Miscibility study of chitosan/polyethylene glycol fumarate blends in dilute solutions

Solution miscibility of chitosan/polyethylene glycol fumarate blends dissolved in acetate buffer solution was investigated in different blend compositions by viscosity, density, and refractive index measurement techniques at 30, 40, and 50°C. In order to quantify the miscibility of the polymer pair, degree of miscibility was studied by means of two criteria known as interaction parameters i.e., μ and α. On the basis of the sign convention involved in these criteria, these values revealed that the blend solution was miscible when the chitosan content was more than 80% (w/w) of the composition. The results were confirmed by density, and refractive index measurements. Furthermore, the results showed that the miscibility window of chitosan/polyethylene glycol fumarate blends was independent with respect to the changes in solution temperature. Therefore, these results suggested due to intermolecular hydrogen‐bonding interaction between amino and hydroxy groups of chitosan and hydroxy groups of polyethylene glycol fumarate which play an important role in the formation of miscible phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Highly Conductive Carbon Nanotube‐Graphene Hybrid Yarn

An efficient procedure for the fabrication of highly conductive carbon nanotube/graphene hybrid yarns has been developed. To start, arrays of vertically aligned multi‐walled carbon nanotubes (MWNT) are converted into indefinitely long MWNT sheets by drawing. Graphene flakes are then deposited onto the MWNT sheets by electrospinning to form a composite structure that is transformed into yarn filaments by twisting. The process is scalable for yarn fabrication on an industrial scale. Prepared materials are characterized by electron microscopy, electrical, mechanical, and electrochemical measurements. It is found that the electrical conductivity of the composite MWNT‐graphene yarns is over 900 S/cm. This value is 400% and 1250% higher than electrical conductivity of pristine MWNT yarns or graphene paper, respectively. The increase in conductivity is asssociated with the increase of the density of states near the Fermi level by a factor of 100 and a decrease in the hopping distance by an order of magnitude induced by grapene flakes. It is found also that the MWNT‐graphene yarn has a strong electrochemical response with specific capacitance in excess of 111 Fg^?1. This value is 425% higher than the capacitance of pristine MWNT yarn. Such substantial improvements of key properties of the hybrid material can be associated with the synergy of MWNT and graphene layers in the yarn structure. Prepared hybrid yarns can benefit such applications as high‐performance supercapacitors, batteries, high current capable cables, and artificial muscles.     

Fluoroalkylsilane treatment of TiO2 nanoparticles in difference pH values: Characterization and mechanism

In this research, TiO₂ nanoparticles were treated with hydrophobic 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (fluorosilane) in acidic, neutral and alkaline conditions. The treated nanoparticles were characterized using FTIR spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction spectroscopy. Reflectance spectra were obtained using UV–vis diffuse reflectance spectroscopy and band gap energy of the various nanoparticles was determined. Zeta potential measurements were used to evaluate colloidal stability of nanoparticles in aqueous media. The mechanism of fluorosilane adsorption on the surface of TiO₂ nanoparticles was investigated using ATR-FTIR spectroscopy and turbidimetric technique.The characterization results revealed that the amorphous fluorosilane adsorbs on the surface of TiO₂ nanoparticles in both neutral (pH 6) and alkaline (pH 11) solutions. The values of the band gap energy for all treated nanoparticles were almost the same, in the range of 3.10–3.18 eV. Zeta potential measurements showed that isoelectric point of the TiO₂ nanoparticles shifts from 6.8 for untreated TiO₂ to 4.4 for treated one. Based on the zeta potential measurement results, it is expected that treated TiO₂ nanoparticles in neutral or alkaline conditions have higher colloidal stability and better dispersion in the aqueous solutions. Hydrophobic character of fluoro specious on the surface of nanoparticles leads the treated nanoparticles migrate towards the suspension surface. Therefore, these treated nanoparticles may be useful for developing self-cleaning coatings with minimal destructive effect on the polymeric matrix.     

Synthesis, characterization and enhanced photocatalytic activity of TiO2/SiO2 nanocomposite in an aqueous solution and acrylic-based coatings

In this study, TiO₂/SiO₂ nanocomposites were synthesized via a sol-gel route by adding tetraethylorthosilicate (TEOS) to a solution containing different molar ratios of Degussa P25 TiO₂ nanoparticles. FTIR, TGA, EDAX and XRD techniques were used to characterize the modified nanoparticles. Photocatalytic activity of the nanoparticles in an aqueous solution and into the acrylic based coating was evaluated using colour coordinate data measurements, SEM analysis, gloss measurements and FTIR spectroscopy, in the presence of Rhodamine B (Rh.B) dyestuff, as a pollutant model, before and after exposure to the UVA (340 nm) irradiation and compared to their unmodified counterparts.The results showed that silica grafting effectively reduced the photocatalytic activity of the TiO₂ nanoparticles as evidenced by absorption spectra and colour changes of Rh.B aqueous solutions during the UVA irradiation. The results revealed the effectiveness of sol-gel route for preparation of TiO₂/SiO₂ nanocomposites. The optimum result was obtained with 1% molar ratio of TiO₂:TEOS. Addition of TiO₂/SiO₂ nanocomposites into the acrylic based coating revealed reduction of photo-degradation of Rh.B compared to untreated nanoparticles. Finally, inclusion of TEOS treated TiO₂ nanoparticles into the aqueous organic coatings, provides photocatalytic property and as a result, it can possibly be considered for self-cleaning coatings.     

Correction to: Employing singular value decomposition and similarity criteria for alleviating cold start and sparse data in context-aware recommender systems

Electronic Commerce Research -     

Comparison of drag characteristics of self-polishing co-polymers and silicone foul release coatings: A study of wettability and surface roughness

An experimental study has been carried out to evaluate the drag characteristics of different self-polishing co-polymers (SPC) (tin based and tin-free) and a silicone foul release (FR) coating. Drag measurements have been performed on a smooth aluminum cylinder connected to a rotor device. Various coatings on cylinders were examined and differential length technique was also used to avoid the end effects during rotation. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of the coated surfaces were evaluated with atomic force microscopy (AFM) technique.

Drag measurements showed that the frictional resistance of the FR coated cylinders was lower than that of SPC coated samples.

Contact angle results showed that the critical surface tension and its polar component for silicone FR coating are less than SPC coatings. This prevents firm adhesion of fouling organisms on underwater hulls.

AFM studies revealed a lower surface roughness for silicone FR coating as compared to SPC coatings. Also, its surface texture is considerably different from SPC coatings.

It can be concluded that the drag characteristics of a surface are affected by its free energy and roughness parameters.     

FLAR: AN ADAPTIVE FUZZY ROUTING ALGORITHM FOR COMMUNICATIONS NETWORKS USING MOBILE ANTS

Swarm intelligence, as demonstrated by a natural biological swarm, such as an ant colony, has many powerful properties that are desirable for effective routing in communications networks. In this paper, we propose an intelligent routing algorithm that we are calling Fuzzy Logic Ant-based Routing (FLAR), which is inspired by ant colonies and enhanced by fuzzy logic techniques. Using a fuzzy system as an intelligent and expert mechanism allows multiple constraints to be considered in a simple and intuitive way. Simulation results and a comparison of the proposed method with two state-of-the-art routing algorithms show better performance and a higher fault tolerance for our approach, particularly in regard to link failures.     

A comparative study between experimentally measured mechanical attributes and users’ perception of soft feel coatings: Correlating human sense with surface characteristics of polyurethane based coatings

Different soft feel coating formulations using waterborne resins composed of soft and hard polyurethane resins were prepared. The effects of resins mixtures on the soft feel properties were studied. Attempts were made to find out the correlation between users perception and experimentally measured surface characteristics of the coatings. To this end, 72 people were asked to touch the coatings in a similar testing environment and to express their feeling in order to rank them between 1 (lowest soft feel effect) and 4 (highest soft feel effect). The coatings physical characteristics were studied by tensile test, micro Vickers hardness, atomic force microscope (AFM) and friction coefficient measurement. It was shown that the mixtures of 25:75 of soft and hard resins resulted in the best soft feel effect. Users did not consider low or high hardness films as soft. Instead, those coatings having greater toughness were ranked as the best soft feel effect. Also, coatings with lower friction coefficient and lower surface roughness were preferred by users. However, the lowest friction coefficient did not result in the best soft feel appeal. In fact, the mechanical properties, surface roughness and friction coefficient were found to play as the criteria to show soft feel effect. It is thus concluded that by selecting appropriate surface characteristics of coatings related to soft feel effect, good agreement between these properties and human feeling can be made.