Optimization of mechanical properties of epoxy-based hybrid nanocomposite: Effect of using nano silica and high-impact polystyrene by mixture design approach

Effects of Vinyl Functionalized Silica Particles on Thermal and Mechanical Properties of Liquid Silicone Rubber Nanocomposites

It is very important to develop a new method of preparing high-performance liquid silicone rubber-reinforcing filler. Herein, the hydrophilic surface of silica (SiO₂) particles was modified by a vinyl silazane coupling agent to prepare a new type of hydrophobic reinforcing filler. The structures and properties of modified SiO₂ particles were confirmed using Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectrometer (XPS), specific surface area and particle size distribution and thermogravimetric analysis (TGA), the results of which demonstrated that the aggregation of hydrophobic particles is greatly reduced. Additionally, the effects of the vinyl-modified SiO₂ particle (f-SiO₂) content on the dispersibility, rheology, and thermal and mechanical properties of liquid silicone rubber (SR) composites were studied for application toward high-performance SR matrix. The results showed that the f-SiO₂/SR composites possessed low viscosity and higher thermal stability, conductivity, and mechanical strength than of SiO₂/SR composites. We believe that this study will provide ideas for the preparation of high-performance liquid silicone rubber with low viscosity.

Characterization of Hybrid Composites with Polyester Waste Fibers, Olive Root Fibers and Coir Pith Micro-Particles Using Mixture Design Analysis for Structural Applications

In the present work, hybrid composites were developed by using polyester waste fibers along with natural origin materials: olive root fibers and coir pitch filler. Such composite panels can be used as a potential alternative for fiber glass sunshade panels and room dividers in buildings. Hybrid composites were fabricated by mixing polyester waste fibers and olive root fibers in different ratios (0:100, 33:67, 67:33 and 100:0). Coir pith micro-particles with an average size of 312 d.nm were used as filler in the polyester matrix at three different levels (0%, 5%, and 10%) of the overall matrix weight. Mechanical properties, e.g., tensile strength, flexural strength and impact strength, thermal properties, e.g., coefficient of linear thermal expansion, thermo-gravimetric analysis (TGA) and environmental properties, e.g., water absorption, loss of density after exposure to weathering were characterized. For comparison purposes, a commercially available fiber glass sunshades sample was also investigated. Mixture design analysis was used to optimize the ratio of all components in the composite. Graphical comparison of experimental results using regression models showed a high degree of correlation. An optimized formulation of composite with an objective of maximization of tensile strength, flexural strength, impact strength and minimization of water absorption, density loss, as well as coefficient of linear thermal expansion, was determined at 70.83 wt%, 15.15 wt%, and 14.01 wt% of polyester waste fibers, olive root fibers and coir pith micro-fillers, respectively. Overall, it can be concluded that the developed hybrid composites from waste fibrous materials can be used as a promising alternative and a value-added application in buildings and construction purposes.

Study of Mechanical and Moisture Absorption Behavior of Epoxy/Cloisite-15A Nanocomposites Processed Using Twin Screw Extruder

This paper presents the effect of process parameters of twin screw extruder and addition of Cloisite-15A on mechanical, thermal and moisture barrier properties of epoxy/Cloisite-15A nanocomposites. Four lobed kneading blocks were used the in shearing zone of the extruder, based on their effectiveness in dispersing nanofillers in epoxy. Screw speeds from 100 min−1 to 400 min−1, number of passes up to 15, temperature from 5°C to 80°C and Cloisite-15A contents from 1 wt.% to 2.5 wt.% were considered for designing the L12 Orthogonal Array. Improvements in tensile strength, compression strength, flexural strength, impact strength, hardness and moisture diffusivity in the nanocomposites were 11.89%, 20.06%, 27.73%, 37.26%, 25.48% and 56.22% respectively, when compared to neat epoxy. The improvements were achieved for screw speed of 400 min–1, 5 passes through the extruder, processing temperature of 5°C and 2 wt.% of Cloisite-15A. Dispersion of Cloisite-15A in epoxy was studied by XRD, SEM and TEM. Thermal stability and moisture barrier properties were superior in the nanocomposites.

Adsorption of hazardous atoms on the surface of TON zeolite and bilayer silica: a DFT study

In the present study, the adsorption of two types of hazardous atoms including arsenic and lead with TON zeolite and bilayer silica (2D-SiO₂) have been investigated by employing Ab initio-based density functional theory (DFT) calculations. To reach a full structural optimization and the most stable configuration, four sites were considered for TON zeolite as well as five sites for 2D-SiO₂, and adsorption energy along with equilibrium geometry was determined. The adsorption energies of arsenic atom on the surface of 2D-SiO₂ absorbents and TON zeolite have obtained equal to and - 1.25 eV and - 2.76 eV, respectively, which both of them are chemisorption type. We also found that the adsorption of lead on the surface of 2D-SiO2 was physisorption type with the adsorption energy accounting for - 0.13 eV, while the adsorption energy between lead and TON was calculated equal to - 2.32 eV which was chemisorption type. Furthermore, our results demonstrate that the TON zeolite was more capable of adsorbing hazardous atoms compared with 2D-SiO2 due to having greater adsorption energy. The adsorption of arsenic on the 2D-SiO2 and TON adsorbents is also stronger than those of lead atom. Furthermore, we modeled and considered graphene, as a common adsorbent nanostructure, to compare and validate the accuracy of our simulations and obtained results. Finally, the electronic density of states (DOS) calculations and charge analysis were done by the use of Mulliken method, and the results confirmed those results that had already been obtained from adsorption energies. Graphical abstract.

Development of low-cost iron mixed porous pellet adsorbent by mixture design approach and its application for arsenate and arsenite adsorption from water

In this study, natural clay, iron oxide, and iron powder were combined to develop low-cost iron mixed porous pellet adsorbent for arsenate and arsenite removal from aqueous solution in batch experiments. The augmented simplex centroid mixture design was applied to obtain the optimum proportion of each constituent. Higher correlation coefficient of the models (R2 > 0.95), good distribution of residuals, and lower values of p value (<0.05) indicated that the method is suitable for determining the optimum mixture proportion. Extensive decrease of both arsenate and arsenite adsorption occurred in the alkaline condition (pH > 9). Kinetic and isotherm experimental data of both arsenate and arsenite were well described by the pseudo-second order and Sips models, respectively. The maximum adsorption capacity of arsenate and arsenite derived from Sips model were 13.33 and 19.06 mg/g, respectively. The separation and heterogeneity factors showed that both arsenate and arsenite were favorably adsorbed. Among coexisting anions, phosphate significantly showed negative effect on the adsorption of either arsenate or arsenite. The adsorbent could be effectively reused for several times after its regeneration and was considered as non-hazardous material after adsorption.

Influence of particle size and interfacial interactions on the physical and mechanical properties of particle-filled myofibrillar protein gels

The mechanical properties of glass and wax particle-filled myofibrillar protein gels were characterized based on filler size and surface effects. Increases in elastic moduli were explained using established models describing particle-filled networks.

Epoxy Resin Composite Based on Functional Hybrid Fillers

A study was carried out involving the filling of epoxy resin (EP) with bentonites and silica modified with polyhedral oligomeric silsesquioxane (POSS). The method of homogenization and the type of filler affect the functional and canceling properties of the composites was determined. The filler content ranged from 1.5% to 4.5% by mass. The basic mechanical properties of the hybrid composites were found to improve, and, in particular, there was an increase in tensile strength by 44%, and in Charpy impact strength by 93%. The developed hybrid composites had characteristics typical of polymer nanocomposites modified by clays, with a fine plate morphology of brittle fractures observed by SEM, absence of a plate separation peak in Wide Angles X-ray Scattering (WAXS) curves, and an exfoliated structure observed by TEM.