Search Results (236)

Biofilms, structured communities of microorganisms encased in an extracellular matrix, are a major cause of persistent infections, particularly when formed on medical devices. This study investigated the kinetics of biofilm formation by Escherichia coli and Pseudomonas aeruginosa, two clinically significant pathogens, on two medical-grade polymers: polyether ether ketone (PEEK) and polyamide 12 (PA12). Using a modified crystal violet staining method and spectrophotometric quantification, we evaluated biofilm development over time on polymer granules and catheter segments composed of these materials. Results revealed that PEEK surfaces supported significantly more biofilm formation than PA12, with peak accumulation observed at 24 h for both pathogens. Conversely, PA12 demonstrated reduced bacterial adhesion and lower biofilm biomass, suggesting surface characteristics less conducive to microbial colonization. Additionally, the study validated a reproducible protocol for assessing biofilm formation, providing a foundation for evaluating anti-biofilm strategies. While the assays were performed under static in vitro conditions, the findings highlight the importance of material selection and early prevention strategies in the design of infection-resistant medical devices. This work contributes to the understanding of how surface properties affect microbial adhesion and underscores the critical need for innovative surface modifications or coatings to mitigate biofilm-related healthcare risks. Full article

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer widely recognized for its distinct mechanical strength, chemical resistance, and biocompatibility. These characteristics make it suitable for a wide range of applications, particularly in medical, aerospace, chemical, and electronics fields. Conventional processing techniques, such as 3D printing, molding, and extrusion, are widely employed for PEEK fabrication. This review critically examines recent advancements in PEEK research, with an emphasis on additive manufacturing techniques that are expanding its applications in the medical field. We provide an in-depth analysis of PEEK’s intrinsic properties, diverse processing methods, and current challenges that hinder its wider adoption. In addition to evaluating PEEK’s performance, this review compares it with alternative biomaterials—such as titanium and ultra-high molecular weight polyethylene (UHMWPE)—to explore its advantages and limitations in biomedical applications. Furthermore, this review discusses cost considerations, regulatory constraints, long-term clinical performance challenges, and failure modes that are essential for validating and ensuring the reliability of PEEK in clinical use. By synthesizing the recent literature, particularly from the last decade, this review highlights the significant potential of PEEK and underscores ongoing research efforts aimed at overcoming its limitations, paving the way for its broader implementation in advanced technological applications. 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

Background: This study evaluated and compared the effects of thermal aging on the color stability and mechanical properties of CAD/CAM polymers utilized for provisional restorations. Material and Methods: Three CAD/CAM polymers in this study: CAD-Temp (CAT), Everest C-Temp (CT), and PEEK (PK). Forty specimens of each material were randomly assigned to two subgroups. Subgroup A was immersed in distilled water for 24 h, whereas Subgroup B was subjected to 5000 thermal cycles. The color stability, flexural strength (FS), survival probability, and microstructures were evaluated following thermal cycling. Data analysis was conducted utilizing two-way ANOVA along with Tukey’s test. Results: The CAT (3.74 ± 0.39) and CT (3.51 ± 0.54) groups exhibited the highest color variations, while PEEK (2.95 ± 0.45) showed the lowest color change. The baseline groups showed that the CT group had the highest flexural strength value (p < 0.05). The flexural strength values of CAT and CT groups significantly decreased (p < 0.05) following thermal cycling. No significant decrease in FS was observed following thermal cycling in the Pk group (p = 0.16). Conclusions: The color measurement and flexural strength outcomes were significantly influenced by CAD/CAM materials and thermal cycling. The CT group demonstrated superior flexural strength compared to the other groups, both before and after thermal cycling. The PK group shows the lowest color change compared to other groups. Regardless of aging condition, C-Temp and PEEK materials recorded the highest survival probability, a 95% significance level compared to CAD-Temp. Full article

The purpose of this study was to investigate the effect of different drying methods on the structure and properties of semicrystalline polymer aerogels. Aerogels, consisting of either globular or strut-like morphologies, were prepared from poly(ether ether ketone) (PEEK) or poly(phenylene sulfide) (PPS) and dried using vacuum drying, freeze-drying, or supercritical CO₂ extraction. Vacuum drying was found to result in aerogels with a higher shrinkage, smaller mesopores (with pore widths of 2–50 nm), and smaller surface areas compared to the use of supercritical extraction as the drying method. Freeze-dried aerogels tended to have properties between those of vacuum-dried aerogels and aerogels prepared with supercritical extraction. High network connectivity was found to lead to improved gel modulus, which increased the ability of aerogels to resist network deformation due to stresses induced during drying. The PEEK and PPS aerogel networks consisting of highly connected strut-like features were considerably stiffer than those composed of globular features, and thus shrank less under the forces induced by vacuum drying or freeze-drying. The aerogels prepared from PPS were found to have larger mesopores and smaller surface areas than the aerogels prepared from PEEK. The larger mesopores of the PPS aerogels induced lower capillary stresses on the aerogel network, and thus shrank less. This work demonstrates that preparing PEEK and PPS gels with strut-like features can allow aerogel processing with simpler evaporative drying methods rather than the more complex supercritical drying method. Full article

In recent years, the rapid development of three-dimensional (3D)-printed continuous fiber-reinforced polymer (CFRP) technology has provided novel strategies for customized manufacturing of high-performance composites. This review systematically summarizes research advancements in material systems, processing methods, mechanical performance regulation, and functional applications of this technology. Material-wise, the analysis focuses on the performance characteristics and application scenarios of carbon fibers, glass fibers, and natural fibers, alongside discussions on the processing behaviors of thermoplastic matrices such as polyetheretherketone (PEEK). At the process level, the advantages and limitations of fused deposition modeling (FDM) and photopolymerization techniques are compared, with emphasis on their impact on fiber–matrix interfaces. The review further examines the regulatory mechanisms of fiber orientation, volume fraction, and other parameters on mechanical properties, as well as implementation pathways for functional designs, such as electrical conductivity and self-sensing capabilities. Application case studies in aerospace lightweight structures and automotive energy-absorbing components are comprehensively analyzed. Current challenges are highlighted, and future directions proposed, including artificial intelligence (AI)-driven process optimization and multi-material hybrid manufacturing. This review aims to provide a comprehensive assessment of the current achievements in 3D printing CFRP technology and a forward-looking analysis of existing challenges, offering a systematic reference for accelerating the transformation of 3D printing CFRP technology from laboratory research to industrial-scale implementation. Full article

The increasing demand for orthopedic and neurosurgical implants has driven advancements in biomaterials, additive manufacturing, and antimicrobial strategies. With an increasingly aging population, and a high incidence of orthopedic trauma in developing countries, the need for effective, biocompatible, and infection-resistant implants is more critical than ever. This review explores the role of polymers in 3D printing for medical applications, focusing on their use in orthopedic and neurosurgical implants. Polylactic acid (PLA), polycaprolactone (PCL), and polyetheretherketone (PEEK) have gained attention due to their biocompatibility, mechanical properties, and potential for antimicrobial modifications. A major challenge in implantology is the risk of periprosthetic joint infections (PJI) and surgical site infections (SSI). Current strategies, such as antibiotic-loaded polymethylmethacrylate (PMMA) spacers and bioactive coatings, aim to reduce infection rates, but limitations remain. Additive manufacturing enables the creation of customized implants with tailored porosity for enhanced osseointegration while allowing for the incorporation of antimicrobial agents. Future perspectives include the integration of artificial intelligence for implant design, nanotechnology for smart coatings, and bioresorbable scaffolds for improved bone regeneration. Advancing these technologies will lead to more efficient, cost-effective, and patient-specific solutions, ultimately reducing infection rates and improving long-term clinical outcomes. Full article

Accurately evaluating the strength of adhesively bonded joints is essential for ensuring structural reliability, but size-dependent effects remain a challenge in consistent strength assessment. This study performs finite element simulations of Single Lap Shear (SLS) tests, focusing on the local stress state at fracture initiation. The analysis considers unidirectional and quasi-isotropic carbon fiber reinforced plastic (CFRP) adherends combined with three adhesives: polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and epoxy. Adhesive thicknesses ranging from 0.1 mm to 0.5 mm are evaluated. The results indicate that the optimal thickness ranges between 0.1–0.3 mm to maximize joint strength, while excessively thin or thick layers reduce performance. These findings align with experimental trends and support the development of precise design guidelines for polymer-based joints in structural applications. Full article

Additive manufacturing is currently regarded as one of the enabling technologies for Space Economy since it allows for the reduction of lead time and costs of payloads and platforms. Typically, metal-based additive manufacturing technologies are considered for the development of microwave components for Space applications since they exhibit the best trade-off in radio-frequency performance, benefits, and withstanding adverse environmental conditions. In this view, composite polymers may further increase the benefits arising from the 3D printing of microwave components since lighter parts with the required thermal, mechanical, and RF performances can be placed on board satellites. This paper explores the feasibility of 3D-printed composite polymers, including Ultem and PEEK reinforced with carbon fiber, for the development of microwave waveguide devices intended for Space applications. To this end, three different manufacturing routes were investigated by selecting a specific composite polymer, the corresponding manufacturing system and post-processing, and the necessary metal-plating technique. Hence, relevant radio-frequency test vehicles operating at 10 ÷ 14 GHz were designed, manufactured, and tested. The experimental results prove that waveguide components operating in X and Ku bands can be developed through the material extrusion of PEEK reinforced with carbon fiber, which is subsequently metalized by means of a two-stage electroless/electroplating process. Full article

The increasing demand for fully recyclable composites has spurred extensive research on thermoplastics, valued for their recyclability and excellent mechanical properties. High-performance thermoplastics such as PEEK and PPS have been widely adopted in aerospace applications due to their outstanding load-bearing capabilities, which are well documented. Recently, thermoplastic polymer blends have gained attention for their enhanced recyclability and sustainability, as well as their ability to improve thermal stability, viscosity, and manufacturability. However, limited data are available on the mechanical characterization of composites that incorporate these blends, particularly when recycled thermoplastics are used. In this study, we first examine the stress–strain behavior of the following three polymer blends relevant for structural applications: PES/PEEK, PPS/PEEK, and HDPE/PP. We then perform a numerical analysis to predict the mechanical performance of unidirectional fiber-reinforced composites using each blend as the matrix. This involves a micromechanical Representative Volume Element (RVE) approach combined with an advanced polymer model previously validated against experimental data. The findings are discussed to critically assess the suitability of these blends for producing fully matrix-recycled composites. Full article

Poly(ether ketone ketone) (PEKK), as a representative of high-performance poly(aryl ether ketones), shows outstanding thermomechanical properties, opening up a huge range of different applications in various technical fields. Its appearance as a quasi-amorphous polymer with a certain suppression of the crystallization process facilitates melt processing via additive manufacturing processes like material extrusion (MEX), especially in fused filament fabrication (FFF). The quality of the printing process is proven in this work by tensile testing and surface roughness measurements of suitable specimens. The MEX printing of semicrystalline PEKK faces two major challenges: on the one hand, the very high printing temperature is in contrast to established engineering plastics, and on the other hand, it is difficult to avoid crystallization after printing. The first issue can be addressed by using suitably enhanced MEX printers and the second one by selecting adapted printing parameters. The measured Young’s modulus (3.49 GPa) and tensile strength (104 MPa) values are higher than the related vendors’ data given for filaments (3.0 GPa and 92 MPa, respectively). In addition, the temperature-dependent thermal conductivity is determined, and the values of well-established PEEK (poly(ether ether ketone)) in the temperature range from 20 to 180 °C are mostly slightly higher in comparison to the related PEKK data. Based on the results, PEKK can be a useful substitute for well-established PEEK because of their comparable properties. However, PEKK has a pronouncedly lower FFF printing temperature, combined with a reduced tendency of the device to warp after printing. A larger printed test part with some surface structures shows the improved printability of PEKK in comparison to PEEK. Full article

This review summarizes recent research advancements in thermoplastic composites used in Fused Deposition Modeling (FDM) processes. Since its development in 1988, FDM has emerged as one of the primary emerging technologies of Industry 4.0, receiving attention in fields such as industrial manufacturing, automotive, aerospace, and others, particularly for rapid prototyping and customization. The intention is to make available a guideline for 3D printing researchers, analyzing the properties and performance characteristics of different polymers and polymeric composites. The review analysis covers various reinforcing agents, including particles/nanoparticles, short fibers, and long fibers, identifying critical parameters of the FDM process which affect printed part quality, integrity and final geometry. Major attention is devoted to the different techniques employed for composite filament fabrication, mostly for structural elements and parts. An extensive overview of various FDM composites and fiber-reinforced composites by polymer matrices such as PLA, ABS, and PEEK is presented, with their mechanical and thermal properties reported for specific applications. Current challenges and prospective future research directions are also outlined, mainly focusing on the enhancement of material performance and sustainability. Full article

The gold standard materials used for frameworks of full-arch implant-supported fixed prostheses (ISFPs) have traditionally been metal alloys, but recently, high-performance polymers such as polyetherketones and fibre-reinforced resins have been gaining popularity despite the lack of evidence of load-bearing capacity. The aim of the present study was to evaluate the displacements and strains of milled polymeric frameworks for full-arch ISFPs using 3D digital image correlation. Methods: Twelve frameworks were milled from four polymeric materials (three per group): polyetheretherketone (PEEK), polyetherketoneketone (PEKK), poly(methyl methacrylate) (PMMA) and fibre-reinforced composite (FRC). Each framework was fitted with titanium links and screwed to implant analogues embedded in resin and tested for static load-bearing capacity up to 200N. Displacements were captured with two high-speed photographic cameras and analysed with a video correlation system on three spatial axes, U, V, and W, along with principal tensile, compressive and von Mises strains. Results: PEEK exhibited the highest displacement, indicating greater flexibility, while FRC showed the lowest displacement, suggesting enhanced rigidity. Von Mises strain analysis revealed that PMMA and PEEK experienced higher strain, whereas PEKK and FRC demonstrated lower strain distribution. Bayesian ANOVA provided strong evidence for material differences. Conclusion: FRC exhibited superior load-bearing characteristics, reinforcing its potential as a viable clinical alternative to metal-based ISFPs. Full article

Polyetheretherketone (PEEK) is a high-performance, biocompatible polymer with remarkable mechanical properties, making it a promising candidate for medical implants. However, its intrinsic radiolucency poses a challenge for post-operative imaging. This study investigates the photon shielding capabilities and X-ray imaging qualities of pure PEEK and its composites with barium sulfate (BaSO₄), tantalum (Ta), bismuth oxide (Bi₂O₃), and hydroxyapatite (HA). The Monte Carlo-based Geant4 toolkit and the EpiXS application were used to evaluate key photon interaction parameters, including mass attenuation coefficients, effective atomic number (Z_eff), and effective electron density (N_eff), as well as the imaging performance metrics such as energy deposition and signal-to-noise ratio (SNR). Results indicate that high atomic number composites significantly enhance PEEK’s photon attenuation and imaging contrast. PEEK-Bi₂O₃ exhibited the highest attenuation coefficients and energy deposition, making it the most effective X-ray shielding material. PEEK-Ta provided a balanced performance with enhanced shielding and lower secondary radiation effects, making it suitable for applications requiring both radiopacity and imaging stability. PEEK-BaSO₄ moderately improved attenuation while maintaining a lower density, offering a trade-off between radiopacity and mechanical properties. Conversely, PEEK-HA demonstrated minimal enhancement in photon attenuation, limiting its effectiveness for radiographic applications. The findings suggest that incorporating high atomic number elements into PEEK significantly enhances its suitability for radiopaque medical implants, allowing for improved post-operative monitoring. Full article

It is uncertain whether the interchangeable use of two adhesive systems would yield comparable shear bond strength (SBS) for both Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK); investigating this was the main objective of this study. Milled PEEK (Bredent, Senden, Germany) and PEKK (Pekkton Ivory, AnaxDent, Stuttgart, Germany) blocks were prepared with standardized roughness (0.20 μm) and randomly assigned into two groups (n = 72): with and without aluminum oxide air abrasion (AquaCare Twin, Medivance Instruments, London, UK). Two adhesive systems (Visio.link, Bredent, Senden, Germany, or PEKKBond, AnaxDent, Stuttgart, Germany) were randomly applied (n = 36). Flowable gingival composite (AnaxGum Gingiva, AnaxDent, Stuttgart, Germany) was bonded, and the samples were stored in water (37 °C, 24 h). SBS was measured (MPa) and data were analyzed using three-way ANOVA, followed by Tukey’s test (α = 0.05). All main effects and interactions were significant (p < 0.05), except for polymer (p = 0.163) and the triple interaction (p = 0.601). In the PEEK group, Visiolink showed higher SBS (p < 0.001), regardless of prior air abrasion. For the PEKK group, PEKKBond significantly increased SBS values (p < 0.001) for both pre-treatment groups. Previous air abrasion only significantly increased the SBS of controls without adhesive. This study highlights the importance of material-specific adhesive selection, rather than interchangeable use, for optimal results. The bond strength of PEEK and PEKK is influenced by the adhesive system applied. Moreover, PEKK consistently demonstrated higher SBS values in comparison to PEEK, even without the need for pre-treatment or adhesive conditioning. This characteristic renders PEKK a preferred choice for the fabrication of adhesive restorations. Full article