Crystallization Behavior Research Articles

Investigation of thermal, crystal and magnetic behavior of addition of Nd rare earth element effect on CuAlMn shape memory alloy

Investigation of thermal, crystal and magnetic behavior of addition of Nd rare earth element effect on CuAlMn shape memory alloy

Toward Highly Toughened Polylactide/Polycaprolactone‐Based Polyurethane Blends With Shape Memory Property via Reactive Blending

ABSTRACTReactive blending has proven to be a versatile and efficient method for enhancing the impact toughness of polylactide (PLA). PLA/cross‐linked polycaprolactone‐based polyurethane (c‐PCLU) blends are prepared by reactive blending of PLA with PCL triol and hexamethylene diisocyanate (HDI). The reaction mechanism, compatibility, crystallization behavior, rheology behavior, mechanical performance, and shape memory property are thoroughly studied. The FTIR results confirmed that the NCO groups of HDI reacted with the hydroxyl groups of PLA and PCL triol, leading to the in situ formation of c‐PCLU and PLA‐co‐PCLU. The phase morphology exhibits a sea‐island structure, suggesting incompatibility between the two phases. The compatibility of the blends is improved with the increase of the PCL triol feeding ratio. The crystallization ability of PLA is retarded in the reactive blend. Both the elongation at break and the shape recovery ratio increase with c‐PCLU content, reaching up to 94.0% and 92.6%, respectively. These findings show that the formation of c‐PCLU greatly enhanced the toughness and shape memory performance of PLA.

Non-isothermal Crystallization and Thermal Transformation Behaviors of Plasma Sprayed Fe48Cr15Mo14Cl5B6Y2 Amorphous Coating

Non-isothermal Crystallization and Thermal Transformation Behaviors of Plasma Sprayed Fe48Cr15Mo14Cl5B6Y2 Amorphous Coating

Role of harmonic and anharmonic interactions in controlling the cooperativity of spin-crossover molecular crystals

We present a theoretical model of spin transitions in homogeneous spin-crossover (SCO) materials, based on the description of the interactions between SCO molecules by the Lennard-Jones potential in which the equilibrium distances depend on the spin states of the linked molecules. By expanding the potential to order 3 considering a homogeneous lattice spacing, we demonstrate that the present model is isomorphic with an Ising-like model combining infinite long-range “ferromagnetic-like” interactions, competing with short-range “antiferromagnetic-like” between nearest neighbors in the case of harmonic interactions. When an anharmonic contribution is included, the short-range interaction becomes dependent on the average high-spin fraction, and changes its sign along the spin transition. The thermodynamic properties of the model were first investigated analytically in mean field approximation for both harmonic and anharmonic cases, for which we clarify the conditions for obtaining gradual and first-order transitions. Moreover, we demonstrated that within this approximation, the strength of the antiferromagnetic-like interactions are insufficient to produce multistep transitions. In contrast, the resolution of the previous emerging Ising-like model by Monte Carlo simulations demonstrated the possibility of obtaining gradual, first-order and two-step transitions as a result of the antagonism between long- and short-range interactions. Overall, the obtained results demonstrate the suitability of the present theoretical model to describe cooperative SCO materials. The key message of our paper is that our model can be used to predict complex behavior of spin-crossover crystals. Published by the American Physical Society 2024

Crystallization, thermal, and compatibility performances of poly (butylene succinate) (PBS)/poly((R)‐3‐hydroxybutyrate‐co‐(R) 3‐hydroxyhexanoate) (PHBHHx) blends

AbstractBiodegradable materials provide protective properties comparable to conventional plastics while diminishing reliance on nonrenewable resources. Environmentally friendly polymer blends were prepared by melting poly(R)‐3‐hydroxybutyrate‐co‐(R)‐3‐hydroxyhexanoate) (PHBHHx) with poly (butylene succinate) (PBS). PBS was synthesized through esterification and polycondensation using 1,4‐butanediol and succinic acid, with tetrabutyltitanate as the catalyst. The PHBHHx is supplied by Bulepha®PHA Company of China, model number BP330. The effects of PHBHHx content on thermal behavior, compatibility, and thermal stability of PBS/PHBHHx blends were systematically investigated. Differential scanning calorimetry (DSC) results indicated that the addition of PHBHHx influenced the crystallization behavior, the crystallization temperature (Tc) of PBS decreased meanwhile, the crystallization half‐time of PBS is reduced to 1.5 min compared with neat PBS (5 min) after isothermal is crystallized at 95°C. Polarized Optical Microscopy (POM) images also revealed that crystallization rate accelerated in the blend with increasing PHBHHx content. Rheological and Scanning Electron Microscopy (SEM) analysis demonstrated that incorporating a significant content of PHBHHx reduced compatibility between PBS and PHBHHx. Mechanical property testing indicates that the addition of PHBHHx reduced the toughness of blends. Additionally, the addition of a small amount of PHBHHx imparts a higher crystallinity (56%) and heat resistance of the PBS/PHBHHx blends (78°C) was higher than neat PBS (74°C).Highlights Laboratory synthesis of high molecular weight PBS. Optimal ratios improved crystallinity and thermal stability of blends. A systematic study of the crystallization properties of blends.

Surface modified cellulose nanospheres with simultaneous nucleation and degradation-accelerating effects on poly(lactic acid)

As a novel type of nanocellulose material, cellulose nanospheres (CNSs) have gained significant attention and rapid development in recent years. In this work, the surface hydrophobic modification of CNSs was achieved by employing maleic anhydride as an esterifying agent. The effects of modified cellulose nanospheres (CNS-MA) on the crystallization and hydrolysis behaviors of polylactic acid (PLA)-based composites were systematically investigated. The results demonstrate that surface modification improves the dispersion of CNSs in the PLA matrix. Well-dispersed particles act as nucleation sites, which increases the crystallization rate and crystallinity of PLA and endows the composites with remarkable heat distortion resistance. The storage modulus of the PLA/CNS-MA composites exceeds 300 MPa, even at an elevated temperature of 90 °C. Furthermore, the hydrolytic degradation of PLA is dramatically accelerated with the addition of CNS-MA. Combining the morphology observations and theoretical calculations, it is speculated that the fast hydrolytic degradation is related to a transition in the main hydrolytic degradation mechanism from surface erosion to bulk erosion, because the presence of CNS-MA provides particular pathways for water molecules to diffuse into the interior of the composites. This research highlights the potential of CNSs as a multifunctional filler with both reinforcing and degradation-promoting effects, offering valuable insights for the study of other biomass nanomaterials.

Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and Degradation Behavior of Star-Shaped Poly(Lactic Acid)

Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and Degradation Behavior of Star-Shaped Poly(Lactic Acid)

Liquid Crystal Behavior of Uniform Short Rods Made from Computationally Designed Parallel Coiled Coil Building Blocks.

Parallel, homotetrameric coiled coils were computationally designed using 29 amino acid peptides. These parallel coiled coils, called "bundlemers", have C2 symmetry, with all N-termini displayed from one end of the nanoparticle and all C-termini from the opposite end. This anisotropic display of the peptide termini allowed for the functionalization of two sets of nanoparticles with either maleimide or thiol functionality at the N-terminal region of the constituent peptides. The thiol-Michael conjugation reaction between the N-terminal end of complementary bundlemer nanoparticles formed monodisperse, rigid bundlemer dimer, called "dibundlemer", rods. The constituent, individual bundlemer nanoparticles were characterized with small-angle X-ray scattering (SAXS), Förster resonance energy transfer (FRET), and circular dichroism (CD) spectroscopy to confirm the parallel assembly of the coiled coils, consistent with the computational design. The dibundlemer rods were characterized with SAXS to reveal the uniform dibundlemer nature of the rods. Optical birefringence is observed in concentrated samples of the rods, with polarized optical microscopy (POM) revealing a nematic liquid crystalline behavior.

Effects of spherical, disk-like and lamellar nanocomposite particles on cold flow behaviors of waxy crude oil

Wax precipitation and deposition are challenging hurdles in pipeline transportation of waxy crude oil. This study focuses on transforming SiO2, Laponite, and montmorillonite particles into hydrophobic particles through polymer grafting. Chemical structure analysis and grafting ratio calculation were performed. Through thermogravimetric analyzer (TGA) test, Laponite showed the highest grafting ratio. The effects of adding nanocomposites, TDA-2024-22, and commercial pour point depressants on the rheological behavior and wax crystallization behavior of African crude oil were compared. Addition of the nanocomposite PDA-22@SiO2 to crude oil, reduced the viscosity by 85.6% at 20 °C and the thixotropy by 60.2%. Wax crystal size decreased in the order of PDA-22@SiO2, PDA-22@Laponite, KS-10, TDA2024-22, and PDA-22@MMT. The pour point decreased by 6 °C with PDA-22@ SiO2 particles but only 3 °C with Laponite and montmorillonite composites. Spherical nanocomposites are promising flow improvers for waxy crude oil.

High-efficiency pure-red perovskite quantum dots glass via Dy modification for high quality backlight display

Perovskite quantum dots (QDs) glass has been considered as high efficiency, high color-purity, and high stability luminescent materials for display application. Herein, high emissive Dy doped CsPb(Br, I)3 (CPBI: Dy) QDs glass has been prepared, and the effects of doping concentration on the crystallization behavior of QDs were discussed carefully. The low and high concentration of Dy doping brings diametrically opposite tuning effects for the emission wavelength. When high Dy doping, DyBO3 nanocrystals were precipitated from the glass along with CPBI QDs. The highest photoluminescence quantum yield of CPBI: Dy QDs glass reached 53.79 %. The LEDs using the CPBI: Dy QDs glass as color converter could express pure-red light of 630 nm peak with a full width at half maximum of only 25.6 nm. What’s more, the color gamut of a white backlight unit based on prepared CPBI: Dy QDs glass film was 125.8 % of National Television System Committee color gamut standard and 94.0 % of Rec.2020, which has great potential in display application.

Preparation of chlorinated polyethylene/carbon black/benzoxazine composites with positive temperature coefficient effects

Chlorinated polyethylene (CPE)/carbon black (CB)/ benzoxazine composites with Positive Temperature Coefficient (PTC) characteristics are prepared using the conventional melt-mixing method. The research investigates how benzoxazine content and curing time impact the PTC/NTC characteristics, resistivity, microstructure, and crystallization behavior of these composites.The findings demonstrated a positive correlation between the room temperature resistivity of CPE/CB/benzoxazine composites and benzoxazine content, making the control of benzoxazine content particularly important. Scanning electron microscopy (SEM) reveals that these composites maintain a porous isolated structure regardless of curing time. However, crystallinity decreases as curing time increases. Optimal conditions are achieved with benzoxazine concentration of 2 wt% and a curing time of 45 minutes, resulting in a PTC intensity peak exceeding 5 after R-T cycling. Additionally, at 2 wt% benzoxazine content and a curing time of 60 minutes, a three-dimensional cross-linked network is formed. This network confines carbon black within specific regions, preventing large-scale aggregation and eliminating the NTC effect. After three thermal cycles, the PTC intensity stabilizes around 3.8, indicating good cycling stability.

Optimizing the low-temperature performance of high-wax-content crude oil with emulsion-based wax inhibitors: Mechanisms and efficacy.

Wax deposition in constant-temperature transportation of waxy oil with high pour points poses a significant challenge for the oil industry. The demand for efficient methods to solve wax deposition has gained attention. To elucidate the impact of emulsion-based wax inhibitors on the performance of crude oils with varying wax content at low temperatures, experiments, rheological analyses, and microscopic analyses were conducted to study their pour point regulation, low-temperature flow improvement, wax prevention effectiveness, and wax crystallization behavior. The results indicate that emulsion-based wax inhibitors significantly reduce the pour point of crude oil, especially for high-wax-content oil, while for low-wax-content oil, the pour point only decreased by 3°C. By penetrating and dispersing wax crystals, the inhibitor reduced the viscosity of crude oil at low temperatures, enhancing its flowability. At 28°C, crude oil transitioned from a shear-thinning non-Newtonian fluid to a Newtonian fluid at wax inhibitor dosages of 500-750ppm. At 1000ppm, the wax prevention rate for high-wax-content oil reached 87.5%, but the effect plateaued beyond this concentration. Additionally, the wax prevention and removal mechanism of the emulsion-based wax inhibitors is discussed. This study confirms that emulsion-based wax inhibitors significantly enhance the low-temperature processability of crude oil, offering a viable strategy for the conveyance and refinement in cold climates.

Cellulose nanocrystal dispersion-ability in polylactides with various molecular weights prepared in dichloromethane/dimethyl sulfoxide solvents for electrospinning applications

In this study, effects of polylactide molecular weight, i.e., high (HPLA), medium (MPLA), low (LPLA), and dichloromethane (DCM)/dimethyl sulfoxide (DMSO) blend ratio on cellulose nanocrystal (CNC) dispersion quality in solution casted PLA/CNC nanocomposites were investigated via small amplitude oscillatory shear rheological analysis, while crystallization behavior, thermal degradation, morphological structure of the nanocomposites were also reported. Due to its low dielectric constant, none of the nanocomposites with 100DCM indicated a change in their complex viscosity as a result of poor CNC dispersion. This is while the increase in DMSO content (50%vv−1) improved CNC dispersion. The superior CNC dispersion-ability in PLAs with lower molecular weight was confirmed. The poorer CNC dispersion in HPLA attributes to hindering effect of higher molecular weight on solvent and nanoparticle diffusion. The better dispersed CNCs influenced crystal nucleation behavior of PLAs and increased crystallinity degree. In addition, the impact of well-dispersed CNCs on fiber formation quality of nanocomposites was reported. Introducing finely dispersed CNCs (1 wt%) in LPLA refined fiber diameters around 1200 nm with more homogenous structure. Besides, the use of 100DCM and the use of DMSO at high contents (50%vv−1) deteriorated fiber formation, respectively, due to low conductivity of DCM and high boiling temperature of DMSO.

The Effect of Surface Chemistry on the Caking Behaviour of Sucrose Crystals

The caking behaviour of organic crystals presents a significant challenge in both the food and pharmaceutical industries. This study aimed to investigate how surface impurities influence the caking behaviour of sucrose (sugar) crystals. Sucrose crystals were selected as the model material due to their relevance in various industries such as food processing and pharmaceuticals. The impact of surface chemistry was assessed for sucrose crystals with varying levels of impurities, namely white sugar, light brown sugar, and dark brown sugar. These crystals were subjected to controlled cycles of humidity exposure, compaction, and drying to induce caking, simulating real-world scenarios. The caking propensity was evaluated using a compression test, while the surface chemistry was characterized through Inverse Gas Chromatography (IGC). Moisture sorption properties were evaluated using a Dynamic Vapor Sorption (DVS) technique, and the formation of solid bridges was studied using scanning electron microscopy (SEM) and X-ray tomography. The results indicate that impurities play a crucial role in enhancing the caking behaviour of sucrose crystals by influencing their hygroscopicity and facilitating solid bridge formation. This study provides valuable insights into the relationship between surface chemistry, moisture sorption properties, and the caking behaviour of sucrose crystals, offering strategies to mitigate caking issues.

Utilizing foxtail millet husk waste for sustainable new bioplastic composites with enhanced thermal stability and biodegradability

Foxtail millet husk (FMH) is a byproduct that is not suitable for consumption and is often discarded as solid waste. However, it can be used as a raw material to develop novel bioplastic composites that transform agro-based leftovers into value-added goods. Herein, new bioplastic composites were developed from poly(lactic acid), poly(butylene adipate-co-terephthalate) and FMH based granules by Injection Molding. The required granules were generated via a solvent evaporation method. The resulted bioplastic composites were analyzed for their morphologies, mechanical properties, crystal structures, thermal stability, and melting and crystallization behaviors using various techniques, such as scanning electron microscopy, universal testing machine, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Expressly, chemical bonding between FMH fibers and poly(lactic acid)/poly(butylene adipate-co-terephthalate) PLA/PBAT was confirmed through Fourier Transform infrared spectroscopy analysis. The inclusion of FMH lowered the impact strength of the PLA/PBAT combination, which was confirmed by mechanical analysis. Morphological findings confirmed that the PLA/PBAT combination had FMH aggregation. DSC thermograph revealed negligible differences in glass transition and melting temperatures of PLA/PBAT blend with and without FMH. The thermogravimetry results exhibit that the FMH can improve bioplastic thermal stability. The addition of FMH improved the biodegradability of the PLA/PBAT bioplastic composites. Overall, FMH waste can be repurposed for bioplastic composites with enhanced thermal stability and biodegradability. This reduces solid waste from agricultural practices and creates eco-friendly products. Further research could lead to more sustainable alternatives.

A Survey of Solid Form Landscape: Trends in Occurrence and Distribution of Various Solid Forms and Challenges in Solid Form Selection

This survey provides a comprehensive analysis of solid form screens for 476 new chemical entities (NCEs) conducted at Pharmaron from 2016 to 2023. The findings from this survey reveal notable trends in polymorphism, salt formation, crystallization behavior and molecular weight (MW) distribution of the NCEs evaluated. Most solid form screens were conducted to select the preferred solid form for Investigational New Drug (IND) enabling projects, others were for candidate selection or late-stage development. Comparison to published historical data was made to show changes in occurrence of counterions/co-formers for salts/co-crystals, polymorphs, and the distribution of MWs over time. Increased complexity in the solid-form landscape and selection of the development form are discussed, including challenges in crystallization and selection of lead forms. The distribution of types of crystal forms and the observation of emerging and disappearing polymorphs are presented. These results highlight the evolving challenges and considerations in solid form screening and form selection and offer insights for future pharmaceutical development and crystallization strategies.

Proposal of a Biobased and Biodegradable Polymer as a Hot Embossing Substrate for Holographic Security Marks Fabrication

ABSTRACTThe alarming increase in counterfeiting has determined a more intensive application of authentication solutions such as holographic security marks. Polycarbonate or polymethyl methacrylate currently used in the hot embossing process to produce security marks are discarded as non‐biodegradable waste after utilization. For the first time, poly(lactic acid) (PLA) was studied here as a hot‐embossing substrate to imprint a micro‐relief containing diffractive gratings, as a stage in the fabrication of holographic security marks. Four PLA grades, which differ by crystallinity and mechanical properties, were used to define the suitability of PLA for hot embossing. The 3D topography of embossed micro‐relief in PLA plates was investigated by quantitative phase imaging, scanning electron microscopy, and atomic force microscopy (AFM). The analyses showed that a high crystallinity and a low d‐lactide content of PLA render the hot‐embossing process more difficult and decrease the quality of the imprinted micro‐relief. The average height of the micro‐relief and the difference in height values, which were determined by AFM, allowed the ranking of the PLA grades according to the quality of the diffracted image. The possibility of recycling the embossed PLA substrate several times before composting was also demonstrated in this work. The variation of the mechanical properties, thermal stability, melting, and crystallization behaviors after each recycling cycle has shown that PLA can be reprocessed six times without significant damage to the properties. This study demonstrated that PLA can replace petroleum‐based polymers in the fabrication of holographic security marks and its suitability for a plethora of optoelectronics applications.

Phase transition studies of a fluorinated antiferroelectric liquid crystal probed by temperature dependent Raman spectroscopy

Fluorinated liquid crystals (LCs) have emerged as a valuable option for display technologies, rapid switching applications, and photonic devices. Addition of fluorine atoms in the LCs change the electronic distribution within the molecule, introducing required LC properties for various display techniques. In this study, the structural properties of an antiferroelectric LC, (S)-octan-2-yl 2,3-difluoro-4′’-((6-((2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanoyl)oxy) hexyl) oxy)-[1,1′,4′,1′’-terphenyl]-4-carboxylate is investigated using Raman spectroscopy. This LC exhibits a unique orthoconic antiferroelectric arrangement along with chiral smectic C (SmC*) and smectic A (SmA*) phases. Raman spectra were recorded over a temperature range of 20 °C to 130 °C, covering the spectral region of 500–3500 cm−1. Additionally, theoretical Raman spectra at room temperature is simulated using density functional theory (DFT) with the B3LYP functional and 6-31G (d, p) basis set, showing good agreement with experimental results. Through meticulous fitting of the spectral features using Lorentzian profiles, precise values for peak positions, linewidths, and integrated intensities of selected Raman bands are obtained. Changes in Raman spectral parameters at the crystalline-SmCA*, SmCA*-SmC*, SmC*-SmA*, and SmA*-isotropic phase transitions are analyzed in terms of molecular alignment and intra/intermolecular interactions. The Raman spectral results provide a detailed understanding of the molecular and structural behaviour of the liquid crystal as it undergoes various phase transitions with increasing temperature.

Design of toughed bio-based polylactide/polyamide 11 blends with regulatable size of dispersed phase and spherulites by interfacial stereocomplex crystallites

Enhancing the ductility of polylactide (PLA) through toughening modification to expand the application range of PLA aligns with the requirements of green development. In this study, eco-friendly bio-based plastic polyamide 11 (PA11) was chosen to modify poly(l-lactide) (PLLA). PA11 and poly(d-lactide) (PDLA) were grafted onto the main chain of ADR via simple reactive processing and utilized as reactive compatibilizers to improve toughening efficiency of PA11. The successful preparation of the graft copolymer was confirmed through 1H NMR, FT-IR and DSC, and a detailed investigation was conducted on how the composition and concentration of the compatibilizer influence the mechanical properties, phase morphology, crystallization, and nucleation behaviors of PLLA/PA11 blends. Elongation at break of the 5 % PDLA/PA11 graft copolymers toughed PLLA was as high as 222 % at 30 % PA11 content, which was 17 times greater than the PLLA toughened by pristine PA11 without compromising the strength. PLLA and PA11 were immiscible binary blends with PA11 droplet/PLLA matrix phase separated morphologies in the molten state. Based on the calculation of interfacial tension, the grafted copolymer would be mainly distributed at the interface between the two phases. The dispersion of PA11 droplet in PLLA matrix was improved since the interfacial interaction force was enhanced through in-situ reaction. The increase of the nucleation site and decrease of the spherulites size were worked synergistically by stereocomplex (SC) crystallites and PA11. Under the impact of reducing the size of the dispersed phase and spherulites, the toughness of blends was enhanced. This study provided valuable insights into the control of PLLA immiscible blend morphology and elucidated the relationship between the size of dispersed phase and spherulites and the ultimate mechanical performance of bio-based PLA materials.

Liquid crystal phase behavior of oxalated cellulose nanocrystal and optical films with controllable structural color induced by centripetal force

Cellulose nanocrystal (CNC) is a sustainable bio-nanomaterial. The distinctive left-handed polarization properties render cellulose nanocrystal a promising candidate for optical film. Due to eco-friendliness, reliability, mildness and simplicity, the oxalate hydrolysis method stands out among various preparation methods for CNC. This study delved into the liquid crystal phase behavior of oxalated cellulose nanocrystal derived from pulp, and discovered the influences of CNC concentration and pH on suspension stability and phase transition, and evaluated its optical properties. The results demonstrated that oxalated CNC presented two different liquid crystal phases, the nematic phase and the cholesteric phase. The stability mechanism of CNC suspension and the regulatory principle of the liquid crystal phase transition were revealed. A novel CNC film-forming technology, the multilayer spin-coating technique, was developed for cellulose nanocrystal optical films. Driven by centrifugal force, cellulose nanocrystals were induced to self-assembly and formed the optical film with circular dichroism and structural color. This simple and efficient film-forming technology promised rapid processing (1 h) and controllable film structure and optical properties compared to traditional technologies. This work provided a theoretical understanding and practical prospects for integrating oxalated cellulose nanocrystal into sustainable advanced optical film materials.