The effect of maleic anhydride grafted polypropylene addition on the degradation in the mechanical properties of the PP/wood composites.

This work focuses on studying the influence of coupling agents on the degradation in the mechanical properties of Polypropylene (PP)/wood composites. Maleic anhydride polypropylene (MAPP) was used as a coupling agent between the wood flour and PP matrix. As the coupling agent plays an important role in the stability of the WPC, a 10 wt% wood flour was mixed with PP granules along with a UV stabilizer and varying percentages (1, 3, 5 wt%) of MAPP in a twin-screw extruder to obtain PWC granules. The composite granules were injection molded to produce tensile samples for the mechanical characterization of the composites. To test the environmental degradation of the PWCs, the tensile samples were exposed to the environmental conditions for 0, 336 h (14 days), and 672 h (28 days) prior to testing. After the specified exposure time, the samples were mechanically characterized using tensile testing. The degradation characteristics of the WPCs were quantified in terms of the failure strains of the composite with exposure time. The experiments were designed, and various analyses, including ANOVA, regression equation, and prediction tests, were carried out to investigate the impact of parameters on the failure strain of the PWCs. Moreover, the study aimed to examine the effect of parameters such as MAPP and time, on the failure strain of the composites. From the experimental results, it is concluded that the composites containing 1 wt% of MAPP showed superior retention in the degradation of composites when compared with 3 and 5 wt% MAPP content.

Biomechanical performance of resin composite on dental tissue restoration: A finite element analysis.

This study investigates the biomechanical performance of various dental materials when filled in different cavity designs and their effects on surrounding dental tissues. Finite element models of three infected teeth with different cavity designs, Class I (occlusal), Class II mesial-occlusal (MO), and Class II mesio-occluso-distal (MOD) were constructed. These cavities were filled with amalgam, composites (Young's moduli of 10, 14, 18, 22, and 26 GPa), and glass carbomer cement (GCC). An occlusal load of 600 N was distributed on the top surface of the teeth to carry out simulations. The findings revealed that von Mises stress was higher in GCC material, with cavity Class I (46.01 MPa in the enamel, 23.61 MPa in the dentin), and for cavity Class II MO von Mises stress was 43.64 MPa, 39.18 MPa in enamel and dentin respectively, while in case of cavity Class II MOD von Mises stress was 44.67 MPa in enamel, 27.5 in the dentin. The results showed that higher stresses were generated in the non-restored tooth compared to the restored one, and increasing Young's modulus of restorative composite material decreases stresses in enamel and dentin. The use of composite material showed excellent performance which can be a good viable option for restorative material compared to other restorative materials.

Characteristics of Carbon-Fiber-Reinforced Polymer Face Sheet and Glass-Fiber-Reinforced Rigid Polyurethane Foam Sandwich Structures under Flexural and Compression Tests.

Composite sandwich structures are extensively used in aircraft applications. Aircraft components are required to be robust and lightweight. Sandwich structures made of carbon-fiber-reinforced polymer as the facing sheets and milled-glass-fiber-reinforced rigid polyurethane foam with a different glass fiber content as the core structure were prepared. The influence of glass fiber content in the foam on the sandwich structure's mechanical properties was investigated. Flexural and compression tests were performed to assess the mechanical properties of the sandwich structures. Visual inspection and an optical microscope were used to observe the morphology of the polyurethane composite foams at different contents. From the flexural test, the force, facing stress and core shear stress improved with the increase in the milled fiber loading with the maximum increase at 10 wt.% loading and then a drop. Meanwhile, the compression modulus and strength increased up to 20 wt.% loadings and then dropped subsequently. The increase in the polyurethane composite foam's compression strength shifted the bending load's failure type from facing crack failure into core shear failure. The loadings range of 8-10 wt.% showed a transitional of the bending loading failure type. The density of the foams increased with the increase in milled glass fiber loading. At 10 wt.% loading, the density increased by 20%, and it increased by 47% at 30 wt.% loading. At 30 wt% loading, the optical microscope images of the foam showed wall thinning and broken walls that were responsible for the drop in the mechanical properties of the sandwich.

Enhanced Open-Hole Strength and Toughness of Sandwich Carbon-Kevlar Woven Composite Laminates.

Fiber-reinforced plastic composites are sensitive to holes, as they cut the main load-carrying member in the composite (fibers) and they induce out-of-plane stresses. In this study, we demonstrated notch sensitivity enhancement in a hybrid carbon/epoxy (CFRP) composite with a Kevlar core sandwich compared to monotonic CFRP and Kevlar composites. Open-hole tensile samples were cut using waterjet cutting at different width to diameter ratios and tested under tensile loading. We performed an open-hole tension (OHT) test to characterize the notch sensitivity of the composites via the comparison of the open-hole tensile strength and strain as well as the damage propagation (as monitored via CT scan). The results showed that hybrid laminate has lower notch sensitivity than CFRP and KFRP laminates because the strength reduction rate with hole size was lower. Moreover, this laminate showed no reduction in the failure strain by increasing the hole size up to 12 mm. At w/d = 6, the lowest drop in strength showed by the hybrid laminate was 65.4%, followed by the CFRP and KFRP laminates with 63.5% and 56.1%, respectively. For the specific strength, the hybrid laminate showed a 7% and 9% higher value as compared with CFRP and KFRP laminates, respectively. The enhancement in notch sensitivity was due to its progressive damage mode, which was initiated via delamination at the Kevlar-carbon interface, followed by matrix cracking and fiber breakage in the core layers. Finally, matrix cracking and fiber breakage occurred in the CFRP face sheet layers. The specific strength (normalized strength and strain to density) and strain were larger for the hybrid than the CFRP and KFRP laminates due to the lower density of Kevlar fibers and the progressive damage modes which delayed the final failure of the hybrid composite.

Effect of the Matrix Melt Flow Index and Fillers on Mechanical Properties of Polypropylene-Based Composites.

In this work, mechanical properties of reinforced polypropylene composites were studied. PP in particulates shape with two different melt flow indexes (MFI) was used, i.e., 3 and 23 g/10 min, namely PP3 and PP23, respectively. Three different materials, namely TiO2 nanoparticle (nTiO2, spherical, 0D), micro-size short carbon fiber (SCF, fiber, 1D), and graphite nanoplatelet (GNP, sheet, 2D), were used as reinforcements/fillers. PP and fillers (in the desired composition) were first pre-mixed by a mechanical mixer. The mixture was then fed to a co-rotating twin-screw extruder for melt-compounding, followed by injection molding to fabricate testing samples. The microstructure and fracture surface of the composites were observed by a scanning electron microscope (SEM). Additionally, tensile, flexural, impact, and hardness tests were conducted to evaluate their mechanical properties. The SEM images stipulate that PP23 had better adhesion and dispersion with the fillers. The results from the SEM images support the mechanical testing results. PP23 composites exhibited more significant improvement in mechanical properties in comparison to PP3. At 5 wt. % filler loading, PP/GNP composite exhibited a greater improvement in mechanical properties compared with two other composites, which are PP/SCF and PP/nTiO2 composites for both PPs.

The Multiple Uses of Polypropylene/Polyethylene Terephthalate Microfibrillar Composite Structures to Support Waste Management-Composite Processing and Properties.

Composite processing and subsequent characterization of microfibrillar composites (MFC) were the focus of this work. Compression molding of wound MFC filaments was used to fabricate MFC composites. The MFC composites were composed of polypropylene (PP) as matrix materials and polyethylene terephthalate (PET) as reinforcement fibers. The PP/PET blends were mixed with PET contents ranging from 22 wt% to 45 wt%. The effect of processing parameters, pressure, temperature, and holding time on the mechanical properties of the MFCs was investigated. Tensile tests were conducted to optimize the processing parameter and weight ratio of PET. Tensile strength and modulus increased with the increase in PET content. PP/45 wt% PET MFC composites properties reached the value of PP/30 wt% GF. Falling weight tests were conducted on MFC composites. The MFC composites showed the ability to absorb the impact energy compared to neat PP and PP/30 wt% GF.

Mechanical and Physical Properties of Short Carbon Fiber and Nanofiller-Reinforced Polypropylene Hybrid Nanocomposites.

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.

Synthesis, Electrochemical Studies, and Antimicrobial Properties of Fe3O4 Nanoparticles from Callistemon viminalis Plant Extracts.

Less toxic, environmentally safe green-mediated iron (III) oxide nanoparticles (Fe3O4-NP) synthesized using Callistemon viminalis (C. viminalis) leaf (Fe3O4-NPL) and flower (Fe3O4-NPF) extracts is reported in this work for the first time. Total flavonoids and phenols present in the plant extracts were determined. Characterization of the nanoparticles was carried out using Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Malvern zeta sizer. Other properties of the nanoparticles were investigated using the thermogravimetric analyser and cyclic voltammetry. The average particle sizes obtained for Fe3O4-NPL and Fe3O4-NPF were 17.91 nm and 27.93 nm, respectively. Fe3O4-NPL exhibited an excellent electrochemical activity when compared with Fe3O4-NPF based on a stability study using cyclic voltammetry and regression value. Additionally, Fe3O4-NPF displayed excellent antimicrobial activity against Bacillus cereus, Salmonella enteritidis, and Vibrio cholerae with zones of inhibition of 13, 15, and 25 mm, respectively. Simple, cheap, and less toxic green-mediated iron (III) oxide nanoparticles synthesized from C. viminalis leaf (Fe3O4-NPL) and flower (Fe3O4-NPF) extracts hold the potential of being used to control the activity of pathogenic bacteria of health importance and as an electrochemical sensor for both biological and environmental analytes.

Green Wastes Mediated Zinc Oxide Nanoparticles: Synthesis, Characterization and Electrochemical Studies.

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.