Search Results (572)

In the present study, post-heat treatment was applied to improve the mechanical and tribological performance of 3D-printed polymer components. Two polymers, i.e., polylactic acid (PLA) and polyether ether ketone (PEEK), were used as base materials. Re-entrant structures were incorporated into printed specimens to mitigate friction-induced vibrations (FIV). The results showed that the heat-treatment process effectively enhanced the mechanical properties of both materials by increasing their elastic modulus and yield strength. Specifically, the tensile and compressive strengths of heat-treated PLA increased from 44.14 MPa to 47.66 MPa and from 68 MPa to 82 MPa, respectively. A similar trend was observed for heat-treated PEEK, with tensile strength increasing from 75.53 MPa to 84.91 MPa and compressive strength from 106 MPa to 123 MPa. Furthermore, the increased stiffness enabled the re-entrant structures to more effectively reduce FIV during the sliding process of specimens. However, heat treatment produced contrasting effects on the wear performance of the two polymers. The specific wear rate of the heat-treated PLA sample with the re-entrant structure increased from 2.36 × 10⁻⁵ mm³/(N · m) to 4.5 × 10⁻⁴ mm³/(N · m), while it decreased for the PEEK sample from 3.18 × 10⁻⁶ mm³/(N · m) to 6.2 × 10⁻⁷ mm³/(N · m). Microscopic observations revealed that this difference was due to the variations in the brittleness of the treated materials, which influenced wear-debris formation and the development of the transfer film on the steel counterface. These findings demonstrate that post-heat treatment is an effective method for tailoring and optimizing the mechanical behavior of printed polymers while also emphasizing the necessity of systematically evaluating its influence on the tribological performance of printed engineering parts subjected to different sliding conditions. Full article

On-orbit cutting is a critical process for the on-orbit manufacturing of carbon fiber reinforced polyetheretherketone composites (CF/PEEK) truss structures, with pulsed laser cutting serving as one of the feasible methods. Achieving high-quality cutting of CF/PEEK remains a major challenge for on-orbit manufacturing. Therefore, the cutting process of CF/PEEK prepreg tape was studied by an ultraviolet (UV) nanosecond laser. A three-factor, five-level orthogonal experiment was carried out to analyze the influence of laser repetition rate (LRR), laser cutting speed (LCS), and laser scanning times (LCTs) on cutting quality. The ablation mechanism dominated by the photothermal effect between the UV nanosecond laser and CF/PEEK was analyzed, and the by-products in the cutting process were explored. Finally, the optimal cutting quality (the width of slit (W_s) = 41.69 ± 3.54 μm, the heat-affected zone (HAZ) = 87.27 ± 7.30 μm) was obtained under the process conditions of LRR 50 kHz-LCS 50 mm/s-LCT 16 times. The findings show that the W_S and HAZ increase with the increase in LRR and LCT and the decrease in LCS, and the carbon fiber decomposes and escapes due to the photothermal effect. Full article

Lightweight, lead-free polymer–mineral composites have attracted increasing interest as radiation-attenuating materials for applications where reduced mass and environmental compatibility are required. In this work, the $\gamma$-ray attenuation behavior of poly(ether ether ketone) (PEEK) reinforced with natural palygorskite and pumice was evaluated at filler concentrations of 10–40 wt%. Photon interaction parameters, including the linear attenuation coefficient ($\mu$), half-value layer (HVL), mean free path ($\lambda$), and effective atomic number ($Z_{\mathrm{eff}}$), were computed over the energy range 15 keV–15 MeV using the Phy-X/PSD platform and validated through full Geant4 Monte Carlo transmission simulations. At 15 keV, $\mu$ increased from $1.46{\mathrm{cm}}^{-1}$ for pure PEEK to $4.21{\mathrm{cm}}^{-1}$ and $8.499{\mathrm{cm}}^{-1}$ for the 40 wt% palygorskite- and pumice-filled composites, respectively, reducing the HVL from 0.69 cm to 0.24 cm and 0.11 cm. The corresponding $Z_{\mathrm{eff}}$ values increased from 6.5 (pure PEEK) to 9.4 (40 wt% palygorskite) and 15.3 (40 wt% pumice), reflecting the influence of higher-Z oxide constituents in pumice. At higher photon energies, the attenuation curves converged as Compton scattering became dominant, although pumice-filled PEEK retained marginally higher $\mu$ and shorter $\lambda$ up to the MeV region. These findings demonstrate that natural mineral fillers can enhance the photon attenuation behavior of PEEK while retaining the known thermal stability and mechanical performance of the polymer matrix as reported in the literature, indicating their potential use as lightweight, secondary radiation-attenuating components in medical, industrial, and aerospace applications. Full article

This narrative review examines contemporary applications of polymeric materials in dentistry from 2020 to 2025, spanning prosthodontics, restorative dentistry, orthodontics, endodontics, implantology, diagnostics, and emerging technologies. We searched PubMed, Scopus, Web of Science, and Embase for peer reviewed English language articles and synthesized evidence on polymer classes, processing routes, mechanical and chemical behavior, and clinical performance. Approximately 116 articles were included. Polymers remain central to clinical practice: poly methyl methacrylate (PMMA) is still widely used for dentures, high performance systems such as polyether ether ketone (PEEK) are expanding framework and implant-related indications, and resin composites and adhesives continue to evolve through nanofillers and bioactive formulations aimed at improved durability and reduced secondary caries. Thermoplastic polyurethane and copolyester systems drive clear aligner therapy, while polymer-based obturation materials and fiber-reinforced posts support endodontic rehabilitation. Additive manufacturing and computer aided design computer aided manufacturing (CAD CAM) enable customized prostheses and surgical guides, and sustainability trends are accelerating interest in biodegradable or recyclable dental polymers. Across domains, evidence remains heterogeneous and clinical translation depends on balancing strength, esthetics, biocompatibility, aging behavior, and workflow constraints. Full article

The reinforcement mechanism of functionalized graphene nanosheets (GNS) on the mechanical properties of polyetheretherketone (PEEK)/polytetrafluoroethylene (PTFE) composites was investigated. Composite specimens were fabricated using PGNS, as well as GNS grafted with hydroxyl, carboxyl (-COOH) and amino functional groups, and mechanical characterizations were conducted on the prepared specimens. The results demonstrated that carboxyl-functionalized GNS (COOH-GNS) exhibited the most remarkable reinforcing effect on PEEK/PTFE composites, with its elastic modulus, tensile strength, yield strength and compressive modulus increased by 47.09%, 31.1%, 45.16% and 20.91%, respectively, compared with PGNS-reinforced composites. Combined with experimental measurements and molecular dynamics simulations, the reinforcement mechanism of this composite system was elucidated. The functional groups on the surface of GNS can induce interfacial interactions with the PEEK/PTFE matrix, by which the mobility of polymer molecular chains is restricted, the deformation and slippage of molecular chains are suppressed, and the interfacial bonding between GNS and the polymer matrix is simultaneously strengthened. The enhancement of interfacial binding energy, the reduction in free volume in the composite system, and the restriction of polymer molecular chain mobility were identified as the critical atomic-scale mechanisms responsible for the improvement of the macroscopic mechanical properties of the composites. Full article

Printing with high-performance polymers such as polyether ether ketone (PEEK) and polyetherimide (PEI) presents issues regarding shrinkage and warpage due to elevated temperatures. One method highlighted to mitigate against this is through polymer blending. This study explores the development and characterization of PEEK and PEI blends as filament for fused filament fabrication (FFF) in additive manufacturing. Filaments were produced via melt extrusion using PEEK/PEI weight ratios 100/0, 80/20, 70/30, 60/40, 50/50, 40/60, 20/80, and 0/100 (wt.%). The aim is to identify an optimum blend which enhances printability and maintains mechanical and thermal integrity. The extruded filaments were first characterized through differential scanning calorimetry (DSC) to determine miscibility with all ratios presenting a single glass transition temperature. Samples were then 3D-printed and assessed through mechanical testing, DSC, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PEEK/PEI 80/20 (wt.%) blend was recognized as the optimum blend for maintaining crystallinity (35%) as well as good mechanical properties, averaging ultimate tensile strengths (UTSs) of 75.6 MPa and a Young’s modulus of 1338 MPa. Thermal properties also improved while warpage reduced and printability improved. Full article

Repairing bone defects with implants is an important topic in the field of regenerative medicine, but bacterial infection presents a significant barrier in clinical practice. Therefore, bone implants with antibacterial functionality are currently in high demand. Fresh seaweed-derived exosomes (EXOs) exhibited promising antibacterial activity against bacteria, indicating their potential as natural antimicrobial agents. Moreover, equipping the exosomal lipid bilayer with bacteria-targeting aptamers (Apt), termed EXOs-Apt, enabled precise bacterial killing, thereby promoting more effective antibacterial functions. In our design, porous polyetheretherketone (PEEK) scaffolds were 3D-printed using the melt deposition manufacturing process. Subsequently, the scaffold surfaces were modified via dopamine self-polymerization, resulting in the formation of a polydopamine (PDA) coating. Then, EXOs-Apt was applied to functionalize PEEK scaffolds with antibacterial activity. Given that EXOs display bactericidal effects while Apt facilitates bacterial capture, we engineered a surface coating platform that incorporates both components to produce a multifunctional scaffold with synergistic antibacterial activity. The results showed that modifying EXOs-Apt on PEEK scaffolds significantly improved their antibacterial performance against Escherichia coli and Staphylococcus aureus. To our knowledge, this is the first study to use EXOs-Apt as antibacterial coatings modified on PEEK scaffolds. This study provides new strategies and ideas for the development of antibacterial PEEK orthopedic implants with promising clinical value for infection-resistant repair of bone defects. Full article

Orthognathic surgery restores functional balance and facial esthetics in patients with dentofacial deformities. The use of adjunctive facial implants—made from materials such as porous polyethylene, titanium, or polyetheretherketone (PEEK)—has increased to enhance contour and projection, although standardized guidelines for their selection and integration remain scarce. Following PRISMA-ScR guidelines, a systematic search of PubMed, Scopus, Embase, and LILACS identified studies reporting facial implants placed concomitantly with orthognathic surgery. Eligible studies included case reports, case series, observational studies, clinical trials, and reviews involving human patients, without language or date restrictions. Seventeen studies published between 1998 and 2025 met the inclusion criteria, comprising retrospective and prospective designs, case series, and one technical note. Implants were used in the malar, infraorbital, paranasal, chin, mandibular body, and angle regions. Materials included PEEK, porous polyethylene, silicone, hydroxyapatite, polymethylmethacrylate, and titanium. PEEK was mainly used for patient-specific implants, while porous polyethylene was commonly used as stock implants. Follow-up time, outcome reporting, and study design varied widely, reflecting substantial methodological heterogeneity and predominantly observational evidence. As a result, outcomes were primarily reported qualitatively, limiting comparative assessment and long-term inference. Overall, the available literature suggests that alloplastic facial implants may serve as useful adjuncts to orthognathic surgery for contour enhancement, with outcomes influenced by implant design, surgical expertise, fixation, and soft tissue conditions. However, the current evidence base remains limited, underscoring the need for standardized outcome measures, comparative studies, and longer follow-up to better inform clinical decision-making and future research. Full article

Fused deposition modeling of polyether ether ketone offers distinct advantages for fabricating complex and lightweight structures. Although three principal build orientations theoretically exist for practical 3D engineering components, research on their effects remains limited, especially regarding the influence of the interaction between build orientation and printing path on mechanical performance. This study investigated the tensile and shear properties, as well as the failure mechanisms, of FDM-fabricated PEEK under the coupled effects of build orientation and printing path through mechanical testing, fracture morphology analysis, and statistical methods. The results indicate that the printing path exerts a dominant influence on anisotropic behavior, while the interaction between printing path and build orientation jointly governs the shear failure modes. Under identical printing paths, the elongation at break varied by up to twofold across different build orientations, reaching a maximum of 96%, whereas samples printed with W or T paths exhibited elongations at break below 5%. Although shear and tensile moduli remained largely consistent across build orientations, other mechanical properties demonstrated significant differences. Variations in cross-sectional dimensions induced by build orientation markedly affected tensile performance: the coupled effect of build orientation and printing path was found to render the path repetition frequency a critical factor in determining temperature uniformity within the printed region and the quality of interlayer interfaces, thereby constituting the core mechanism underlying anisotropic behavior. Furthermore, larger cross-sections re-duced tensile modulus but enhanced yield strength and elongation at break, highlight-ing the regulatory role of cross-sectional geometry on mechanical response. Based on these findings, a synergistic optimization strategy integrating printing path, build orientation, and tensile–shear performance is proposed to achieve tailored mechanical properties in FDM-fabricated PEEK components. This approach enables controlled enhancement of structural performance to meet diverse application requirements. Full article

Polyetheretherketone (PEEK) is a high-performance engineering plastic widely used in aerospace, automotive, and other industries due to its heat resistance and mechanical strength. However, its high friction coefficient and low thermal conductivity limit its use in heavy-load environments. Existing studies have extensively explored the individual effects of thermal processing or irradiation on PEEK. However, the synergistic mechanism between the initial microstructure formed by mold temperature and subsequent irradiation modification remains unclear. This paper investigates the coupled effects of injection molding temperature and electron beam irradiation on the tribology of carbon fiber-reinforced PEEK composites, with the aim of identifying process conditions that improve friction and wear performance under high load by controlling the crystal morphology and cross-linking network. Carbon fiber (CF) particles were mixed with PEEK particles at a 1:2 mass ratio, and specimens were prepared at injection molding temperatures of 150 °C, 175 °C, and 200 °C. Some specimens were irradiated with an electron beam dose of 200 kGy. The friction coefficient, wear rate, surface shape, and crystallinity of the material were obtained using friction and wear tests, white-light topography, SEM, and XRD. The results show that the injection molding temperature of the material influences the friction performance. Optimal performance is obtained at 175 °C with a friction coefficient of 0.12 and wear rate of 9.722 × 10⁻⁶ mm³/(N·m). After irradiation modification, the friction coefficient decreases to 0.10. This improvement is due to the moderate melt fluidity, adequate fiber infiltration, and dense crystallization at this temperature. In addition, cross-linking of chains occurs, and surface transfer films are created at this temperature. However, irradiation leads to a slight increase in wear rate to 1.013 × 10⁻⁵ mm³/(N·m), suggesting that chain segment fracture and embrittlement effects are enhanced at this dose. At 150 °C, there is weak interfacial bonding and microcrack development. At 200 °C, excessive thermal motion reduces crystallinity and adds residual stress, increasing wear sensitivity. Overall, while irradiation reduces the friction coefficient, the wear rate is affected by the initial microstructure at molding. At non-optimal temperatures, embrittlement tends to dominate the wear mode. This study uncovers the synergistic and competitive dynamics between the injection molding process and irradiation modification, offering an operational framework and a mechanistic foundation for applying CF/PEEK under heavy-load conditions. The present approach can be extended in future work to other reinforcement systems or variable-dose irradiation schemes to further optimize overall tribological performance. Full article

Poly(ether ether ketone)/carbon-fiber (PEEK/CF) composites possess excellent mechanical and thermal stability but exhibit inadequate friction and wear resistance for demanding tribological applications. In this study, femtosecond laser texturing was used to generate sinusoidal–circular hybrid microtextures on PEEK/CF surfaces, and the effects of laser power and geometric parameters were systematically evaluated through a Taguchi L9 design. The optimal laser power of 0.85 W produced the highest machining quality factor (MQF = 0.968). The textures caused a hydrophilic-to-hydrophobic transition, increasing the static contact angle from 43° to 96.2°. Under boundary lubrication, all textured specimens exhibited reduced steady-state friction compared with the untreated surface. Among them, specimen L7—corresponding to the largest amplitude (A) and wavelength (B) levels in the orthogonal design—achieved the lowest average coefficient of friction (≈0.12) and generated the narrowest wear track. These results demonstrate that femtosecond-laser-fabricated hybrid microtextures effectively enhance lubricant retention and improve the tribological performance of PEEK/CF composites. Full article

Polymeric materials have become important components in prefilled syringes, drug delivery systems, and advanced medical devices. Background/Objectives: Nitrogen dioxide gas is used for the terminal sterilization of drug delivery systems. For the implementation of sterilization methods, compatibility with materials must be demonstrated such that the materials maintain product requirements and specifications after sterilization and at the time of use (i.e., product shelf life). Methods: Commonly used polymers were selected based on their chemical structures to provide insight into the nature of reactions that occur at the temperature and NO₂ concentration levels used in the sterilization process. After exposure to the NO₂ process, materials were evaluated for chemical, mechanical, and biocompatibility properties. Results: In this paper, we demonstrated the compatibility of polymers comprising carbonyl, unsaturated ester, and ketone groups which have been used in medical devices sterilized with NO₂. No significant chemical or physical changes were observed upon the treatment of Amorphous Polyester, Polysulfone (PSU), Polycarbonate (PC), PolyEtherEtherKetone (PEEK), PolyArylEtherKetone (PAEK), and Polypropylene (PP) with NO₂ at a sterilization temperature of 20 °C. At this relatively low sterilization temperature, the reactions of NO₂ with the polymer do not typically occur because the activation energies of these reactions require much higher temperatures. Conclusions: Not all materials will be compatible with NO₂ sterilization, and even with the established data, many devices will need to have their polymers evaluated for compatibility before moving to NO₂ sterilization. These results will provide guidance to device designers selecting materials for new drug delivery devices and to regulators that review the safety and efficacy of these devices. Full article

The blowout preventer (BOP) is the most important and the last line of safety defense in drilling engineering. Once a blowout occurs and the BOP fails, engineers will lose control of the entire wellbore pressure, and combustible fluids in the formation will continuously sprayed out, which can easily cause huge losses of life and property. At present, reliable and highly recognized emergency measures for BOP failure are lacking. Therefore, we propose a plugging method after the failure of the BOP that can maintain good control within the secondary well control. Numerical and experimental results indicate that using a small-to-medium displacement (1–2 m³/min) during the early stage of plugging and applying multiple plugging and killing cycles significantly improves plugging stability and killing efficiency. PEEK (polyether ether ketone) was selected as the bridging material for field plugging tests on full-scale blowout preventers, verifying its sealing effectiveness at pressures up to 80 MPa. Subsequently, the CFD–DEM was used to simulate the well killing process after plugging. This study mainly focused on the transportation of particles in a pipeline and the analysis of the process of well killing after plugging. The research results indicate that PEEK demonstrates sufficient pressure-bearing capacity under real blowout conditions. Also reveal that PEEK’s exceptional wear resistance and impact strength help maintain sealing stability during repeated particle–wall collisions, effectively reducing secondary erosion and prolonging the operational lifespan of temporary plugging structures. After undergoing six high-pressure tests of 70 MPa and two high-pressure tests of 80 MPa within 25 min, it remained intact. Both cylindrical and spherical particles can smoothly pass through the storage tank and double-bend pipeline at different displacements. Considering the retention effect of the plugging material, it is recommended to use 1–2 m³/min of pumping the plugging material at medium and small displacements in the early stage of plugging. During the process of plugging and killing, it is recommended to use alternating plugging and killing across multiple operations to prevent further blowouts to achieve the best plugging and killing effect. Full article

Background/Objectives: The precision and bonding reliability of space maintainers are critical to their clinical success longevity. This study aimed to evaluate and compare the fit accuracy and shear peel bond strength of digitally fabricated space maintainers—cobalt–chromium (Co-Cr) and polyetheretherketone (PEEK)—against conventional space maintainers. Methods: Seventy-eight space maintainer bands were fabricated—milled PEEK, selective laser-melted (SLM; an additive manufacturing technique) Co-Cr, and conventional stainless steel (SS)—and tested. Fit accuracy was evaluated on 39 bands by measuring the root mean square (RMS) deviation from a master model using digital 3D analysis. Shear peel bond strength (SPBS) was tested on another 39 samples using a universal testing machine, and the adhesive remnant index (ARI) was recorded after debonding. Statistical analyses included a Welch ANOVA for fit accuracy and the Kruskal–Wallis test for the SPBS test; the ARI was analyzed using Fisher’s exact test (significance level p < 0.05). Results: Digitally fabricated bands demonstrated significantly higher fit accuracy than the stainless steel bands (mean RMS deviation: Co-Cr = 0.151 mm, PEEK = 0.152 mm, SS = 0.344 mm; p < 0.001). Co-Cr and PEEK demonstrated comparable adaptation. In contrast, bond strength was significantly greater in Co-Cr (1.657 MPa) and SS (1.481 MPa) compared to PEEK (0.393 MPa). ARI distribution varied significantly across the three groups. Conclusions: Both milled PEEK and Co-Cr bands demonstrated excellent adaptation compared with conventional SS bands. However, Co-Cr exhibited reliable bonding performance, yet PEEK may require additional surface treatment or bonding optimization to enhance adhesion. Full article

The purpose of this study was to evaluate the effect of different framework materials and thermal aging on the shear bond strength (SBS) of gingiva-colored composites used in fixed dental restorations. A total of 270 samples (10 × 10 × 2 mm³) were prepared using titanium, zirconia, and modified polyetheretherketone (modified PEEK). Three gingiva-colored composites (Gradia Gum, Anaxgum, Nexco) were applied after surface polishing and sandblasting. All specimens were stored in water at 37 °C for 24 h, then half of each group was subjected to thermal aging consisting of 10,000 cycles at temperatures between 5 and 55 °C. SBS testing was performed using a universal testing machine with a crosshead speed of 1 mm/min. Bonding failures were analyzed under a stereomicroscope, and one sample from each group was examined using a scanning electron microscope. SBS data were analyzed using three-way ANOVA with composite type, framework material, and thermal aging as factors, followed by pairwise comparisons (SPSS 23.0; p < 0.05). The highest SBS was recorded for the zirconia framework combined with Gradia Gum, specifically in the group without thermal aging (p < 0.05), while the lowest was observed for zirconia combined with Nexco after thermal aging (p < 0.05). Adhesive failures were predominant in the modified PEEK groups, whereas mixed failures occurred more frequently in titanium and zirconia groups. Both composite type and framework material significantly influenced SBS values, with thermal aging having a detrimental effect across all groups. This study demonstrates that both framework material and composite type affect bond strength, with specimens not subjected to thermal aging maintaining better adhesion. Thermal cycling reduced SBS in all groups, although the extent varied by material combination. Full article