In this study, we synthesized a novel phosphorus-containing imidazole compound (CHAPIP) and employed it as a latent flame-retardant curing agent for epoxy resins. The structure of CHAPIP was characterized by NMR and FTIR spectra, which was confirmed by theoretical calculations with the B3LYP/6-311++G(d,p) method. CHAPIP integrates flame-retardant phosphorus moieties with imidazole's catalytic activity, enabling dual-phase (condensed and gas) flame-retardant mechanisms. The Bisphenol A epoxy resin system cured with 20 wt% CHAPIP exhibited a longer latent period compared to the 4 wt% CEMI-cured counterpart. Thermogravimetric analysis (TGA) revealed that the CHAPIP-cured epoxy resin exhibited an enhanced char residue of 18 %, indicating improved thermal stability. The 20 wt% CHAPIP-cured epoxy resin achieved a limiting oxygen index (LOI) of 35.4 % and attained a UL-94 V-0 rating. Furthermore, cone calorimetry demonstrated a 29 % reduction in peak heat release rate (PHRR) and a 30 % decrease in total heat release (THR), confirming the excellent flameretardant properties of the CHAPIP-cured resin. Notably, the flame-retardant mechanism of CHAPIP involves synergistic condensed-phase and vapor-phase actions.

Carbon fiber reinforced polymer (CFRP) composites have rapidly expanded to specialty areas such as lightweight electromagnetic interference (EMI) shielding structures. However, such uses are constrained by the inherent insulation of the matrix resin which leads to low through-thickness electrical conductivity and EMI shielding effectiveness. Another shortcoming restricting the use of thermoset CFRPs is its low interlaminar fracture toughness inherent to the highly crosslinked resin matrix. This study introduced a novel multifunctional interlaminar veil, composed of electrospun nanofibers of a high molecular weight epoxy resin (HMWE) which were subsequently dip-coated with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) as a conductive medium. When the veils dissolve in the epoxy matrix during the curing process, HMWE co-cures with the matrix resin, effectively enhances the fracture toughness. Simultaneously, the leftover conductive media remain an orderly scaffold in the interlaminar region, significantly increases the through-thickness conductivity with minimal conductive material dosage, as well as minimal thickening of the interlaminar region. With a 1 wt% PEDOT:PSS loading, the modified laminates achieved a through-thickness electrical conductivity of 4.48 S/m, an over 500% increase, while the Mode I and Mode II interlaminar fracture toughness (G(Ic) and G(IIc)) reached 476 J/m(2) and 954 J/m(2), representing increases of over 53% and 62%, respectively, compared to the blank one. This multifunctional veil approach provides a potential solution to achieve high through-thickness conductivity which improves overall EMI SE of the CFRP composite structures that also requiring high fracture toughness.

Conventional epoxy thermosets, with irreversible crosslinking networks, cannot be reprocessed and recycled. Furthermore, the utilization of petroleum-based materials accelerates the depletion of non-renewable resources. The introduction of dynamic covalent bonds and the use of bio-based materials for thermosets can effectively address the above issues. Herein, a series of bio-based epoxy vitrimers with dynamic covalent imine bonds were synthesized via a simple solvent-free, one-pot method using vanillin-derived aldehyde monomers, 4,4-diaminodiphenylsulfone (DDS) and bisphenol F diglycidyl ether (BFDGE) as raw materials. The effect of crosslinking density, crosslinking structure and imine bond content on the resulting bio-based vitrimers was studied, demonstrating their excellent thermal properties, UV shielding and solvent resistance, as well as outstanding mechanical properties compared to those of the previously reported vitrimers. In particular, the cured neat resin of vitrimer had a maximum tensile strength of 109 MPa and Young’s modulus of 6257 MPa, which are higher than those of previously reported imine-based vitrimers. The dynamic imine bonds endow these vitrimers with good reprocessability upon heating (over 70% recovery) and degradation under acidic conditions, enabling recycling by physical routes and gentle degradation by chemical routes. This study demonstrates a simple and effective process to prepare high-performance bio-based and recycled epoxy thermosets.

BACKGROUND:Screw loosening remains a serious complication for patients undergoing pedicle screw fixation surgeries. An accurate risk prediction is significant for prevention of screw loosening through preoperative planning. In this study, we proposed a novel index, namely the bone mineral density surrounding the screw thread (thread BMD), and tested its predictability in screw loosening. METHODS:86 screws (18 loosening and 68 non-loosening) from L3-L5 of 20 patients who experienced pedicle screw loosening were analyzed. The preoperative and postoperative quantitative CT scans of the same vertebra were spatially registered and a helix-based approach was developed to extract the thread BMD. BMDs of the vertebral body, the pedicle and the screw trajectory were also measured from the preoperative CT scans. Finite element analysis was conducted to determine pullout strength and tissue failure around the screw. Receiver operating characteristic (ROC) curve analysis was used to assess the performances of all BMD indices and pullout strength in predicting screw loosening. Linear regression was used to examine correlations between different BMD indices and screw pullout strength. RESULTS:The thread BMD had the greatest value of area under the curve (AUC = 0.73, p = 0.004) compared to vertebral BMD (AUC = 0.51, p = 0.923), pedicle BMD (AUC = 0.56, p = 0.474) and trajectory BMD (AUC = 0.67, p = 0.020). Also, the thread BMD showed a stronger correlation with the pullout strength (r = 0.83, p < 0.001) than vertebral BMD (r = 0.59, p < 0.001), pedicle BMD (r = 0.65, p < 0.001) and trajectory BMD (r = 0.60, p < 0.001). CONCLUSIONS:We developed a novel approach to measure a newly-defined thread BMD, which indicates superior capacities over other BMD indices in predicting pedicle screw loosening.

In inorganic crystals, phonons are the elementary excitations describing the collective atomic motions. The study of phonons plays an important role in terms of understanding thermal transport behavior and acoustic properties, as well as exploring the interactions between phonons and other energy carriers in materials. Thus, efficient and accurate prediction of phonon transport properties such as thermal conductivity is crucial for revealing, designing, and regulating material properties to meet practical requirements. In this paper, typical strategies used to predict phonon transport properties in modern science and technologies are introduced, and relevant achievements are emphasized. Moreover, insights into the remaining challenges as well as future directions of phonon transport-related exploration are proposed. The viewpoints of this paper are expected to provide a valuable reference to the community and inspire relevant research studies on predicting phonon transport properties in the near future.

To develop high-performance epoxy resins (EP) that can be used to produce aircraft primary structure composite parts via vacuum-assisted resin infusion technology (VARI), low resin viscosity and high fracture toughness requirements must be met as well as maintaining the usual thermomechanical properties. Polymeric core/shell nanoparticles have demonstrated effectiveness in achieving these objectives, but their use at high level causes reduction of composites' glass transition temperature and modulus. By investigating the fracture toughness of 180 degrees C-cured epoxy resins containing poly(2-ethylhexyl acrylate) core/poly(methyl methacrylate) shell nanoparticles (E/M), together with a poly(ether sulfone) (PES) thermoplastic polymer, the synergistic toughening effect is obtained and high fracture toughness is achieved, which is an over 101% increase in K IC over the untoughened resin, without lowering the resin properties and still having viscosities suitable for resin infusion. Morphological studies using scanning electron microscopy (SEM) led to a mesoscopic toughening model comprising macroscale "core/shell particles" formed with thermoplastic PES domains as "cores" and the polyacrylate core/shell nanoparticles as the "shells", resulting in much more effective functioning of common toughening mechanisms, i.e., crack deflection, bridging, and pinning, plastic deformation, and shear banding.

The coating, also called sizing, of Carbon fiber (CF) tows is vital for their protection. The frictional properties resulting from the presence of this sizing are an important factor for protection and processing. Today, most CF tows are sized with epoxy-based formulations, but new formulations are being developed to make the sizing compatible with Thermoplastic (TP) matrix. A study of the friction of these sizings depending on their nature is thus vital. In this work, CF tows with sizing that are TP matrix compatible (Acrylic-Styrene based) are compared for frictional properties using a capstan type friction machine. TP tow prepregs with Polyamide 6 resin are also tested. The addition of Graphene Oxide (GO) and ferrite modified-GO to Acrylic-Styrene sizing and their effect on the friction of CF tows is finally studied. Mostly, tow to metal contacts are investigated. This work shows the relationship between the Acrylic-Styrene based sizing and friction changes. The addition of GO to the formulations further shows a reduction in the friction coefficient compared to the virgin Acrylic-Styrene for tow to metal contact, but with a deperdition of the nanoparticles after friction for the ferrite-modified one.Highlights Acrylic-Styrene sizing reduces CF tow-metal friction 33% versus epoxy. Nano-modified GOFe3O4 sizing lowers friction but causes particle depletion. Optimal 2% Acrylic-Styrene sizing for CF tow cohesion and friction balance. PA6 towpregs show stable metal friction but high variability in self-contact. Ferrite-modified graphene sizing degrades post-friction, increases roughness.

Classic epoxy resins are characterized as nonrecyclable and nondegradable once a covalently crosslinked structure is formed. The introduction of dynamic covalent bonds endows thermosets with reprocessability and degradability features to promote the development of sustainable and high-performance materials; however, designing recyclable epoxy resins with fast degradation and recyclability is still a challenge. Herein, three acetalcontaining diepoxides were synthesized via a two-step reaction involving the formation of the dynamic covalent acetal-containing diolefins (with formal, acetal and ketal bonds), followed by epoxidation. The chemical structures of the acetal-containing diolefins and acetal-containing diepoxides were confirmed by 1H NMR, 13C NMR and FTIR. All three acetal-containing diepoxides exhibited a viscosities of 0.31-0.62 Pa s with similar refractive indices, and curing behaviors. The cured acetal-containing epoxies had a maximum tensile strength of 66-71 MPa, a high glass transition temperature of 194 degrees C and outstanding thermal stability above 290 degrees C. In particular, compared to previously reported acetal-containing epoxy resins, cured ketal-containing epoxy resins containing demonstrated good reprocessability and fast degradability under mild conditions. This work demonstrates the fabrication of degradable carbon fiber-reinforced composites based on acetal-containing epoxy resins and the recovery of carbon fibers.

Water shortage and pollution are the main problems facing the world. Adsorption is a promising wastewater treatment technology. Graphene is a good adsorbent. However, graphene is difficult to separate from water, which limits its application. Magnetic graphene not only has excellent adsorption capacity, but also can be quickly separated from aqueous solution by increasing the external magnetic field, which solves the limitations of traditional adsorbents. In addition, the selectivity and efficiency of MGO for specific pollutants were enhanced by the functionalization of materials such as chitosan, cyclodextrin and EDTA. For example, the removal rates of Pb (II), Hg (II) and Cu (II) by EDTA-functionalized MGO were 96.2 %, 95.1 % and 96.5 %, respectively. This review breaks through the limitations of single pollutant research and scientifically divides the pollutant system into three categories: ions (heavy metal ions, radioactive metal ions, and arsenic), organic pollutants (dyes, antibiotics, and aromatic compounds), and agricultural pollutants (herbicides, pesticides). The antibacterial properties of magnetic graphene were systematically described for the first time, revealing its ability to remove pathogenic microorganisms such as Escherichia coli (sterilization rate up to 95 %). In summary, MGO has broad prospects in the field of wastewater treatment.

This study investigates the optimization of polyphenylene oxide (PPO) electrospinning for interlaminar toughening in composites, using sulfonation modification and physical blending with polylactic acid (PLA) and polystyrene (PS). Both strategies showed excellent electrospinning performance, significantly reducing fiber diameter (PPO: 12.1 ± 5.8 μm; sulfonated PPO: 524 ± 42 nm; PPO-PLA: 4.73 ± 0.94 μm; PPO-PS: 3.43 ± 0.34 μm). In addition, the PPO-PS fibers were uniform, while PPO-PLA exhibited a mixture of fine and coarse fibers due to phase separation. Interlaminar fracture toughness testing showed that PPO-PS offered the greatest toughening, with GICini and GICpre increasing by 223% and 232%, respectively, compared to the values of the untoughened sample, and by 65% and 61.5% compared to those of the PPO sample. GIIC of the PPO-PS sample was 196% greater than that of the untoughened sample and 30% higher than that of the PPO sample. Scanning electron microscope (SEM) analysis of fracture morphology revealed that the high-toughness system dissipated energy through fiber bridging, plastic deformation, and multi-scale crack deflection, while the low-toughness samples failed due to interface debonding or cohesive failure. This work demonstrates that PPO-PS veils enhance interlaminar toughness through interface reinforcement and multiple toughening mechanisms, providing an effective approach for high-performance composites.

Vitrimers represent an emerging field warranting comprehensive investigation into fundamental aspects of dynamic covalent bond design. Herein, three acetal-containing cycloaliphatic epoxides (ACEs) with different cyclic substituents (cyclopentyl, furyl, and phenyl groups) were synthesized. These three liquid ACEs have different viscosities and refractive indices. After curing with anhydride, the cured ACEs show elevated glass transition temperature of up to 189 degrees C, and superior tensile strengths of up to 71 MPa. Interestingly, the dangling groups attached to the acetal bonds have a significant impact on the structure dynamics, reprocessability, degradation rates and hot wet aging resistance of cured ACEs. The effect of different dangling groups on the dynamic behaviors of acetal bonds was verified by small molecular modeling reactions. Among them, the epoxy resin containing the furyl group shows the fastest stress relaxation rate at the same temperature. The epoxy resin containing the phenyl group has the highest retention of tensile strength after reprocessing or hot wet aging, while the epoxy resin containing the cyclopentyl group exhibits the fastest degradation rate in various acid solutions. These cured ACEs can also be effectively repaired and welded owing to their dynamic structures. These noteworthy discoveries provide essential insights for understanding the structure-property relationship of acetalcontaining recyclable thermosetting polymers.

BackgroundTo assess the accuracy of robot-assisted Magerl screw placement and explore the factors affecting the accuracy.MethodsA retrospective analysis of patients who underwent robot-assisted Magerl screw placement was performed. The accuracy of Magerl screw placement was evaluated according to the Gertzbein and Robbins scale.Results47 Magerl screws were placed in 24 consecutive patients. 32 Magerl screws were narrower than the C2 isthmus height and 26 of them were grade A. 15 Magerl screws were wider than the C2 isthmus height and all of them were grade B. Temporary fixation after decompression and a smaller difference between the C2 isthmus height and screw diameter were associated with a higher probability of cortical breach.ConclusionThe accuracy of robot-assisted Magerl screw placement was excellent. Temporary fixation after decompression and a smaller difference between the C2 isthmus height and screw diameter increased the risk of cortical breach.

Both environmental and economic concerns are pioneering the development of recyclable thermosetting polymers. In this study, three liquid acetal-containing di-epoxide monomers (ADEs) with different para-substituted (-OCH3, -Cl and -NO2) phenyl groups were synthesized. The refractive indices and viscosities of the three diepoxide liquids increase in the sequence of ADE-3 (-OCH3), ADE-1 (-Cl) and ADE-2 (-NO2). Once cured with methylhexahydrophthalic anhydride, the three cured ADEs exhibit high glass transition temperatures (181-218 degrees C). Due to the presence of dynamic acetal bonds, all three cured ADEs are reprocessable, repairable, weldable, and degradable. Interestingly, the electronic effect of the substituents on the phenyl group significantly impacts the structural configuration, reprocessability and degradation behaviors of the resultant cured ADEs. As the electron-withdrawing effect of the substituents on the phenyl group increases, the stress relaxation rates of the cured ADEs decrease at the same temperature. Under optimized reprocessing conditions, the reprocessed ADE-1 (-Cl) and ADE-2 (-NO2) resins show the highest (117 %) and lowest (67 %) retention rates for tensile strength, respectively. The degradation rates of the three cured ADEs in the acidic solutions decrease with increasing the electron-withdrawing effect of the substituent on the phenyl group. Finally, a di-epoxide curing system based on ADE-3 was applied to prepare carbon fiber-reinforced composites, and nondestructive recovery of the carbon fibers was attained by degradation of the resin matrix.

The rapid growth of telecommunication technology calls for express evaluation and development for low dielectric constant (D-k) materials with higher performance requirements. At mean time, the extensive use of these dielectric materials generates increasing concerns over their crosslinking structures that cannot be readily recycled without causing environment pollution. Herein, a curing agent comprising dynamically exchangeable imine bonds was synthesized via the condensation of terephthalaldehyde (TPA) and isophorondiamine (IPDA). Epoxy vitrimers cured by this curing agent exhibited low D-k (2.75-2.79) and excellent wave transmission efficiency (>90.5 %) at high frequency range of 8.2-12.4 GHz. The cured resins can also be recycled through chemical degradation, producing reusable monomers. The cured resins demonstrate vitreous properties and its dielectric, thermal properties and wave transmission efficiency maintained unchanged after reprocessing. This work offers a strategy to prepare low Dk epoxy vitrimer used in communication field.

PurposeTo evaluate the accuracy and feasibility of robot-assisted cervical screw placement and factors that may affect the accuracy.MethodsA comprehensive search was made on PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang Med for the selection of potential eligible literature. The outcomes were evaluated in terms of the relative risk (RR) or standardized mean difference (MD) and corresponding 95% confidence interval (CI). Subgroup analyses of the accuracy of screw placement at different cervical segments and with different screw placement approaches were performed. A comparison was made between robotic navigation and conventional freehand cervical screw placement.ResultsSix comparative cohort studies and five case series studies with 337 patients and 1342 cervical screws were included in this study. The perfect accuracy was 86% (95% CI, 82-89%) and the clinically acceptable rate was 98% (95% CI, 95-99%) in robot-assisted cervical screw placement. The perfect accuracy of robot-assisted C1 lateral mass screw placement was the highest (96%), followed by C6-7 pedicle screw placement (93%) and C2 pedicle screw placement (86%), and the lowest was C3-5 pedicle screw placement (75%). The open approach had a higher perfect accuracy than the percutaneous/intermuscular approach (91% vs 83%). Compared with conventional freehand cervical screw placement, robot-assisted cervical screw placement had a higher accuracy, a lower incidence of perioperative complications, and less intraoperative blood loss.ConclusionWith good collaboration between the operator and the robot, robot-assisted cervical screw placement is accurate and feasible. Robot-assisted cervical screw placement has a promising prospect.

The advancement of communication technology has significantly promoted the development of dielectric polymers. However, the quantitative prediction of dielectric constant for rapid material screening is hard due to the low precision of existing theories. In this paper, a new model was developed to calculate the dielectric constants of organic materials through theoretical deduction correlating to the dielectric and polar Hansen solubility parameter (HSP) functions (epsilon = K-z delta(2)(p) + Bz). This model treated the permanent dipole moments as the primary function determining the dielectric constant and the corresponding polar HSP, which was demonstrated to be in good agreement with experimental data and produced reasonable fitting for organic solvents, thermoplastic polymers, and thermoset polymers, yielding R-2 of 0.7488, 0.8104, and 0.7450, respectively, and it demonstrated better fitting with R-2 of 0.9043 when applied to organic solvents having low hydrogen bonding component (delta(h), <12.5). This new correlation produces the highest accuracy of prediction when compared to the existing models and provides a better mathematical tool to help design and screen dielectric polymers

In modern society, there is widespread interest in the development of sustainable and functional polymer materials. Herein, three imine-containing diphenol hardeners with different numbers of conjugated benzene rings and one trifunctional phenol-amine hardener were successfully synthesized using vanillin, a biobased feedstock derived from lignin. The curing kinetics of epoxy systems based on these hardeners was studied using Kissinger and Ozawa methods. The obtained liquid crystalline epoxy resins cured by these hardeners show high glass transition temperatures (136-144 degrees C), mechanical strengths (76.2-119.3 MPa), and intrinsic thermal conductivities (0.26-0.32 W m-1 K-1). The X-ray diffraction results indicate that the structural order of the cured epoxy resins increases with the number of benzene rings in the hardeners. In addition, the incorporation of aromatic imine bonds endows the cured epoxy resins with dynamic structures and recyclability. These epoxy resins can be reprocessed through hot pressing and are degradable in acid or amine solutions. Notably, the degradation products in the acid solution can be used to prepare the epoxy resins. Compared with their pristine counterparts, the reprocessed and chemically recycled epoxy resins demonstrate high retention of glass transition temperature, tensile strength, and thermal conductivity. Overall, the findings in this work offer a simple and effective approach to develop recyclable liquid crystalline epoxy resins with high thermal conductivity from biobased hydroxybenzaldehydes.

Tight oil reservoirs in the south Ordos Basin are characterized by fractured, heterogeneous oil-bearing strata (an oil saturation of less than 55% on average), normal pressure (0.8±) and extra-low permeability (less than 0.3 mD). In the Chang 8 tight sandstone reservoir in Honghe oilfield, micro- and nano-pores, especially those with a pore-throat radius of less than 1 μm, account for more than 90%. Fluid flow in the matrix is non-linear and crude oil flow rates are very low under normal pressure gradients. An improved understanding of oil mobility in a tight matrix is key to further development of normal-pressure tight-oil resources in the continental basin. In this study, constant-velocity and high-pressure mercury injection experiments were conducted using samples of typical tight sandstone cores obtained from the south of Ordos Basin. A new method for reconstructing the full-scale pore-throat distribution characteristics of tight sandstone reservoirs was established successfully, based on which multistage centrifugal tests, tests of low-pressure differential displacement of oil by water, and nuclear magnetic resonance tests were conducted in order to obtain the distribution characteristics of moveable fluid in different pores. The moveable oil saturation (MOS) and degree of oil recovery (i.e. ratio of accumulative oil production to producing geologic reserves) of the core samples under different differential pressures for displacement were determined. As for the tight oil reservoirs in the south Ordos Basin, the moveable fluids are mainly stored in sub-micron (0.10–0.5 μm) pores. For Type Ⅰ reservoirs (k > 0.1 mD), the volume percentage of moveable fluid in pores with a radius larger than 0.5 μm is relatively high (greater than 40%). The degree of oil recovery of water flooding serves as the basis for forecasting recoverable reserves for tight oil reservoirs. Recoverable reserves under water flooding, mainly occur in pores with a radius greater than 0.5 μm. The contribution of Type Ⅰ reserves to oil production is observed to be greater than 60%, and the degree of oil recovery reaches up to 17.1%. These results help improve our understanding on the evaluation and classification of Chang 8 tight sandstone reservoirs in Honghe oilfield and serve as theoretical basis for pilot tests to explore effective injection media and development methods to improve the matrix-driven pressure differences and displacement efficiency for oil.

Recently, biobased high-performance vitrimers have been developed due to the lacking of raw materials from petroleum resources that can be processable as like thermoplastic to meet the urgent demand for sustainable development. Herein, the fully biobased imine curing agent (VBI-HMDA) was synthesized from bio-resources vanillin and hexamethylenediamine and its chemical structure was ensured in detail through FTIR, 1 H-NMR and 13 C-NMR before being cross-linked by commercially available Diglycidyl ether of Bisphenol-F (DGEBF). Cyclic 4-methyl-1,3-cyclohexendiamine (HTDA) was used as a co-curing agent with VBI-HMDA at different weight ratios in terms of improving the properties of cured thermoset. The curing behaviors, mechanical, thermal and self-healing performance of the cured thermosets were investigated by DSC, strength tester, DMA and TGA analyzer. However, the viscosity and activation energy of curing are decreased as the weight ratio of HTDA increases, while flexible properties and T g values are increased gradually. In addition, the heat-resistant temperature ( T s ) and char residue at 700 °C of the cured thermosets also decreased. Overall results of 50% containing HMDA sample S03 exhibited the utmost thermomechanical performances as well as admirable self-healing ability and processability. Moreover, the recycling property of S03 is over 74%, T g of reprocessed S03 is still as high as 99 °C and it is entirely solvent resistant at room temperature. This result suggests the optimizing mechanical and thermomechanical properties of cured thermosets with potential recyclability were efficiently controlled by adjusting the co-curing agent ratio.