Mariam Al-Ali AlMaadeed

Eco-Friendly Synthesis of Graphene Oxide Reinforced Hydroxypropyl Methylcellulose/Polyvinyl Alcohol Blend Nanocomposites Filled with Zinc Oxide Nanoparticles for High-k Capacitor Applications

ABSTRACT Polymer/inorganic nanocomposites comprising of hydroxypropyl methylcellulose and polyvinyl alcohol as a polymer matrix and unique combination of graphene oxide and zinc oxide nanoparticles as fillers have been prepared using colloidal processing technique and characterized using various analytical methods. The dielectric properties of the nanocomposites are investigated using impedance analyzer. The nanocomposites show improvement in the dielectric properties compared to hydroxypropyl methylcellulose/polyvinyl alcohol (50/50) blends, which results from the homogeneous dispersion of fillers into the polymer matrix. The results indicate that these nanocomposites have a potential to meet the technological demands of high-k dielectrics and/or embedded capacitors. GRAPHICAL ABSTRACT

Flexible Pressure Sensor Based on PVDF Nanocomposites Containing Reduced Graphene Oxide-Titania Hybrid Nanolayers

A novel flexible nanocomposite pressure sensor with a tensile strength of about 47 MPa is fabricated in this work. Nanolayers of titanium dioxide (titania nanolayers, TNL) synthesized by hydrothermal method are used to reinforce the polyvinylidene fluoride (PVDF) by simple solution mixing. A hybrid composite is prepared by incorporating the TNL (2.5 wt %) with reduced graphene oxide (rGO) (2.5 wt %) synthesized by improved graphene oxide synthesis to form a PVDF/rGO-TNL composite. A comparison between PVDF, PVDF/rGO (5 wt %), PVDF/TNL (5 wt %) and PVDF/rGO-TNL (total additives 5 wt %) samples are analyzed for their sensing, thermal and dielectric characteristics. The new shape of additives (with sharp morphology), good interaction and well distributed hybrid additives in the matrix increased the sensitivity by 333.46% at 5 kPa, 200.7% at 10.7 kPa and 246.7% at 17.6 kPa compared to the individual PVDF composite of TNL, confirming its possible application in fabricating low cost and light weight pressure sensing devices and electronic devices with reduced quantity of metal oxides. Increase in the β crystallinity percentage and removal of α phase for PVDF was detected for the hybrid composite and linked to the improvement in the mechanical properties. Tensile strength for the hybrid composite (46.91 MPa) was 115% higher than that of the neat polymer matrix. Improvement in the wettability and less roughness in the hybrid composites were observed, which can prevent fouling, a major disadvantage in many sensor applications.

A review on composite materials based on recycled thermoplastics and glass fibres

Abstract The purpose of this paper is to review recent work on composite materials based on recycled thermoplastics and glass fibres (GFs). The high collection and separation cost of plastics waste, and the legislative push to increase recycling rates, require the inclusion of increasing proportions of low‐quality plastic waste into recycled products. A robust method for upgrading mixed plastics recyclates is the incorporation of fillers and reinforcements. In particular, addition of chopped GF can lead to material systems with more favourable and consistent sets of mechanical properties. Provided a good interfacial adhesion is achieved, the key structural properties of the composite (stiffness and strength) are mainly dictated by the reinforcement. Therefore, a wide range of polymers, including blends, are accessible for recycling into semistructural products. Glass fibres are one of the most cost‐effective ways of reinforcing recycled polymers, as testified by several patents and commercial products which appeared in the last decade.

Flexible and stretchable electronic composites

Natural Polyisoprene Composites and its Electronic Applications.- Electronic Applications of Polymer Electrolytes of Epoxidized Natural Rubber and its Composites.- Electronic Applications of Ethylene Vinyl Acetate and its Composites.- Electronic Applications of Polyurethane and its Composites.- Electronic Applications of Polyamide Elastomers and its Composites.- Electronic Applications of Polyacrylic Rubber and its Composites.-Electronic Applications of Polydimethylsiloxane and its Composites.- Chlorosulfonated Polyethylene and its Composites for Electronics Applications.- Electronic Applications of Styrene-Butadiene Rubber and its Composites.- Electronic Applications of Chloroprene Rubber and its Composites.- Electronic Applications of Ethylene Propylene Diene Monomer Rubber and its Composites.- Poly(Isobutylene-co-isoprene) Composites for Flexible Electronic Applications.-Nanomaterials Embedded Liquid Crystal Elastomers in Electronics Devices application.

Mechanical and Thermal Properties of Recycled Poly(ethylene terephthalate) Reinforced Newspaper Fiber Composites

This study presents the mechanical and thermal properties of environment-friendly composites made from recycled newspaper fibers reinforced recycled poly(ethylene terephthalate) (rPET) resin with the addition of styrene-ethylene-butylene-styrene grafted maleic anhydride (SEBS-g-MA) as compatibilizer. The effect of SEBS-g-MA addition (i.e., 10 phr) by using a twin-screw extruder to the rPET resin, followed by different fiber content (5, 10 and 15 wt.%) on the tensile, flexural and impact properties of the composites were determined. Stiffness of composites increased significantly compared to those of rPET/SEBS-g-MA blend. Fiber addition resulted in moderate increases in both tensile and flexural strength of the composites. Scanning electron microscope (SEM) photomicrographs of the impact fracture surfaces demonstrate good adhesion at 5 and 10 % fiber content. Differential scanning calorimetry (DSC) showed that the presence of newspaper fibers enhanced the nonisothermal crystallization kinetics and crystallinity. Thermal stability of the composites was improved as indicated by thermogravimetric analysis (TGA).

TiO2 nanotubes and mesoporous silica as containers in self-healing epoxy coatings

The potential of inorganic nanomaterials as reservoirs for healing agents is presented here. Mesoporous silica (SBA-15) and TiO2 nanotubes (TNTs) were synthesized. Both epoxy-encapsulated TiO2 nanotubes and amine-immobilized mesoporous silica were incorporated into epoxy and subsequently coated on a carbon steel substrate. The encapsulated TiO2 nanotubes was quantitatively estimated using a ‘dead pore ratio’ calculation. The morphology of the composite coating was studied in detail using transmission electron microscopic (TEM) analysis. The self-healing ability of the coating was monitored using electrochemical impedance spectroscopy (EIS); the coating recovered 57% of its anticorrosive property in 5 days. The self-healing of the scratch on the coating was monitored using Scanning Electron Microscopy (SEM). The results confirmed that the epoxy pre-polymer was slowly released into the crack. The released epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch.

Preparation and characterization of green graphene using grape seed extract for bioapplications.

The development of functionalized graphene materials concerning health and environmental aspects via green approaches is currently the most recent topic in the field of nanoscience and nanotechnology. Herein, we report the green reduction of graphene oxide (GO) to reduced graphene oxide (RGO) using grape seed extract (GSE). Structural properties of the prepared RGO were investigated using Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetric analysis (TGA), UV-Visible spectroscopy and X-ray diffraction analysis. These all characterization techniques clearly revealed that the RGO has been successfully prepared. Moreover, the average thickness (4.2nm) of RGO layers was also confirmed by transmission electron microscopy (TEM). Optical properties such as band gap and photoluminescence of the synthesized RGO were evaluated. The band gap of RGO was found to be 3.84eV and it showed emission in the visible region. Efficient antimicrobial activity against Escherichia coli and Staphylococcus aureus was observed with 4μgml(-1) & 5μgml(-1) of RGO and also the cell wall damage of these strains has been proved by atomic force microscopy (AFM). The in vitro study of RGO (500μg) disclosed the effective anti-proliferative activity (88%) against HCT-116 cell lines.

Improvement of thermal conductivity of paraffin by adding expanded graphite

This paper investigated the use of graphite with different configuration designs to improve the thermal energy storage of phase change material systems. Two types of graphite have been combined with paraffin in order to improve thermal conductivity of phase change material: synthetic graphite (Timrex SFG75) and graphite waste obtained from damaged tubular graphite heat exchangers. Paraffin/graphite phase change material composites have been prepared by the cold uniaxial compression technique. Their morphologies have been observed and analyzed by scanning electron microscope, and their thermophysical properties have been estimated using new experimental tools. Results show that the thermal conductivity and thermal diffusivity can be accurately measured by these new experimental tools. Moreover, results highlight the fact that the phase change material thermal properties are greatly influenced by the graphite addition.

Improved electrical conductivity of carbon/polyvinyl alcohol electrospun nanofibers

Carbon nanofibers (CNFs) gained much interest in the last few years due to their promising electrical, chemical, and mechanical characteristics. This paper investigates a new nanocomposite composed of carbon nanofibers hosted by PVA and both are integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs using traditional deposition techniques. The results show that electrical conductivity of the formed nanofibers has been improved up to 1.63 × 10-4 S/cm for CNFs of weight 2%. The peak temperature of mass loss through TGA measurements has been reduced by 2.3%. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and gas adsorption.

Mechanical and thermal characterisation of multifunctional composites incorporating phase change materials

The paper reports an experimental investigation on the mechanical and thermal properties of multifunctional composite laminates integrated with microencapsulated phase change materials. The different microstructures were created by incorporating microencapsulated phase change materials in glass–epoxy composites at weight fraction between 0 and 20 wt.%. To characterise the mechanical properties, tension, compression and flexural tests were conducted. The scanning electron microscope studies were used to investigate the damage mechanisms associated with these loading conditions. Thermal storage capability of the multifunctional composites was characterised using heat flux meters. The apparent heat capacity of the composites was linearly proportional to the concentration of microencapsulated phase change materials. Alternative design analysis resulted in an optimised laminate configuration with high thermal storage capability coupled with excellent mechanical properties.