Band 41, Heft 3

The effects of the conventional heating method and the microwave heating method on polyacrylonitrile-based fibres in the temperature range of 180–280 °C were investigated. Fourier transform infrared spectroscopy, X-ray wide-angle scattering, Raman spectroscopy, energy-dispersive spectrometer, scanning electron microscopy and bulk density were used to characterise the properties of the samples. Results show that the microwave heating method can shorten the pre-oxidation time, reduce pre-oxidation temperature and reduce the number of surface defects. The pre-oxidised fibres obtained by the microwave heating method exhibit not only good crystallite size but also a smooth surface. Atomic morphology and molecular arrangement are orderly inside the fibre. The FT-IR spectrum shows that the oxidation reaction occurs at 220 °C, and the CI value of PAN fibers stabilised by microwave heating is the larger than the fibers stabilised by conventional heating. XRD analysis shows that fibers stabilised by microwave heating have low stack domains. The SEM and Raman spectra indicate that hydrogen peroxide can improve the surface finish of the fibers and reduce defects. Microwave heating can reduce the pre-oxidation temperature by about 20 °C and shorten the heating time. The economic benefits of using this method are significantly improved.

The ruthenium (Ru) catalyst is the most recently developed poly dicyclopentadiene (p-DCPD) polymer catalyst known to promote stable reactions, even upon contact with oxygen. However, the experimental results showed that exposure times exceeding three days can cause problems during curing due to reaction between oxygen and Ru catalyst. Consequently, 12 days of exposure degraded the mechanical and interfacial properties of p-DCPD or p-DCPD composites reinforced with 40 wt% 50-mm GF by 60%. The structural analysis simulation of the target product also showed noticeable changes in the catalyst that was exposed to air atmosphere for more than six days, which can deteriorate quality. This study demonstrated that when molding structures using p-DCPD, special care should be taken to control atmospheric exposure of the ruthenium catalyst.

The present study aimed to develop adhesives for bonding natural rubber (NR) to steel based on modified NR bearing grafted poly(acetoacetoxyethyl methacrylate), NR-g-PAAEM. Graft copolymers of NR-g-PAAEMs were prepared by emulsion polymerization at 50 °C. A significant increase in the polar component of NR from 1.62 to 6.84 mN/m was observed after grafting modification, indicating an increase in its hydrophilicity. After that, both one-coat and two-coat adhesives (or adhesive/cover-coat system) were then prepared, using polyisocyanate (poly‐HDI) as a bonding agent. The NR/steel joints were made by vulcanization bonding, using the NR-g-PAAEM adhesive in the presence or absence of cover-coat layer. The results reveal that the NR/steel joint bonded using the two-coat system exhibited higher peel strength than that bonded using the one-coat system. For the two-coat system, the peel strength of 874 N/m was attained when the NR-g-PAAEM adhesive was used in combination with the NR cover-coat. The replacement of the NR cover-coat by the NR-g-PAAEM20 cover-coat led to 49% increase in peel strength of the NR/steel joint. Moreover, the X-ray photoelectron spectroscopy analysis also indicated the formation of urethane-like bonding in this adhesive system, as a result of the reaction between the poly‐HDI and metal oxides on the steel surface.

Linear diepoxide-terminated poly(ethylene glycol) (PEG) of molar mass 600, 1000 and 2000 g mol −1 was end-linked with dendrimer-star polymer (PAMAM) of generations 1.0 in water to prepare architecturally well-defined copolymer hydrogels. The structures and properties of the products were characterized using infrared, 1 H NMR, DSC measurements, scanning electron microscopy (SEM) and swelling behavior tests. The swelling behavior of these hydrogels was tested in distilled water at constant temperature and the equilibrium swelling ratio (ESR) was determined for structurally different hydrogels and various environmental conditions, which showed that ESR was influenced by the molecular weight of PEG, the molar ratio of H amine groups/epoxy groups, temperature and pH. Higher ESR was obtained for either longer-chain PEG, non-stoichiometric H amine/epoxy groups ratio, acidic pH or lower temperatures. When the hydrogel was switched from 10 °C to 65 °C and pH 3.5 to 11.5, the swelling behavior of the hydrogels showed good reversibility for swelling–deswelling. When the molecular weight of PEG was changed in the range of 600–2000, the lower critical solution temperature (LCST) of hydrogel increased from 30 to 40 °C. When the molar ratio of H amine/epoxy groups was changed, the LCST was not significantly changed.

Imidazolium functionalized polymer electrolytes for the electrochemical reduction of gaseous CO 2 (ERGC) were studied for the first time in a developed reactor at room temperature and atmospheric pressure. It was found that reaction environment favors the CO 2 reduction reaction by overcoming the mass transfer of CO 2 with the use of imidazolium fixed functional groups. The selectivity and Faradaic efficiency of products formed during ERGC is enhanced due to the modified functional groups in the solid polymer matrix. This work may open up new research opportunities for the conversion of gaseous CO 2 to green fuels.

Poly(ethylene terephthalate) (PET) and polyamide (PA) are immiscible polymers, which requires the use of compatibilizers to stabilize the morphology and achieve acceptable property levels. Therefore, controlling the degree of dispersion, especially the size of the disperse PA droplets in the PET matrix is of paramount importance. This study aims to improve the mixing, i.e., minimize PA droplet size, in immiscible and compatibilized PET/PA and PET/Nylon-MXD6 (MXD6) blends by resorting to extension-dominated mixing in twin-screw extrusion (TSE). MXD6 is an aromatic polyamide similar in polarity to PET, so it is expected that it will blend more effectively than is the case with aliphatic nylon-6 and PET. Two screw configurations are used, a benchmark shear-dominated screw with kneading blocks (KBs) in an aggressive configuration, and an extension-dominated screw configuration with static mixers with hyperbolic C–D channels, recently developed by our group, in place of the KBs. The results show that the use of extensional mixing elements (EMEs) in place of KBs results in a significant decrease of both average and maximum droplet size for all blends, and up to more than one order of magnitude between the most extreme cases of the KB-processed immiscible blend and EME-processed compatibilized blends.

Sub-microparticles have many applications in different fields today. In this study, it is aimed to develop hydrophobic microparticles as an alternative to existing methods and to determine the 17β-estradiol adsorption performance of this adsorbent to purify the 17β-estradiol hormone which is found as an endocrine disruptor in environmental waters with high capacity and low cost. In this study, l -phenylalanine containing Poly(HEMA-MAPA) microparticles were synthesized by microemulsion polymerization and used as adsorbent. Microparticles were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) methods. The size of the Poly(HEMA-MAPA) microparticles used was measured as 120–200 nm. Specific surface area and elemental analysis studies were also conducted. While the surface area of the particles was found to be a very high value of 1890 m 2 /g, the amount of incorporation of MAPA into the polymeric structure was calculated as 0.43 mmol/g. Adsorption studies were carried out in the batch system under different ambient conditions (17β-estradiol concentration, temperature, ionic intensity). The adsorption capacity of Poly(HEMA-MAPA) microparticles was calculated to be 98.4 mg/g. Isotherm models for adsorption interaction were investigated deeply, and it was determined that the adsorption mechanism is suitable for Langmuir isotherm.

This study aims to clarify the relationship between the layer structure transition of fibers caused by the change in the flow field and the thermal properties and fiber interaction when the glass fiber content is changed. Polyamide 6 samples with different short glass fiber contents were prepared, and changes in layer structure during the flow process of injection molding were compared using X-ray computed tomography. An injection-molding simulation was performed to compare the changes in the layer structure of fibers during the flow process, and the temperature distribution and shear rate distribution were obtained by numerical analysis. Furthermore, the effect of fiber interaction on the layer structure transition of fibers was considered using a relaxation function composed of the fiber content, fiber shape factor, and strain rate.