Search Results (278)

Polyimide, a class of high-performance polymers, is renowned for its exceptional thermal stability, mechanical strength, and chemical resistance. However, in the context of high-integration and high-frequency electronic packaging, polyimides face critical challenges including relatively high dielectric constants, inadequate thermal conductivity, and mechanical brittleness. Recent advances have focused on molecular design and composite engineering strategies to address these limitations. This review first summarizes the intrinsic properties of polyimides, followed by a systematic discussion of chemical synthesis, surface modification approaches, molecular design principles, and composite fabrication methods. We comprehensively examine both conventional polymerization synthetic routes and emerging techniques such as microwave-assisted thermal imidization and chemical vapor deposition. Special emphasis is placed on porous structure engineering via solid-template and liquid-template methods. Three key modification strategies are highlighted: (1) surface modifications for enhanced hydrophobicity, chemical stability, and tribological properties; (2) molecular design for optimized dielectric performance and thermal stability; and (3) composite engineering for developing high-thermal-conductivity materials with improved mechanical strength and electromagnetic interference (EMI) shielding capabilities. The dielectric constant of polyimide is reduced while chemical stability and wear resistance can be enhanced through the introduction of fluorine groups. Ultra-low dielectric constant and high-temperature resistance can be achieved by employing rigid monomers and porous structures. Furthermore, the incorporation of fillers such as graphene and boron nitride can endow the composite materials with high thermal conductivity, excellent EMI shielding efficiency, and improved mechanical properties. Finally, we discuss representative applications of polyimide and composites in electronic device packaging, EMI shielding, and thermal management systems, providing insights into future development directions. Full article

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of synthetic fluorine-containing organic compounds that exhibit chemical and thermal stability due to the highly stable carbon–fluorine bonds present in their molecular structures. This characteristic makes them slow to degrade in the natural environment. With the widespread application of these compounds in the industrial and consumer goods sectors, environmental media such as water, air, soil, and food have been severely polluted, posing a range of significant threats to public health. Therefore, the development of efficient, economical, and environmentally friendly PFAS removal technologies has become a current research hotspot. This review systematically summarizes the current technologies for removing PFASs from four perspectives—physical, chemical, biological, and combined treatments—enabling a clear understanding of the existing treatment strategies to be discussed. In addition, suggestions for future research on PFAS removal are provided. Full article

Polytetrafluoroethylene (PTFE) has been widely used as a high-frequency dielectric substrate due to its excellent dielectric properties and thermal stability. However, with its low intrinsic thermal conductivity, PTFE falls short in meeting the escalating heat dissipation demands of high-power density, high-frequency communication systems. Although the thermal conductivity of PTFE composites can be effectively improved by the high thermal conductivity fillers, it is always accompanied by a decline in dielectric properties. Molecular chain ordering is regarded as an effective strategy to improve the intrinsic thermal conductivity of polymers while maintaining dielectric properties. Unfortunately, the conventional preparation methods for ordered molecular chains, such as electrostatic spinning and uniaxial stretching, are not applicable to the preparation of PTFE substrates. In this work, fluorinated graphite (FGi) is employed to induce the in-plane orientation of PTFE molecular chains. As a result, the PTFE composite with 0.5 wt% FGi loading exhibits an in-plane thermal conductivity of 1.21 W·m⁻¹·K⁻¹, six times higher than the in-plane thermal conductivity of pure PTFE. In addition, this composite exhibits a superior dielectric constant of 2.06 and dielectric loss of 0.0021 at 40 GHz. This work introduces a facile method to achieve improved thermal conductivity of PTFE while maintaining its excellent dielectric properties. Full article

Fluorinated polyimide (FPI), renowned for its exceptional low-dielectric properties, colorless transparency, high-temperature resistance, and flexibility, has emerged as an ideal material for addressing challenges in 5G/6G high-frequency signal transmission and flexible electronic substrates. Nevertheless, the structure–property relationship between molecular architectures and the dielectric characteristics of FPI films remains insufficiently understood, necessitating urgent elucidation of the underlying mechanisms. In this study, a diamine monomer containing bis-amide bonds, 4-amino-N-{4-[(4-aminobenzoyl)amino]phenyl}benzamide (PABA), was synthesized. Subsequently, six FPI films (FPAIs, FPEIs, and FPEsIs) with distinct structural features were prepared through homopolymerization of PABA and five other diamines (containing amide bonds, ether, and ester groups) with fluorinated dianhydride (6FDA). Systematic characterization of thermal, mechanical, optical, and dielectric properties revealed that these films exhibit excellent thermal stability (T_g: 296–388 °C), mechanical strength (σ: 152.5–248.1 MPa, E: 2.1–3.4 GPa), and optical transparency (T_{550 nm}: 82–86%). Notably, they demonstrated a low dielectric constant (D_k as low as 2.8) and dielectric loss (D_f down to 0.002) under both low- and high-frequency electric fields. Furthermore, molecular dynamics simulations and quantum chemical were employed to calculate critical physical parameters and HOMO–LUMO energy levels of the six FPIs. This computational analysis provides deeper insights into the structure–performance correlations governing dielectric behavior and optical transparency in FPIs. The findings establish valuable theoretical guidance for designing advanced PI films with tailored dielectric properties and high transparency. Full article

This study comprehensively examines the barrier properties, aging behavior, and failure mechanisms of Parylene F-VT4 films, applied at four distinct thicknesses (0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm), as encapsulation layers for implantable medical devices. Parylene F-VT4, a fluorinated polymer known for its mechanical flexibility, thermal stability, and chemical inertness, is a promising candidate for long-term hermetic encapsulation. Parylene F-VT4 was uniformly deposited via a dedicated chemical vapor deposition (CVD) process typically used for Parylene depositions. The investigation of the Parylene F-VT4 films included pinhole density characterization, electrochemical impedance spectroscopy (EIS), and testing of coating lifetime based on the resistance of Cu meanders protected by Parylene F-VT4 when immersed in phosphate-buffered saline (PBS) under accelerated aging conditions (PBS at 60 °C) over 550 days. The EIS results demonstrated that thicker coatings (1.2 µm) exhibited excellent barrier properties and resistance to electrolyte penetration, whereas thinner coatings (0.3 µm and 0.6 µm) showed more rapid degradation due to microvoids and pinholes. The temporal evaluation of EIS spectra highlighted the gradual decrease in impedance magnitude, indicating the ingress of ions and water into the coating. The lifetime in PBS at 60 °C was determined by resistance-based lifetime measurements on Cu meander structures coated with Parylene F-VT4 coatings. The lifetime at 37 °C was calculated, assuming an acceleration factor of 2 per 10 °C increase in temperature, yielding lifetimes of approximately 25 days, 6.4 months, 2.3 years, and 4.5 years for 0.3 µm, 0.6 µm, 0.9 µm, and 1.2 µm coatings, respectively. These findings highlight the critical relationship between thickness and durability, providing valuable insights into the long-term performance of thin Parylene F-VT4 films for implantable devices. Full article

In this work, a density functional theory (DFT) with Hubbard correction (U) approaches implemented through the Quantum ESPRESSO code is utilized to investigate the effects of fluorine (F) doping on the structural, electronic, and optical properties of rutile TiO₂. Rutile TiO₂ is a promising material for renewable energy production and environmental remediation, but its wide bandgap limits its application to the UV spectrum, which is narrow and expensive. To extend the absorption edge of TiO₂ into the visible light range, different concentrations of F were substituted at oxygen atom sites. The structural analysis reveals that the lattice constants and bond lengths of TiO₂ increased with F concentrations. Ab initio molecular dynamics simulations (AIMD) at 1000 K confirm that both pristine and F-doped rutile TiO₂ maintains structural integrity, indicating excellent thermal stability essential for high-temperature photocatalytic applications. Band structure calculations show that pure rutile TiO₂ has a bandgap of 3.0 eV, which increases as the F concentration rises, with the 0.25 F-doped structures exhibiting an even larger bandgap, preventing it from responding to visible light. The absorption edge of doped TiO₂ shifts towards the visible region, as shown by the imaginary part of the dielectric function. This research provides valuable insights for experimentalists, helping them understand how varying F concentrations influence the properties of rutile TiO₂ for photocatalytic applications. Full article

Fluorinated ethylene propylene (FEP) films were subjected to heat, UV, and heat–UV treatments. Structural changes that occurred after these treatments were recorded via X-ray diffraction (XRD), microtensile, and laser ablation testing. XRD macromolecular orientation texture analysis revealed changes in the fraction of crystalline components and the degree of anisotropy of the FEP films after being subjected to different processing conditions. Heat treatment at 200 °C affected structural properties by rearranging the crystallites and resulting in a higher degree of anisotropy. By contrast, the UV treatment of FEP resulted in a lower degree of anisotropy. The changes in anisotropy and crystallinity of FEP films significantly affected their Young’s modulus and yield stress. The UV laser ablation threshold values were found to be lower for the heat-treated FEP films. Full article

Photothermal superhydrophobic surfaces with micro/nano-structured morphologies have emerged as promising candidates for anti-icing and deicing applications due to their exceptional water repellency and efficient solar-to-thermal conversion. These surfaces synergistically integrate the passive icephobicity of superhydrophobic coatings with the active heating capability of photothermal materials, offering energy-efficient and environmentally friendly solutions for sectors such as aviation, wind energy, and transportation. Hence, they have received widespread attention in recent years. This review provides a comprehensive overview of recent advances in photothermal superhydrophobic coatings, focusing on their anti-icing/deicing mechanisms, surface wettability, and photothermal conversion performance for anti-icing/deicing applications. Special emphasis is placed on material categories, including metals and their compounds, carbon-based materials, and polymers, analyzing their structural features and application effectiveness. Furthermore, the application of anti-icing/deicing in various fields is described. Finally, perspectives on future development are presented, including pursuing fluorine-free, cost-effective, and multifunctional coatings to meet the growing demand for innovative, sustainable anti-icing/deicing technologies. Full article

Natural rubber (NR) has long been plagued by inferior oil resistance and poor thermal degradation at high temperatures. Despite these limitations, NR remains the most widely used elastomer to date. Fluorine-containing compounds have demonstrated excellent oil resistance and thermal stability. However, they generally exhibit poor compatibility with non-polar polymers. After blending, macroscopic phase separation cannot be easily suppressed, leading to the deterioration of the material’s properties. In this study, fluorination modification was performed using hydroxyl-terminated polybutadiene, and the resulting fluorine-modified polybutadiene (3F-PBu-3F) was incorporated into natural rubber. Following sulfur curing, homogeneous phase morphologies were observed in all vulcanizates, which significantly differed from those of previously reported NR/polybutadiene vulcanizates. Additionally, the oil resistance and thermal stability of the NR/3F-PBu-3F vulcanizates were effectively enhanced. Full article

In this paper, we present our investigations into the detonation performance and stability variations caused by replacing the -CF₃ or -OCF₃ group with -SF₅. The widely applied DFT B3LYP/cc-pVTZ approach was employed to evaluate the HOMO–LUMO gap, cohesive energy, chemical hardness, and electronegativity. Based on these parameters, we predict the changes in chemical and thermal stability resulting from the inclusion of -SF₅ instead of -CF₃ or -OCF₃. Our results indicate that, in some cases, the density of fluorine-containing nitro compounds decreases due to the presence of the pentafluorosulfanyl group. Additionally, machine learning techniques were used to determine the detonation pressure and velocity of fluorine–sulfur-containing compounds. Our findings suggest that fluorine-containing nitro compounds exhibit better detonation performance and stability than fluorine–sulfur-containing ones. Overall, the pentafluorosulfanyl groups inclusion of aromatic polynitro compounds improved neither the stability nor the detonation properties such as -CF₃ or -OCF₃ groups. Full article

A new poly(azomethine) with improved solubility was successfully prepared by the polycondensation of terephthalaldehyde and 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane (4-BDAF) under green chemistry conditions. This new polymer containing hexafluoroisopropylidene was compared with a polymer containing isopropylidenediphenyl to study the influence of the presence of fluorine atoms on the properties of the polymer. Both were characterized by nuclear magnetic resonance (NMR), their molecular weight was measured by gel permeation chromatography (GPC), and their morphology was studied by X-ray diffraction (XRD). The two polymers obtained were soluble in most polar aprotic solvents and even in less polar solvents, which are practical and easily accessible solvents. Their thermal properties were determined by a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These two new polymers showed high resistance to thermal decomposition up to 490 °C, with a glass transition temperature (Tg) of 180 °C. The photophysical properties were studied by UV/Visible absorption. The polymers were doped and then deposited on cellulose filaments, an approach that made it possible to produce self-supporting conductive composites thanks to their mechanical properties. The topography of the resulting materials was characterized at submicron scales before estimating their electronic conductivity and gap energy by diffuse reflection spectroscopy. Full article

This paper aims to evaluate the thermal decomposition temperature and linear thermal expansion coefficient of typical non-metallic materials in aero-engine components. Thermogravimetric analysis and thermomechanical analysis were employed to systematically investigate the thermal and dimensional stability of these materials at varying heating rates, and their performance was validated through fireproof experiments. It was found that the high-strength graphite gasket exhibited the highest thermal decomposition temperature, while the polytetrafluoroethylene and fluorosilicone rubber showed excellent dimensional stability. Fluorine-based materials, such as fluorine rubber, showed higher thermal decomposition temperatures but relatively poor dimensional stability. This paper provides a scientific basis for the selection and design of sealing materials in aero-engines, contributing to the improvement of equipment safety and reliability. Full article

This study addresses the limitations of traditional polyimides (PIs) in high-frequency and high-temperature soft electronic applications, and then introducing trifluoromethylbenzene (TFMB) into the molecular structure and employing various diamines as connecting components to solve the bottleneck. The innovative molecular design enhances thermal, mechanical, and dielectric properties, overcoming challenges in balancing these performances. The optimized fluorinated PI (TPPI50) exhibits exceptional properties, including a glass transition temperature of 402 °C, thermal decomposition temperature of 563 °C, tensile strength of 232.73 MPa, elongation at break of 26.26%, and dielectric constant of 2.312 at 1 MHz with a dielectric loss as low as 0.00676. These improvements are attributed to the unique synergy between TFMB’s fluorinated groups, which reduce molecular polarization, and the biphenyl structure, which reinforces chain stability. Compared to conventional PIs, TPPI50 demonstrates superior comprehensive performance, making it highly suitable for soft circuits, high-frequency signal transmission, and advanced applications such as wearable devices and biosensors. This study provides a robust framework for industrial applications, offering a path to next-generation soft electronics with enhanced reliability and performance. Full article

An experimental investigation is conducted to identify the optimal blend of fluoroethylene carbonate (FEC), 3,3,3-trifluoropropylene carbonate (TFEC), and various fluorinated ethers, including 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and bis(2,2,2-trifluoroethyl) ether (BTE), to enhance the performances of lithium-ion cells at high voltage. The cell incorporating TTE exhibits a significantly superior capacity for retention after long-term cycling at 4.5 V, which might be attributed to the improved kinetics of lithium ions and the generation of a thin, reliable, and inorganic-rich electrode–electrolyte interface. This enhancement facilitates greater lithium ion mobility within the cell, while effectively suppressing active lithium loss and side reactions between the electrodes and electrolytes at elevated voltages. Furthermore, the cell with TTE demonstrates a superior rate capability and high-temperature performance. As a result of the inherent safety characteristics of these all-fluorinated electrolytes, cells using these formulations show excellent safety properties under typical abuse scenarios. Except at elevated temperatures, none of the cells undergo thermal runaway when subjected to mechanical or electrical abuse, and there are minimal differences in safety performance across the different formulations. Considering electrochemical performance, safety, and cost factors, it can be concluded that TTE might be more optimal to cooperate with FEC and TFEC for high-performance high-voltage cells. Full article

Noah-2100A and HFE-649, as two electronics fluorinated liquids (EFLs) with low saturation temperature, high safety, excellent insulation properties, and low environmental impact, are considered as replacements for the refrigerants with high Global Warming Potential (GWP), such as HFC-134a and HFC-245fa, in electronic cooling system. However, there is still a knowledge gap of boiling heat transfer for these two EFLs, especially in pin-fin microchannel. The effect of inlet temperatures, mass flow rates, and inlet vapor qualities on boiling heat transfer for two EFLs were studied experimentally in this paper. Overall, though the Noah-2100 has a higher pressure drop-in microchannel than HFE-649, Noah-2100A shows a higher overall thermal performance than HFE-649. Newly developed correlations of the Nusselt number (Nu) and pressure drop for two EFLs in a pin-fin microchannel heat sink were also presented. The proposed correlations can achieve a 10% and 11% mean average percentage error for Nu number and pressure drop. Full article