Simultaneous Enhancement of Flame Resistance and Antimicrobial Activity in Epoxy Nanocomposites Containing Phosphorus and Silver-Based Additives

The design and manufacture of innovative multifunctional materials possessing superior characteristics, quality and standards, rigorously required for future development of existing or emerging advanced technologies, is of great importance. These materials should have a very low degree of influence (or none) on the environmental and human health. Adjusting the properties of epoxy resins with organophosphorus compounds and silver-containing additives is key to the simultaneous improvement of the flame-resistant and antimicrobial properties of advanced epoxy-based materials. These environmentally friendly epoxy resin nanocomposites were manufactured using two additives, a reactive phosphorus-containing bisphenol derived from vanillin, namely, (4-(((4-hidroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)-2-methoxyphenyl) phenylphosphonate (BPH), designed as both cross-linking agent and a flame-retardant additive for epoxy resin; and additional silver-loaded zeolite L nanoparticles (Ze-Ag NPs) used as a doping additive to impart antimicrobial activity. The effect of BPH and Ze-Ag NPs content on the structural, morphological, thermal, flame resistance and antimicrobial characteristics of thermosetting epoxy nanocomposites was investigated. The structure and morphology of epoxy nanocomposites were investigated via FTIR spectroscopy and scanning electron microscopy (SEM). In general, the nanocomposites had a glassy and homogeneous morphology. The samples showed a single glass transition temperature in the range of 166-194 °C and an initiation decomposition temperature in the range of 332-399 °C. The introduction of Ze-Ag NPs in a concentration of 7-15 wt% provided antimicrobial activity to epoxy thermosets.

Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

In order to obtain highly active catalytic materials for oxidation of carbon monoxide and volatile organic compounds (VOCs), monometallic platinum, copper, and palladium catalysts were prepared by using of two types of ZSM-5 zeolite as supports—parent ZSM-5 and the same one treated by HF and NH₄F buffer solution. The catalyst samples, obtained by loading of platinum, palladium, and copper on ZSM-5 zeolite treated using HF and NH₄F buffer solution, were more active in the reaction of CO and benzene oxidation compared with catalyst samples containing untreated zeolite. The presence of secondary mesoporosity played a positive role in increasing the catalytic activity due to improved reactant diffusion. The only exception was the copper catalysts in the reaction of CO oxidation, in which case the catalyst, based on untreated ZSM-5 zeolite, was more active. In this specific case, the key role is played by the oxidative state of copper species loaded on the ZSM-5 zeolites.

Studies on non-modified and copper-modified coal ash zeolites as heterogeneous catalysts for VOCs oxidation

The present study is aimed at investigations on the catalytic activity for total oxidation of volatile organic compounds (VOCs), such as toluene, acetone, n-hexane and dichlorobenzene onto zeolite-like materials synthesized from coal fly ash (FA) directed to development of an economically efficient approach for degradation of VOCs. Fly ash zeolites (FAZ) were prepared by alkaline conversion of FA collected from Thermal Power Plants supplied with lignite coal from "Maritza-East" basin in Bulgaria. Different synthesis procedures double stage fusion-hydrothermal activation, fusion-atmospheric crystallization and atmospheric aging were applied. The synthesis products were identified by X-ray diffraction, and were assigned to zeolite Na-X. Scanning electron microscopy images reveal submicron dimensions of the composing crystallites. Nitrogen adsorption/desorption measurements reveal a mixed micro-mesoporous structure and specific surface area between 116 and 396 m²/g for the obtained FAZ. Relationships between surface properties, iron content and the catalytic activity of FAZ were investigated and discussed. Copper-modified fly ash zeolites (Cu-FAZ) were prepared by incipient wetness impregnation technique with copper acetylacetonate. The loading of 5 wt. % copper on the zeolite samples was achieved. The catalytic activity of FAZ and Cu-FAZ in the total oxidation of model VOCs mixture containing n-hexane, acetone, toluene, 1,2 dichlorobenzene was evaluated.

Electromechanical properties of polyimide composites containing titanium dioxide nanotubes

Polyimide composite films were prepared by casting solutions resulting from direct mixing of a poly(amic acid) and titanium dioxide (TiO2) nanotubes (TNTs) onto glass plates, followed by thermal imidization. TNTs with outer diameters of approximately 10–12 nm and length of several hundreds of nanometers were synthesized by the hydrothermal method. The morphology of the nanotubes was investigated by using high-resolution transmission electron microscopy. The influence of TNTs content on structural, thermal, and electromechanical properties of pure polyimide and composite films was studied. The scanning electron microscopy and atomic force microscopy showed good compatibility between TNTs filler and polyimide matrix. The value of average roughness of film surface increases with increasing the content of TNTs. The films were flexible, tough, and exhibited high thermal stability. A study of microelectromechanical properties of these films was performed. The films showed nanometric displacements in the range of 250–800 nm when an electric voltage of 500 V was applied on their surface.

Preparation and characterization of new polyimide films containing zeolite L and/or silica

New polyimide (PI) films containing zeolite L and/or silica, having a thickness of tens of micrometers, were prepared using a PI matrix with pendant carboxylic groups. The influence of various ratios of inorganic filler on thermal stability, dielectric behavior, and gas transport properties of the films was studied with respect to their structure. The surface morphology was investigated by scanning electron microscopy. The films were flexible, tough, and showed good thermal properties with a glass transition temperature in the range of 187–218°C. The dielectric spectroscopy revealed γ and β subglass transitions having the corresponding relaxation activation energy in the range of 44.7–51.4 kJ mol−1 and 65.1–121.6 kJ mol−1, respectively. At temperatures above 200°C, a conductivity relaxation process was evidenced. Gas permeation tests using small molecules (O2, N2 and CO2), at 6 atm and 30°C, indicated that the PI films containing higher amount of zeolite showed the highest permeability for all gases.