Polymer Matrix Research Articles

Hybrid nano-biocomposite based on polysaccharide and graphene oxide for the practical separation of proteins in a fixed bed adsorption column

Proteins and amino acids are essential to humans and all living beings. Moreover, these compounds are present in the pharmaceutical, food, and cosmetic industries. Proteins need to be purified for use in industry. This work aims to synthesize and apply a nano-biocomposite based on graphene oxide (GO) and agar (polysaccharide) for protein separation and purification. The hydrogel composite was tested for myoglobin (Mb) adsorption, the effect of changing the initial pH in Mb adsorption, and the ionic strength was evaluated. The adsorptive capacity values were higher at pH=5 and 6 and decreased at higher pH values. The increase in NaCl concentration did not affect the adsorptive capacity significantly. The composite exhibited a notorious value of maximum experimental adsorption capacity in the equilibrium of over 790 mg g−1 at pH=5 and 25 °C. As GO interacts with the polymeric agar matrix, resulting in a 3D material, the material developed could adsorb Mb in a fixed bed column and single and binary (BSA+Mb) systems. There are indications that the GO-based composite possibly forms a complex with the peptide ligands of myoglobin, forming a protein corona, making Mb desorption difficult.

Synthesis of Ultra-Stretchable Thermoelectric Nanofibrous Membrane Based on Wet-Electrospun Polyurethane/MWCNTs Composites

Electrospinning is a versatile method used to create nanofiber membranes with surface-to-volume ratios much higher than those achievable with other film fabrication methods. This technique allows the control of nanofiber morphology, including diameter, shape, and orientation. Such nanostructuring can enhance the thermoelectric performance of composite materials due to quantum confinement and filtering effects. However, the thermoelectric efficiency of a typical electrospun composite is limited due to the insulating nature of the polymer matrix. Therefore, many researchers have combined electrospinning with other techniques or post-treatments to accomplish higher thermoelectric performance. In this study, a new strategy to prepare a stretchable thermoelectric nanofibrous membrane is proposed. The ternary composite of Thermoplastic Polyurethane (TPU)/Multi Wall Carbon Nanotubes (MWCNTs)/Poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT: PSS) is obtained by electrospinning of TPU/MWCNTs solution in coagulation bath of PEDOT: PSS water dispersion. The nonsolvent-induced phase separation (NISP) phenomenon, and consequently, the formation of CNTs/PEDOT: PSS/CNTs electrically-conductive chains, were controlled by tuning the concentrations from binary solvents. The optimal value of the Power Factor, 4.28 μW∙m⁻1∙K⁻2, was obtained for 0.12% MWCNTs and a 1:4 ratio of Tetrahydrofuran (THF) to N, N-Dimethylformamide (DMF) in the binary solvent. The sample exhibits a high value of electrical conductivity of 85 S∙m⁻1 and shows a strain range of 190 %. This study demonstrates the significant potential of the wet-spinning method for producing wearable and sustainable thermoelectric devices, offering an alternative to conventional devices that raise concerns regarding resource scarcity and environmental impact.

Chitosan/Guar gum – Graphene oxide porous scaffolds for tissue engineering applications

The present work investigates the influence of graphene oxide incorporation on the physio-chemical properties and biocompatibility of chitosan-guar gum based porous 3D scaffolds. In this study, a porous 3-dimensional chitosan/guar gum-GO scaffolds was fabricated by freeze drying method with different concentrations of GO (0, 0.5, 1 and 1.5 wt%). To improve their stability in the aqueous medium, the scaffolds was crosslinked using sodium tetraborate (Borax) resulting in borax crosslinked chitosan/guar gum-GO scaffolds (CGB) and characterized using FT-IR, XRD, Raman and TGA analysis. Crosslinking of the polymer matrix by borax was confirmed by FT-IR analysis, and XRD spectra shows that GO and borax incorporation did not affect the crystallinity of the polymer matrix. Increase in thermal stability was observed as the concentration of GO increased in the scaffolds. Porous morphology of the scaffold can be observed under scanning electron microscopy and the scaffolds exhibited around 60 % porosity. Irrespective of GO concentration, all the scaffolds exhibited good surface wettability and the degradation of the scaffolds slowed as the concentration of GO increased. In vitro cytocompatibility studies with Vero cells showed that both the CG and CGB scaffolds exhibited more than 90 % cell viability irrespective of GO concentration and the cell attached well on the scaffolds with GO when compared to control scaffolds. Overall, the prepared scaffold proved to be highly suitable for biological applications such as drug delivery and tissue engineering.

Effect of porous irregular ZrO2 nanoparticles on the performance of alkaline water electrolysis composite separator membranes under complex conditions

Developing composite separator membranes with low area resistance, high bubble point pressure, and long-term safety and stability is crucial for alkaline water electrolysis for hydrogen production as a key component of electrolyzer systems. In this study, PPS mesh fabric reinforced PSF@ZrO2 composite separator membranes were successfully prepared using the immersion-drawing phase inversion method, with PSF as the alkali-resistant polymer matrix and porous irregular ZrO2 nanoparticles as the hydrophilic additive. The experimental results showed that replacing commercial ZrO2 with porous irregular ZrO2 nanoparticles at an 85 wt% ZrO2 nanoparticle loading improved both bubble point pressure and current transmission efficiency, attributed to the change in the morphological structure of the ZrO2 nanoparticles. The P-Z85 composite separator membrane exhibited highly promising characteristics, with a high bubble point pressure of 3.76 bar and a low area resistance of 0.20 Ω cm2. Stability tests conducted in 30 wt% KOH electrolyte at 80 °C and a current density of 0.65 A cm-2 demonstrated excellent continuous electrolysis stability for the P-Z85 composite separator membrane. These results indicate that the PSF@ZrO2/PPS composite separator membrane prepared in this study exhibits excellent performance in 30 wt% KOH electrolyte, significantly extending its service life.

An effect of Fe atom clusters doped CNTs on resistivity of PTFE dielectrics

Polymers are of interest for use on spacecraft surfaces as dielectrics and electrical insulators, and polytetrafluoroethylene (PTFE) is a polymer with mechanical advantages, but low conductivity. Fe-doped carbon nanotubes (CNT) can be added to the polymer matrix and may improve their electrical properties. This work measures the volume and surface resistivity for PTFE and PTFE + Fe-doped CNT test specimens using the Keithley 6517B Electrometer/High Resistance Meter system, by determining current levels through the samples as a function of applied voltage. The system noise current was measured and averaged to be 4.83×10−15 Amps. The results obtained show that both volume and surface resistivities of pristine PTFE increase with increasing voltage. The volume resistivity is higher if compared to the surface resistivity at the same voltage. The conductivities of PTFE + Fe doped CNTs composites are higher as compared to the pristine PTFE, which can be contributed to the Fe-doped CNTs. The conductivity of the PTFE + Fe doped CNTs composite material increases with the concentration of the Fe-doped CNTs.

Experimental investigation and micromechanical analysis of glass fiber reinforced polyamide 6

Achieving process stability in the thermoforming of fiber reinforced polymer materials (FRPs) for aerospace or automotive manufacturing is usually associated with a costly trial-and-error process, where experimental boundary conditions and other influencing factorsRWTHblau such as, for example, material composition RWTHblau need to be adjusted over time. This is especially true when material phenomena on the microlevel, such as the crystallization kinetics of the polymer matrix or resulting stresses from temperature gradients, are the cause of the process instability. To reduce the experimental effort and reliably predict the material behavior during thermoforming, finite element simulation tools on multiple scales are a useful solution. RWTHblauHereby, incorporating micromechanical phenomena into the model approaches is crucial for an accurate prediction by further reducing the deviation between simulation and experiment, in particular with regard to the underlying nonlinear material behavior. In this work, unit cell simulations on the microscale of a unidirectional glass fiber reinforced polymer (UD GFRP) are conducted to predict effective thermomechanical properties of a single material ply and ascertain the effect of individual ply constituents on the homogenized material behavior. The polymeric matrix material model used was identified in a prior publication with experimental data at various temperatures for polyamide 6 blends with varying degrees of crystallinities. Various randomization methods are tested to generate the unit cells and replicate the composites’ random fiber distributionRWTHblau with a focus on process automation. The simulative results are successfully compared to an experimental study on glass fiber reinforced polyamide 6 tested at various temperatures, demonstrating the potential of the approach to reduce RWTHblauboth time and cost required for material characterization. Finally, the unit cells are used to generate a RWTHblaudatabase RWTHblauto predict untested load cases that will be used in future work to characterize a homogenized macroscopic material model.

Tough, high-strength, flame-retardant and recyclable polyurethane elastomers based on dynamic borate acid esters

With the wide application of polyurethane elastomers, it is necessary to develop recyclable, fire-retardant polyurethane elastomers with great mechanical properties to comply with industrial requirements. Herein, we fabricated a flame-retardant, recyclable, strong yet tough polyurethane elastomer (PIDB-1) based on dynamic borate acid esters. The introduction of phosphaphenanthrene and boron-containing groups endow PIDB-1 with great flame retardancy, as reflected by it achieving the vertical burning (UL-94) V-0 rating. The PIDB-1 film shows high visible light transmittance, and its transmittance reaches 90 % at the wavelength of 800 to 900 nm. The tensile strength of PIDB-1 is 54.9 MPa, and its toughness reaches 207.8 kJ/m3, indicative of superior mechanical properties. Meanwhile, the dynamic borate acid esters allow the PIDB-1 elastomer to possess physical and chemical recyclability. When using PIDB-1 as a polymer matrix for carbon fiber-reinforced polymer composites, the carbon fibers can be fully recycled. This work provides an integrated design strategy for creating transparent, flame-retardant, recyclable polyurethane elastomers combining high strength and toughness based on dynamic borate ester bonds, which is expected to find wide applications in different industries.

Incorporation of myrtle essential oil into hydrolyzed ethyl cellulose films for enhanced antimicrobial packaging applications

This research delved into examining the impact of hydrolysis and incorporation of Myrtle essential oil (MEO) on the film-forming and antimicrobial characteristics of ethyl cellulose polymer (EC). Three plasticizers (glycerol, mono ethylene glycol, and oleic acid) were evaluated for film-forming ability. The composite biofilms' structure was assessed through SEM, XRD, FT-IR, and DSC. Eventually, the combination of hydrolyzed EC with oleic acid yielded a flexible film with optimal thickness. Utilizing GC-MS analysis, α-pinene was identified as the predominant compound within MEO, conferring both antioxidant and antibacterial attributes. FTIR spectroscopy confirmed MEO's participation in the film-forming matrix through hydrogen bonding. By incorporating the MEO into the matrix, the WVP decreased significantly to 6.15*10-12 gmm/hmm2Pa considering that the hydrophobic feature of MEO can block the diffusion of water and decrease the WVP. The melting point and enthalpy of the polymer matrix containing MEO decreased that could be attributable to the EOs plasticizing impact, which increases the polymer chain mobility, and thereby hinders the strong interactions between polymer molecules. From the morphological finding, even at higher concentrations, MEO did not form agglomerations in the film matrix, highlighting its excellent compatibility with the microstructure of the resulting films. The film containing MEO showed the acceptable antioxidant activity. Furthermore, films containing MEO substantially decreased S. aureus biofilm development at 24 and 48 hours, compared to P. aeruginosa and E. coli. These findings suggest potential applications of the developed film in packaging and preservation.

Structure and tribological behavior of a polyetherimide/polytetrafluoroethylene matrix filled with negative thermal expansion zirconium tungstate particles

Thermal expansion mismatch stresses may be a reason for premature failure of sealing and bearing components made of polymer composites that are rubbed against metallic surfaces at elevated temperatures. It is of particular importance for polymer matrix composites loaded with anti-friction inclusions of polytetrafluoroethylene (PTFE) that possesses high coefficient of thermal expansion. In this regard, a study was undertaken to elucidate the effect of the thermal mismatch on wear and friction of amorphous polyetherimide (PEI) matrix loaded with either polytetrafluoroethylene (PTFE) particles (i) or PTFE particles covered with negative thermal expansion zirconium tungstate (ZT) α-ZrW2O8 (ii) at temperatures 23 °C, 120 °C and 180 °C. The ball-on-disk testing scheme was used according to standard with AISI 52100 steel balls rubbed against a polymer composite disks at normal force P=5 N and sliding velocity V=0.3 m/s. The PEI/PTFE/ZT composite demonstrated a tendency for wear rate (WR) reduction in sliding at 120 °C and 180 °C as compared to corresponding WR enhancement on the PEI/PTFE. The rationale is provided that the ZT additive effectively reduced thermal expansion of the PTFE in the PEI matrix and thus improved wear resistance of the composite. New thermal expansion-controlled wear and friction instability mechanism has been proposed and discussed.

Dual Li ion transport channels in a dynamical supramolecular solid electrolyte toward safety and high-performance Li metal batteries

The polymer based quasi-solid electrolyte (QSE), which combines the high ionic conductivity of the liquid electrolytes with the excellent mechanical flexibility of the polymer matrix, is highly desired and most promising for Li metal batteries (LMBs). However, the Li+ transfer pathways in QSE is not clear enough, and the practical applications in LMBs are also hindered by safety hazards arising from risks of mechanical damage, flammability and high voltage instability. Here, a dynamical supramolecular QSE with abundant hydrogen bonds to fabricate stable and safety LMBs, is reported. In this designed electrolyte, both thermal stability and superior interface stability with anode/cathode electrodes were achieved. Notably, the dual Li+ transport channels in QSE were investigated using in-situ FTIR technology and DFT calculations, providing insights into both the “wet” liquid phase and “dry” polymer chain channels. Benefiting from this design, the Li||NCM622 full batteries based on this QSE exhibit excellent long-term cycling stability.

Biocomposite Materials from Natural Rubber/Polylactic Acid Blends Reinforced Rubberwood Sawdust for Producing Children's Toys

Biocomposite materials are prepared by blending natural rubber (NR) and polylactic acid (PLA) reinforced with rubberwood sawdust (RWS). This study aimed to investigate the effects of PLA grade, NR/PLA blend ratio, and RWS content on flexure, tension, hardness, and water absorption characteristics, including thermal stability. The RWS content significantly affected the physical and mechanical properties of the biocomposite materials. The increasing additions of RWS from 30 to 50 wt% increased the mechanical modulus, hardness, and water absorption but decreased the thermal stability of the biocomposites. Polymer blended with an NR/PLA ratio of 30/70 reinforced with 30 wt% RWS exhibited the highest mechanical strength, whereas a blend ratio of 40/60 was found to be reinforced with 40 wt% RWS. The polymer matrix blended with a higher PLA content resulted in superior biocomposite properties. Thus, the biocomposites with an NR/PLA ratio of 30/70 had better properties than those with a ratio of 40/60. Further, biocomposites with PLA grade of low melt flow rate (6 g/10 min) improved their properties more than that of a high melt flow rate (80 g/10 min). Therefore, the appropriate formulation of biocomposites for producing children's toys is a blend ratio of 30/70 with 2003D PLA grade of low melt flow rate and reinforcement with 30 wt% RWS. The tensile, flexural, and compressive forces of a toy boat prototype were 70.08, 104.9, and 124.8 N, respectively, while the specified standard is 69.0, 69.0, and 113.5 N, respectively, thus meeting the requirements of the American Society for Testing and Materials F963.

Exploring the influence of specimen types on the intralaminar fracture behavior of fiber-reinforced polymer matrix composites

The accurate determination of fracture toughness of fiber-reinforced composites is critical for the assessment of structural integrity. Although there have been many studies on the intralaminar fracture behavior of composites, satisfactory results have not yet been obtained regarding the influence of specimen types. In this paper, commonly used fracture specimens (DCT, CT, ESET, pin-loaded SENT and clamped SENT specimen) are applied to study their applicability in the fracture behaviors of composites with different orientations. And the impact of data processing methods for the area method, GC-compliance and GC-stress intensity factors on fracture performance was analyzed. The results showed that the above three data processing methods have obtained relatively consistent fracture properties. Different specimens obtained significantly various results, showing a gradually decreasing trend from clamped SENT, ESET, pin-loaded SENT, CT to DCT. Furthermore, considering that the clamped SENT specimen is closest to the Mode-I fracture toughness obtained from the DCB specimen, and there is no compression damage in the experiments under different orientations, this specimen type is the most recommended specimen. Finally, the failure mechanisms of carbon fiber-reinforced composite under different specimen types and orientations were revealed. As the orientation angle increases (β from 0° to 90°), the failure mode gradually transitions from matrix cracking and interface debonding to matrix shear and fiber fracture. The above achievements will contribute to a deeper understanding of the intralaminar fracture process and failure mechanism of fiber-reinforced composites.

Enhancement of Wound Dressings Through Cerium Canadate and Hydroxyapatite-Infused Hyaluronic acide and PVA Membranes: A Comprehensive Characterization and Biocompatibility Study

This study explores the development of advanced wound dressings by enhancing traditional bandages with suitable biomedical materials. We utilized Hyaluronic Acid (HA) and Polyvinyl Alcohol (PVA) as a polymeric matrix to create a novel membrane. Employing a film casting technique, we incorporated varying ratios of biological nanoparticles—Hydroxyapatite (HAP) and Cerium Vanadate (Ce₃(VO₄)₄)—to improve the wound dressing's properties. The resulting films were characterized using several techniques, including X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Raman spectroscopy, and Thermogravimetric Analysis (TGA). Wettability assessments provided insights into the surface characteristics of the scaffolds, revealing a diverse range of contact angles that reflect varying hydrophilic properties. Notably, the pure PVA/HA sample exhibited a contact angle of approximately 31.2° ± 12.1°, indicating excellent hydrophilicity and a strong capacity for drug absorption. However, the incorporation of nanoparticles resulted in an increase in contact angles, suggesting a slight reduction in hydrophilicity. Specifically, the addition of HAP produced a contact angle of about 36.5° ± 6.7°, while the addition of Ce₃(VO₄)₄ resulted in a contact angle of approximately 38.6° ± 6.4°. A significant increase in contact angle to 42.23° ± 4.8° was observed when mixing the nanoparticles, though the introduction of Graphene Oxide (GO) reduced the angle to 37.4° ± 0.35°, enhancing the hydrophilic properties of the composite. Furthermore, in vitro cell viability testing was conducted to confirm the biocompatibility and bioactivity of the fabricated scaffolds. The results demonstrated the ability of the scaffolds to promote cell growth, with an increase of 88.4% in cell growth ratio observed at a suitable drug concentration of approximately 0.68 μg/ml. These findings highlight the potential of the developed scaffolds to enhance the wound healing process.

Exploring the antibiofilm potential of chitosan nanoparticles by functional modification with chloroquine and deoxyribonuclease

Planktonic bacteria tend to form sessile community architectures to shield resident bacteria from various environmental stresses. The formed biofilm leads to the failure of conventional antimicrobial therapy. Extracellular macromolecules, including extracellular DNA (eDNA), proteins, lipids, and polysaccharides, crosslink into gel-like structures through electrostatic forces in the mature biofilm matrix. The stereo-structural integrity and chemical inertia of the extracellular polymeric matrix result in comprehensive antimicrobial resistance to antibacterial polysaccharides. Herein, an ionic gelation method was employed to functionalize cationic chitosan nanoparticles (CSNPs) with chloroquine and deoxyribonuclease. The modification involved shifting eDNA chirality through a DNA-intercalating agent, chloroquine, and hydrolyzing an eDNA scaffold with deoxyribonuclease. The antibiofilm activity was assessed against a standard Staphylococcus aureus strain and clinical subtype isolates. Functional modifications targeting eDNA improved the chitosan anti-biofilm efficiency (residual biomass decreased from 74.2 to 90.3 % to 16.7–24.6 %) by disrupting the biofilm matrix. The functional CSNPs worked as a sensitizer prodrug, contributing to a bactericidal process of chitosan itself (cell wall damage increased from 11.38–18.16 % to 55.2–61.4 %) by dispersing the biofilm-enclosed bacteria. In vivo, the bacterial burden of infected mouse joints was reduced by 4.1 lg CFU/mL. Our results indicate the potential of this chitosan-based anti-infection strategy in biofilm-related infections.

Cu-bearing stainless steel inhibits biofilm by modulating bacterial motility

Biofilm is a structured community of bacteria enclosed in a self-produced polymeric matrix. Bacterial motility intimately associated with the growth and extension in biofilm development. Here, we carried out a parallel cell-tracking process to capture the motility of bacteria in situ real-time. Scanning electron microscopy (SEM) and confocallaserscanning microscope (CLSM) were employed to validate the morphology and structure of biofilm. Results show that Cu-bearing stainless steel (SS) elevated bacterial motility of surface exploration and diminished swarming motility of planktonic bacteria. We concluded that Cu-bearing SS modulated bacterial motility towards detrimental biofilm formation.

Enhanced High-Temperature performance of PEI dielectrics via deep trap energy levels and physically crosslinked effects

Dielectric capacitors are indispensable energy storage components in both civilian applications and industrial processes. Under elevated temperatures and intense electric fields, polymer dielectrics usually suffer from an inevitably increase in conductivity, leading to a significant reduction in breakdown strength, energy density and efficiency. This investigation aims to design an all-organic dielectric with enhanced high-temperature capacitive performance by introducing a small molecule P-xylene F (PF) into polyetherimide (PEI). Two mechanisms including the incorporation of deep trap energy levels via wide bandgap fillers and the electrostatic interactions by hydrogen bonding between the fillers and the polymer matrix are proposed to support the enhancement. The hydrogen bonding between PF and polyamic acid (PAA)chains induces the formation of physical cross-linking between PF and the negatively charged benzene rings in PEI after imidization. This influences benzene ring stacking within the polymer chains and enhances the film’s mechanical strength. Additionally, PF’s wider bandgap compared to PEI introduces deep trap energy levels, hindering carrier transport and reducing conductive losses at high temperatures. As results, the dielectric achieves an energy density (Ud) of 4.47 J/cm3 with an efficiency (η) above 90 % at 200 °C. Its excellent stability is also demonstrated with over 210,000 charge–discharge cycles at 200 °C. This study promotes the development of high-performance dielectrics at high temperature.

Insights and perspectives on PVDF/MgO NCs films: Structural and optical properties for optoelectronic device applications

In the current investigation, pure polyvinylidene fluoride (PVDF) and PVDF-MgO nanocomposite (NC) thin films are fabricated via solvent casting method using PVDF as a polymer matrix with different proportions of magnesium oxide (MgO) (0.5–2 wt%). The structural, morphological and optical properties of the prepared polymer NCs are studied by using XRD, FTIR, SEM, Raman and UV–Vis spectroscopy techniques. The α and β phases are detected in XRD measurements. MgO powder peaks are in good agreement with the reported literatures. The average crystallite size, lattice strain, and dislocation density of the prepared thin films are estimted by using Williamson-Hall (W-H) plot. SEM micrographs reveals the fluorine-containing carbon chain network that forms the spherulite and fiber-like structure in the PVDF/MgO NCs films. The Raman and FTIR spectra of PVDF/MgO and pure PVDF films are also evaluated. UV–Vis spectroscopy is used to examine the absorbance, transmittance, and reflectance spectra of pure PVDF and PVDF/MgO NCs thin films. The dipole polarization interaction causes the absorption coefficient, direct band gap, indirect band gap, optical activation energy, and skin depth of pure PVDF and PVDF/MgO thin films to decrease, whereas increasing the dielectric constant at high frequency value, refractive index, loss, optical conductivity, and dielectric constant per effective mass of NCs films. Optical dispersion parameters are estimated by the single oscillator model. The obtained results can be employed in the possible applications in supercapacitors. The method used for the preparation of thin films are inexpensive and eco-friendly.

Progress in Application of Silane Coupling Agent for Clay Modification to Flame Retardant Polymer.

Polymer composites are widely used in various fields of production and life, and the study of preparing environmentally friendly and flame retardant clay/polymer composites has gradually become a global research hotspot. But how to efficiently surface modify clay and apply it to the field of flame retardant polymers is still a potential challenge. One of the most commonly used surface modification methods is the modification of clay with silane coupling agents. The hydrolysable groups of the silane coupling agent first hydrolyze to generate hydroxyl groups. These hydroxyl groups then undergo a condensation reaction with the hydroxyl groups on the surface of the clay, allowing for organic functional groups to be grafted onto the clay surface. The organic functional groups and polymer matrix react to generate chemical bonds so that the composite material's interface is more closely combined. Thus, the dispersion of clay in the organic polymer material and the compatibility of the two is better, which improves the flame retardant effect of the composite material. This paper introduces the classification of a silane coupling agent and the mechanism and process of silane coupling agent-modified clay, outlines the mechanism of silane coupling agent-modified clay flame retardant polymers, reviews the research results on flame retardant polymers of various clays after surface treatment with silane coupling agents in recent years, and highlights the synergistic flame retardant effect of clay and flame retardant organized by silane coupling agents. Finally, it is found that the current research in the field of silane coupling agent-modified clay in flame retardants is focused on the modification of montmorillonite, sepiolite, attapulgite, and kaolinite by KH-550, KH-560, and KH-570, and the development trends in this field are also prospected.

Biotransformation of nanoplastics in human plasma and their permeation through a model in vitro blood-brain barrier: An in-depth quantitative analysis

Challenges in characterizing and quantifying nanoplastics within the human body hinder understanding of their transport, biotransformation, and potential for cellular penetration and barrier crossing. By implementing an innovative analytical workflow, including incorporation of gadolinium (Gd) as a tracer into the polymer matrix of nanoplastics, the fate of nanoplastics relative to an in vitro blood-brain barrier (BBB) model is elucidated in the absence or presence of a biomomolecule corona. The nanoplastics were incubated in human plasma for 5 min, 1 h, 6 h, and 24 h, after which the absorbed proteins and lipids (biocorona) were determined. A total of 268 proteins were identified in the biological coronas on polystyrene (PS) and polyvinyl chloride (PVC) nanoplastics, with the initial compositions being broadly similar on both PS and PVC. Both nanoplastics exhibited a strong affinity for phosphatidylcholines (PC) and lysophosphocholines (LPC) from human plasma. The inherent chemical composition of the nanoplastics plays a pivotal role in the corona’s evolution over time. Human induced pluripotent stem cell (iPSC)-derived endothelial cells (iECs) and astrocytes were exposed for 2 h to 5 µg L−1 of pristine nanoplastics or nanoplastics covered with a biological corona (following incubation in plasma for 6 h). A relatively low concentration of PS and PVC nanoplastics was determined to be present within the cellular layer of the BBB. The number of PVC nanoplastics crossing the BBB was higher than the number of PS nanoplastics. The presence of a biological corona on these particles decreases their uptake and transcytosis. This understanding might further the development of preventive measures or therapeutic strategies to counteract potential nanoplastic-induced neurotoxicity, and provide a foundation for development of in silico models to predict the neurotoxic implications of nanoplastics.

Kinetic of Light Transmission during Setting and Aging of Modern Flowable Bulk-Fill Composites.

The current development of dental materials aims to improve their properties and expand their clinical application. New flowable bulk-fill composites have been released which, unlike what was previously common in this material category, are intended to be used alone and without a top layer, in various cavities. The study compares their kinetic of light transmission during monomer-to-polymer conversion on a laboratory-grade spectrometer, as well as their elastoplastic and aging behavior under simulated clinical conditions. Major differences in the kinetic of light transmission was observed, which is related to the degree of mismatch between the refractive indices of filler and polymer matrix during polymerization and/or the type of initiator used. Compared to the literature data, the kinetic of light transmission do not always correlate with the kinetic of functional group conversion, and therefore should not be used to assess polymerization quality or to determine an appropriate exposure time. Furthermore, the initial mechanical properties are directly related to the volumetric amount of filler, but degradation during aging must be considered as a multifactorial event.