No abstract

The effect of various combinations of filler materials on the performance of polypropylene (PP)-based composites was investigated. PP in particulate form was used as the matrix. Milled short carbon fiber (SCF) micro-size, graphite nano-platelet (GNP), and titanium dioxide nanoparticles (nTiO2) were used as fillers. These fillers were incorporated in the polymer matrix to produce mono-filler (PP/SCF and PP/nanofiller) and hybrid composites. Hybrid composites consist of PP/10SCF/GNP, PP/10SCF/nTiO2, and PP/10SCF/GNP/nTiO2. The effect of the addition of SCF, GNP, and nTiO2 on PP-based composites was investigated by analyzing their morphological, mechanical, and physical properties. The addition of mono-filler to the PP matrix improved the mechanical properties of the composites when compared to the neat PP. The ultimate tensile strength (UTS), flexural modulus, flexural strength, and impact toughness of the hybrid composites with 15 wt % total loading of fillers, were higher than that of mono-filler composites with 15 wt % SCF (PP/15SCF). A maximum increase of 20% in the flexural modulus was observed in the hybrid composite with 10 wt % of SCF with the additional of 2.5 wt % GNP and 2.5 wt % nTiO2 when compared to PP/15SCF composite. The addition of 2.5 wt % nTiO2 to the 10 wt % SCF reinforced PP, resulted in increasing the strain at break by 15% when compared to the PP/10SCF composite. A scanning electron microscope image of the PP/10SCF composite with the addition of GNP improved the interfacial bonding between PP and SCF compared with PP/SCF alone. A decrease in the melt flow index (MFI) was observed for all compositions. However, hybrid composites showed a higher decrease in MFI.

In this work, the ductile to brittle transition behavior of short carbon fiber (SCF)-reinforced polypropylene (PP) composite is studied. Initially, the SCF-reinforced PP composites with a varying composition of SCF in the range of 0–40 wt% loading were first melt-mixed in a twin-screw extruder and later injection-molded to produce the testing samples. The experimental results indicate that with an increase in SCF loading, an increase in the tensile modulus and strength was observed along with a rapid decrease in the values of strain at break. A sudden decrease in strain at break was observed in composites in the range of 10–15 wt% SCF. To further study the sudden decrease in strain at break, an investigation was performed on composites that contained 10–15 wt% of SCF loading, starting from 10 wt% with a 1% increment to 15 wt% of SCF. The results of this study show that a decrease in strain at break was not linear; on the contrary, it was accompanied by a ductile to brittle transition, which specifically occurred in the range of 12–13 wt% of SCF loading and then continued to decrease with an increase in SCF loading.

Polyester-based composites filled with various contents of alumina (Al2O3) (i.e., 0, 1, 5, and 10 vol%) have been fabricated in this study. Physical and mechanical properties of the composites have also been analysed. The analysis results showed that the experimental density of the polyester/alumina composites was smaller than the theoretical density, which could be attributed to the formation of voids during preparation of the composites. Meanwhile, the tensile strength, stiffness, and hardness of the composites increased with increasing alumina content, while the strain-at-break of the composites decreased. It was observed that the composites containing 5 vol% of alumina had the best tensile strength, stiffness, and hardness. The uniform distribution and dispersion of alumina particles were likely responsible for the improvement of the mechanical properties. In other hand, small decrease in tensile strength, stiffness, and hardness of composite was found in the composites with 10 vol% of alumina. The formation of agglomerates and voids was believed to be the main factor for the decrease of the both properties.

Zinc Oxide (ZnO) nanoparticles were prepared using a simple green synthesis approach in an alkaline medium, from three different extracts of citrus peels waste. The synthesized nano-crystalline materials were characterized by using ultraviolet-visible spectroscopy (UV-vis), x-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive x-ray spectroscopy (EDS), environmental scanning electron microscopy (ESEM), and transmission electron microscopy (TEM). UV-vis analysis of the nanoparticles showed broad peaks around 360 nm for the ZnO NPs (Zinc oxide nanoparticles) from three citrus peels’ extracts. ZnO NPs exhibited Zn–O band close to 553 cm−1, which further verified the formation of the ZnO NPs. A bandgap of 3.26 eV, 3.20 eV and 3.30 eV was calculated for the ZnO NPs from grape (ZnO NPs/GPE), lemon (ZnO NPs/LPE), and orange (ZnO NPs/OPE) peels extract, respectively. The average grain sizes of the ZnO nanoparticles were evaluated to be 30.28 nm, 21.98 nm, and 18.49 nm for grape (ZnO NPs/GPE), lemon (ZnO NPs/LPE), and orange (ZnO NPs/OPE) peel extract, respectively. The surface morphology and sizes of the nanoparticle were confirmed by ESEM and TEM analysis, respectively. Furthermore, the zeta potential of the as-prepared ZnO NPs from OPE, LPE, and GPE was −34.2 mV, −38.8 mV, and −42.9 mV, respectively, indicating the high stability of the nanoparticles. Cyclic voltammetric properties of the synthesized nanoparticles were investigated across extracts, and the results showed that the citrus peels extracts (CPE) mediated ZnO NPs modified screen plate carbon (SPC/ ZnO NPs/CPE) electrodes exhibited enhanced catalytic properties when compared with the bare SPCE. The electroactive areas computed from the enhancement of the bare SPCE was approximately three times for SPCE/ ZnO NPs/LPE, and SPCE/ZnO NPs/GPE, and two times for SPCE/ZnO NPs/OPE, higher than that of the bare SPCE. Comparison across the extracts suggested that the catalytic properties of the nanoparticles were unique in ZnO NPs from GPE.