Band 36, Heft 3

Glass polyalkenoate cements (GPCs) have been used in dentistry for over 40 years. These novel bioactive materials are the result of a reaction between a finely ground glass (base) and a polymer (acid), usually poly(acrylic acid) (PAA), in the presence of water. This article reviews the types of PAA used as reagents (including how they vary by molar mass, molecular weight, concentration, polydispersity and content) and the way that they control the properties of the conventional GPCs (CGPCs) formulated from them. The article also considers the effect of PAA on the clinical performance of CGPCs, including biocompatibility, rheological and mechanical properties, adhesion, ion release, acid erosion and clinical durability. The review has critically evaluated the literature and clarified the role that the polyacid component of CGPCs plays in setting and maturation. This review will lead to an improved understanding of the chemistry and properties of the PAA phase which will lead to further innovation in the glass-based cements field.

A rapid, specific and sensible polystyrene latex-based reagent has been developed to detect rheumatoid factor (RF) in human sera. Detection of RF is one of the criteria for rheumatoid arthritis (RA) diagnosis. RF includes immunoglobulins IgG, IgM or IgA targeting human-IgG Fc region, found in sera of 70–90% of patients with RA. Spherical, clean polystyrene particles of 480±80 nm with a Z -potential of -28 mV were synthesized. Purified gamma-globulin human blood fraction, used as IgG source, was adsorbed on particles in glycine-buffered saline with a fivefold excess of the immunoglobulins needed to saturate the calculated total surface area of the particles. The reagent was calibrated against the World Health Organization international serum reference preparation and tested with commercial positive and negative RF controls. Reactivity of the developed diagnostic reagent with human sera, either positive or negative for RF, was evaluated. The sera were tested both intact and following complement inactivation. When complement-inactivated sera were used, our reagent showed 100% coincidence of results with a commercial diagnostic kit of specificity of 80% and sensibility of 93%. The in-house reagent developed in the present work is easy to prepare and at relatively low cost, making it ideal for RF detection in low-income settings.

This paper illustrates the aim to introduce biodegradable vegetable filler in synthetic polymers to prepare novel biodegradable composites. Low density polyethylene/alkali treated corn flour (LDPE/ATCF) composites were prepared by reactive extrusion using a twin-screw extruder. The microstructure, thermal properties and tensile properties were evaluated and compared with virgin LDPE. The Fourier transform infrared (FTIR) spectra showed a decrease in the hydrophilic nature of corn flour (CF) after alkali treatment. Scanning electron microscopy (SEM) micrographs showed good dispersion between matrix and filler. The tensile and elongation at break decreased by increasing the filler content in the composites. However, the Young’s modulus increased with the increase in filler content. The biodegradation of composites was studied in the environment using the soil burial test for 6 months. Differential scanning calorimetry (DSC) analysis showed an increase of the melting enthalpy (ΔH m ) and crystallinity of LDPE with evidence of degradation. The biodegradability of the composites was enhanced with increasing ATCF content in the matrix. This result was supported by weight loss and degraded surface of composites observed through morphological studies. From the results, we conclude that the use of ATCF as filler in LDPE reduces pollution problems. This is advantageous for both the economy and the environment.

People across the world are primarily concerned with the importance of inserts in footwear in terms of their effectiveness to accomplish therapeutic benefits. Body weight has been implicated as a factor in plantar heel pain, and foot orthoses are commonly used in its conservative treatment and are helpful in reducing symptoms of strain in the fascia during standing and ambulation. It is necessary to investigate the effectiveness of footwear inserts and their impact especially for people with high body mass index (BMI). Hence, research on polyurethane (PU) foams is warranted to identify an ideal material that provides comfort for high-BMI individuals. This article presents details on the physical characteristics of PU foam and its efficacy on functional performances as footwear inserts. PU foam materials have been assessed on various physical characteristics such as density, hardness, compression set followed by resilience, and cushioning behaviors. Of the four densities evaluated, D120 has the highest resilience on static and dynamic conditions. The cushion energy behaviors with respect to walking/running on static and dynamic condition were superior, as they possess better cushioning performance on footwear applications. Hence, the D120 PU foam material is concluded to be the best material for footwear insert for alleviating foot and ankle pain-related problems and for providing therapeutic benefits to high-BMI individuals.

In this work, an attempt was made to evaluate the effects of ultraviolet (UV) irradiation period on the intrinsic and separation properties of composite membrane composed of organic polyvinylidene fluoride and inorganic titanium dioxide (TiO 2 ) nanoparticles by exposing the membrane to UV-A light for up to 250 h. The changes on membrane structural morphologies and chemical characteristics upon UV exposure were studied by field-emission scanning electron microscope and Fourier transform infrared, respectively. It was observed that some cracks and fractures were formed on the membrane outer surface when it was exposed to 120-h UV light. Further increase in UV irradiation time to 250 h had caused membrane structure to collapse, turning it into powder form. Filtration experiments showed that the permeate flux of irradiated membrane was significantly increased from 10.89 L/m 2 h to 21.84 L/m 2 h (>100% flux increment) while oil rejection decreased with increasing UV exposure time from 0 h to 120 h. Furthermore, the mechanical strength and thermal stability of irradiated membrane were also reported to decrease with increasing UV exposure time, suggesting the negative impacts of UV light on the membrane overall stability. This research is of particular importance to evaluate the suitability and sustainability of polymeric membrane, which is widely considered as the host for photocatalyts and used for wastewater treatment process under UV irradiation.

This study presents the successful development of cellulose fiber based membranes embedded with silver nanoparticles. These fine fiber membranes were developed utilizing the Forcespinning (FS) technique followed by alkaline hydrolysis treatment. The fiber morphology, homogeneity and yield were optimized by varying spinning parameters such as polymer concentration and angular velocity of the spinnerets. The structure, thermal and mechanical properties, and water absorption capability of the developed membranes were investigated. The cellulose acetate (CA) present in the membrane was converted to cellulose in the presence of embedded silver nanoparticles by alkaline hydrolysis. The silver nanoparticles embedded cellulose membrane exhibits outstanding water absorption capacity with fast uptake rate. Its high porosity, three-dimensional network structure with well-interconnected pores, as well as the intrinsically highly hydrophilic nature of cellulose material greatly favor its potential application as wound dressings. The antimicrobial activity was evaluated by the disk diffusion method. The composite membranes exhibit excellent antimicrobial activity against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa , and Gram-positive Staphylococcus aureus , owing to the slow and sustained release of embedded silver nanoparticles.

In this study, the influence of wax content on the electrical, thermal and tribological properties of a polyamide 6 composite filled with 15% wt. graphite was investigated. The wax filler contents of the composite were by 2, 4 and 6 wt.%. Characterisation of the composites was obtained using a Fourier transform infrared spectroscopy test. Electrical performance tests were carried out, and the dielectric real values ( ε ′) and imaginary values ( ε ″) were recorded. Thermal differential scanning calorimetry tests were carried out, and the glassy and melting temperatures of the composite materials were recorded. Furthermore, tribological tests were carried out and the friction coefficient and wear rate of the composites were recorded. The results show that the increase in wax content led to the increase in the permittivity values ( ε ′ and ε ″) of the composites. The increase in wax content also led to the decrease in the friction coefficient and wear rates of the composite materials. Furthermore, the glassy and melting temperatures of the composite materials showed a sensitivity to the wax content. Finally, it is concluded that optimum properties, in total, were obtained in the composite filled with 6 wt.% wax.

Copper nanoparticles (CuNPs) are formed inside a microgel assembly by an in situ reduction method, confirmed by changes observed in the absorption spectra of CuNPs at different pH values. The presence of CuNPs has been also confirmed by X-ray diffraction (XRD) studies. The terpolymer microgel p(N-isopropylacrylamide-vinyl acetic acid-acrylamide) (p[NIPAM-VAA-AAm]), which is reported for the first time, was synthesized by free radical emulsion polymerization of a temperature-sensitive NIPAM monomer, pH sensitive VAA monomer and a hydrophilic AAm monomer. The effect of temperature below and above the pKa of VAA and the effect of pH at 20°C in the absence and presence of CuNPs on the hydrodynamic radius of microgel was studied. Size of microgel particles is a function of temperature due to the presence of NIPAM, and a function of pH due to the presence of VAA. The presence of CuNPs has little or no effect on the size of microgels by varying pH, which allows these gels to retain their properties with added benefits of CuNPs for possible drug delivery applications.

Unipolar resistive switching behavior was observed in the as-fabricated Al/PVA/PbS QD/ITO device with R OFF / R ON ratio of 3.15×10 3 with retentivity for prolonged time and repeatability of hysteresis loops. Schottky emission mechanism dominates conduction mechanism in low-resistance state and high-resistance state of the device. Unipolar resistive switching behavior observed in the device is attributed to Coulomb blockade. The observed characteristic in the device points toward possible application of PbS QDs in memory device.

This study reports on the synthesis of polymer polyaniline, a conductive polymer by nature, and the preparation of polyaniline/carbon particle (PANI/CP) composites by in situ polymerization. The solution properties and conductivities in solution of synthesized PANI and PANI/CP materials were analyzed. The viscosity of PANI and PANI/CP composite materials in N -methylpyrrolidinone (NMP) solvent at different temperatures was measured to examine their behavior in solution. Initially, the viscosity-molecular weight of PANI polymer was measured and calculated to be 78,521. The viscosities of PANI and PANI/CP composite materials decreased as the temperature increased. However, the viscosities of PANI/CP composite materials increased as the percent CP content in the composites increased. The ionic conductivities and pH changes in NMP solvent, measured at different concentrations of PANI and PANI/CP composite materials, and prepared in different ratios, were measured to investigate their behavior in solution. The ionic conductivities of PANI/CP composite materials increased as the percent CP content in the composites increased. Changes in the pH of PANI/CP composite materials decreased as the percent CP content in the composites increased. The conductivity of PANI/10% CP composite material in solution was greater than that of neat PANI polymer in solution; this indicated that CPs in PANI/10% CP composite materials made important positive contributions to the conductivities.

Organic/inorganic hybrid materials were formed using the sol-gel process, in which SiO 2 /fluoroalkyl-trialkoxysilane (FAS)/2-hydroxyethyl methacrylate (2-HEMA)/trimethylolpropane triacrylate (TMPTA) and SiO 2 /3-(trimethoxysilyl)propyl methacrylate (MSMA)/ 2-HEMA/TMPTA thin films were formed on a glass substrate using dip coating. Experimental results revealed that FAS and MSMA improved the pencil hardness of SiO 2 /2-HEMA/TMPTA thin films without affecting their optical properties. FAS strengthened the hydrophobic and hydrophilic characteristics of SiO 2 /2-HEMA/TMPTA thin films more than did MSMA. However, an excess of FAS and an increase in withdrawal rates deteriorates the gloss, because both increased the SiO 2 content, reducing the reflectivity.

Acrylonitrile-butadiene-styrene (ABS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene (St) and acrylonitrile (AN) on polybutadiene (PB) particles. Poly (methyl methacrylate) (PMMA)/styrene-acrylonitrile (SAN)/ABS blends were prepared by melt blending ABS graft copolymers with PMMA and SAN resins. The properties, morphology and grafted chains behaviors of PMMA/SAN/ABS blends were investigated. The results showed that with the increase of the ratio of PMMA/SAN, the toughness of PMMA/SAN/ABS blends slightly decreased, the transmittance first increased and then decreased, and tensile strength was not dependent on the ratio of PMMA/SAN. The evolution of impact strength of the blends was similar with the tendency of grafted degree (GD) with the increase of cumene hydroperoxide (CHP) and tert-dodecyl mercaptan (TDDM). From transmission electron microscopy (TEM), it was found that ABS graft copolymers were uniformly dispersed in PMMA/SAN matrix.