Curcuma longa L. Rhizome Extract as a Poly(vinyl chloride)/Graphene Nanocomposite Green Modifier.

In this work, a method to increase the dispersion of graphene (GN) in the matrix of rigid poly(vinyl chloride) (PVC) by using a natural plant extract from Curcuma longa L. (CE) is proposed. Currently, despite the increasing number of reports on the improvement of GN dispersion in PVC blends, still there is a need to find environmentally friendly and economical dispersion stabilizers. We proposed a stabilizer that can be easily obtained from a plant offering thermal stability and high effectiveness. PVC/GN nanocomposites stabilized with the proposed extract were investigated by SEM, AFM (structure), TGA, and Congo red test (thermal properties). Additionally, static and dynamic mechanical properties and electrical resistivity were measured. The use of CE as a graphene dispersant improved its dispersion in the PVC matrix, influenced tensile properties, increased the storage modulus and glass transition temperature, and extended the thermal stability time of nanocomposites. In this work, a CE extract is proposed as an efficient eco-friendly additive for the production of nanocomposites with an improved homogeneity of a nanofiller in the matrix and promising characteristics.

Moisture Resistance, Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid.

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m2) and total smoke release (3535 m2/m2) compared to unmodified polymer (792 kW/m2 and 6895 m2/m2) were recorded. However, some important disadvantage with respect to water resistance was observed.

Physical and chemical properties and stability of sodium cefazolin in buffered eye drops determined with HPLC method.

The aim of the studies was to analyze the stability of 1% and 5% eye drops containing sodium cefazolin, prepared in citrate buffer of pH 6.11-6.27, which were stored at the temperature of 4 degrees C and 20 degrees C with light protection. The drops were prepared under aseptic conditions by dissolving sodium cefazolin (Biofazolin, IBA Bioton), dry injection form of the drug, in citrate buffer. The viscosity of the drops was increased using polyvinyl alcohol. The drops were preserved with phenylmercuric borate of 0.001% concentration mixed with beta-phenylethyl alcohol of 0.4% concentration in the drops. The concentration of cefazolin was determined at every three days using HPLC method. Besides, the measurements of pH, osmotic pressure and viscosity were performed as well as the organoleptic analysis of the drops (clarity, color, odor). The concentration of cefazolin in 1% drops after the 30-day-storage at the temperature of 4 degrees C, depending on their composition, decreased in the range of 2.17-6.02%. In 5% drops the decrease in cefazolin concentration was similar, i.e., after 30-day-storage at the temperature of 4 degrees C it was 1.62-6.76%. In 1% and 5% drops stored at the temperature of 20 degrees C the stability of the drops determined as the 10% degradation time of cefazolin was in the range of 9-15 days.