Stability Efficiencies of POSS and Microalgae Extracts on the Durability of Ethylene-Propylene-Diene Monomer Based Hybrids

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.

Biodegradable Hydrogel Scaffolds Based on 2-Hydroxyethyl Methacrylate, Gelatin, Poly(β-Amino esters), and Hydroxyapatite

New composite 3D scaffolds were developed as a combination of synthetic polymer, poly(2-hydroxyethyl methacrylate) (PHEMA), and a natural polymer, gelatin, with a ceramic component, nanohydroxyapatite (ID nHAp) dopped with metal ions. The combination of a synthetic polymer, to be able to tune the structure and the physicochemical and mechanical properties, and a natural polymer, to ensure the specific biological functions of the scaffold, with inorganic filler was applied. The goal was to make a new material with superior properties for applications in the biomedical field which mimics as closely as possible the native bone extracellular matrix (ECM). Biodegradable PHEMA hydrogel was obtained by crosslinking HEMA by poly(β-amino esters) (PBAE). The scaffold’s physicochemical and mechanical properties, in vitro degradation, and biological activity were assessed so to study the effects of the incorporation of nHAp in the (PHEMA/PBAE/gelatin) hydrogel, as well as the effect of the different pore-forming methods. Cryogels had higher elasticity, swelling, porosity, and percent of mass loss during degradation than the samples obtained by porogenation. The composite scaffolds had a higher mechanical strength, 10.14 MPa for the porogenated samples and 5.87 MPa for the cryogels, but a slightly lower degree of swelling, percent of mass loss, and porosity than the hybrid ones. All the scaffolds were nontoxic and had a high cell adhesion rate, which was 15–20% higher in the composite samples. Cell metabolic activity after 2 and 7 days of culture was higher in the composites, although not statistically different. After 28 days, cell metabolic activity was similar in all scaffolds and the TCP control. No effect of integrating nHAp into the scaffolds on osteogenic cell differentiation could be observed. Synergetic effects occurred which influenced the mechanical behavior, structure, physicochemical properties, and interactions with biological species.

Probing the charge injection and dissipation in graphene oxide–epoxy composite

The inorganic filler can modify the electrical and dielectric properties of polymeric composites. However, it is challenging to understand the local charge injection and dissipation in composites through traditional characterization at nanoscale. In this work, we provide a potential mapping of the charge injection and dissipation in the local area of graphene oxide/epoxy resin (GO/EP) composite under various biases by Kelvin probe force microscopy (KPFM) with high spatial resolution. Thus, an improved KPFM experimental setup is used to inject charges at the fixed point to demonstrate surface charge dissipation around the interface between GO and EP. It is found that the charge is more easily injected into the GO/EP nanocomposites and dissipates more quickly in nanocomposite than in neat epoxy resins. Meanwhile, the electrons diffuse more rapidly than holes in pure EP and nanocomposites. The faster charge injection and dissipation of GO/EP composite are ascribed to the filler of GO which has much higher conductivity than that of neat epoxy. This work offers significant insights into the understanding of charge injection and dissipation in dielectric composites.

SHORT NOTES: APPLICATION OF MINERAL FILLER IN MEDIUM DENSITY FIBERBOARD (MDF) AND ITS EFFECT ON MATERIAL PROPERTIES AS A FUNCTION OF PARTICLE SIZE

The addition of inorganic filler material in medium density fiberboard (MDF) and the effect on material properties as a function of particle size was examined. Medium density fiberboard was manufactured in a laboratory scale environment to a target raw densityof 750 kgm-3. Wood fibers were replaced by using calcium carbonate at 3 and 10 wt.% using fillers with weighted median particle sizes of d50= 2.0 μm and d50= 30 μm, respectively. Urea formaldehyde resin was used as binder in all MDF. The influence of filler addition on the modulus of elasticity, bending and tensile strength, dimensional stability and liquid permeability was investigated. The results demonstrate the effect of filler content and its dependence on particle size. The addition of filler with d50= 30 μm does not have any influence on material properties up to a filler content of 10 wt.%. Using the finer filler with d50= 2.0 μm at 10 wt.% filler, the quantity significantly increases the water adsorption and swelling behavior and reduces the strength properties of the MDF.

Improved CO2/CH4 Separation Properties of Cellulose Triacetate Mixed–Matrix Membranes with CeO2@GO Hybrid Fillers

The study of the effects associated with the compatibility of the components of the hybrid filler with polymer matrix, which ultimately decide on achieving mixed matrix membranes (MMMs) with better gas separation properties, is essential. Herein, a facile solution casting process of simple incorporating CeO2@GO hybrid inorganic filler material is implemented. Significant improvements in material and physico-chemical properties of the synthesized membranes were observed by SEM, XRD, TGA, and stress-strain measurements. Usage of graphene oxide (GO) with polar groups on the surface enabled forming bonds with ceria (CeO2) nanoparticles and CTA polymer and provided the homogeneous dispersion of the nanofillers in the hybrid MMMs. Moreover, increasing GO loading concentration enhanced both gas permeation in MMMs and CO2 gas uptakes. The best performance was achieved by the membrane containing 7 wt.% of GO with CO2 permeability of 10.14 Barrer and CO2/CH4 selectivity 50.7. This increase in selectivity is almost fifteen folds higher than the CTA-CeO2 membrane sample, suggesting the detrimental effect of GO for enhancing the selectivity property of the MMMs. Hence, a favorable synergistic effect of CeO2@GO hybrid fillers on gas separation performance is observed, propounding the efficient and feasible strategy of using hybrid fillers in the membrane for the potential biogas upgrading process.

Hybrid Composite Membrane of Phosphorylated Chitosan/Poly (Vinyl Alcohol)/Silica as a Proton Exchange Membrane

Chitosan is one of the natural biopolymers that has been studied as an alternative material to replace Nafion membranes as proton change membranes. Nevertheless, unmodified chitosan membranes have limitations including low proton conductivity and mechanical stability. The aim of this work is to study the effect of modifying chitosan through polymer blending with different compositions and the addition of inorganic filler on the microstructure and physical properties of N-methylene phosphonic chitosan/poly (vinyl alcohol) (NMPC/PVA) composite membranes. In this work, the NMPC biopolymer and PVA polymer are used as host polymers to produce NMPC/PVA composite membranes with different compositions (30–70% NMPC content). Increasing NMPC content in the membranes increases their proton conductivity, and as NMPC/PVA-50 composite membrane demonstrates the highest conductivity (8.76 × 10−5 S cm−1 at room temperature), it is chosen to be the base membrane for modification by adding hygroscopic silicon dioxide (SiO2) filler into its membrane matrix. The loading of SiO2 filler is varied (0.5–10 wt.%) to study the influence of filler concentration on temperature-dependent proton conductivity of membranes. NMPC/PVA-SiO2 (4 wt.%) exhibits the highest proton conductivity of 5.08 × 10−4 S cm−1 at 100 °C. In conclusion, the study shows that chitosan can be modified to produce proton exchange membranes that demonstrate enhanced properties and performance with the addition of PVA and SiO2.

Determination of the effect of carbon nanotubes on the microstructure and functional properties of polycarbonate-based polymer nanocomposite materials

Polymer nanocomposites are widely used in various high-tech industries. Due to the combination of the elasticity of the matrix and the strength of the inorganic filler, they have improved functional characteristics compared to unfilled polymers. The article is devoted to determining the effect of carbon nanotubes (CNT) on the microstructure and properties of polymeric nanocomposite materials for 3D printing based on polycarbonate. As a result of this work, a series of composite materials was manufactured using a piston extruder. Their microstructure and functional characteristics were investigated using methods of optical microscopy, thermophysical, electrical and mechanical analysis. It was found that CNTs form clusters in the polymer matrix, which form a percolation network at a content of 0.5–0.8 %. This feature of the structure formation of CNTs provided an abrupt increase in the functional characteristics of the materials obtained. It is shown that with an increase in the filler content in the system to 3 %, the thermal conductivity rapidly increases to 1.22 W/(m∙K). A similar effect is observed for the electrical conductivity, which increases by seven orders of magnitude from 10-12 to 10-5 S/cm at 3 % CNT content in the system, exhibiting percolation behavior. With the introduction of CNTs, the crystallinity degree of the polymer matrix decreases by almost 15 %, due to the fact that the developed surface of the nanotubes creates steric hindrances for polycarbonate macromolecules. This effect almost negates the reinforcing effect of nanotubes; therefore, the mechanical tensile strength with the introduction of 3 % CNTs increases by only 21 % compared to the unfilled matrix. In terms of their functional characteristics, the obtained materials are promising for the creation of filaments for 3D printing on their basis.