast method. IL can improve the dispersion of Gra in PLLA matrix and the samples containing IL have higher growth rate of PLLA spherulite than neat PLLA does. PLLA/IL/Gra and PLLA/2Gra exhibit the same relaxation strength and time of αN relaxation that corresponds to the longest normal mode motion at 110−140 °C. PLLA/IL/Gra shows a faster crystallization rate than PLLA/2Gra does, which might be attributed to the Gra-imidazolium cation interaction in IL modified Gra, the significant dispersion effect of IL at Gra surface, and the increase of nuclei density of PLLA/IL/Gra.

Thermal degradation behaviour and crystallization kinetics of poly (lactic acid) and cellulose nanocrystals (CNC) based microcellular composite foams

The current investigation addresses the thermal degradation and non-isothermal crystallization behaviour of the fabricated poly (lactic acid) foam (nPLA) and poly (lactic acid) (PLA)/cellulose nanocrystal (CNC) based foams at three different loadings of CNC (i.e. 1%, 2% and 3%) as PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 having highly porous, interconnected and microcellular morphology. The formation of various gaseous products at two different conversions (α = 0.3 and α = 0.7) are investigated by using thermogravimetric analyser hyphenated Fourier transmission infrared spectroscopy (TGA-FTIR) analysis in isothermal condition. Effect of porosity and CNC reinforcement towards thermal degradation and crystallization of the PLA is thoroughly investigated by using mercury intrusion porosimetry (MIP). “Model-free” and “modelistic” approaches like Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sinouse (KAS), Kissinger and Augis & Bennet have been utilized for non-isothermal degradation kinetics of the fabricated foams. Non-isothermal melt crystallization kinetics of fabricated foams reveals that both primary and secondary crystallization process taking place. The apparent activation energy calculated from FWO are ~175.8 kJ/mol, ~198.6 kJ/mol, ~175.5 kJ/mol and ~174.7 kJ/mol for nPLA, PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 respectively. It is also observed that at higher conversions, complex three dimensional diffusion mechanism of degradation might be taking place in accordance with Criado plots.

Miscibility of Poly(Ethylene-co-Vinylalcohol)/Poly(δ-Valerolactone) Blend and Tissue Engineering Scaffold Fabrication Using Naphthalene as Porogen

ABSTRACTHerein, various poly(ethylene-co-vinylalcohol)/poly(δ-valerolactone) blends were prepared at different ratios by solvent casting for use in tissue engineering. The miscibility of these polymers was studied in detail using differential scanning calorimetry, Fourier-transform infra-red spectroscopy, and X-ray diffraction. The Avrami model have been applied for determining the isothermal crystallization kinetics of poly(ethylene-co-vinyl alcohol), poly(δ-valerolactone) and their blend with equal compositions, in which the Avrami parameters, the maximum crystallization time and the half-time were deducted. Cell adhesion and cell proliferation of the resultant materials were examined by an (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)MTT assay; the blend containing equal amounts of the two polymers showed the best performance. Micropores and their connections were formed by using a new porogen under vacuum at temperatures slightly less than the glass transition temperature. The produced micropores and their interconnections were studied using scanning electron microscopy.

Accelerated crystallization of high molar mass poly(l/d-lactic acid) by blending with low molar mass poly(l-lactic acid)

The crystallization kinetics of poly(l/d-lactic acid) (PLLA) with a molar mass of around 120 kDa and containing 4% of d-isomers is sizably improved by blending with low amount (<10 m%) of a PLLA of high stereoregularity, made of pure l-isomer, and molar mass of 4 kDa. Blends of the two PLLA’s are prepared by solution mixing. The blends are homogeneous in the melt and display a single, composition-dependent glass transition. Increasing concentration of the highly stereo-regular low-molar mass component in the blends results in an earlier onset of crystallization and a higher crystal growth rate. The blend composition affects the crystal polymorphism of PLLA, as increasing content of the highly stereoregular and low molar mass polymer favors growth of α-crystals at lower temperatures than typically observed in unmodified PLLA. It is suggested that the short PLLA molecules of the low-molar mass component start to crystallize at higher temperature than the long molecules of the high-molar mass component, acting as crystal nuclei for the subsequent crystal growth that involves both species.

Effect of Graphene Oxide on Non-Isothermal Melt Crystallization Kinetics of Poly(Trimethylene Terephthalate)

Poly (trimethylene terephthalate) (PTT)/graphene oxide (GO) nanocomposites were prepared by melt mixing. The effect of GO on non-isothermal melt crystallization kinetics of PTT with different amounts of GO were investigated by differential scanning calorimetry (DSC). The Avrami, Ozawa and Mo were used to analyze the non-isothermal crystallization process. The results of Avrami analysis showed that adding GO into PTT matrix changed the crystallization nucleation of PTT. Ozawa analysis could not be used for the non-isothermal crystallization of PTT/GO nanocomposites. According to the results of Mo analysis, a higher cooling rate would be needed in order to obtain a higher degree of crystallinity at unit crystallization time.

Impact of the architecture on the crystallization kinetics of poly(ε-caprolactone)/poly(trimethylene carbonate) block copolymers

Well defined block copolymer architectures based on poly(ε-caprolactone) and poly(trimethylene carbonate) were prepared thanks to the methane sulfonic acid (MSA) organocatalyzed ROP of the corresponding monomers. The interplay between the crystallization kinetics, self-assembling behavior and superstructural morphology was investigated. In order to probe the influence of the block copolymer architecture (molecular weight, number of blocks and sequence), kinetics theories of polymer crystallization were applied to the isothermal crystallization kinetics data obtained by differential scanning calorimetry and polarized optical microscopy. The results suggest that the PCL crystallization kinetic is only slightly disturbed by the segregation strength for weakly segregated systems while the block copolymer sequence shows a strong impact on the overall crystallization kinetics, and particularly on the nucleation step due to topological constraints.