Yongpeng Wang

Aluminium borate whiskers grafted with boric acid containing poly(ether ether ketone) as a reinforcing agent for the preparation of poly(ether ether ketone) composites

A new soluble boron-containing poly(ether ether ketone) (B-PEEK) was synthesized through iridium-catalyzed C–H borylation of soluble meta-poly(ether ether ketone) and grafted on the surface of aluminum borate whiskers as the coupling agent between the whiskers and poly(ether ether ketone) (PEEK) matrix. The grafted aluminum borate whisker (g-W) reinforced PEEK composites were then prepared via a melt blending method. The coupling effect of B-PEEK was investigated by the interface micromorphology analysis and performance evaluation of PEEK composites. After grafting treatment with B-PEEK, aluminum borate whiskers were found to be dispersed evenly in the PEEK matrix without apparent aggregation. Ascribed to the strong interaction between whisker grafted chains and the PEEK matrix, g-W/PEEK composites show better mechanical properties and izod impact strength, higher crystallization temperature and crystalline fraction (χc) than those composites without grafting modification, indicating B-PEEK is an effective coupling reagent for PEEK and aluminum borate whiskers.

Electrospun carboxylic-functionalized poly(arylene ether ketone) ultrafine fibers optimization, characterization, and water absorption behavior

As a high-performance polymer, carboxylic-functionalized poly(arylene ether ketone)s (PCA-PAEK) was electrospun into ultrafine fibers and characterized. To optimize the process, a set of experiments were designed. As a result, the optimum condition was obtained and the polymer concentration was determined as the most important factor. Incidentally, the PCA-PAEK fibers were found to exhibit superabsorbent behavior. In order to investigate processing characteristics, PCA-PAEK fibers fabricated from different solution concentrations were employed and characterized. The results showed that porosity and changes in water contact angle and water absorbency decreased with an increase in concentration. In addition to a high water absorption capacity, the fibers exhibited good water retention and repeated water absorbency as well. The study on kinetics of water absorption and swelling behavior showed that the mechanism was dependent on the polymer concentration from which the fibers were electrospun. Moreover, both dry and wet PCA-PAEK fibers showed high mechanical properties. Due to these properties, the PCA-PAEK ultrafine fibers are potentially useful as a water-absorbent material.

Synthesis, characterization and photoresponsive behaviour of a series of azobenzene-containing poly(ether sulfone)s with high glass transition temperatures

To improve the stability of photoinduced birefringence, a series of azobenzene-functionalized poly(ether sulfone)s (azo-PES) with high glass transition temperature (T g) were successfully synthesized via Ullmann coupling between PES with bromine side groups and azo compound 4-((4-methoxyphenyl)diazenyl)phenol. Their chemical structures and properties were characterized by means of ultraviolet–visible and proton nuclear magnetic resonance spectroscopies. The results of differential scanning calorimetry and thermogravimetric analysis suggested that the polymers had high T gs and good thermal stability. Upon irradiation with a 532 nm neodymium-doped yttrium aluminium garnet (Nd:YAG) laser beam, these azo polymers presented large photoinduced birefringence with a remnant value up to 94%, indicating good stability of the photoinduced orientation. Furthermore, multiple writing/erasing experiments indicate that the azo polymers have potential applications in reversible optical storage.

Investigations on the tribological properties of poly(arylene ether ketone) copolymer with 3-(trifluoromethyl) phenyl pendants and biphenyl units

High-molecular-weight poly(arylene ether kekone) (PAEK) containing 3-(trifluoromethyl) phenyl pendants and biphenyl units with a mole ratio of 3:7 (FP30-PEDEKK) has been synthesized by nucleophilic substitution copolymerization from 3-(trifluromethyl) phenylhydroquinone, 4,4′-biphenol, and 1,4-bis(p-flurobenzoyl) benzene. FP30-PEDEKK shows good mechanical strength and high thermal stability. The friction and wear behaviors of the copolymer were investigated on pin-on-disk tribological test method using UMT-2. Compared to poly(ether ether ketone) (PEEK), FP30-PEDEKK has better friction reduction property and more stable friction behavior, although it shows lower wear resistance. These results could be supported by the scanning electron microscope investigations which showed that FP30-PEDEKK did have smoother worn surface than PEEK under given conditions. From microscopic images and the evolution of the friction coefficient and specific wear rate, the wear mechanisms of FP30-PEDEKK were suggested. This work significantly highlights the potential of molecular design as a route toward the tribological development of PAEK.

High-effective preparation of ultrafine poly-(l-lactide-co-∊-caprolactone-diOH) fibers containing silver nanoparticles

A novel method utilizing combination of N, N-dimethylformamide (DMF) and ultraviolet (UV) irradiation to reduce silver (Ag+) ions in situ in ultrafine poly-(l-lactide-co-∊-caprolactone-diOH) (PCLA) fibers was developed. Compared with traditional solvent reduction method, the new method exhibited much higher efficiency. UV–visible spectra indicated that the addition of UV irradiation could shorten the reaction time dramatically. Transmission electron microscope and x-ray photoelectron spectroscopy results demonstrated that the new method had produced a larger number of uniform Ag nanoparticles (AgNPs). After statistical analysis, their mean size was determined as 6.96 nm, which was smaller than that of traditional AgNPs. In addition, as a biodegradable polymer, PCLA was first used to carry AgNPs. It was found that PCLA can be a stabilizing agent of Ag+ ions. Therefore, the formation mechanism of AgNPs with larger number and smaller size can be determined.

Effect of barium-containing glass filler reinforcement on shear bond strength of poly(ether ether ketone) to resin cement

The purpose of this study was to evaluate how barium-containing glass filler (BGF) reinforcement and pretreatment methods affect shear bond strength (SBS) of poly(ether ether ketone) (PEEK) to resin cement. PEEK composites with various amounts of BGF (10, 20, 30 and 40 wt%) were prepared as PEEK-BGF10, PEEK-BGF20, PEEK-BGF30 and PEEK-BGF40. Afterward, PEEK and PEEK-BGF40 specimens were treated with hydrofluoric acid, sulfuric acid (H2SO4), silica coating and polishing, respectively. Acrylic hollow cylinders were luted with Dentex dual-curing resin cement to the specimens. Finally, SBS measurements were conducted with a universal testing machine. The introduction of BGFs greatly enhanced SBS of PEEK to resin cement. After simply polishing with 150 grit silicon carbide papers (G150), PEEK-BGF40 exhibited the SBS value up to 19.73 ± 4.30 MPa, similar to the PEEK treated with H2SO4 etching. Scanning electron microscopy and x-ray photoelectron spectroscopy were used to investigate the surface morphological and chemical changes in PEEK and PEEK-BGF composites before and after surface treatment. The results indicate that the introduction of BGF particles plays a key role in improving the adhesion between PEEK and resin cement. This study provides a new method to enhance the adhesion to PEEK without breaking its surface structure, which encourage further research in PEEK composite application in dentistry.

Synthesis and properties of a novel poly(aryl ether sulfone) functionalized with pinacol phenylboronate pendants

A novel poly(arylene ether sulfone) (PAES) with pinacol phenylboronate pendants (PAES-B) was prepared by the borylation of brominated PAES (PAES-Br). The reaction was carried out under mild conditions in the presence of cuprous iodide and tri-n-butylphosphine in tetrahydrofuran solution. After heat treatment at 150°C for 132 h, the PAES-B exhibited an interesting solvent resistance. Fourier transform infrared spectroscopy (FTIR) and thermal analysis were performed to investigate the reason. FTIR spectra showed that heat treatment could facilitate losing of pinacol groups and formation of phenylboronic acid in the polymer. Meanwhile, differential scanning calorimetric (DSC) curves demonstrated that the polymer had cross-linking behaviors during heat treatment. In addition, the thermal oxidative stability of PAES-B was researched by the thermogravimetric analysis (TGA).

The mechanical and frictional properties of poly(ether ether ketone) composites with modified aluminum borate whiskers

Poly(ether ether ketone)s (PEEKs) are increasingly used in tribological application. Reinforcing materials such as aluminum borate whiskers are often incorporated into polymeric materials to improve mechanical properties. In this work, aluminum borate whiskers were modified by the boron-containing poly(ether ether ketone)s (B-PEEKs). The modified aluminum borate whiskers (g-W)-reinforced PEEK composites were then prepared via melt-blending method. B-PEEKs showed the good coupling effect by the interface micromorphology analysis and performance evaluation of PEEK composites. After grafting treatment with B-PEEKs, aluminum borate whiskers were found to be dispersed evenly in PEEKs matrix without apparent aggregation. Ascribed to the strong interaction between whisker-grafted chains and PEEKs matrix, g-W/PEEK composites show better mechanical properties, lower friction coefficient, and wear ratio than those composites without grafting modification, indicating that the grafted aluminum borate whiskers (g-W)-reinforced PEEK composites may become a wear-resistant material.