Search Results (15)

Poly-ether ether ketone (PEEK) is a high-performance thermoplastic known for its excellent mechanical properties, making it relevant for aerospace and medical applications. Additive manufacturing (AM) represents a critical step towards integrating PEEK into these sectors, particularly for complex geometries and custom parts. However, the mechanical properties achieved through AM have not yet reached those obtained via conventional techniques. Recent studies have sought to optimize the printing parameters to bridge this gap, but their findings remain inconsistent and difficult to generalize—suggesting a strong dependence on the experimental conditions. This is partly due to the Fused Filament Fabrication of PEEK being an emerging technology, with many studies relying on in-house built printers. Moreover, the underlying microstructural mechanisms governing its performance have rarely been explored in depth. In this work, we establish clear processing–structure–property relationships by integrating a rigorous DoE approach with comprehensive microstructural characterization. Our results highlight the dominant role of the processing environment near the glass transition temperature in promoting chain mobility, enhancing the amorphous phase ordering, and improving the mechanical performance: crystallinity alone does not fully explain the mechanical behavior of additively manufactured PEEK. Further, higher nozzle temperatures lower the porosity and increase the filament bonding, while faster printing speeds reduce the crystallinity and increase the porosity, negatively affecting the mechanical integrity. The results of this study are generalizable to any FFF printer of PEEK. Other materials or printing technologies are out of the scope of this work. Full article

Poly(lactic acid) (PLA) is one of the most important bio-based and industrial compostable materials in food packaging. Its barrier properties towards oxygen and moisture are well documented. However, data on barrier properties of PLA towards organic molecules are scarce in the literature. This study investigated the diffusion of various organic molecules, including n-alkanes, 1-alcohols, 2-ketones, ethers, esters, amines, and aromatics, in two commercial PLA films with thicknesses of 20 µm and 30 µm. The diffusion coefficient (D_P) values were determined from lag time in permeation tests conducted at temperatures ranging from 20 °C to 90 °C. The films were also characterized in terms of crystallinity, rigid and mobile amorphous fractions, and molecular weight. Activation energies (E_A) were calculated based on the temperature dependence of the D_P using the Arrhenius approach. In total, 290 D_P values for 55 individual substances were determined, and 38 E_A values were derived from these data. The E_A correlated well with the molecular volume of the investigated substances. Moreover, the pre-exponential factor D₀ showed a correlation with E_A. These correlations enabled the establishment of diffusion modeling parameters for PLA, allowing the prediction of D_P for untested substances. The diffusion behavior of PLA was further compared with the literature data for polyethylene terephthalate and polyethylene naphthalate, providing insights into the relative performance of these materials. Full article

Low-frequency peaks in the Raman spectra of amorphous poly(ether ether ketone) (PEEK) were investigated. An amorphous sample with zero crystallinity, as confirmed by wide-angle X-ray diffraction, was used in this study. In a previous study, two peaks were observed in the low-frequency Raman spectra of the crystallized samples. Among these, the peaks at 135 cm⁻¹ disappeared for the amorphous sample. Meanwhile, for the first time, the peak at 50 cm⁻¹ was observed in the crystallized sample. Similar to the peak at 135 cm⁻¹, the peak at 50 cm⁻¹ disappeared in the amorphous state, and its intensity increased with increasing crystallinity. The origins of the two peaks were associated with the Ph-CO-Ph-type intermolecular vibrational modes in the simulation. This suggests that the Ph-CO-Ph vibrational mode observed in the low-frequency region of PEEK was strongly influenced by the intermolecular order. Full article

Poly(ether ether ketone) (PEEK) was found to form gels in the benign solvent 1,3-diphenylacetone (DPA). Gelation of PEEK in DPA was found to form an interconnected, strut-like morphology composed of polymer axialites. To our knowledge, this is the first report of a strut-like morphology for PEEK aerogels. PEEK/DPA gels were prepared by first dissolving PEEK in DPA at 320 °C. Upon cooling to 50 °C, PEEK crystallizes and forms a gel in DPA. The PEEK/DPA phase diagram indicated that phase separation occurs by solid–liquid phase separation, implying that DPA is a good solvent for PEEK. The Flory–Huggins interaction parameter, calculated as χ₁₂ = 0.093 for the PEEK/DPA system, confirmed that DPA is a good solvent for PEEK. PEEK aerogels were prepared by solvent exchanging DPA to water then freeze-drying. PEEK aerogels were found to have densities between 0.09 and 0.25 g/cm³, porosities between 80 and 93%, and surface areas between 200 and 225 m²/g, depending on the initial gel concentration. Using nitrogen adsorption analyses, PEEK aerogels were found to be mesoporous adsorbents, with mesopore sizes of about 8 nm, which formed between stacks of platelike crystalline lamellae. Scanning electron microscopy and X-ray scattering were utilized to elucidate the hierarchical structure of the PEEK aerogels. Morphological analysis found that the PEEK/DPA gels were composed of a highly nucleated network of PEEK axialites (i.e., aggregates of stacked crystalline lamellae). The highly connected axialite network imparted robust mechanical properties on PEEK aerogels, which were found to densify less upon freeze-drying than globular PEEK aerogel counterparts gelled from dichloroacetic acid (DCA) or 4-chlorphenol (4CP). PEEK aerogels formed from DPA were also found to have a modulus–density scaling that was far more efficient in supporting loads than the poorly connected aerogels formed from PEEK/DCA or PEEK/4CP solutions. The strut-like morphology in these new PEEK aerogels also significantly improved the modulus to a degree that is comparable to high-performance crosslinked aerogels based on polyimide and polyurea of comparable densities. Full article

As a high-performance engineering plastic, polyarylene ether nitrile (PEN) is widely used in many fields. The presence of cyano groups of PEN ensures its good adhesion to other substrates, but the inherent low crystallinity of PEN limits its application. In this work, the poly(aryl ether ketone) segment was introduced into PEN via copolymerization using both 2,6-Dichlorobenzonitrile and 4,4′-Difluorobenzophenone as the starting reagents to prepare poly (ether nitrile ketone) (BP-PENK). The effect of composition and thermal treatment on the crystallization behavior and properties of poly (ether nitrile ketone) were systematically studied. It was found that when the content of DFBP is 30%, the copolymer BP-PENK30 had the best mechanical properties, with a tensile strength of 109.9 MPa and an elongation at a break value of 45.2%. After thermal treatment at 280 °C for 3 h, BP-PENK30 had the highest crystallinity with a melting point of 306.71 °C, a melting enthalpy of 5.02 J/g, and crystallinity of 11.83%. Moreover, with the increase in crystallinity, the dielectric constant and energy density increased after thermal treatment. Therefore, the introduction of poly(aryl ether ketone) chain segments and thermal treatment can effectively improve the crystallization and the comprehensive properties of PEN. Full article

Fused deposition modeling (FDM) processed Poly-ether-ether-ketone (PEEK) materials are widely used in aerospace, automobile, biomedical, and electronics industries and other industries due to their excellent mechanical properties, thermal properties, chemical resistance, wear resistance, and biocompatibility, etc. However, the manufacture of PEEK materials and parts utilizing the FDM process faces the challenge of fine-tuning a list of process parameters and heat treatment conditions to reach the best-suiting mechanical properties and microstructures. It is non-trivial to make the selection only according to theoretical analysis while counting on a vast number of experiments is the general situation. Therefore, in this paper, the extrusion rate, filling angle, and printing orientation are investigated to adjust the mechanical properties of 3D-printed PEEK parts; then, a variety of heat treatment conditions were applied to tune the crystallinity and strength. The results show that the best mechanical performance is achieved at 1.0 times the extrusion rate, varied angle cross-fillings with ±10° intervals, and vertical printing. Horizontal printing performs better with reduced warpage. Additionally, both crystallinity and mechanical properties are significantly improved after heat treatment, and the best state is achieved after holding at 300 °C for 2 h. The resulting tensile strength is close to 80% of the strength of injection-molded PEEK parts. Full article

Poly(aryl-ether-ketone) materials (PAEKs), a class of high-performance polymers comprised of polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), have attracted interest in standard dental procedures due to their inherent characteristics in terms of mechanical and biological properties. Polyetheretherketone (PEEK) is a restorative dental material widely used for prosthetic frameworks due to its superior physical, mechanical, aesthetic, and handling features. Meanwhile, polyetherketoneketone (PEKK) is a semi-crystalline thermoplastic embraced in the additive manufacturing market. In the present review study, a new way to fabricate high-performance polymers, particularly PEEK and PEKK, is demonstrated using additive manufacturing digital dental technology, or 3-dimensional (3D) printing. The focus in this literature review will encompass an investigation of the chemical, mechanical, and biological properties of HPPs, particularly PEEK and PEKK, along with their application particularly in dentistry. High-performance polymers have gained popularity in denture prosthesis in advance dentistry due to their flexibility in terms of manufacturing and the growing interest in utilizing additive manufacturing in denture fabrication. Further, this review also explores the literature regarding the properties of high-performance polymers (HPP) compared to previous reported polymers in terms of the dental material along with the current advancement of the digital designing and manufacturing. Full article

Poly(ether ether ketone) (PEEK) is an important engineering plastic and evaluation of its local crystallinity in composites is critical for producing strong and reliable mechanical parts. Low wavenumber Raman spectroscopy and X-ray diffraction are promising techniques for the analysis of crystal ordering but a detailed understanding of the spectra has not been established. Here, we use molecular dynamics combined with a newly developed approximation to simulate local vibrational features to understand the effect of intermolecular ordering in the Raman spectra. We found that intermolecular ordering does affect the low wavenumber Raman spectra and the X-ray diffraction as observed in the experiment. Raman spectroscopy of intermolecular vibration modes is a promising technique to evaluate the local crystallinity of PEEK and other engineering plastics, and the present technique offers an estimation without requiring heavy computational resources. Full article

(1) Background: BioHPP^® (Bredent, UK) is a partially crystalline poly ether ether ketone (PEEK) that is strengthened using ceramic. PEEK and its various formulations represent a very interesting alternative, and has been in-depth with its literature in recent years; (2) Methods: A PubMed and Scopus search for the term “BioHPP” yielded 73 results and 42 articles which were included in this short review. Considering the scarce literature on the subject, each article was considered in this review; (3) Results: the articles analyzed are very recent, all published in the last 5 years. Their clinical evaluation of BioHPP^® highlights many positive aspects, and few articles have highlighted critical issues in its multiple clinical applications; (4) Conclusions: this material is not only extremely interesting for the future, but possesses characteristics suitable for clinical application today, for endocrowns, small adhesive bridges, temporary prostheses and for immediate loads on implant restorations. The excellent aesthetics and the possibility of simple reprocessing of the restorations made with this material invite its clinical application. Full article

As part of the experiments herein, the mechanical properties of specimens made of poly-ether-ether-ketone (PEEK) material using 3D printing technology were determined. Two populations of specimens were investigated, the first of which contained an amorphous structure, while the other held a crystal structure. The studies also investigated the influence of the print directionality on the mechanical properties obtained. Static tensile, three-point bending, and impact tests were carried out. The results for the effect of the structure type on the tensile properties showed that the modulus of elasticity was approximately 20% higher for the crystal than for the amorphous PEEK form. The Poisson’s ratios were similar, but the ratio was slightly higher for the amorphous samples than the crystalline ones. Furthermore, the studies included a chemical PEEK modification to increase the hydrophilicity. For this purpose, nitrite and hydroxyl groups were introduced into the chain by chemical reactions. The results demonstrate that the modified PEEK specimens had worse thermoplastic properties than the unmodified specimens. Full article

Compared with laser-based 3D printing, fused deposition modelling (FDM) 3D printing technology is simple and safe to operate and has a low cost and high material utilization rate; thus, it is widely used. In order to promote the application of FDM 3D printing, poly-ether-ether-ketone (PEEK) was used as a printing material to explore the effect of multi-factor coupling such as different printing temperatures, printing directions, printing paths, and layer thicknesses on the tensile strength, bending strength, crystallinity, and grain size of FDM printed PEEK parts. The aim was to improve the mechanical properties of the 3D printed PEEK parts and achieve the same performance as the injection molded counterparts. The results show that when the thickness of the printed layer is 0.1 mm and the printing path is 180° horizontally at 525 °C, the tensile strength of the sample reaches 87.34 MPa, and the elongation reaches 38%, which basically exceeds the tensile properties of PEEK printed parts reported in previous studies and is consistent with the tensile properties of PEEK injection molded parts. When the thickness of the printed layer is 0.3 mm, the printing path is 45°, and with vertical printing direction at a printing temperature of 525 °C, the bending strength of the sample reaches 159.2 MPa, which exceeds the bending performance of injection molded parts by 20%. It was also found that the greater the tensile strength of the printed specimen, the more uniform the size of each grain, and the higher the crystallinity of the material. The highest crystallinity exceeded 30%, which reached the crystallinity of injection molded parts. Full article

Poly (ether ether ketone) (PEEK) is a high-performance engineering thermoplastic polymer with potential for use in a variety of metal replacement applications due to its high strength to weight ratio. This combination of properties makes it an ideal material for use in the production of bespoke replacement parts for out-of-earth manufacturing purposes, in particular on the International Space Station (ISS). Additive manufacturing (AM) may be employed for the production of these parts, as it has enabled new fabrication pathways for articles with complex design considerations. However, AM of PEEK via fused filament fabrication (FFF) encounters significant challenges, mostly stemming from the semi crystalline nature of PEEK and its associated high melting temperature. This makes PEEK highly susceptible to changes in processing conditions which leads to a large reported variation in the literature on the final performance of PEEK. This has limited the adaption of FFF printing of PEEK in space applications where quality assurance and reproducibility are paramount. In recent years, several research studies have examined the effect of printing parameters on the performance of the 3D-printed PEEK parts. The aim of the current review is to provide comprehensive information in relation to the process-structure-property relationships in FFF 3D-printing of PEEK to provide a clear baseline to the research community and assesses its potential for space applications, including out-of-earth manufacturing. Full article

Poly(ether ether ketone) (PEEK)-based nanocomposites have been realized with incorporation (0–30 wt %) of anhydrous calcium terephthalate salts (CATAS), synthetized by reaction of terephtalic acid with the metal (Ca) oxide, by means of a melt processing. Their structure, morphology, thermal, and mechanical properties have been investigated. Scanning electron microscopy observations confirmed homogeneous dispersion of nanometer-sized fillers and a toughened fracture morphology even at the higher content, while thermal characterization confirmed an unvaried thermal stability and unmodified crystalline structure of the reference PEEK matrix. A negligible nucleating effect was evidenced, while a blocking effect of the amorphous phase fraction provide composites with increased stiffness, confirmed by enhanced values of G’ and shifts of glass transition peak to higher temperatures, for restriction in chain mobility imposed by CATAS. The proposed solutions aimed to enlarge the application range of high performance costly PEEK-based composites, by using thermally stable nanofillers with limited costs and easily controllable synthesis phase. Full article

Sulfonated poly (ether ether ketone) (SPEEK) with four different sulfonation degrees (SDs) were prepared, and mixed with polyvinylidene fluoride (PVDF) to prepare four series of SPEEK/PVDF blend membranes. The miscibility between SPEEK and PVDF was investigated by observing the micro-morphologies. The miscible blend membranes were found in the SPEEK/PVDF blend membranes in which either SPEEK had relatively low SD or consisted of low content of one component (either SPEEK or PVDF). The PVDF crystallinity was found to decrease in the SPEEK/PVDF membranes that had better blend miscibility. With the increase of PVDF content, all the blend membranes exhibited the decreased proton conductivity and methanol permeability, and the miscible blend membranes decreased more slowly than the immiscible ones. Full article

Continuous carbon fiber (CF)-reinforced poly (ether ether ketone) (PEEK) composites have excellent mechanical properties, but their processing techniques are limited. Therefore, we promoted a braiding method based on the hybrid fiber method by hot-compacting CF/PEEK plain weave fabrics to solve the problem of difficult wetting between CF and PEEK. Four parameters—melting temperature, molding pressure, crystallization temperature and the resin contents—were investigated for optimized fabrication. After studying the melting range, thermal stability and the contact angle of PEEK under different temperatures, the melting temperature was set at 370 °C. An ultra-depth-of-field 3D microscope was adopted to investigate the effects of molding pressure in the melting stage. The tensile strength or modulus along and perpendicular to the carbon fiber direction and crystallinity under different crystallization temperatures were analyzed. As a result, the sample crystalized at 300 °C showed an excellent tensile properties and crystallinity. The increased mass ratio of PEEK ranging from 50.45% to 59.07% allowed for much stronger interfacial strength; however, the higher resin content can lead to the dispersion of CFs, loss of resin and the formation of defects during processing. Finally, the optimal resin mass content was 59.07%, with a tensile strength of 738.36 ± 14.49 MPa and a flexural strength of 659.68 ± 57.53 MPa. This paper studied the optimized processing parameters to obtain better properties from CF/PEEK plain weave fabrics and to further broaden the specific applications of CF/PEEK composites, demonstrating a new direction for its fabrication. Full article