High-performance Engineering Plastics Research Articles

Synthesis and Properties of Semicrystalline Poly(ether nitrile ketone) Copolymers.

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.

Interlayer bonding improvement of PEEK and CF-PEEK composites with laser-assisted fused deposition modeling

Fused deposition modeling (FDM) is a cost-effective additive manufacturing technique used to fabricate industrial-grade products with intricate designs using high-performance engineering plastics like Polyetheretherketone (PEEK) and their carbon fiber (CF)-reinforced composites. However, the inherent weak interlayer bonding in the FDM results in anisotropic properties, limiting the mechanical strength and hindering widespread applications. In this study, a layer-wise, in-process laser treatment is proposed to enhance the interlayer bonding in the FDM process of both PEEK and CF-PEEK composites. The laser-assisted process selectively treats previously deposited layers, significantly improving the interlayer bonding by enlarging surface contact, reducing voids, and increasing crystallinity. To validate the effectiveness of this method, tensile and bending tests are conducted, accompanied by observations of surface morphology, roughness analysis, and crystallinity measurements. The results demonstrate significant enhancements with over a 20 % increase in tensile strength and 10–20 % increase in bending strength for both materials. This hybrid additive manufacturing method revolutionizes the mechanical properties of printed parts and opens up new possibilities for processing PEEK and CF-PEEK composites.

Design of Superlubricity System Using Si3N4/Polyimide as the Friction Pair and Nematic Liquid Crystals as the Lubricant.

Polyimide (PI) is a high-performance engineering plastic used as a bearing material. A superlubricity system using Si3N4/PI as the friction pair and nematic liquid crystals (LCs) as the lubricant was designed. The superlubricity performance was studied by simulating the start-stop condition of the machine, and it was found that the superlubricity system had good reproducibility and stability. In the superlubricity system, friction aligned with the PI molecules, and this alignment was less relevant compared to which substance was rubbing on the PI. Oriented PI molecules induced LC molecule alignment when the pretilt angle was very small, and the LC molecules were almost parallel to the PI molecules due to the one-dimensional ordered arrangement of LC molecules and low viscosity, which is conducive to the occurrence of the superlubricity phenomenon.

Ultralow Coefficient of Thermal Expansion and a High Colorless Transparent Polyimide Film Realized Through a Reinforced Hydrogen-Bond Network by In Situ Polymerization of Aromatic Polyamide in Colorless Polyimide.

Colorless polyimides (CPIs) are a key substrate material for flexible organic light-emitting diode (OLED) displays and have attracted worldwide attention. Here, in this paper, the dispersion and interfacial interaction of aromatic polyamide (PA) in CPI (synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFMB)) were significantly improved by in situ polymerization, and colorless transparent macromolecular polyimide composites (CPI-PAx) were successfully prepared by PA and CPI. By adjusting the ratio of PA to CPI, a high-performance engineering plastic with excellent film-forming properties was obtained. Molecular simulations confirmed the uniform distribution of PA in CPI and its interaction in polymers. In CPI-PAx, the CPI was locked by the PA chain, and numerous molecular chains were mutually entangled to form a hydrogen-bond network structure. Due to the strong interaction between the chains imparted by the hydrogen bonds of the PA, they do not slide under external forces and heating. In addition, the additive PA has excellent dimensional stability, thermal, and mechanical properties, and CPI has outstanding optical properties, so the synthesized CPI-PAx combines the comprehensive properties of PA and CPI. The CPI-PAx has excellent thermal and mechanical properties, with a thermal decomposition temperature of 499 °C, a glass transition temperature of 385 °C, a coefficient of thermal expansion of 0.8 ppm K-1, a tensile strength of 50.9 MPa, and an elastic modulus of 3.9 GPa. Particularly, CPI-PAx has a 90% transmittance in the visible region. These data prove that the strategy of combining PA and CPI by in situ polymerization is an effective method to circumvent the bottleneck of CPI in the current flexible window application, and this design strategy is universal.

Machine-Learning-Enabled Framework in Engineering Plastics Discovery: A Case Study of Designing Polyimides with Desired Glass-Transition Temperature.

Great and continuous efforts have been made to discover high-performance engineering plastics with specific properties to replace traditional engineering materials in many fields. The utilization of machine learning (ML) has brought more opportunities for the discovery of high-performing engineering plastics. However, hindered by either the relatively small database or a lack of accurate structure descriptors with clear physical and chemical meanings relating to polymer properties, the current ML studies show some flaws in the accuracy and efficiency in polymer development. Herein, we collected a dataset of 878 polyimides (PI), one of the best engineering plastics, with experimentally measured glass-transition temperature (Tg) values, and developed a rapid and accurate ML approach to design PI candidates with the desired Tg value. After the conversion from PI structures into "mechanically identifiable" SMILES (Simplified molecular input line entry system) language, the eight most critical descriptors were ultimately obtained by multiple analysis methods. The physiochemical meaning of the key descriptors was further analyzed carefully to translate the implicit "machine language" to chemical knowledge. The artificial neural network (ANN)-based model gave the most accurate results with a root-mean-square error of ∼11 K among the studied ML methods. More importantly, three potential PI candidates with desired Tg (DPIs) were designed according to the chemical insight of the key descriptors, which were then verified by experiments. The experimental and predicted Tg values of DPIs have an acceptable average deviation of ca. 3.66%. This accuracy has reached the level of the traditional molecular simulation, but the time consumption and hold-up computing resource are tremendously reduced. Furthermore, the current ML approach could offer a scalable and adaptable framework in future engineer plastics innovation.

A sustainable approach for developing biocarbon from lignin and its utilization in recycled ocean nylon based biocomposites

Nylon/polyamide (PA6) is a major cause of ocean plastic pollution because of its extended use in commercial fishing activities. Recovery of this nylon from oceans and its use in manufacturing new materials or composites is urgently required to promote sustainability and circularity. In this work, unlike higher-density mineral fillers, lignin from the forestry industry was converted into biocarbon, which was used as a lightweight filler to manufacture recycled-ocean nylon (RN)-based composites. Biocarbon is a highly stable, competitive, and sustainable filler for high-performance engineering plastics such as nylon. Lignin was pyrolyzed at 600 °C followed by further treatment at 1200 °C (with and without cobalt (II) nitrate catalyst) to induce graphitization in the produced biocarbon. Among the three types of biocarbon samples, such as pyrolyzed at 600 °C, 1200 °C and 1200 °C catalyzed lignin biocarbon, the catalyzed biocarbon showed the maximum electrical conductivity. Catalyzed lignin biocarbon pyrolyzed at 1200 °C showed an increase of 85% in electrical conductivity compared to commercial mineral graphite. The biocomposites consisting of 600 °C biocarbon were manufactured by injection molding at different filler contents up to 40 wt.%. The biocomposites consisting of 40% of pyrolyzed lignin at 600 °C showed increased flexural strength, flexural modulus, and heat deflection temperature by 41, 76 and 76%, respectively, compared to neat RN. Improved properties of the prepared biocarbons and biocomposites showed the potential of RN-based composites in the automotive industries.

SYNTHETIC PROTOCOLS AND SIGNIFICANCE OF HETEROCYCLIC FLUORESCENT - REINFORCING POLYMERS: A COMPREHENSIVE REVIEW

Fluorescent High-Performance polymers are well known as high performance engineering thermoplastics because of their good thermal stability, chemical resistance and excellent mechanical properties. Polymers having S-triazine ring become a subject of interest because of enhanced toughness and low moisture absorption and commercially available high performance engineering plastic materials. However, the thermal stability of triazine ring makes it an attractive monomer for use in high temperature polymers. Synthesis of polymers containing chromophoric groups which are responsible for fluorescent property have significant applications in fields such as biosensors, clean energy technologies, explosive sensing, pH/temperature sensor, biological imaging, life science, material science, ultrasensitive molecular diagnosis and novel light - emitting nano devices. The aromatic azo group is being more interest because of the existence of cis-trans isomerism and its effect on the photochromic properties of the polymers. Therefore, polymers having azo group have potential use in a variety of applications. Fluorescent polymers can be developed with different methods; generally, there are two methods for preparation of fluorescent polymers. One of them is polymerization of a monomer having a fluorescent chromophore such as fluorescent compounds as initiator, fluorescent compounds as chain transfer agents, chemical bonding between fluorescent groups and polymers. The second way, chemical alteration of commercially available polymers having reactive groups by using fluorescent dyes or organic molecules.

Room temperature, simple and efficient synthesis and functionalization of aromatic poly(arylene sulfide)s, poly(arylene sulfoxide)s and poly(arylene sulfone)s

Aromatic polysulfides and polysulfones are a large group of sulfur-containing polymers representing an important class of materials with diverse applications, ranging from high performance engineering plastics, gas separation, ultrafiltration, nanofiltration, ion-exchange membranes, and materials for biomedical applications. All these polymers are produced by high temperature nucleophilic substitution reactions of dichlorobenzene with sodium sulfide (PPS) and dichlorodiphenyl sulfone with bis-phenols in the presence of basic catalysts (PAES). In the present work, novel poly(arylene sulfide)s were obtained in nearly quantitative yields, by one-pot, room temperature, metal-free, highly regioselective, non-stoichiometric step-polymerizations of diphenyl sulfide (DPS) with 1,1,1-trifluoroacetone and isatin, in a mixture of trifluoromethanesulfonic acid (TFSA) with CH2Cl2. The polymers obtained were soluble in common solvents. The oxidation of the poly(arylene sulfide)s with H2O2 at room temperature afforded poly(arylene sulfoxide)s and poly(arylene sulfones) with high oxidation selectivity. On heating, sulfoxide groups of the poly(arylene sulfoxide)s are converted into sulfide groups and oxygen, which acts as an expanding agent, is released in the process to form nanofoams with homogeneous pore distribution. Controlled incorporation of hydroxymethyl-, carboxy-, and “click” able allyl- and propargyl- functionalities is carried out by room temperature, post-modification reactions of the polymers bearing reactive oxindole groups.

Fabrication of High-Performance Colorimetric Membrane by Incorporation of Polydiacetylene into Polyarylene Ether Nitriles Electrospinning Nanofibrous Membranes.

Polyarylene ether nitrile (PEN) is a novel high-performance engineering plastic with various applications, particularly in thermoresistance-required fields. In this study, a well-known stimuli-response polydiacetylene monomer, 10, 12-pentacosadiynoic acid (PCDA), was encapsulated within electrospun PEN nanofibers to fabricate a colorimetric membrane with satisfactory thermal and corrosion resistance. To optimize the compatibility with PCDA, two PENswith distinct molecular chains were utilized: PEN-PPL and PEN-BPA. The chemical structure and elemental mapping analysis revealed that the PCDA component was successfully incorporated into the PEN fibrous. The PCDA bound significantly better to the PEN-PPL than to the PEN-BPA; due to the carboxyl groups present on the side chains of PEN-PPL, the surface was smooth and the color changed uniformly as the temperature rose. However, owing to its poor compatibility with PEN-BPA, the PCDA formed agglomerations on the fibers. The thermal analysis demonstrated that the membranes obtained after PCDA compounding maintained their excellent heat resistance. The 5% weight loss temperatures of composite nanofibrous membranes manufactured by PEN-PPL and PEN-BPA were 402 °C and 506 °C, respectively, and their glass transition temperatures were 219 °C and 169 °C, respectively, indicating that the blended membranes can withstand high temperatures. The evaluation of application performance revealed that the composite membranes exhibited good dimensional stability upon high thermal and corrosive situations. Specifically, the PEN-P-PCDA did not shrink at 170 °C. Both composite membranes were dimensionally stable when exposed to the alkali aqueous solution. However, PEN-P-PCDA is more sensitive to OH-, exhibiting color transition at pH > 8, whereas PEN-B-PCDA exhibited color transition at high OH- concentrations (pH ≥ 13), with enhanced alkali resistance stability owing to its nanofibrous architecture. This exploratory study reveals the feasibility of PEN nanofibers functionalized using PCDA as a desirable stimulus-response sensor even in high-temperature and corrosive harsh environments.

EVALUATION OF FRICTION AND WEAR BEHAVIORS OF HIGH PERFORMANCE POLYETHERETHERKETONE THERMOPLASTIC POLYMER UNDER HIGH PRESSURE AND SLIDING SPEED CONDITIONS

Bu deneysel çalışmada, yüksek performanslı mühendislik plastikleri arasında yer alan poli-eter-eter-keton (PEEK) polimerinin AISI304 paslanmaz çelik diske karşı kuru kayma şartları altındaki tribolojik performansları incelenmiştir. Aşınma deneyleri, 1.77, 3.54, 5.30 ve 8.84MPa gibi yüksek basınçlarda, 0.5, 1.0, 2.0 ve 4.0m/s gibi yüksek kayma hızlarında pim-disk aşınma cihazında gerçekleştirilmiştir. Aşınma test sonuçlarına göre, artan kayma hızı ile birlikte sürtünme katsayısı ve aşınma oranı değerleri artmıştır. Düşük yük ve kayma hızlarında düşük P.V değerleri elde edilirken artan yük ve kayma hızı ile birlikte P.V faktörünün arttığı belirlenmiştir. Genel olarak deneylerde kullanılan basınç ve kayma hızı aralıklarında sürtünme katsayısının 0.17 ile 0.39 aralığında elde edilirken, aşınma oranının ise 5.2×10-15 ile 21.4×10-15 m2/N arasında değiştiği tespit edilmiştir. Deneylerde kullanılan PEEK malzemenin yüksek P.V değerlerinde abrazif aşınma mekanizması gözlenirken düşük P.V değerlerinde adhezif aşınma mekanizması gözlenmiştir.

KARBON FİBER TAKVİYELİ GRAFİT ve PTFE KATKILI POLİ-ETER-ETER-KETON (PEEK) POLİMER KOMPOZİTİN TRİBOLOJİK PERFORMANSLARINA KAYMA HIZININ ETKİSİNİN BELİRLENMESİ

Farklı endüstriyel sektörlerde kullanılan makinalarda plastik esaslı rulman, makara ve burç gibi makine elemanları kullanılmaktadır. Bu uygulamalardaki makine elemanlarının çalışma esnasındaki hızları ve taşıma yükleri malzemenin ömrünü belirlemektedir. Bu deneysel çalışmada, rulman, makara ve burç yapımında kullanılan yüksek performanslı mühendislik plastikleri arasında yer alan karbon fiber takviyeli grafit ve poli-tetra-flor-etilen (PTFE) katkılı poli-eter-eter-keton (HV-PEEK) polimeri kullanılarak tribolojik performansları incelenmiştir. Testlerde AISI304 paslanmaz çelik karşı disk kullanılmış, deneyler kuru kayma şartları altında ve oda sıcaklığında yapılmıştır. Aşınma deneyleri, 3.53 MPa basınç altında, düşük (1.0 m/s) ve yüksek (4.0 m/s) kayma hız aralıklarında pim-disk aşınma test cihazında gerçekleştirilmiştir. Aşınma test sonuçlarına göre, kayma hızına bağlı olarak HPV-PEEK polimerinin sürtünme katsayısı ve spesifik aşınma oranı değişimi incelenmiştir. Elde edilen deney sonuçlarına göre artan kayma hızı ile birlikte polimerin sürtünme katsayısı azalırken spesifik aşınma oranı değerleri artmıştır. Genel olarak sürtünme katsayısı 0.14 ile 0.19 aralığında elde edilmiş, aşınma oranı ise 1.66×10-6 ile 0.48×10-6 mm3/Nm aralığında değişim göstermiştir. Deneylerde kullanılan HV-PEEK polimer kompozitinde düşük kayma hızlarında abrazif aşınma mekanizması gözlenirken yüksek kayma hızlarında adhezif aşınma mekanizması gözlenmiştir.

Poly(2,6-dimethyl-1,4-phenylene ether)/poly(phenylene sulfide)/styrenic block copolymer blends compatibilized with reactive polystyrene

Blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(phenylene sulfide) (PPS) have shown potential as a new class of high-performance engineering plastics by reciprocally complementing the drawbacks of each component. However, improving their inherently poor toughness remains a challenge. Here, we report the design of PPE/PPS-based quaternary blends with increased impact strength without a significant loss of mechanical and flame-retardant properties. Introducing reactive polystyrene (RPS) with an oxazoline functional group as a compatibilizer improved the miscibility between the discrete PPE domain and continuous PPS matrix phases. The impact modifier styrene-ethylene-butadiene-styrene (SEBS) was compatibilized within the PPS matrix phase in the presence of RPS, enabling extraordinary impact strength. The tensile strength of the quaternary blends decreased slightly with increasing SEBS content, but the values exceeded the criteria for engineering plastic. All quaternary blends passed the V-0 grade in the UL-94 test because of the inherently excellent flame retardancy of the majority components.

Polyether-ether-ketone/poly(methyl methacrylate)/carbon fiber ternary composites prepared by electrospinning and hot pressing for bone implant applications

Currently, metals such as titanium and various new high-performance engineering plastics such as polyether-ether-ketone (PEEK) are widely used in clinics. Compared with human cortical bone, traditional metals may cause stress shielding. In contrast, the elastic modulus of PEEK is slightly lower than that of human bones. In this study, PEEK and polymethyl methacrylate (PMMA) were electrospun into fibers and mixed with carbon fiber (CF). The mixture was then hot-pressed to prepare PEEK/PMMA/CF ternary composites. Mechanical tests showed that the Young's moduli of the PEEK/PMMA/CF ternary composites were between 4.67 ± 0.38 and 6.37 ± 0.81 GPa, similar to human bones. In vitro cytotoxicity tests, after 7 days of cell culture, showed that the relative growth rates were 86–97%, and the corresponding cytotoxicity levels were 0 or 1. In addition, in vivo experiments demonstrated that the ternary composites exhibited good histocompatibilities and displayed no rejection or inflammatory reactions. No artifacts were observed when the material was examined using X-ray, CT (computerized tomography computed tomography), and MRI (magnetic resonance imaging) scanning. Thus, the PEEK/PMMA/CF ternary composites fabricated in this study may be used as promising bone implant materials in orthopedic applications.

Evaluation of process parameters for poly(ether ether ketone) to poly(ether ether ketone) friction welded joint

Poly(ether ether ketone) is a semicrystalline organic polymer. It has widely been used as high-performance engineering plastic owing to its high melting point (343 °C), excellent mechanical strength, and outstanding chemical resistance. Therefore, poly(ether ether ketone) and its composites have shown lots of applications in aerospace and medical fields. However, its application is restricted due to poor strength at the mechanically joint components. Thus, this scope leads us to study an alternative method of the joint process that will lead to finding a new joining process for poly(ether ether ketone)-based materials. In this study, a solid-state joining process was conducted to join two poly(ether ether ketone) rods by a friction welding process. Here, we statistically optimized the values of forge load, friction load, and friction welding time as 100 N, 450 N, and 8 s, respectively, which have more influence on tensile stress and hardness of the material after the friction welding process. It has been found that the forge load had the highest influence and the forge time had the least influence on tensile strength. Their optimal values were calculated after considering the trend in hardness values by statistical analysis using Minitab software. However, after the optimal values, the above parameter showed a negative effect on the high tensile stress due to the change in crystallinity of the friction welding processed poly(ether ether ketone) as confirmed by X-ray diffraction and thermal analyses.

Biobased and mechanically stiff lignosulfonate/cationic-polyelectrolyte/sugar complexes with coexisting ionic and covalent crosslinks

We prepared moldable materials from lignosulfonate, an industrial lignin derivative, using a combination of ionic crosslinking between lignosulfonate and cationic polyelectrolytes and covalent crosslinking via the Maillard reaction. The mechanical properties of the lignosulfonate/cationic-polyelectrolyte/sugar complex at the optimal composition (stress at break: 55.1 MPa; Young’s modulus: 2791.8 MPa; strain at break: 3%) were comparable to those of poly(phenylene sulfide), which is used as a high-performance engineering plastic. In addition to the good mechanical properties, the lignosulfonate/cationic-polyelectrolyte/sugar complex was water-insoluble, in contrast with the high water solubility of the complex without the reducing sugar. Furthermore, the addition of a reducing sugar (fructose) to the complexes increased adhesion to a metal substrate. These improvements in the mechanical properties, water resistance, and adhesive strength of the lignosulfonate complex will expand the applications of lignosulfonate under high mechanical stress conditions and in water and biobased adhesives. Lignosulfonate is one of the major industrial products from wood. To utilize this compound as a moldable and strong material, we prepared a complex of lignosulfonate with cationic polyelectrolytes and reducing sugars. This complex contains two different crosslinking structures, i.e., ionic crosslinking between lignosulfonate and cationic polyelectrolytes and covalent crosslinking via the Maillard reaction of amino groups with reducing sugars. The coexisting of two different crosslinking greatly improved mechanical strength, Young’s modulus, water resistance, and adhesive strength compared with solely crosslinked complexes composed of the same ingredients.

Hardness and Abrasion Resistance Characteristics of Poly(ethylene terephthalate) Films without and with Hard and Adhesive Coatings

In this study, we reports the first quantification details of the pencil hardness, eraser abrasion resistance and steel wool abrasion resistance of optically-transparent and biaxially-oriented poly(ethylene terephthalate) (PET) films in various thicknesses before and after hard coating (HC) and/or optically clear adhesive (OCA) coating. Surprisingly, the PET base films were determined to exhibit unrealistically very low hardness and abrasion resistances although their stress-strain behavior followed a ductile and tough plastic nature as a high performance engineering plastic: the pencil hardness was only ≤ 9B even at a low loading force, 0.100 kgf, and the onset loading force to cause scratches was far below 0.013 kgf in both eraser and steel wool abrasions. These collectively confirmed that, without surface protections, PET base films are not suitable for any advanced applications. Such the low hardness and poor abrasion resistances could be improved substantially by only thin HC coating of di(trimethylolpropane) tetraacrylate (HC-a, an ultraviolet curable acrylic resin). In addition, the OCA coating based on an acrylic copolymer adhesive provided adhesion function to the PET films, showing excellent adhesion strength onto chemically-toughened glass. However, the OCA layer causes cushioning effect because of its easy plastic deformation nature, making negative impact on the hardness and abrasion resistance performances of the PET film. Thus, the OCA coating should be thinned until retaining good adhesion to adherends. Overall, PET films coated with HC and/or OCA are suitable for advanced applications in various fields including smart phones, foldable phones, and flexible display devices.

Synthesis of Ethylene/1-Octene Copolymers with Ultrahigh Molecular Weights by Zr and Hf Complexes Bearing Bidentate NN Ligands with the Camphyl Linker

Ultrahigh molecular weight polyethylene (UHMWPE) is a class of high-performance engineering plastics, exhibiting a unique set of properties and applications. Although many advances have been achieved in recent years, the synthesis of UHMWPE is still a great challenge. In this contribution, a series of zirconium and hafnium complexes, [2,6-(R1)2-4-R2-C6H2-N-C(camphyl)=C(camphyl)-N-2,6-(R1)2-4-R2-C6H2]MMe2(THF) (1-Zr: R1 = Me, R2 = H, M = Zr; 2-Zr: R1 = Me, R2 = Me, M = Zr; 1-Hf: R1 = Me, R2 = H, M = Hf; 2-Hf: R1 = Me, R2 = Me, M = Hf), bearing bidentate NN ligands with the bulky camphyl backbone were synthesized by the stoichiometric reactions of α-diimine ligands with MMe4 (M = Hf or Zr). All Zr and Hf metal complexes were analyzed using 1H and 13C NMR spectroscopy, and the molecular structures of complexes 1-Zr and 1-Hf were determined by single-crystal X-ray diffraction, revealing that the original α-diimine ligand was selectively reduced into the ene-diamido form and generated an 1,3-diaza-2-metallocyclopentene ring in the metal complexes. Zr complexes 1-Zr and 2-Zr showed moderate activity (up to 388 kg(PE)·mol−1(M)·h−1), poor copolymerization ability, but unprecedented molecular weight capability toward ethylene/1-octene copolymerization. Therefore, copolymers with ultrahigh molecular weights (>600 or 337 × 104 g∙mol−1) were successfully synthesized by 1-Zr or 2-Zr, respectively, with the borate cocatalyst [Ph3C][B(C6F5)4]. Surprisingly, Hf complexes 1-Hf and 2-Hf showed negligible activity under otherwise identical conditions, revealing the great influence of metal centers on catalytic performances.

Investigation on phenolphthalein and bisphenol AF based Poly(arylene ether nitrile) copolymers: Preparation, thermal, mechanical and dielectric properties

Poly (arylene ether nitrile) (PEN) is a kind of high-performance engineering plastic and their properties can be tuned by the copolymerization of various structural diphenols and dichloro (fluoro)-benzonitrile. In this work, a series of phenolphthalein and bisphenol AF based PEN (PP/BPAF-PEN) copolymers were designed and synthesized. Structures, molar weights, mechanical and thermal properties were studied. Results showed that PP/BPAF-PEN copolymers were successfully synthesized and exhibited good compatibility, outstanding thermal and mechanical properties. Besides, PP/BPAF-PEN exhibited excellent Tg up to 260 °C (DSC), tensile strength of 120 MPa, high Td5% and char yields (>70%). With incorporation of –CF3 into molecular chains, dielectric constant of PP-PEN (3.41 at 1 MHz) was decreased to 3.05 of PP/BPAF-PEN and dielectric loss was around 0.01. Hence, the obtained PP/BPAF-PEN copolymers possessing excellent properties could be applied as the candidates in flexible printed circuit (FPC) substrate.

3D network super-hydrophobic hexafluorbisphenol A poly(aryl ether ketone) membrane prepared by one-step electrospraying

Novel super-hydrophobic poly(aryl ether ketone) (PAEK) membranes have been firstly prepared by modifying ordinary PAEK into hexafluorbisphenol A-PAEK through traditional nucleophilic condensation polymerization and subsequently simple electrospraying technique. With the solution concentration increased, the micromorphology exhibited nanofibers, nanofiber with spindles, 3D network with microspheres embedded, microspheres and dense films, successively. The static water contact angle increased from 99° to 155°, while the sliding angle from 1.3° to 6.8° (±1°), in which the 3D network presented the strongest super-hydrophobicity. After 200 h of water flushing, the rough surface structure and super-hydrophobicity of the membranes were well retained. Moreover, the membrane exhibited wonderful self-cleaning property, oil/water separation property, and stability due to the hierarchical micro/nanostructures. This work provides a new route for the creation of super-hydrophobic high performance engineering plastic fabrics with the potential values in large-scale application of filtration, oil/water separation, and antifouling.

Enhanced mechanical and thermal properties of carbon fiber-reinforced thermoplastic polyketone composites

Advances in thermoplastic composites have attracted interest among researchers for the development of new high-performance and recyclable engineering plastics. Herein, a novel polyketone (PK) composite containing carbon fiber (CF), as well as its thermophysical characteristics, was investigated. PK composites with different CF contents ranging from 0 to 30 wt% were fabricated through the two-stage extruder-injection molding process. The performances of the raw and composite materials were measured by various methods, and we found that the incorporation of CF into PK enhances the thermal stability, conductivity, and mechanical properties of the composites simultaneously. To theoretically evaluate the thermomechanical characteristics of the PK composites, a series of numerical simulation was carried out. The Kapitza resistance, which was assumed to be a model constant in this study, was determined through a genetic algorithm. The predicted properties of composites with varying CF were observed to be in good qualitative agreement with the experimental results.