Search Results (271)

The polytetrafluoroethylene/aluminum (PTFE/Al) granular composite, a common formulation in impact-initiated energetic materials, undergoes mechanochemical coupling reactions under sufficiently strong dynamic loading. This investigation discusses the dynamic properties and the constitutive relationship of the PTFE/Al granular composite to provide a preliminary guide for the research on mechanical properties of a series of composite materials based on PTFE/Al as the matrix. Firstly, the 26.5Al-73.5PTFE (wt.%) composite specimens are prepared by preprocessing, mixing, molding, high-temperature sintering, and cooling. Then, the quasi-static compression and Hopkinson bar tests are performed to explore the mechanical properties of the PTFE/Al composite. Influences of the strain rate of loading on the yield stress, the ultimate strength, and the limited strain are also analyzed. Lastly, based on the experimental results, the material parameters in the Johnson–Cook constitutive model are obtained by the method of piecewise fitting to describe the stress–strain relation of the PTFE/Al composite. Combining the experimental details and the obtained material parameters, the numerical simulation of the dynamic compression of the PTFE/Al composite specimen is carried out by using the ANSYS/LS-DYNA platform. The results show that the computed stress–strain curves present a reasonable agreement with the experimental data. It should be declared that this research does not involve the energy release behavior of the 26.5Al-73.5PTFE (wt.%) reactive material because the material is not initiated within the strain rate range of the dynamic test in this paper. Full article

Fe³⁺-incorporated hydrogels are particularly valuable for wearable devices due to their tunable mechanical properties and ionic conductivity. However, conventional immersion-based fabrication fundamentally limits hydrogel performance because of heterogeneous ion distribution, ionic leaching, and scalability limitations. To overcome these challenges, we report a novel one-pot strategy where controlled amounts of Fe³⁺ are directly added to polyacrylamide-sodium acrylate (PAM-SA) precursor solutions, ensuring homogeneous ion distribution. Combining this with Photoinduced Electron/Energy Transfer Reversible Addition–Fragmentation Chain Transfer (PET-RAFT) polymerization enables efficient hydrogel fabrication under open-vessel conditions, improving its scalability. Fe³⁺ concentration achieves unprecedented modulation of mechanical properties: Young’s modulus (10 to 150 kPa), toughness (0.26 to 2.3 MJ/m³), and strain at break (800% to 2500%). The hydrogels also exhibit excellent compressibility (90% strain recovery), energy dissipation (>90% dissipation efficiency at optimal Fe³⁺ levels), and universal adhesion to diverse surfaces (plastic, metal, PTFE, and cardboard). Finally, these Fe³⁺-incorporated hydrogels demonstrated high effectiveness as strain sensors for monitoring finger/elbow movements, with gauge factors dependent on composition. This work provides a scalable, oxygen-tolerant route to tunable hydrogels for advanced wearable devices. Full article

The design of friction materials with integrated friction reduction and wear resistance functions has been a research challenge for many researchers and scholars, based on this problem, this paper proposes a nickel-based hard-soft composite coating structure. With 20CrMo steel as the matrix material, Ni20 powder doped with reinforced phase WC as hard coating material, using laser melting technology to prepare nickel-based hard coating on the surface of 20CrMo. PTFE emulsion and MoS₂ as a soft coating are prepared on the hard coating, and the nickel-based hard-soft composite coating is formed. At 6N-0.3 m/s, the new interface structure obtains the optimum tribological performance, and compared to 20CrMo, the friction coefficient and wear amount are reduced by 83% and 93% respectively. The new friction interface can obtain stable and prominent tribological properties at wide load and low to high speed, which can provide the guidance on the structural design of friction reduction and wear resistance materials. Full article

This paper proposes and demonstrates a domain-adapted ensemble machine learning approach for enhanced prediction of surface roughness (Ra) during the machining of polymeric materials. The proposed model methodology employs a two-stage pipelined architecture, where classified data are fed into the model for regressive analysis. First, a classifier (Logistic Regression or XGBoost, selected based on performance) categorizes machining data into distinct regimes based on cutting Speed (Vc), feed rate (f), and depth of cut (ap) as inputs. This classification leverages output discretization to mitigate data imbalance and capture regime-specific patterns. Second, a regressor (Support Vector Regressor or XGBoost, selected based on performance) predicts Ra within each regime, utilizing the classifier’s output as an additional feature. This structured hybrid approach enables more robust prediction in small, noisy datasets characteristic of machining studies. To validate the methodology, experiments were conducted on Polyoxymethylene (POM), Polytetrafluoroethylene (PTFE), Polyether ether ketone (PEEK), and PEEK/MWCNT composite, using a L₂₇ Design of Experiments (DoEs) matrix. Model performance was optimized using k-fold cross-validation and hyperparameter tuning via grid search, with R-squared and RMSE as evaluation metrics. The resulting meta-model demonstrated high accuracy (R² > 90% for XGBoost regressor across all materials), significantly improving Ra prediction compared to single-model approaches. This enhanced predictive capability offers potential for optimizing machining processes and reducing material waste in polymer manufacturing. 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

To investigate the temperature rise characteristics and tribological performance of angular contact ball bearings equipped with polymer-based self-lubricating retainers under oil-depleted conditions. PTFE-based composite retainers were fabricated using cold-press sintering technology. Comparative experiments on 7206C were conducted on three bearing configurations (domestic, imported NSK, and YSU-S1/S2 self-lubricating retainer bearing) using a dedicated fatigue tester under oil-depleted lubrication. This study demonstrates that angular contact ball bearings equipped with PTFE-based self-lubricating retainers exhibit superior thermal behavior under oil-depleted conditions. Compared to domestic and imported NSK bearings, the retainer-equipped bearing reduced equilibrium temperatures by 2~3 °C versus NSK/domestic bearings, with 60% lower peak temperatures. The high speed further facilitates the formation of transfer films, resulting in a smoother raceway and notably enhancing the bearing’s temperature rise characteristics. This study establishes a material–process–performance framework, bridging polymer composites and industrial bearing design. Full article

Wave gliders’ power system shafts face complex conditions. To enhance their operational stability, it is crucial to study PTFE, a polymer material that could replace traditional metals. This study added carbon fiber (CF), titanium carbide (Ti-C), and both to a PTFE matrix. The impact of seawater immersion on water absorption and the mechanical properties was examined, as well as friction and wear characteristics under constant amplitude cyclic (CAC) loading and seawater lubrication. The results indicated that while Ti-C boosts PTFE matrix hardness, its poor binding with the PTFE matrix leads to high water absorption in Ti-C/PTFE (PTFE-3), causing a significant decrease in the mechanical properties post-immersion and poor friction and wear performance. In contrast, CFs and the PTFE matrix have good interfacial bonding and greatly improve the resistance of the PTFE matrix to cyclic loading and seawater immersion. Therefore, CF/PTFE (PTFE-2) shows good mechanical and tribological properties. Moreover, incorporating a certain amount of CFs into Ti-C enhances its adhesion to the PTFE matrix, reducing the occurrence three-body wear and allowing Ti-C to fully utilize its high hardness. Thus, the combination of Ti-C and CFs markedly improves PTFE’s mechanical and tribological properties under cyclic loading and in seawater. Full article

This study develops novel superhydrophobic UHMWPE/PTFE/PVA composites via hot-pressing sintering to achieve ultra-low friction and enhanced wear resistance. The ternary system synergistically combines UHMWPE’s mechanical stability, PTFE’s lubricity, and PVA’s dispersion/binding capability. Results show PTFE disrupts UHMWPE crystallization, reducing melting temperature by 2.77 °C and enabling energy dissipation. All composites exhibit hydrophobicity, with optimal formulations (UPP3/UPP4) reaching superhydrophobicity. Tribological testing under varied loads and frequencies reveals low friction, where UPP1 achieves a COF of 0.043 and wear rate below 1.5 × 10⁻⁵ mm³/(N·m) under low-load conditions. UHMWPE oxidative degradation forming carboxylic acids at the interface (C=O at 289 eV, C–O at 286 eV). Formation of tungsten oxides (WO₃/WO₂), carbides (WC), and transfer films on steel counterparts. A four-step tribochemical reaction pathway is established. PVA promotes uniform transfer films, while PTFE lamellar peeling and UHMWPE chain stability enable sustained lubrication. Carbon-rich stratified accumulations under high-load/speed increase COF via abrasive effects. The composites demonstrate exceptional biocompatibility and provide a scalable solution for biomedical and industrial tribological applications. Full article

This study investigates the influence of drilling-induced delamination damage on the compressive mechanical behavior of open-hole carbon fiber-reinforced composite laminates and explores the failure mechanisms under dual-defect coupling effects. Specimens with circular delamination defects of varying sizes were fabricated by embedding polytetrafluoroethylene (PTFE) films during the layup process. Ultrasonic C-scan and digital image correlation (DIC) techniques were used to monitor delamination propagation and deformation behavior. A cohesive zone-based numerical model was developed and validated against experimental results to reveal the three-stage failure process in single-defect cases. The validated model was then used to analyze the coupling effects of dual defects (same side and opposite side). The results show that dual delamination defects significantly reduce the compressive load-bearing capacity of open-hole composite laminates. Specifically, same-side defects exhibit a failure mode similar to single-defect structures, while opposite-side defects display a unique failure behavior characterized by dual-crack propagation, further reducing the compressive load-bearing capacity. Full article

A promising direction in polymer material processing is the development of self-reinforced polymer composites (SRPMs), representing a relatively new group of composite materials. The self-reinforcement method allows for materials of one polymer to be combined with different molecular, supramolecular, and structural features. The high adhesive and mechanical properties of SRPMs are due to the formation of a homogeneous system with no inter-phase boundary. Moreover, self-reinforcement considers the possibility of using polymer waste to create high-strength composites, which reduces the environmental load. In the current work, the phase composition, structure, and properties of SRPMs based on polytetrafluoroethylene (PTFE) were studied. SRPMs were prepared by mixing industrial and regenerated PTFE powders and then subjected to pressing and sintering. Two types of regenerated PTFE were used for the SRPM preparation: a commercial PTFE of the TOMFLON^TM trademark and mechanically grinded PTFE waste. The degree of crystallinity of the obtained materials (41–68%) was calculated by XRD analysis; the crystallite size was determined to be 30–69 nm. Thermal analysis of the composites was carried out by the DSC method in the temperature range of 25–370 °C. The characteristics of thermal processes in self-reinforced composites correlate with the data from structural studies of XRD and FTIR analyses. The results of dynamic mechanical analysis showed that the introduction of regenerated PTFE powder into an industrial one increased the elasticity modulus from 0.6 GPa up to 2.0–3.1 GPa. It was shown that the phase state of the SRPMs depended on the method of processing polymer waste (the type of regenerated PTFE) that determined the heat resistance and mechanical properties of the obtained composite material. Full article

The current economic growth and increasing needs of society have led to developing processes that harm our environment and have severe long-term consequences. For this reason, different attempts have been made to mitigate these effects by substituting conventional toxic materials with environmentally friendly ones. Industry sectors related to energy storage, printed electronics, and wearable technology are moving towards applying sustainable strategies. Renewable biopolymers such as cellulose and its derivatives, as well as carbon-based alternatives, which include carbon nanotubes (CNTs), single-wall carbon nanotubes (SWCNTs), graphite, graphene, and carbon black (CB), are leading the advances in this field. The present research aimed to develop conductive cellulose paper using environmentally friendly components compatible with the paper recycling process. Coating formulations based on carbon black were proposed using three different types of binders: polytetrafluoroethylene (PTFE), latex (styrene butadiene), and sodium carboxymethyl cellulose (CMC). The formulation, composition, and preparation were studied, and they were related to the coating’s electrical resistance and integrity. This last parameter was determined through a new method described in this research, implementing a mechanical/optical technique to measure the coating’s durability. The formulation with the best performance in terms of electrical resistance (0.29 kΩ), integrity, and non-toxicity was obtained using sodium carboxymethyl cellulose (CMC) as a binder and dispersant. Full article

This study employs simulation tools to design and evaluate lightweight, lead-free polymer composites incorporating polytetrafluoroethylene (PTFE), polyethylene (PE), and polyetherimide (PEI) for gamma radiation shielding in nuclear medicine. Targeting clinically relevant photon energies from Tc-99m (140 keV), I-131 (364 keV), and Cs-137 (662 keV), composites’ structural and shielding performance with Bi₂O₃ and WO₃ was assessed using XCOM and Phy-X/PSD. PEI emerged as the most suitable polymer for load-bearing and thermally exposed applications, offering superior mechanical stability and dimensional integrity. Bi₂O₃-WO₃ fillers for Tc-99m achieved a ~7000-fold increase in MAC, I-131 ~2063-fold, and Cs-137 ~1370-fold compared to PbO₂. The PEI-75Bi₂O₃-25WO₃ achieved a ~21-fold reduction in half-value layer (HVL) compared to lead for Tc-99m. For higher-energy isotopes of I-131 and Cs-137, HVL reductions of ~0.44-fold and ~0.08-fold, respectively, were achieved. The results demonstrate that high-Z dual filler polymer composites have an equal or enhanced attenuation properties to lead-based shielding, whilst also enhancing the polymer composites’ mechanical and thermal characteristics. As the use of ionizing radiation increases, so does the potential risks; high-Z dual filler polymer composites provide a sustainable, lightweight, non-toxic alternative to conventional lead shielding. Full article

In this study, a composite substrate with adjustable dielectric properties was prepared, and its promising application in wearable medical device antennas was demonstrated. 3-Methacryloxypropyltrimethoxysilane (KH570) was used to modify titanium dioxide (TiO₂) nano-powder, and the modified powder was blended with a mixture of polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE) under the action of anhydrous ethanol. The resulting polymer material had the advantages of hydrophobicity, softness, low loss, and a high dielectric constant. Meanwhile, the effects of the KH570 mass fraction on the microstructure and dielectric properties of TiO₂-PTFE-PDMS composites were investigated, and the results showed that when the mass fraction was 5%, the composites exhibited better dielectric properties in the range of 2–12 GHz. Finally, an ultra-wideband antenna with an operating frequency band in the range of 2.37–11.66 GHz was prepared based on this composite substrate. The antenna demonstrated significant potential for future applications in detecting environmental thermal changes due to its special temperature-sensitive linear frequency shift characteristics, and its effect on the human body under bending conditions was studied. In addition, specific absorption rate (SAR) measurements were performed to assess the effects of antenna radiation on the human body in practical applications. Full article

A method for enhancing the adhesion properties of polytetrafluoroethylene (PTFE) surfaces is presented. The approach employs a fast neutrals flow generated by a DC glow discharge plasma with a grid neutralizer. Low power levels (≈6 W) provided by the stable DC discharge prevent physical sputtering and surface damage, while strong UV radiation from pure argon promotes efficient defluorination. The choice of working gas composition, discharge parameters, and treatment duration was informed by plasma emission spectroscopy, water contact angle (WCA) measurements, and systematic optimization. The combined effect of low-energy neutral particles and UV radiation leads to a significant increase in surface energy to 82 mN/m and a reduction in WCA to 13°, confirming the effectiveness of the proposed method. Thanks to its simplicity, scalability, and reliability, the method holds significant potential for industrial applications. Full article

In order to study the microstructure evolution of polytetrafluoroethylene–copper (PTFE-Cu) composites under compression load and reveal the molecular dynamics mechanism of deformation failure, three PTFE-Cu composites with different densities (3.0 g/cm³, 3.5 g/cm³, 4.0 g/cm³) were prepared in this study. The crystallinity of PTFE in each sample was determined via differential scanning calorimetry (DSC). The quasi-static compression mechanical properties test was carried out to analyze the effect of PTFE crystallinity on the macroscopic mechanical response of the composites. It is found that the crystallinity of the three PTFE-Cu composites was 43.05%, 39.49% and 40.13%, respectively, showing a non-monotonic trend of decreasing first and then increasing with an increase in copper powder content. The elastic modulus and yield strength of the material are negatively correlated with the crystallinity. The failure mode is the axial splitting failure and the composite morphology of axial splitting failure and shear tearing. Finally, the molecular dynamics simulation method is used to reveal the microstructure evolution and deformation failure mechanism of PTFE-Cu composites under compression load from the atomic scale, which provides a theoretical basis and experimental support for understanding the mechanical properties of PTFE-Cu composites. Full article