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The formation of polylactide stereocomplex (sc-PLA), involving the blending of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), enhances PLA materials by making them stronger and more heat-resistant. This study investigated the competitive crystallization behavior of homocrystals (HCs) and stereocomplex crystals (SCs) in a 50/50 PLLA/PDLA blend with added polyethylene glycol (PEG). PEG, with molecular weights of 400 g/mol and 35,000 g/mol, was incorporated at concentrations ranging from 5% to 20% by weight. Differential scanning calorimetry (DSC) analysis revealed that PEG increased the crystallization temperature, promoted SC formation, and inhibited HC formation. PEG also acted as a plasticizer, lowering both melting and crystallization temperatures. The second heating DSC curve showed that the pure PLLA/PDLA blend had a 57.1% fraction of SC while adding 5% PEG with a molecular weight of 400 g/mol resulted in complete SC formation. In contrast, PEG with a molecular weight of 35,000 g/mol was less effective, allowing some HC formation. Additionally, PEG consistently promoted SC formation across various cooling rates (2, 5, 10, or 20 °C/min), demonstrating a robust influence under different conditions.

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The polar sulfonate groups in cationic dyeable polyester (CDP) lead to complex crystallization behavior, affecting CDP production's stability. In this study, cationic dyeable polyesters (CDP) with different sulfonate group contents were prepared via one-step feeding of sodium isophthalic acid-5-sulfonate (SIPA), terephthalic acid (PTA), and ethylene glycol (EG). The non-isothermal crystallization behavior of these copolyesters was analyzed by differential scanning calorimetry (DSC). Results show that the crystallization temperature of the sample shifts to lower values with the increase in SIPA content. The relaxation behavior of the molecular chain is enhanced due to the ionic aggregation effect of sulfonate groups in CDP. Therefore, at low cooling rates (2.5 °C/min and 5 °C/min), some molecular chain segments in CDP are still too late to orderly stack into the lattice, forming metastable crystals, and melting double peaks appear on the melting curve after crystallization. When the cooling rate increases (10-20 °C/min), the limited region of sulfonate aggregation in CDP increases, resulting in more random chain segments, and a cold crystallization peak appears on the melting curve after crystallization. The non-isothermal crystallization behavior of all samples was fitted and analyzed by the Jeziorny equation, Ozawa equation, and Mo equation. The results indicate that the nucleation density and nucleation growth rate of CDP decrease with the increase in SIPA content. Meanwhile, analysis of the Kissinger equation reveals that the activation energy of non-isothermal crystallization decreases gradually with the increase in SIPA content, and the addition of SIPA makes CDP crystallization more difficult.

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The visualization of the variation of the inter/intra molecular interaction (C = O⋯CH3) between poly[(R)-3-hydroxybutyrate] (PHB) and poly-L-lactic acid (PLLA) in the PHB/PLLA miscible blend during phase separation and crystallization process was successfully investigated using Raman imaging. Images of the blend were developed using high- and low-frequency Raman spectra acquired during the isothermal crystallization of the blend, and both of them were compared. The low-frequency region allowed to observe the changes in the hydrogen bonds between the molecular chains in the blend during phase separation and crystallization via a band at 75 cm-1 derived from PHB. The imaging results obtained using the band at 75 cm-1 due to hydrogen bonding (C = O⋯CH3) between molecular chains were in good agreement with the results obtained using the C = O stretching band at 1720 cm-1. Herein, we demonstrated that the low-frequency region of the Raman spectrum is more sensitive to detecting the start of the phase separation and crystallization of PHB than the corresponding high-frequency region.

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During the secondary thermoforming of carbon fiber-reinforced polyphenylene sulfide (CF/PPS) composites, a vital material for the aerospace field, varied thermal parameters profoundly influence the crystallization behavior of the PPS matrix. Notably, PPS exhibits a distinctive self-nucleation (SN) behavior during repeated thermal cycles. This behavior not only affects its crystallization but also impacts the processing and mechanical properties of PPS and CF/PPS composites. In this article, the effects of various parameters on the SN and non-isothermal crystallization behavior of PPS during two thermal cycles were systematically investigated by differential scanning calorimetry. It was found that the SN behavior was not affected by the cooling rate in the second thermal cycle. Furthermore, the lamellar annealing resulting from the heating process in both thermal cycles affected the temperature range for forming the special SN domain, because of the refined lamellar structure, and expelled various defects. Finally, this study indicated that to control the strong melt memory effect in the first thermal cycle, both the heating rate and processing melt temperature need to be controlled simultaneously. This work reveals that through collaborative control of these parameters, the crystalline morphology, crystallization temperature and crystallization rate in two thermal cycles are controlled. Furthermore, it presents a new perspective for controlling the crystallization behavior of the thermoplastic composite matrix during the secondary thermoforming process.

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We performed a nanoscale study based on X-ray scattering to understand the impact of a promotor of crystallization, palmitic acid (PA), at high concentration, on the networks of triacylglycerols (TAGs) in anhydrous milk fat (AMF). Melted blends containing 10 wt% PA were quenched at 25 °C. X-ray scattering data were compared with those obtained for pure AMF, pure PA, and AMF containing 1 wt% PA. While PA at low concentration did not modify the nanostructure of TAG crystals (direct crystallization in the ß'-2L form), a high concentration of this promotor favored the formation of polymorphic forms suggesting that PA first crystallizes and then directs crystallization of AMF TAGs towards α and ß forms.

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Thermoplastic resin transfer molding (T-RTM) technology was applied to synthesize graphene nanoplatelets-based nanocomposites via anionic ring-opening polymerization (AROP). Polyamide 6 (PA6) was obtained by AROP and was used as the polymeric matrix of the developed nanocomposites. The non-isothermal crystallization behavior of PA6 and nanocomposites was analyzed by differential scanning calorimetry (DSC). Nanocomposites with 0.5 wt.% of graphene nanoplatelets (GNPs) with two different diameter sizes were prepared. Results have shown that the crystallization temperature shifted to higher values in the presence of GNPs. This behavior is more noticeable for the nanocomposite prepared with smaller GNPs (PA6/GN). The crystallization kinetic behavior of all samples was assessed by Avrami and Liu's models. It was observed that GNPs increased the crystallization rate, thus revealing a nucleating ability, and also validated the reduction of half-time crystallization values. Such tendency was also supported by the lower activation energy values determined by Friedman's method.

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The properties, features of thermal behavior and crystallization of copolymers containing various types of valerate monomers were studied depending on the set and ratio of monomers. We synthesized and studied the properties of three-component copolymers containing unusual monomers 4-hydroxyvalerate (4HV) and 3-hydroxy-4-methylvalerate (3H4MV), in addition to the usual 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) monomers. The results showed that P(3HB-co-3HV-co-4HV) and P(3HB-co-3HV-co-3H4MV) terpolymers tended to increase thermal stability, especially for methylated samples, including an increase in the gap between melting point (Tmelt) and thermal degradation temperature (Tdegr), an increase in the melting point and glass transition temperature, as well as a lower degree of crystallinity (40-46%) compared with P(3HB-co-3HV) (58-66%). The copolymer crystallization kinetics depended on the set and ratio of monomers. For terpolymers during exothermic crystallization, higher rates of spherulite formation (Gmax) were registered, reaching, depending on the ratio of monomers, 1.6-2.0 µm/min, which was several times higher than the Gmax index (0.52 µm/min) for the P(3HB-co-3HV) copolymer. The revealed differences in the thermal properties and crystallization kinetics of terpolymers indicate that they are promising polymers for processing into high quality products from melts.

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In this paper, a polyacrylic elastomer latex with butyl acrylate (BA) as the core and methyl methacrylate (MMA) copolymerized with glycidyl methacrylate (GMA) as the shell, named poly(BA-MMA-GMA) (PBMG), was synthesized by seeded emulsion polymerization. Cellulose nanocrystal (CNC) was dispersed in the polyacrylic latex to prepare PBMG/CNC dispersions with different CNC contents. The dried product was mixed with polylactic acid (PLA) to fabricate PLA/PBMG/CNC blends. The addition of PBMG and PBMG/CNC improved the mechanical properties of the PLA matrix. Differential scanning calorimetry (DSC) was used to investigate the non-isothermal crystallization kinetics. The Avrami equation modified by the Jeziorny, Ozawa and Mo equations was used to analyze the non-isothermal crystallization kinetics of PLA and its blends. Analysis of the crystallization halftime of non-isothermal conditions indicated that the overall rate of crystallization increased significantly at 1 wt% content of CNC. This seemed to result from the increase of nucleation density and the acceleration of segment movement in the presence of the CNC component. This phenomenon was verified by polarizing microscope observation.

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This study investigated the impact of a multiple epoxy chain extender (ADR) on the rheological behavior, crystallization, and mechanical properties of polyglycolic acid (PGA). Tests of the torque and melt mass flow rate and dynamic rheological analysis were conducted to study the rheological behavior of PGA modified with ADR. The rheological results of the modified PGA showed a significantly increased viscosity and storage modulus with an increase in the ADR amount, which could be attributed to the chain extension/branching reactions between PGA and ADR. It was proved that ADR could be used as an efficient chain extender for tailoring the rheological performance of PGA. The Han plot of the modified PGA showed a transition of viscous behavior to elastic behavior, while the ADR content was increased from 0 to 0.9 phr. The formation of long-chain branches (LCBs) was confirmed via the Cole-Cole plot and weighted relaxation spectrum, wherein the LCBs substantially changed the rheological behavior of the modified PGA. The vGP plots predicted a star-type topological structure for the LCBs. The results of non-isothermal crystallization kinetics suggested that the crystallization of the modified PGA was predominantly homogeneous nucleation and three-dimensional growth. The crystallinity decreased slightly with the increase in the ADR amount. Compared to neat PGA, the modified PGA samples exhibited better tensile and flexural performances.

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The properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx) copolymers with different ratios of monomers synthesized by the wild-type strain Cupriavidus necator B-10646 on sugars, and an industrial sample from Kaneka synthesized by the recombinant strain C. necator NSDG-ΔfadB1 on soybean oil, were studied in a comparative aspect and in relation to poly(3-hydroxybutyrate) P(3HB). The copolymer samples, regardless of the synthesis conditions or the ratio of monomers, had reduced values of crystallinity degree (50-60%) and weight average molecular weight (415-520 kDa), and increased values of polydispersity (2.8-4.3) compared to P(3HB) (70-76%, 720 kDa, and 2.2). The industrial sample had differences in its thermal behavior, including a lower glass transition temperature (-2.4 °C), two peaks in its crystallization and melting regions, a lower melting point (Tmelt) (112/141 °C), and a more pronounced gap between Tmelt and the temperature of thermal degradation (Tdegr). The process, shape, and size of the spherulites formed during the isothermal crystallization of P(3HB) and P(3HB-co-3HHx) were generally similar, but differed in the maximum growth rate of the spherulites during exothermic crystallization, which was 3.5-3.7 µm/min for P(3HB), and 0.06-1.25 for the P(3HB-co-3HHx) samples. The results from studying the thermal properties and the crystallization mechanism of P(3HB-co-3HHx) copolymers are important for improving the technologies for processing polymer products from melts.

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The study delves into the kinetics of non-isothermal crystallization of Poly (ɛ-caprolactone) (PCL) and MgO-incorporated PCL nanofibers with varying cooling rates. Differential Scanning Calorimetry (DSC-3) was used to acquire crystallization information and investigate the kinetics behavior of the two types of nanofibers under different cooling rates ranging from 0.5-5 K/min. The results show that the crystallization rate decreases at higher crystallization temperatures. Furthermore, the parameters of non-isothermal crystallization kinetics were investigated via several mathematical models, including Jeziorny and Mo's models. Mo's approach was suitable to describe the nanofibers' overall non-isothermal crystallization process. In addition, the Kissinger and Friedman methods were used to calculate the activation energy of bulk-PCL, PCL, and MgO-PCL nanofibers. The result showed that the activation energy of bulk-PCL was comparatively lower than that of nanofibers. The investigation of the kinetics of crystallization plays a crucial role in optimizing manufacturing processes and enhancing the overall performance of nanofibers.

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Non-isothermal crystallization kinetics of montmorillonite (MMT)/polyamide 610 (PA610) composites were readily prepared by in situ melt polymerization followed by a full investigation in terms of their microstructure, performance, and crystallization kinetics. The kinetic models of Jeziorny, Ozawa, and Mo were used in turn to fit the experimental data, in all of which Mo's analytical method was found to be the best model for the kinetic data. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) studies were used to investigate the isothermal crystallization behavior and MMT dispersion levels in the MMT/PA610 composites. The experiment results revealed that low MMT content can promote the PA610 crystallization, whilst high MMT content result in MMT agglomeration, and reduce the PA610 crystallization rate.

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A new bio-based polyamide 56/512 (PA56/512) has been synthesized with a higher bio-based composition compared to industrialized bio-based PA56, which is considered a lower carbon emission bio-based nylon. In this paper, the one-step approach of copolymerizing PA56 units with PA512 units using melt polymerization has been investigated. The structure of the copolymer PA56/512 was characterized using Fourier-transform infrared spectroscopy (FTIR) and Proton nuclear magnetic resonance (1H NMR). Other measurement methods, including relative viscosity tests, amine end group measurement, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), were used to analyze the physical and thermal properties of the PA56/512. Furthermore, the non-isothermal crystallization behaviors of PA56/512 have been investigated with the analytical model of Mo's method and the Kissinger method. The melting point of copolymer PA56/512 exhibited a eutectic point at 60 mol% of 512 corresponding to the typical isodimorphism behavior, and the crystallization ability of PA56/512 also displayed a similar tendency.

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Non-isothermal crystallization of Poly(butylene succinate) (PBSu)/biochar composites was studied at various constant cooling rates using differential scanning calorimetry. The analysis of the kinetics data revealed that the overall crystallization rate and activation energy of the PBSu polymer were significantly influenced by the addition of biochar. Specifically, the PBSu/5% biochar composite with a higher filler content was more effective as a nucleation agent in the polymer matrix, as indicated by the nucleation activity (ψ) value of 0.45. The activation energy of the PBSu/5% biochar composite was found to be higher than that of the other compositions, while the nucleation activity of the PBSu/biochar composites decreased as the biochar content increased. The Avrami equation, which is commonly used to describe the kinetics of crystallization, was found to be limited in accurately predicting the non-isothermal crystallization behavior of PBSu and PBSu/biochar composites. Although the Nakamura/Hoffman-Lauritzen model performed well overall, it may not have accurately predicted the crystallization rate at the end of the process due to the possibility of secondary crystallization. Finally, the combination of the Sesták-Berggren model with the Hoffman-Lauritzen theory was found to accurately predict the crystallization behavior of the PBSu/biochar composites, indicating a complex crystallization mechanism involving both nucleation and growth. The Kg parameter of neat PBSu was found to be 0.7099 K2, while the melting temperature and glass transition temperature of neat PBSu were found to be 114.91 °C and 35 °C, respectively, very close to the measured values. The Avrami nucleation dimension n was found to 2.65 for PBSu/5% biochar composite indicating that the crystallization process is complex in the composites.

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The results of studying the structural features of nanocomposites by electron microscopy, X-ray diffraction analysis, derivatography and stepwise dilatometry are presented. The kinetic regularities of crystallization of nanocomposites based on Exxelor PE 1040-modified high density polyethylene HDPE* and carbon black (CB) are considered by the method of stepwise dilatometry: the dependence of specific volume on temperature. Dilatometric studies were carried out in the temperature range of 20-210 °C. The concentration of nanoparticles was varied within 1.0, 3.0, 5.0, 10, and 20 wt%. In the process of studying the temperature dependence of the specific volume of nanocomposites, it was found that a first-order phase transition occurs for HDPE* samples with 1.0-10 wt% CB content at 119 °C, and for a sample with 20 wt% CB at 115 °C. The study of the process kinetics of nanocomposites isothermal crystallization showed that, for nanocomposites with 1.0-10 wt% CB content, the mechanism of the process is characterized by the formation of a three-dimensional spherulite structure with continuously formed homogeneous and heterogeneous nucleation centers. A substantiated theoretical analysis and interpretation of the discovered regularities of the crystallization process and the growth mechanism of crystalline formations is given. Derivatographic studies of nanocomposites were carried out, according to which the features of changes in the thermal-physical properties of nanocomposites depending on the content of carbon black were established. The results of X-ray diffraction analysis of nanocomposites with 20 wt% carbon black content are presented, according to which there is a slight decrease in their degree of crystallinity.

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The raw material of polylactide (PLA) is lactic acid obtained by biological fermentation. PLA is the most promising degradable polymer to replace traditional plastics to address the pollution problems caused by their non-degradability. However, the application of PLA is hindered by its low softening temperature, easy hydrolysis, and poor toughness. Herein, the ternary composites with PLLA, PDLA and Poly (butylene adipate-co-terephthalate) (PBAT) were prepared by melt blending to balance its thermal stability, hydrolysis, and toughness. The effects of PBAT content (3 %, 6 %, 9 % and 12 %) and isothermal crystallization temperature on composite properties were fully investigated. The results show that the composite of stereo-complexed PLA (sc-PLA) with 6 % PBAT crystallized at 110 °C exhibits good comprehensive properties. Its vicat softening temperature (VST), mass loss rate under alkaline (pH = 12) and breaking elongation are 166 °C, 21.6 % and 4.40 %, respectively. Compared with the pure PLLA sample crystallized at same condition, the VST, mass loss rate and breaking elongation are 159 °C, 24.7 % and 3.76 % respectively, which increased by nearly 5 %, 13 % and 20 %. This indicates that this strategy is feasible to balance the heat resistance, hydrolysis resistance and toughness of PLA, while it sacrifices the tensile strength a little. This work provides a new way to modify and improve the PLA properties. Nonetheless, it is also necessary to coordinate the compatibility of PLA and PBAT.

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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.

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Crystallization kinetics is the key factor in controlling the polymer crystallization process and affecting crystallinity and crystalline morphology, which determine the polymer's main properties. In this work, the non-isothermal crystallization kinetics of graphene/PA10T composites are investigated by the Jeziorny method and Mo method, and the crystallization activation energy is calculated by the Kissinger method. It is found that the addition of an appropriate amount of graphene to PA10T can significantly promote the crystallization of PA10T and accelerate its crystallization rate. The Jeziorny equation does not have a linear relationship across the whole crystallization range, while the Mo equation does a good linear fitting. In addition, the crystallization activation energy decreases when the graphene content is below 1 wt.%. TGA results indicate that the addition of graphene improves the thermal stability of PA10T.

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This work presents, for the first time, a detailed report on how the nucleation and crystallization of polylactide (PLLA) are affected by biobased aliphatic polyesters plasticizers. Three biobased polyesters were synthesized via solvent-free two-stage melt polycondensation of adipic acid (AdA) with three different biobased aliphatic diols and used as plasticizers for poly (L-lactic acid) (PLLA). The molecular structure of the synthesized polyesters was proved using 1H NMR, 13C NMR and Fourier transform infrared (FTIR) spectroscopy. PLLA/AdA-based blends containing 10 wt% of the polyester plasticizers were studied by tensile tests, dynamic mechanical analysis (DMA), wide-angle x-ray scattering (WAXS), differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM). Adding the plasticizers to PLLA decreased Tg by up to 11 °C and significantly increased the elongation at break by about 8 times compared with neat PLLA. The addition of 10 wt% of any AdA-based plasticizer to PLLA increases the nucleation rate from the glassy state by around 50-110 % depending on the plasticizer. The overall crystallization rate from the glassy state was 2-3 times faster for the plasticized PLLAs than neat PLLA. These results are a consequence of the lower energy barrier for both nucleation and growth processes. The incorporation of AdA-based linear polyesters had an incremental impact on the crystal growth rate (or secondary nucleation) of PLLA spherulites from the melt and glassy states. In conclusion, the AdA-based aliphatic polyesters allowed to enhance PLLA crystallization rates and showed interesting potential for the formulation of fully biobased PLLA blends.

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In this study, the influence of non-isothermal conditions on multi-component oleogel (lecithin, LEC and ceramide, CER) was systematically investigated by rheological characterization, polarized light microscopy, and differential scanning calorimetry. Jeziorny and Mo models were applied to reveal the crystallization behavior. When the cooling rate increased, the LEC/CER oleogel exhibited lower G' and larger crystal size. The crystallization kinetics showed that at lower cooling rate, the LEC/CER co-assembled crystals grew at 2-3 dimensions by one step crystallization process. While at high cooling rate, the crystals first grew at 1-2 dimensions through self-assembly of CER. Then, the primary CER crystals served as nuclei for further co-assembly of CER/LEC growing in 2-3 dimensions. Our findings indicated that the cooling rate not only modulated the crystal structure and physical properties, but also the assembly mechanism of multi-component oleogels. Such information is useful for engineering the functional properties of oleogel-based lipidic materials.

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