Characterization of Ethylene-propylene Composites Filled with Perlite and Vermiculite Minerals: Mechanical, Barrier, and Flammability Properties

Perlite and vermiculite are naturally occurring minerals, commonly used by industry to obtain highly thermoisolative and/or non-flammable materials. However, there has been little research into the preparation and application of rubber compounds containing these inexpensive mineral fillers. Here, we show the benefits of perlite and vermiculite minerals as fillers for ethylene-propylene rubber (EPM) composites. To obtain more uniform dispersion and improved compatibility between the minerals and the elastomer matrix, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (AMIMTFSI) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTFSI) imidazolium ionic liquids (ILs) were added. The mineral fillers were found to be attractive semi-reinforcing fillers, which also act as flame retardants in the elastomer composites. Furthermore, a higher content of vermiculite mineral significantly reduced the air permeability of the composites. The incorporation of ionic liquids into the EPM-filled systems had a considerable effect on the torque increment, crosslink density, and more importantly the flammability of the studied compounds. The application of 2.5 parts per hundred parts of rubber (phr) BMIMTFSI, in particular, reduced the flammability of the EPM composite, as the maximum heat release rate (HRR_max) decreased from 189.7 kW/m² to 170.2 kW/m².

Characterization and Structure⁻Property Relationships of Organic⁻Inorganic Hybrid Composites Based on Aluminum⁻Magnesium Hydroxycarbonate and Azo Chromophore

In this study, novel organic⁻inorganic composites were prepared by the complexation of dicarboxylic azo dye (AD) with aluminum⁻magnesium hydroxycarbonate (AlMg⁻LH). This procedure provides an effective method for the stabilization of dicarboxylic organic chromophores on an AlMg-LH host. The structures of the hybrid composites were examined by X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) and scanning transmission electron microscopy (STEM). The TOF-SIMS method was applied to investigate the metal⁻dye interactions and to monitor the thermal stability of the organic⁻inorganic complexes. Secondary ion mass spectrometry confirmed the presence of a characteristic peak for C₁₈H₁₀O₅N₂Mg₂²⁺, indicating that both carboxylic groups interacted with AlMg-LH by forming complexes with two Mg²⁺ ions. Modification with hybrid pigments affected the crystal structure of the AlMg-LH mineral, as shown by the appearance of new peaks on the X-ray diffraction patterns. Adsorption of the dicarboxylic chromophore not only led to significantly enhanced solvent resistance but also improved the thermal and photostability of the hybrid pigments. We propose a possible arrangement of the azo dye in the inorganic matrix, as well as the presumed mechanism of stabilization.

Carminic Acid Stabilized with Aluminum-Magnesium Hydroxycarbonate as New Colorant Reducing Flammability of Polymer Composites

In this study, hybrid pigments based on carminic acid (CA) were synthesized and applied in polymer materials. Modification of aluminum-magnesium hydroxycarbonate (LH) with CA transformed the soluble chromophore into an organic-inorganic hybrid colorant. Secondary ion mass spectroscopy (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectroscopy were used to study the structure, composition, and morphology of the insoluble LH/CA colorant. Successful modification of the LH was confirmed by the presence of interactions between the LH matrix and molecules of CA. XPS analysis corroborated the presence of CA complexes with Mg2+ ions in the LH host. The batochromic shift in UV-Vis spectra of the organic-inorganic hybrid colorant was attributed to metal-dye interactions in the organic-inorganic hybrid colorants. Strong metal-dye interactions may also be responsible for the improved solvent resistance and chromostability of the modified LH. In comparison to uncolored ethylene-norbornene copolymer (EN), a modified EN sample containing LH/CA pigment showed lower heat release rate (HRR) and reduced total heat release (THR), providing the material with enhanced flame retardancy.

Characteristics of Hybrid Pigments Made from Alizarin Dye on a Mixed Oxide Host

This paper describes the fabrication of a new hybrid pigment made from 1,2-dihydroxyanthraquinone (alizarin) on a mixed oxide host (aluminum-magnesium hydroxycarbonate, LH). Various tools were applied to better understand the interactions between the organic (alizarin) and inorganic (LH) components, including ion mass spectroscopy (TOF-SIMS), 27-Aluminm solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). TOF-SIMS showed that modification of the LH had been successful and revealed the presence of characteristic ions C₁₄H₇O₄Mg⁺ and C₁₄H₆O₅Al^-, suggesting interactions between the organic chromophore and both metal ions present in the mixed oxide host. Interactions were also observed between Al³⁺ ions and Alizarin molecules in ²⁷Al NMR spectra, with a chemical shift detected in the case of the modified LH matrix. Any changes in color following reactions with Mg²⁺ and Al³⁺ ions were observed. Some of the physicochemical properties of alizarin, such as resistance to dissolution and color stability at elevated temperatures, were improved in comparison to the pure dye. This effect can be attributed to strong dye-LH interactions and the effective transformation of alizarin into an insoluble form. Moreover, the pigments exhibited higher thermal resistance and greater color stability in comparison to commercially available alizarin lakes (Alizarin Crimson).

Aluminum-Magnesium Hydroxycarbonate/Azo Dye Hybrids as Novel Multifunctional Colorants for Elastomer Composites

This study presents the preparation and characterization of new organic-inorganic pigments based on aluminum-magnesium hydroxycarbonate (LH) and azo dyes. Solvent resistance studies, XRD, SEM, and TGA confirmed the successful formation of hybrid pigments, which were characterized in terms of their physicochemical properties. The new hybrid pigments were applied in acrylonitrile-butadiene (NBR) and ethylene-propylene (EPM) rubber composites and cured with sulfur and peroxide curing systems, respectively. The mechanical properties, dispersion quality, and flame-retardant properties of the NBR/hybrid and EPM/hybrid pigment composites were determined by dynamic mechanical analysis (DMA), SEM, and microscale combustion calorimetry (MCC). Complex experimental investigations revealed that the layered nature of hybrid pigments could improve the barrier ability and flame retardancy of elastomer composites. In comparison to unmodified aluminum-magnesium hydroxycarbonate, the modified LH dye structures contributed to significantly decrease the heat release rate and the total heat release of the NBR and EPM composites, offering a new approach to imparting low flammability to elastomer materials.

Effect of Zinc Oxide Modified Silica Particles on the Molecular Dynamics of Carboxylated Acrylonitrile-Butadiene Rubber Composites

This work examines the molecular dynamics of carboxylated acrylonitrile-butadiene rubber crosslinked with zinc oxide modified silica particles. ZnO/SiO₂ with the wide range of ZnO concentrations were used as both a crosslinking agent and filler. A series of thermal measurements were applied to the characterization of the samples: differential scanning calorimetry, dynamical mechanical thermal analysis, and dielectric relaxation spectroscopy. A complementary experimental technique, which is equilibrium swelling in solvents, confirms the presence of ionic crosslinks, which are created between zinc ions and the functional carboxyl groups of the rubber, within the structure of the vulcanizates. These interactions influenced not only the affinity of the vulcanizates to solvents, but also their dynamic mechanical and dielectric properties. In these investigations, the influence of concentration of ZnO on the surface of the ZnO/SiO₂ on the properties of the vulcanizates are described.

Influence of hydroxyl substitution on flavanone antioxidants properties

The aim of our study was to determine the effect of the position of the hydroxyl group on the antioxidant properties of flavonoid derivatives. For this purpose, we performed electrochemical analysis and quantum-mechanical calculations to describe the mechanisms of electrochemical oxidation, and we selected the two methods of ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), which allowed us to determine the ability to scavenge free radicals. On the basis of the research, we found that the derivatives of flavonoids, which have a hydroxyl group substituted at the R-3 position on the C ring, have outstanding antioxidant activity. Flavone, which had an OH group substituted at the R-6 and R-7 position on the ring A, showed similar antioxidant activity to flavone without -OH groups in the structure and slightly higher activity than the di-substituted flavone on the ring A.

Reinforcement of carboxylated acrylonitrile-butadiene rubber (XNBR) with graphene nanoplatelets with varying surface area

Graphene nanoplatelets (xGnP-C) with specific surface areas varying from 300 to 750 m2/g were investigated as novel reinforcing fillers for carboxylated acrylonitrile- butadiene rubber (XNBR). The effects of graphene nanoflakes loadings up to 15 parts per hundred rubber (phr) on the rheometric characteristics, stress-strain behavior, crosslink density (ν), resistance to UV radiation and thermo-oxidative aging of the XNBR/ZnO/graphene xGnP-C composites were investigated. Substantial improvement in the mechanical properties of XNBR with increased contents of xGnP-C filler was achieved. It was found that the addition of 5 phr of graphene significantly increased UV stability, tensile strength (TS) and modulus at 100%, 200% and 300% elongation of rubber material. The effect was more pronounced for composites containing graphene with the highest specific surface area 750 m2/g. The chemical information on the functional groups on the xGnP-C surface was obtained by X-ray photoelectron spectroscopy (XPS) method. In this case, the reinforcing effect of graphene xGnP-C may result from an additional chemical bonding which is possible between the -COOH groups of the rubber and the reactive, oxygen-containing groups on the filler surface.

Characteristics of compounds in hops using cyclic voltammetry, UV-VIS, FTIR and GC-MS analysis

The article presents the antioxidant properties of the extracts of hop EI and EII, by the electrochemical methods on a platinum electrode and comparative analysis of the composition of the extracts of hops using UV-VIS, FTIR and GC-MS methods. The hops extract EI, was obtained from the waste of the hops cone. The hops extract EII, was obtained from the hops cone itself. Hops contain a wide range of polyphenolic compounds with antioxidant properties divided in various chemical classes. Flavonoids and other polyphenolic compounds contained in hops show antioxidant capacity because of the presence of hydroxyl groups in various configurations and numbers within their molecules. The electrochemical properties and antioxidant capacity of hop samples were determined to select the most effective antioxidant. Based on the cyclic and pulse voltammograms, it was observed that hop extract EI contains polyphenols that are oxidised at a less positive potential than extract EII, i.e., it shows better antioxidant capacity. From the analysis of the UV-VIS and FTIR spectra and the GC-MS analysis, it was observed that extract EI contains less phenyl compounds than EII. In addition to flavonoids, EII contains hop acids and chlorophyll. The solutions of hop extracts show very good antioxidant capacities; therefore, they can effectively inhibit or slow negative oxidation reactions and scavenge free radicals and reactive oxygen species (ROS).

Optimization of the heavy metal (Bi-W-Gd-Sb) concentrations in the elastomeric shields for computer tomography (CT)

Eight elastomeric composites (NRU, GR1-GR4, NRBG08-NRBG24) containing mixtures of different proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesized and examined as protective shields. The NRU sample was a pure rubber matrix and served as a reference sample for heavy metal modified composites. Experimental procedure used for evaluation of the composite shields and their attenuation properties was based on the utilization of HPGe spectrometry and analysis of X-ray fluorescence radiation intensity of the heavy metal additives in the following energy ranges for: Sb (20-35 keV), Gd (35-55 keV), W (55-70 keV) and Bi (70-90 keV). The main contributor to the induced X-ray fluorescence radiation within the shield is Bi additive and the intensity of the X-ray radiation generated within the energy range of 70-90 keV strongly depends on its concentration. It was found that decreasing concentration of the Bi fraction from 0.35 (GR samples) to 0.15 (NRBG samples) results in significant lowering Bi X-ray fluorescence radiation within the 70-90 keV energy range. Secondary effect of decreasing Bi concentration was efficient diminishing excitation processes for lower Z heavy metal additives (W, Gd and Sb, GR vs. NRBG samples). As the final quality parameter of the shielding properties for the examined elastomers, dose reduction factor (DRF) coefficients were calculated for each shield. It was found, that the best shielding properties are observed for composites with lower Bi concentration (0.15 vs. 0.35 Bi mass fraction) with only slight further improvement of their parameters (DRF) with increasing of Gd concentration (Gd mass fraction 0.08, 0.16 and 0.24). The most efficient dose reduction composite was found to be NRBG24 elastomer with DRF value 0.47 (53 % dose reduction) for ca. 2 mm and 0.44 g/cm2 layer thickness.

Generation of the additional fluorescence radiation in the elastomeric shields used in computer tomography (CT)

Two commercially available (EP, Z) and eight new elastomeric composites (M1-M4, G1-G4, of thickness ≈1 mm) containing mixtures of differing proportions of heavy metal additives (Bi, W, Gd and Sb) have been synthesised and examined as protective shields. The intensity of the X-ray fluorescence radiation generated in the typical elastomeric shields for CT, containing Bi and other heavy metal additives influence on the practical shielding properties. A method for assessing the radiation shielding properties of elastomeric composites used in CT examination procedures via X-ray spectrometry has been proposed. To measure the radiation reduction ability of the protective shields, the dose reduction factor (DRF) has been determined. The lead equivalents for the examined composites were within the ranges of 0.046-0.128 and 0.048-0.130 mm for 122.1 and 136.5 keV photons, respectively. The proposed method, unlike to the common approach, includes a dose contribution from the induced X-ray fluorescence radiation of the heavy metal elements in the protective shields. The results clearly indicate that among the examined compositions, the highest values DRF have been achieved with preparations containing Bi+W, Bi+W+Gd and Bi+W+Sb mixtures with gradually decreasing content of heavy metal additives in the following order: Bi, W, Gd and Sb. The respective values of DRF obtained for the investigated composites were 21, 28 and 27 % dose reduction for a 1 mm thick shield and 39 and ~50 % for a 2 mm thick layer (M1-M4).

Highly organized self-assembled dendriplexes based on poly(propylene imine) glycodendrimer and anti-HIV oligodeoxynucleotides

Dendrimers are artificial polymeric macromolecules which are widely considered to be a promising tool for future gene therapy applications. They have been used as efficient delivery vehicles for antisense oligonucleotides targeting the interior of cells. We demonstrate that dendriplexes formed from anti-HIV oligodeoxynucleotides ANTI-TAR, GEM91, and SREV in complex with generation 4 maltose (PPI-Mal G4) and maltotriose (PPI-Mal-III G4) modified poly(propylene imine) dendrimers are able to self-assemble into highly organized 1D and 3D nanostructures. The resulting nanostructures were characterized by fluorescence methods, laser Doppler electrophoresis, dynamic light scattering (DLS), atomic force microscopy (AFM) and molecular modeling. The results show that ANTI-TAR and GEM 91 dendriplexes self-assemble into fibrils with length scales up to several hundreds of nm. SREV, on the contrary, forms quadrilateral- like 3D nanostructures. A good correlation between the various experimental methods and molecular modeling indicates the formation of those nanostructures in solution. Space symmetry of the oligonucleotides and the resulting dendriplex monomeric units are probably the most important factors which influence the way of self-assembling.

U-2932: two clones in one cell line, a tool for the study of clonal evolution

Genetic heterogeneity is common in tumors, explicable by the development of subclones with distinct genetic and epigenetic alterations. We describe an in vitro model for cancer heterogeneity, comprising the diffuse large B-cell lymphoma cell line U-2932 which expresses two sets of cell surface markers representing twin populations flow-sorted by CD20 vs CD38 expression. U-2932 populations were traced to subclones of the original tumor with clone-specific immunoglobulin IgVH4-39 hypermutation patterns. BCL6 was overexpressed in one subpopulation (R1), MYC in the other (R2), both clones overexpressed BCL2. According to the combined results of immunoglobulin hypermutation and cytogenetic analysis, R1 and R2 derive from a mother clone with genomic BCL2 amplification, which acquired secondary rearrangements leading to the overexpression of BCL6 (R1) or MYC (R2). Some 200 genes were differentially expressed in R1/R2 microarrays including transcriptional targets of the aberrantly expressed oncogenes. Other genes were regulated by epigenetic means as shown by DNA methylation analysis. Ectopic expression of BCL6 in R2 variously modulated new candidate target genes, confirming dual silencing and activating functions. In summary, stable retention of genetically distinct subclones in U-2932 models tumor heterogeneity in vitro permitting functional analysis of oncogenes against a syngenic background.

Carbosilane dendrimers are a non-viral delivery system for antisense oligonucleotides: characterization of dendriplexes

The success of gene therapy depends on the development of suitable carriers, and because of their architecture dendrimers are promising tools for gene delivery. This research concerns the use of second generation carbosilane dendrimers as carriers for anti-HIV oligodeoxynucleotides (ODNs). The aim was to characterize complexes formed by positively charged dendrimers and negatively charged oligonucleotides using a fluorescence method, laser Doppler electrophoresis, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and molecular modeling. The zeta-potential of ODNs increased from -25 mV to positive values after the addition of dendrimers. DLS and TEM revealed that the diameters of dendriplexes ranged from 75 to 240 nm and from 50 to 260 nm, respectively, and this was dependent on the type of dendrimer and the molar ratios of the complexes formed; complexes were stable for between 100 and 300 minutes. AFM measurements and molecular modeling studies were carried out to determine the structure and size of dendriplexes. The physicochemical properties of the dendriplexes studied and data from previous research suggest that carbosilane dendrimers are good candidates for nucleic acid delivery.