Crystal Polymer Research Articles

In Situ Fluorescent Visualization of the Interfacial Layer of Induced Crystallization in Polyvinyl Chloride

Despite the remarkable progress in the modification and application of polyvinyl chloride (PVC), developing processing aids for the induced crystallization of PVC and characterizing its interfacial layer remain challenges. Herein, we propose a new polymeric nucleating agent, polyamidea12-graft-styrene–maleic anhydride copolymer (PA12-g-SMA), which possesses high compatibility and crystallinity, effectively improving the crystallinity to 15.1%, the impact strength to 61.03 kJ/m2, and the degradation temperature of PVC to 267 °C through a single and straightforward processing step. Additionally, after the introduction of two different fluorescent sensors in PA12-g-SMA and PVC, the interfacial layer of the induced crystallization can be monitored in situ via a confocal laser scanning microscope (CLSM). This study highlights a rare strategy for significantly enhancing the physical properties of rigid PVC through simply adding a polymeric nucleating agent during processing, while also emphasizing the importance of visualizing the interfacial layer to understand various polymer crystallization processes.

A 1D micromechanics-based constitutive model for the thermoviscoelastic behavior of crosslinked semicrystalline shape memory polymers: numerical simulation and experimental validation

Abstract The paper develops a 1D thermoviscoelastic constitutive model for the crystallization- and melting-induced one-way and two-way shape memory effects, as well as isothermal yielding behaviors, of crosslinked semi-crystalline polymers. A micromolecular chain model is proposed to characterize the transition between the amorphous and crystalline phases. Structural equations including a modified Eying model that combine phase transition and viscoelasticity equations are employed to predict the shape memory effects. An extensive experimental campaign has been carried out on poly (ethylene-co-vinyl acetate) based semi-crystalline elastomers to characterize the thermoviscoelastic temperature-stress-strain relations of the material under different loading and rate conditions. Some results guide the determination of the model parameters, while the rest validate the model capabilities. Comparisons with the experimental results show that the model can well reproduce the stress-strain-temperature responses, providing valuable insights for application development.

Surface Engineering of Polymeric Colloidal Crystals by Temperature - Pressure Annealing.

Polymer colloidal crystals (PCCs) have been widely explored as acoustic and optical metamaterials and as templates for nanolithography. However, fabrication impurities and fragility of the self-assembled structures are critical bottlenecks for the device's efficiency and applications. We have demonstrated that temperature-assisted pressure [ annealing results in the mechanical strengthening of PCCs, which improves with the annealing temperature. Here, the enhancement of elastic properties and morphological features of self-assembled PCC's is evaluated using Brillouin light scattering and scanning electron microscopy. The pressure-induced effects on the vibrational modes of PCCs are also illustrated at temperatures well below the polymer glass transition. While the PCCs colloid constituents display reversibility, the PCC material is strongly irreversible in the performed thermodynamic cycle. The effective elastic modulus enhances from 0.7GPa for the pristine sample to 0.8GPa, solely by pressure annealing at room temperature. [ annealing at higher temperatures leads to a maximum effective elastic modulus of 1.7GPa, more than twice the value in the pristine sample. Above a cross-over pressure, 725bar at 348K), the PCCs respond elastically and, hence, reversibly to pressure changes.

Comparison of Au Nanoparticle/Poly(9-vinylcarbazole) Thin-Film Electrogeneration at 3 Distinct Liquid/Liquid Interfaces: Water/1,2-Dichloroethane, /α,α,α-Trifluorotoluene, Or/Ionic Liquid.

Metal nanoparticle (NP) incorporated conductive polymer films are attractive for their mechanical stability for biomedical applications and as heterogeneous electrocatalysis materials. Novel approaches to generate these materials with tunable properties are still being sought. Herein, the interface between two immiscible electrolyte solutions (ITIES) has been employed as a molecularly sharp and reproducible platform for simultaneous Au NP and poly(9-vinylcarbazole) generation. Three interfaces have been compared, including between water|1,2-dichloroethane (w|DCE), water|α,α,α-trifluorotoluene (w|TFT), and water|ionic liquid (w|IL). In this case the IL was P8888TB (tetraoctylphosphonium tetrakis(pentafluorophenyl)borate). 9-Vinylcarbazole (VC) can polymerize via two routes, either propagating through the vinyl substituent or the aryl rings. The former gives rise to a white semiconducting polymer with a wide bandgap, while the latter produces a green, conducting polymer. External potential control through voltammetric cycling was found to generate the film more rapidly favoring heterogeneous electron transfer with formation of the green poly(VC) variant at the ITIES. This was a free-standing film that could be easily removed from the interface. In the absence of external control, white polymer crystals formed within the oil phase spontaneously likely via AuCl4- w → o transfer followed by a homogeneous electron transfer reaction mechanism. Scanning electrochemical microscopy probe approach curve experiments were used to quantify the electroactivity of the film and are complemented by direct conductivity measurements.

Crystallization and crystal morphology of polymers: A multiphase-field study

In this paper, we introduce a coarse-grained model of polymer crystallization using a multiphase-field approach. The model combines a multiphase-field method, Nakamura’s kinetic equation, and the equation of heat conduction for studying microstructural evolution of crystallization under isothermal and non-isothermal conditions. The multiphase-field method provides flexibility in adding any number of phases with different properties making the model effective in studying blends or composite materials. We apply our model to systems of neat PA6 and study the impact of initial distribution of crystalline grains and cooling rate on the morphology of the system. The relative crystallinity (conversion) curves show qualitative agreement with experimental data. We also investigate the impact of including carbon fibers on the crystallization and grain morphology. We observe a more homogeneous crystal morphology around fibers. This is associated with the higher initial volume fraction of crystal grains and higher heat conductivity of the fiber (compared to the polymer matrix). Additionally, we observe that the crystalline grains at the fiber surface grow perpendicular to the surface. This indicates that the vertical growth observed in experiments is merely due to geometrical constraints imposed by the fiber surface and neighbouring crystalline regions.

The Influence of Carbon Fiber on Crystallization and Morphology of Poly(Ether Ketone Ketone) Composites Towards High Rate Thermoplastic Manufacturing Processes

Recent interest in thermoplastic composites for aerospace applications is driven by the need for high-volume manufacturing of materials that display excellent mechanical, thermal, and solvent resistive properties. Specifically, a large component of the composite properties of thermoplastic composites are highly dependent on the crystalline fraction of the semi-crystalline polymer matrix of the reinforced system. This work investigates the melting behavior of poly (ether ketone ketone) (PEKK) and the influence of temperature and fiber on crystallization kinetics and morphology of (PEKK) composites utilizing, differential scanning calorimetry, Velaris-Sefaris modelling, and polarized optical microscopy (POM). Annealing temperatures of 380°C and above were required to fully erase crystalline ordering in the PEKK matrix. Furthermore, carbon fibers accelerated crystallization kinetics in PEKK at a range of temperatures observed via DSC, and Velaris-Sefaris modelling implied a shift from bulk to surface induced nucleation by the addition carbon fiber to the PEKK matrix, reducing activation energy of crystallization events. This nucleation behavior was visually confirmed through POM with observation of transcrystalline domains nucleated from the surface of a single carbon fiber.

The Influence of Carbon Fiber on Crystallization and Morphology of Poly(Ether Ketone Ketone) Composites Towards High Rate Thermoplastic Manufacturing Processes

Recent interest in thermoplastic composites for aerospace applications is driven by the need for high-volume manufacturing of materials that display excellent mechanical, thermal, and solvent resistive properties. Specifically, a large component of the composite properties of thermoplastic composites are highly dependent on the crystalline fraction of the semi-crystalline polymer matrix of the reinforced system. This work investigates the melting behavior of poly (ether ketone ketone) (PEKK) and the influence of temperature and fiber on crystallization kinetics and morphology of (PEKK) composites utilizing, differential scanning calorimetry, Velaris-Sefaris modelling, and polarized optical microscopy (POM). Annealing temperatures of 380°C and above were required to fully erase crystalline ordering in the PEKK matrix. Furthermore, carbon fibers accelerated crystallization kinetics in PEKK at a range of temperatures observed via DSC, and Velaris-Sefaris modelling implied a shift from bulk to surface induced nucleation by the addition carbon fiber to the PEKK matrix, reducing activation energy of crystallization events. This nucleation behavior was visually confirmed through POM with observation of transcrystalline domains nucleated from the surface of a single carbon fiber.

Crystallization modeling of two semi-crystalline polyamides during material extrusion additive manufacturing

In this work, a heat transfer model is developed for thermally-driven material extrusion additive manufacturing of semicrystalline polymers that considers the heat generated during crystallization by coupling crystallization kinetics with heat transfer. The materials used in this work are Technomelt PA 6910, a semicrystalline hot melt adhesive with sub-ambient glass transition temperature (Tg) and slow crystallization, and PA 6/66, a traditional semicrystalline polyamide with a higher Tg and fast crystallization. The coupled model shows that the released heat during crystallization depends on material selection, with Technomelt PA 6910 and PA 6/66’s temperatures increased by less than 1 °C and up to 6.3 °C, respectively, due to enthalpy of crystallization. Increasing the layer time decreases the layer temperature as well as the initial crystallinity. However, its effect on final crystallinity in Technomelt PA 6910 is negligible due to continued crystallization of the material after printing. Experimental validation shows good agreement for Technomelt PA 6910, but consistently underpredicts PA 6/66 crystallinity. Increasing modeled environmental temperature leads to better agreement with experimental results for PA 6/66, suggesting that higher temperatures may have been experienced. Shear-induced crystallization may also be contributing to crystallinity in this material. The results from this model highlight the importance of and interrelationships between material and processing parameter selection and can aid in achieving quality prints from semicrystalline thermoplastics.

Development of a Novel ECTFE Melt-blown Nonwoven Material and Its Application in Oil-Water Separation

The removal of oil from water surfaces is crucial for protecting the environment and living organisms from the hazards posed by industrial oily wastewater and offshore oil spills. However, achieving enhanced mechanical robustness, corrosion resistance, and durability in oil-water separation membranes presents a significant challenge. In this study, poly(ethylene chlorotrifluoroethylene) (ECTFE) resin, a novel semicrystalline polymer material composed of alternating ethylene and chlorotrifluoroethylene molecules, was fabricated into melt-blown fabric (MB) by melt-blowing technology. By optimizing the side wind temperature, collector distance, roller speed, and hot air pressure, ECTFE MB with superior mechanical properties was established. Additionally, the obtained ECTFE MB exhibited excellent hydrophobicity with a water contact angle reaching 127.8°. The separation efficiency for various oil-water mixtures (oil phase including carbon tetrachloride, petroleum ether, dichloromethane, n-hexane, and isooctane) exceeded 99%. Furthermore, after 90 cycles of oil-water separation, ECTFE MB maintained high flux (72183.16 L m−2 h−1) and separation efficiency of 99.40% when carbon tetrachloride was used as oil phase. Notably, ECTFE MB demonstrated exceptional resistance to harsh environments, including strong acids, bases, and mild high temperature. The investigation of failure modes of ECTFE MB revealed that the primary failure mode of ECTFE MB was the disruption of the oil-water interface. The maximum water height that the ECTFE MB could withstand was 1376 mm. Consequently, ECTFE MB exhibit excellent mechanical properties, chemical stability, and cycling stability, indicating the potential application in the field of oil-water separation.

Supersaturated drug delivery system of albendazole salt-polymer complex for improving oral bioavailability and efficacy anti-secondary E. multilocularis

Based on the supersaturation theory, this study devised two albendazole (ABZ) salt-polymer complexes that enhance the oral bioavailability and efficacy of secondary hepatic alveolar echinococcosis (HAE) in rats. Solid characteristics, microstructure, and stability of ABZ benzenesulfonate (ABZ-BSA) and ABZ methanesulfonate (ABZ-MSA) were evaluated. The equilibrium solubility and intrinsic dissolution rate of salt were measured across different pH environments to determine its potential for generating supersaturation. Polymer crystallization inhibitors were subsequently introduced to assess their impact on sustaining supersaturation. The pharmacokinetics and anti-echinococcosis effects of ABZ were evaluated in healthy SD and HAE rats. The characteristic peaks corresponding to amino acid esters and benzimidazole in the ABZ salt structure either shifted or disappeared, corroborated by PXRD, signifying successful ABZ salt preparation. Furthermore, reductions in the melting point and enthalpy of the salts were observed, along with discernible differences in microstructure compared to ABZ. The drug salts exhibited a significant increase in apparent solubility and intrinsic dissolution rate of ABZ, thus laying the groundwork for supersaturation. Stability assessments indicated that salts were susceptible to moisture absorption, necessitating stringent humidity control measures. Notably, HPMC-AS demonstrated promising capabilities in sustaining supersaturation. Finally, pharmacokinetic analyses revealed a substantial increase in the AUC of ABZ-BSA-H and ABZ-MSA-H by 7.6 and 20.3 times, respectively, compared to ABZ in vivo. After a 30-day once-daily oral administration of the Salts and ABZ to SD rats with hepatic alveolar echinococcosis, the ABZ-BSA-H and ABZ-MSA-H formulation demonstrated a cysts inhibition effect 9.2-fold and 15.3-fold greater than that of ABZ. The salt-HPMC-AS complex could potentially be developed into an improved anti-AE drug therapy. Therefore, the salt-HPMC-AS complex could be developed into an enhanced anti-AE drug therapy.

High sodium conductive polymer electrolyte-based nanoclusters in supercapacitor

The sodium-ion polymer electrolytes (PEs) spur the development of the high safe solid batteries due to their merits of safety, flexibility, lower interfacial resistance with electrodes, and easy processing. Herein, a rational strategy is developed to construct the PE, which can integrate the excellent sodium ion conductivity with the mechanical performances. This strategy applies the nano-sized metal oxide clusters (MOCs) not only to supply the sodium ions but also to inhibit the polymer crystallization. The released polymer chains, crosslinked via physical crosslinking points (nanoclusters), form a network that provides the electrolyte film with toughness over a wide temperature range. The targeted electrolyte exhibits excellent Na-ion conductivity of 3.8 × 10−4 S cm−1 at room temperature, tensile strength up to 0.74 Mpa and breaking elongation of 23 %. In addition, this PE widens the electrochemical stability window of the aqueous Na-ion supercapacitor up to 2.0 V since the water molecules are effectively confined via the strong interactions among components. Our research on sodium polymer electrolytes combined by nanoclusters and PVA holds significant promise for advancing solid-state sodium saaupercapacitors— a new generation of high-performance, safe, and cost-effective energy storage solutions.

Dependence of Thermally Activated Relaxation of Crystalline Stems on the Molecular Topology at Crystalline/Amorphous Interfaces in Polyethylene.

We investigate the relaxation dynamics of crystalline stems in relation to the molecular topology of the crystalline/amorphous interface, employing coarse-grained molecular dynamics. To efficiently generate model semicrystalline systems of linear polyethylene with a realistic interphase morphology, we simplified the Monte Carlo method by introducing molecular dynamics for faster relaxation. The structural properties of the generated systems are validated against experimental measurements, theoretical predictions, and existing simulation data. The models suggest that the probability distribution of loop-entry sites on the lamellar surface can be described by a power law in terms of the distance between the entry sites. By considering realistic interphase morphology, we are able to improve the prediction of the overall activation energy for the relaxation of crystalline stems, aligning it closely with experimental measurements. The largest model predicts that crystalline stems connected via large loops, i.e., those that exceed the entanglement length, and long tails are associated with increased activation energy; whereas stems connected to shorter tails show the lowest activation energy. These predictions can guide the future development of tougher semicrystalline polymers by providing insights into how amorphous chain morphology contributes to the activation energy and the relaxation dynamics of crystalline chains.

LOW TEMPERATURE CRYSTALLIZATION BEHAVIOR OF NR BY DYNAMIC MECHANICAL ANALYSIS

ABSTRACT A fundamental study of low temperature crystallization of NR gum polymer (raw elastomer) was conducted using dynamic mechanical analysis (DMA) in oscillatory shear rheology mode. Isothermal crystallization was followed using DMA for crystallization temperatures ranging from −15 to −35 °C, with the maximum rate of crystallization noted at −25 °C. After the isothermal crystallization (annealing) for times from 6 to 9 h, DMA heating scans revealed two melting transitions (α and β) with locations that depended on the prior annealing temperature. The locations of these melting transitions were comparable with literature results for melting peaks by differential scanning calorimetry. At temperatures above these melting transitions, we identified two additional relaxations in the DMA heating trace that did not depend on the prior crystallization history. We also found evidence of the melt memory effect in polymer crystallization, which is discussed. During annealing at −25 °C, high cis-1,4 IR showed considerably slower and lower extent of crystallization than NR and crosslinked NR did not show noticeable crystallization within the 12-h experiment.

Density gradient structure foams prepared by novel two-step foaming strategy: Performance, simulation and optimization

Functional gradient foam materials play a crucial role in meeting the diverse performance and functionality requirements of modern engineering. Density gradients enable the distribution of mechanical, dielectric, and optical properties within materials, exhibiting a gradient representation. However, creating density gradients within foams poses a significant challenge, especially for semi-crystalline polymers. The paper proposed a novel two-step foaming method for preparing polypropylene (PP) foams with density gradient structure (DGS). Initially, a pre-foaming process was conducted to prepare PP pre-foams with uniform structure (US) at low temperatures, followed by a secondary foaming process on partially saturated PP pre-foams to fabricate PP DGS foams. By adjusting the duration of partial saturation time, PP foams with various DGS can be achieved. Compared with the commonly used one-step foaming method and uniform foaming method in the literature, the DGS foams prepared by the two-step foaming method exhibit not only a significant enhancement in mechanical property but also achieve the lowest thermal conductivity, while maintaining comparable and outstanding sound insulation performance. Finally, a comprehensive evaluation model using COMSOL Multiphysics was developed for the DGS foams, providing insights for optimizing foam performance through process enhancements.

In Situ Alloying Enabled by Active Liquid Metal Filler for Self‐Healing Composite Polymer Electrolytes

AbstractSolid inorganics, known for kinetically inhibiting polymer crystallization and enhancing ionic conductivity, have attracted significant attention in solid polymer electrolytes. However, current composite polymer electrolytes (CPEs) are still facing challenges in Li metal batteries, falling short of inhibiting severe dendritic growth and resulting in very limited cycling life. This study introduces Ga62.5In21.5Sn16 (Galinstan) liquid metal (LM) as an active liquid alternative to conventional passive solid fillers, aiming at realizing self‐healing protection against dendrite problems. Compared to solid inorganics, for example silica, LM droplets could more significantly reduce polymer crystallinity and enhance Li‐ion conductivity due to their liquid nature, especially at temperatures below the polymer melting point. More importantly, LMs are unraveled as dynamic chemical traps, which are capable of blocking and consuming lithium dendrites upon contact via in situ alloying during battery operation and further inhibiting dendritic growth due to the lower deposition energy barrier of the formed Li‐LM alloy. As a proof of concept, by strategically designing an asymmetric CPE with the active LM filling, a solid‐state Li/LiFePO4 battery achieves promising full‐cell functionality with notable rate performance and stable cycle life. This active filler‐mediated self‐healing approach could bring new insights into the battery design in versatile solid‐state systems.

In Situ Alloying Enabled by Active Liquid Metal Filler for Self-Healing Composite Polymer Electrolytes.

Solid inorganics, known for kinetically inhibiting polymer crystallization and enhancing ionic conductivity, have attracted significant attention in solid polymer electrolytes. However, current composite polymer electrolytes (CPEs) are still facing challenges in Li metal batteries, falling short of inhibiting severe dendritic growth and resulting in very limited cycling life. This study introduces Ga62.5In21.5Sn16 (Galinstan) liquid metal (LM) as an active liquid alternative to conventional passive solid fillers, aiming at realizing self-healing protection against dendrite problems. Compared to solid inorganics, for example silica, LM droplets could more significantly reduce polymer crystallinity and enhance Li-ion conductivity due to their liquid nature, especially at temperatures below the polymer melting point. More importantly, LMs are unraveled as dynamic chemical traps, which are capable of blocking and consuming lithium dendrites upon contact via in situ alloying during battery operation and further inhibiting dendritic growth due to the lower deposition energy barrier of the formed Li-LM alloy. As a proof of concept, by strategically designing an asymmetric CPE with the active LM filling, a solid-state Li/LiFePO4 battery achieves promising full-cell functionality with notable rate performance and stable cycle life. This active filler-mediated self-healing approach could bring new insights into the battery design in versatile solid-state systems.

Impact of Runner Size, Gate Size, Polymer Viscosity, and Molding Process on Filling Imbalance in Geometrically Balanced Multi-Cavity Injection Molding.

The injection molding process is one of the most widely used methods for polymer processing in mass production. Three critical factors in this process include the type of polymer, injection molding machines, and processing molds. Polypropylene (PP) is a widely used semi-crystalline polymer due to its favorable flow characteristics, including a high melt flow index and the absence of a need for a mold temperature controller. Additionally, PP exhibits good elongation and toughness, making it suitable for applications such as box hinges. However, its tensile strength is a limitation; thus, glass fiber is added to enhance this property. It is important to note that the incorporation of glass fiber increases the viscosity of PP. Multi-cavity molds are commonly employed to achieve cost-effective and efficient mass production. The filling challenges associated with geometrically balanced layouts are well documented in the literature. These issues arise due to the varying shear rates of the melt in the runner. High shear rate melts lead to high melt temperatures, which decrease melt viscosity and facilitate easier flow. Consequently, this results in an imbalanced filling phenomenon. This study examines the impact of runner size, gate size, polymer viscosity, and molding process on the filling imbalanced problem in multi-cavity injection molds. Tensile bar injection molding was performed using conventional injection molding (CIM) and microcellular injection molding (MIM) techniques. The tensile properties of the imbalanced multi-cavity molds were analyzed. Flow length within the cavity served as an indicator of the filling imbalance. Additionally, computer simulations were conducted to assess the shear rate's effect on the runner's melt temperature. The results indicated that small runner and gate sizes exacerbate the filling imbalance. Conversely, glass fiber-filled polymer composites also contribute to increased filling imbalance. However, foamed polymers can mitigate the filling imbalance phenomenon.

Polypropylene Crystallinity Reduction through the Synergistic Effects of Cellulose and Silica Formed via Sol-Gel Synthesis.

This study focuses on the development of environmentally sustainable polypropylene (PP)-based composites with the potential for biodegradability by incorporating cellulose and the oligomeric siloxane ES-40. Targeting industrial applications such as fused deposition modeling (FDM) 3D printing, ES-40 was employed as a precursor for the in situ formation of silica particles via hydrolytic polycondensation (HPC). Two HPC approaches were investigated: a preliminary reaction in a mixture of cellulose, ethanol, and water, and a direct reaction within the molten PP matrix. The composites were thoroughly characterized using rotational rheometry, optical microscopy, differential scanning calorimetry, and dynamic mechanical analysis. Both methods resulted in composites with markedly reduced crystallinity and shrinkage compared to neat PP, with the lowest shrinkage observed in blends prepared directly in the extruder. The inclusion of cellulose not only enhances the environmental profile of these composites but also paves the way for the development of PP materials with improved biodegradability, highlighting the potential of this technique for fabricating more amorphous composites from crystalline or semi-crystalline polymers for enhancing the quality and dimensional stability of FDM-printed materials.

Manipulating the adhesion of electroless plated Cu film on liquid polymer crystal substrate for advanced microelectronic manufacturing

Manipulating the adhesion of electroless plated Cu film on liquid polymer crystal substrate for advanced microelectronic manufacturing

Impact of Ball Milling on the Microstructure of Polyethylene Terephthalate.

Polyethylene terephthalate (PET) is a semi-crystalline polymer that finds broad use. Consequently, it contributes to the accumulation of plastics in the environment, warranting PET recycling technologies. Ball milling is a commonly used technique for the micronization of plastics before transformation. It has also recently been reported as an efficient mixing strategy for the enzymatic hydrolysis of plastics in moist-solid mixtures. However, the effect of milling on the microstructure of PET has not been systematically investigated. Thus, the primary objective of this study is to characterize the changes to the PET microstructure caused by various ball milling conditions. PET of different forms was examined, including pre- and post-consumer PET, as well as textiles. The material was treated to a range of milling frequencies and duration, before analysis of particle size, crystallinity by differential scanning calorimetry and powder X-ray diffraction, and morphology by scanning electron microscopy. Interestingly, our results suggest the convergence of crystallinity to ~30% within 15 minutes of milling at 30 Hz. These results are consistent with an equilibrium between amorphous and crystalline regions of the polymer being established during ball milling. The combined data constitutes a reference guide for PET milling and recycling research.