Band 41, Heft 7

A novel method for estimating the upper critical solution temperature (UCST) of N , N -diethyl- m -toluamide (DEET)-polyethylene systems was developed. It was validated using data for the dimethylacetamide (DMA)-alkane systems which showed that refractive index mixing rules, linear in volume fraction, can accurately predict mixture composition for amide-alkane systems. Furthermore, rescaling the composition descriptor with a single adjustable parameter proved adequate to address any asymmetry when modeling the DMA-alkane phase envelopes. This allowed the translation of measured refractive index cooling trajectories of DEET-alkane systems into phase diagrams and facilitated the estimation of the UCST values by fitting the data with an adjusted composition descriptor model. For both the DEET- and DMA-alkane systems, linear behavior of UCST values in either the Flory–Huggins critical interaction parameter, or the alkane critical temperature, with increasing alkane molar mass is evident. The UCST values for polymer diluent systems were estimated by extrapolation using these two complimentary approaches. For the DEET-polyethylene system, values of 183.4 and 180.1 °C respectively were obtained. Both estimates are significantly higher than the melting temperature range of polyethylene. Initial liquid–liquid phase separation is therefore likely to be responsible for the previously reported microporous microstructure of materials formed from this binary system.

The increasing requirements on plastic parts demand a rising use of combined functional and reinforcing materials. Therefore, often reinforcing particles with different aspect ratios are added to the plastic as additive mixtures. However, the engineering design process of reinforced parts requires an early knowledge of the expected orientation of the reinforcing particles. Numerous models try to predict the orientation of particles in polymer suspensions. However, the interaction coefficient strongly depends on the aspect ratio of the particles and a prediction of the orientation behavior of additive mixtures with differently shaped particles has not been validated using conventional methods. In this work, the orientation of differently shaped particle mixtures in polymer suspensions is investigated for different fluid channel geometries. Finally, the Folgar–Tucker model is applied to filler mixtures and implemented into OpenFOAM ® , which enables the comparison of filler orientation in different fluid channel geometries. Regarding the experiments a characteristic increase of the interaction coefficient was observed at a filling level of 5%. Furthermore, it was shown that a balanced mixing ratio yields higher interaction coefficients. With regard to the performed simulations, it was possible to show qualitatively how a considered interaction between fibers and platelets affects the orientations.

The purpose behind this research was to determine the optimum formulation and investigate the cure kinetics of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin cured by dicyandiamide and diuron for use in prepregs. First, all formulations were examined by the tensile test, and then, the specimens with higher mechanical properties were further investigated by viscometry and tack tests. The cure kinetics of the best formulation (based on tack test) in nonisothermal mode was investigated using differential scanning calorimetry at different heating rates. Kissinger and Ozawa method was used for determining the kinetic parameters of the curing process. The activation energy obtained by this method was 71.43 kJ/mol. The heating rate had no significant effect on the reaction order and the total reaction order was approximately constant (m+n≅2.1$m+n\cong 2.1$). By comparing the experimental data and the theoretical data obtained by Kissinger and Ozawa method, a good agreement was seen between them. By increasing the degree of conversion, the viscosity decreased; as the degree of conversion increased, so did the slope of viscosity. The results of the tack test also indicated that the highest tack could be obtained with 25% progress of curing.

Using the immersion phase inversion process, polysulfone (PSF), grapheme oxide (GO) and modified carbon nanotubes (MCNTs) were dissolved in 1-methyl-2-pyrrolidone (NMP) to prepare nanocomposite membranes. The GO-MCNTs blended PSF membranes were characterized by several analytical methods, such as morphology analysis, group characteristic peak test, hydrophilic measurement and permeation tests, and the synergistic effect of GO and MCNTs on the membrane performance was investigated. Microscope images depict two-layer structure of the composite membrane, in which, the lower layer is finger like porous layer, and the upper layer is a thinner separation layer. M-CNTs have great influence on formation of the upper separation layer, while the hydrophilic nature of GO results in the formation of the lower supporting layer, which changes from finger shaped hole to honeycomb pore. The change of membrane structure not only improves the surface hydrophilicity, but also promotes the membrane performance. In particular, the composite membrane ( m GO:MCNTs  = 2:1) exhibits a much smaller contact angle (48.01°), a high permeation flux (33.25 L/m 2 ·h) and superior rejection rate (95.2%). Furthermore, the fine compaction performance of composite membrane also provides great potential application prospects in water treatment.

The modification of membrane oxygenators to minimize protein adsorption onto the surface is often accompanied by the loss of membrane performance. This study aims to explore polyethersulfone (PES) as a new material for membrane oxygenator applications and to assess its potentials. Accordingly, different modification techniques are applied to improve surface properties of PES membranes. To achieve this goal, two separate modification methods including incorporation of TiO 2 into the membrane matrix as well as grafting polyethylene glycol (PEG) through oxygen plasma treatment are developed and the effects are examined. The results reveal that protein adsorption to the nanocomposite membrane containing 0.50 wt. % TiO 2 and the grafted membrane decreased by 47 and 31%, respectively. In terms of performance, permeability and oxygen transfer rate of all modified membranes exceeded 808 GPU and 2.7 × 10 −4  mol·m −2 ·s −1 , respectively. Contact angle analysis revealed signs of hydrophilicity enhancement of membranes after modifications. The findings suggest that upon proper modifications, membranes based on PES could be considered as promising candidates for membrane oxygenator applications and deserves further investigations.

In the present communication, microwave absorbing property in the frequency range of 12.4–18 GHz and in vitro biocompatibility studies of light weight, flexible, biocompatible, and environment friendly polymer blend films of polyvinylchloride (PVC)-polyvinylpyrrolidone (PVP) (taken in ratio 1:1) and doped with various percentage weight concentration of polypyrrole (PPy) are reported. Addition of PPy in the PVC-PVP matrix exhibited a synergetic effect in improving microwave absorbing property. PVC-PVP blend film with 40 and 50% concentrations of PPy were seen to absorb microwaves of the order of 28–50 dB in ku band of microwave region indicating that this composition can suitably find application as microwave absorbing material. In vitro biocompatibility skin irritation study of PVC-PVP (taken in ratio 1:1) with 50% weight concentration of PPy indicated that the prepared film did not have any irritation upon administration and hence is safe for topical application. Moreover, the blood compatibility study of this film exhibited compatibility with blood and can safely be used in any blood contacting mask/device. Hence, this biocompatible film can potentially be used as microwave absorbing material for masking some parts of human body or can be interfaced to biological systems or devices.

The ramie plain-woven fabric-reinforced epoxy composites with iron oxide (IO) powders and expandable graphite (EG) particles were fabricated by the hand lay-up and vacuum bagging pressing. The flame retardant layers with IO powders and EG particles have been designed on the surface of the composite structure, to improve the composites flame retardancy. The flame retardancy property of the composites was discussed from the limited oxide index (LOI), vertical burning test, and cone calorimeter test, while the flexural property and interlaminar shear strength of the composites were also investigated through the three-point flexural tests, respectively. It was found that the flame retardancy property of the composites, which contains both IO powders and EG particles, can be greatly improved. However, IO powders and EG particles have a negative effect on flexural properties and interlaminar shear strength of the composites. Also, prepreg with IO powders or EG particles which laminated on the surface layer of the composite with different orders would result in different performances.

Lactase, which can cause lactose intolerance in its deficiency, is a vital enzyme concerning digestion. To overcome lactose intolerance for patients with digestion problem depending of this kind of issue, lactose in food should be removed. In this study, lactose imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl- l -aspartic acid), poly(HEMA-MAsp), cryogels were synthesized to reduce the amount of lactose content of milk samples. Occurrence of desired bounds, structural integrity, and surface characteristics were analyzed via Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscope (SEM), micro computed tomography (CT), and confocal microscope methods. Water retention characteristic were tested in solution with different electrolytic nature. Adsorption parameters were optimized in an aqueous medium. The adsorption performance of imprinted cryogels was studied in milk samples obtained from cow, sheep, goat, buffalo, and from human volunteers at different intervals after birth. Amount of lactose adsorbed in aqueous media and milk sample from humans were 322 (56.7%) and 179.5 (5.94%) mg lactose/g polymer, respectively. Selectivity studies revealed an approximately 8-fold increase in adsorption rate of molecularly imprinted cryogels as compared to that of nonimprinted cryogels. In addition, competitive adsorption was conducted using lactose-imprinted cryogels in aqueous media containing lactose, glucose, and galactose molecules resulting in adsorption rates of 220.56, 57.87, and 61.65 mg biomolecule/g polymer, respectively.

The use of magnetic nanoparticles (MNPs) has transformed both diagnostics and therapeutic approaches in cancer treatment. Along with developing novel anti-cancer drugs with high therapeutic potential, researchers are exploring innovative strategies for more targeted delivery in order to alleviate the associated potent side effects. In this study, we describe the synthesis of Mg 0.5 Co 0.5 Fe 2 O 4 ferrite nanoparticles, their functionalisation with polyvinyl alcohol (PVA), and encapsulation of the anti-cancer drug 5-fluorouracil (5-FU). Functionalised nanoparticles viz. PVA-Mg 0.5 Co 0.5 Fe 2 O 4 -5-FU displayed desirable physiochemical properties with regards to the spherical shape, hydrodynamic sizes of <120 nm and relative colloidal stability of up to <−33 mV. The drug encapsulating efficiency was found to be 68%. In vitro cytotoxicity profiles were determined using the MTT and SRB assays, with >65% cell death recorded in MCF-7 and HeLa cancer cell lines. Overall, the nanocomposites exhibited excellent physiochemical elements, high specificity towards cancerous cells and displayed pH-sensitive drug release in a simulated acidic tumour micro-environment. The encapsulation of 5-FU improved bioavailability of the drug in cancer cell lines for a prolonged duration, with the promise to enhance its therapeutic effect, biocompatibility and safety. These MNPs present as promising in vitro delivery systems that can be further developed for therapeutic applications.

Efficient purification technology is crucial to fully utilize hydrogen (H 2 ) as the next generation fuel source. Polyimide (PI) membranes have been intensively applied for H 2 purification but its current separation performance of neat PI membranes is insufficient to fulfill industrial demand. This study employs blending and crosslinking modification simultaneously to enhance the separation efficiency of a membrane. Polyethersulfone (PES) and Co-PI (P84) blend asymmetric membranes have been prepared via dry–wet phase inversion with three different ratios. Pure H 2 and carbon dioxide (CO 2 ) gas permeation are conducted on the polymer blends to find the best formulation for membrane composition for effective H 2 purification. Next, the membrane with the best blending ratio is chemically modified using 1,3-diaminopropane (PDA) with variable reaction time. Physical and chemical characterization of all membranes was evaluated using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). Upon 15 min modification, the polymer membrane achieved an improvement on H 2 /CO 2 selectivity by 88.9%. Moreover, similar membrane has demonstrated the best performance as it has surpassed Robeson’s upper bound curve for H 2 /CO 2 gas pair performance. Therefore, this finding is significant towards the development of H 2 -selective membranes with improved performance.

In this study, polystyrene composites (PS–GO f ) with variable concentration (0.5; 1; 2; 3; 4; and 5 wt%) of GO f  were obtained through the in-situ polymerisation of the styrene in the presence of benzoyl peroxide and graphene oxide(GO) functionalized with 3-(methacryloyloxy)-propyltrimethoxysilane(γ-MPTS). For determining the morphological and structural particularities of polymeric composites transmission electron microscopy (TEM) measurements were performed. The influence of functionalized GO on thermal and combustion properties of polystyrene (PS)-based composite materials was determined through several methods: Thermogravimetry (TGA); derived thermogravimetry (DTG); microscale combustion calorimetry analysis (MCC); and chemical kinetic studies through TGA and MCC determinations at similar heating rates.