Studies on (polytrimethylene terephthalate)/graphene oxide/f-MWCNT hybrid nanocomposites.

Natural resource-driven approaches to bioengineering plastics are being developed to compete in the automobiles, power, and other sectors. Polytrimethylene terephthalate (PTT) is a particular of them, and it was chosen for the current investigation to build an advanced nanocomposite material. Using a twin-screw micro compounder, injection moulded PTT/Graphene-Oxide (GO)/Carboxyl functionalized Multiwall Carbon nanotube (f-MWCNT) hybrid nanocomposites were prepared. The impact of GO and f-MWCNT reinforcement on the composite's thermal and mechanical characteristics of hybrid nanocomposites was examined. GO was synthesized from the graphite powder by modified Hummer's method and MWCNTs were functionalized using the concentrated sulfuric acid (H2SO4) and nitric acid (HNO3) with a volume ratio of 3:1 in an ultrasonic bath at room temperature. In all formulations, the investigation was done at a constant filler amount of 2 wt%. To understand the chemical interaction between PTT and nanofiller, Raman spectroscopy was used and to examine the state of dispersion, scanning electron microscopy (SEM) was systematically analysed. In comparison to pristine PTT, the water absorption, tensile strength, flexural strength and impact strength of hybrid nanocomposites were improved marginally. It was also observed that GO has more prominent in increasing the mechanical properties of the hybrid and f-MWCNT in thermal properties. The 3-D geometrical bridge between GO (2-D) and f-MWCNT (1-D) made the hybrid more dispersible and effective for different applications.

Processing of Low-Density HGM-Filled Epoxy-Syntactic Foam Composites with High Specific Properties for Marine Applications.

A solution casting approach is used to create hollow glass microsphere (HGM)-filled epoxy-syntactic foam composites (e-SFCs) by varying the concentrations of HGM in epoxy according to different particle sizes. Density analysis is used to investigate the impact of concentration and particle size regularity on the microstructure of e-SFCs. It was observed that e-SFCs filled with an HGM of uniform particle sizes exhibit a reduction in density with increasing HGM concentration, whereas e-SFCs filled with heterogeneous sizes of HGM exhibit closeness in density values regardless of HGM concentration. The variation in e-SFC density can be related to HGM packing efficiency within e-SFCs in terms of concentration and particle size regularity. The particle size with lowest true density of 0.5529 g/cm3, experimental density of 0.949 g/cm3 and tensile strength of 55.74 MPa resulted in e-SFCs with highest specific properties of 100.81 (MPa·g/cm3), with a 35.1% increase from the lowest value of 74.64 (MPa·g/cm3) at a true density of 0.7286 g/cm3, experimental density of 0.928 g/cm3 and tensile strength of 54.38 MPa. The e-SFCs' theoretical density values were obtained. The variance in theoretical and experimental density values provides a thorough grasp of packing efficiency and inter-particle features.

A Review on Barrier Properties of Cellulose/Clay Nanocomposite Polymers for Packaging Applications.

Packaging materials are used to protect consumer goods, such as food, drinks, cosmetics, healthcare items, and more, from harmful gases and physical and chemical damage during storage, distribution, and handling. Synthetic plastics are commonly used because they exhibit sufficient characteristics for packaging requirements, but their end lives result in environmental pollution, the depletion of landfill space, rising sea pollution, and more. These exist because of their poor biodegradability, limited recyclability, etc. There has been an increasing demand for replacing these polymers with bio-based biodegradable materials for a sustainable environment. Cellulosic nanomaterials have been proposed as a potential substitute in the preparation of packaging films. Nevertheless, their application is limited due to their poor properties, such as their barrier, thermal, and mechanical properties, to name a few. The barrier properties of materials play a pivotal role in extending and determining the shelf lives of packaged foods. Nanofillers have been used to enhance the barrier properties. This article reviews the literature on the barrier properties of cellulose/clay nanocomposite polymers. Cellulose extraction stages such as pretreatment, bleaching, and nanoparticle isolation are outlined, followed by cellulose modification methods. Finally, a brief discussion on nanofillers is provided, followed by an extensive literature review on the barrier properties of cellulose/clay nanocomposite polymers. Although similar reviews have been presented, the use of modification processes applied to cellulose, clay, and final nanocomposites to enhance the barrier properties has not been reviewed. Therefore, this article focuses on this scope.

Analysis of Particle Variation Effect on Flexural Properties of Hollow Glass Microsphere Filled Epoxy Matrix Syntactic Foam Composites.

Syntactic foam made from hollow glass microspheres (HGM) in an epoxy matrix has proven to be a good material with a strong structural strength. Understanding filler particle size variation is important in composite material formation, especially in syntactic foam, because of its numerous applications such as aerospace, marine, and structural purposes. In this present work, the effects of particle variation in different sizes (20-24 µm, 25-44 µm, 45-49 µm, and 50-60 µm) on the mechanical properties of the syntactic foam composites with a focus on flexural strength, modulus, and fracture surfaces are investigated. The particle sizes are varied into five volume fractions (5, 10, 15, 20, and 25 vol%). The results show that the highest flexural strength is 89 MPa at a 5 vol% fraction of 50-60 µm particle size variation with a 69% increase over the neat epoxy. This implies that the incorporation of HGM filler volume fraction and size variation has a strong effect on the flexural strength and bending modulus of syntactic foam. The highest particle size distribution is 31.02 at 25-44 µm. The storage modulus E' increased at 30 °C, 50 °C, and 60 °C by 3.2%, 47%, and 96%, respectively. The effects of wall thickness and aspect ratio on the size of the microstructure, the fracture surfaces, and the viscoelastic properties are determined and reported accordingly.

An eclectic approach to monitor and manage the disposal of carbon nanotubes.

Nanotechnology, in general, and nanomaterials in particular, have conferred and are continuing to confer many benefits to mankind, just as the advent of "plastics" did in previous generations. In the case of carbon nanotubes, which can be produced in vast quantities, documented methods to manage this carbon nanotube waste by recycling and or safe disposal are so minimal that it is a matter of great concern that the paucity of studies on managing carbon nanotube waste may lead to complacency. The latter could be a trigger for human illnesses, through poor handling of carbon nanotube waste. The present study investigated ways to manage recycling and disposal of waste carbon nanotubes and a limited study of some aspects of the toxicity of waste carbon nanotubes in the environment. An eclectic approach was adopted for this study, involving an application and analysis of questionnaires, to ascertain the current practices used by practitioners in carbon nanotube research, as well as experimental work to determine the potential toxicity of carbon nanotubes. This investigation was undertaken to determine if a change from current practice is warranted in the light of the potential toxicity of carbon nanotubes (CNTs). Analysis of the questionnaires revealed the use of differing practices for the recycling and disposal of engineered nanomaterials (ENMs), implying that there is a dire need for a uniform code of practice. The toxicity study showed that carbon nanotubes did not kill earthworms in soil. However, worms were observed to be highly sensitive to increased concentrations of carbon nanotubes. The leaching in a soil column test showed that the movement of carbon nanotubes was inhibited, being confined mainly to the topmost layers of the soil. This is taken to imply that the water table is safe from possible contamination by CNTs.

Physicochemical characterization of a dental eggshell powder abrasive material.

BACKGROUND: This study aimed to determine the physicochemical characteristics of an eggshell-based dental abrasive material. METHODS: The eggshell powder abrasive material (EPAM) was synthesized by ball milling eggshell powder and surfactants. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and a laser diffraction particle size analyzer (PSA) were used to characterize EPAM. In addition, the abrasive characteristics of EPAM were evaluated by comparison using poly(methyl methacrylate) (PMMA) resins. Surface roughness (Ra) was measured using a profilometer. RESULTS: The FTIR spectroscopy and XRD analysis confirmed that the carbonate product was primarily calcite (97.3%) with traces of graphite 2H (1.3%) and thenardite (1.4%). The TEM imagery revealed irregular particles in EPAM. The PSA analysis of the particle size distribution showed EPAM to be a superfine powder (0.3 µm to 50 nm). In addition, the 50-nm EPAM (Ra = 0.04 µm) measured the lowest Ra value when compared with pumice (Ra = 0.08 µm). CONCLUSIONS: The salient features of this study indicate that EPAM can naturally replace calcite, which is generally mined and used as a dental abrasive material. In addition, and regarding the abrasive characteristics of EPAM in reducing the surface roughness of PMMA resin specimens, this study conclusively showed that EPAM effectively reduces the surface roughness below the threshold limit value of 0.2 µm. Potentially, EPAM could reduce waste disposal problems while enabling an economic benefit from using eggshell waste material.

Reducing the surface roughness of dental acrylic resins by using an eggshell abrasive material.

STATEMENT OF PROBLEM: Excessive surface roughness of denture base resins adversely impacts oral health. PURPOSE: The purpose of this in vitro study was to examine the abrasive potential of eggshell powder in reducing the surface roughness of denture base resins. MATERIAL AND METHODS: Thirty poly(methyl methacrylate) specimens were fabricated and polished with eggshell powders of different particle sizes and with pumice. The average surface roughness (Ra) after polishing was measured with a profilometer. Scanning electron microscope and optical electron microscope techniques were used to assess the surface roughness morphology of the specimens. ANOVA was used to analyze the Ra values. The Tukey honest significant differences and Bonferroni tests were used to identify differences between the 2 abrasive materials (α=.05). RESULTS: Significant differences in the Ra values were observed between the fine and medium eggshell powder abrasives (P<.05). Similarly, significant differences were found between pumice and the fine eggshell powder abrasives (P<.001). No significant differences were found between pumice and the medium eggshell powder abrasive (P>.05). Specimens polished with pumice had the highest Ra values, whereas specimens polished with the fine eggshell powder abrasive had the lowest Ra values. CONCLUSIONS: By connecting the Ra values to the threshold limit value of 0.2 µm, eggshell powder abrasive finished denture acrylic resin surfaces better than pumice.

Development of novel protein-Ag nanocomposite for drug delivery and inactivation of bacterial applications.

The potential applications, in the biomedical fields, of curcumin loaded silver nanocomposite were studied by using bovine serum albumin (protein) and acrylamide. The design and development of silver nanoparticles with small size and adequate stability are very important, in addition to their applicability, particularly in bio-medicine. In this study, silver nanoparticles were prepared by chemical reduction method, employing sodium borohydride as the reducing agent for silver nanoparticles. The properties of the protein hydrogels formed were characterized via Fourier transform infrared spectroscopy and X-ray diffraction analyses. The size and its distribution, and formation of metal nanoparticles were confirmed by transmission electron microscopy indicating the diameter of the silver nanoparticles in the range of 3-8 nm. The thermal study of curcumin-silver nanocomposite hydrogels was determined by thermo-gravimetric analysis. In order to increase the antibacterial activity of theses inorganic nanomaterials, natural biological curcumin was incorporated into the protein hydrogel. The main emphasis in this investigation is to increase the antibacterial activity of the hydrogels by loading curcumin, for advanced medical application and as a model drug.