Moisture absorption and diffusivity of epoxy filled layered-structure nanocomposite

This paper studies moisture absorption and diffusivity of epoxy reinforced layered structure nanocomposites and its effect on fracture toughness. Two different types of layered fillers employed in the study were clay and graphene platelets, in which both surface layers were unmodified and modified by characterized by swelling analysis and fracture toughness measurement. The outcomes surfactant. The nanocomposites were showed that the moisture absorption and diffusivity decreased with the addition of layered fillers. It was found that the modified graphene platelets and clay outperformed the unmodified layers and neat epoxy in terms of reduction of moisture absorption and diffusivity. The modified graphene platelets reduced the moisture uptake and diffusivity about 30% and 33%, respectively compare to neat epoxy, thus indicates its outstanding performance in barrier applications. However, once the nanocomposites were swelling in the water for 5 days, it is noticed that the fracture toughness of nanocomposites were reduced significantly about 35% in average. Nevertheless, the modified graphene platelets still display the better performance compare to the other samples although there was reduction of fracture toughness

From clay to graphene for polymer nanocomposites-a survey

The development of aerospace and automotive in- dustries requests lightweight, high-performance materials, and polymer nanocomposites are ideal candidates in this case, which is shown by the increasingly more publications in this research field over the past two decades. However, the perfor- mance of nanocomposite not only depend on the properties of their individual constituents, but on their morphology and surface characteristics of fillers as well. Selections of nanofillers geometries, e.g. particulate, fibrous or layered have a tremendous influence on the properties of nanocomposites and their processing methods. In this paper, we review the chronological works performed in the field of polymer nano- composites, in particular epoxy nanocomposites reinforced with layered fillers, such as clay and graphene. Surprisingly layered fillers are commercially available and more cost- effective than nanoparticles and carbon nanofibres, and these make them to the most extensively studied fillers that can be geared toward future applications, particularly in large-scale polymer nanocomposite production

From clay to graphene for polymer nanocomposites-a survey

The development of aerospace and automotive in- dustries requests lightweight, high-performance materials, and polymer nanocomposites are ideal candidates in this case, which is shown by the increasingly more publications in this research field over the past two decades. However, the perfor- mance of nanocomposite not only depend on the properties of their individual constituents, but on their morphology and surface characteristics of fillers as well. Selections of nanofillers geometries, e.g. particulate, fibrous or layered have a tremendous influence on the properties of nanocomposites and their processing methods. In this paper, we review the chronological works performed in the field of polymer nano- composites, in particular epoxy nanocomposites reinforced with layered fillers, such as clay and graphene. Surprisingly layered fillers are commercially available and more cost- effective than nanoparticles and carbon nanofibres, and these make them to the most extensively studied fillers that can be geared toward future applications, particularly in large-scale polymer nanocomposite production

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene–propylene–diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene–propylene–diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment

Influence of Interface on epoxy/clay Nanocomposites: 1. Morphology Structure

AbstractA current challenge for the material scientists nowadays is the design and invention of new material systems that have a low weight, low cost but possess high levels of mechanical performance, good design flexibility and processability. This challenge has arisen due to the modern trend of utilizing lightweight and high performance materials, which has the potential to contribute to the advanced future applications, such as in aerospace, automotives, biotechnology, electronics and many more. In this new world, polymer nanocomposites have developed to be one of the latest evolutionary steps in the polymer technology, besides showing a great deal to become the most versatile industrial advanced materials. In comparison with conventional composites, nanocomposites demonstrate significantly higher levels of mechanical performance with less content of particles. The particle interface has been known to play a critical role in conventional composites. Nevertheless, the understanding of the role of interface in morphology polymer nanocomposites remains in its infancy. Thus, this study aims to develop a series of epoxy polymer layered-clay nanocomposites with levels of interface strength by designing chemical reactions or physical entanglements between nanoparticles and matrix polymer. In order to achieve this goal, three types of modifier were adopted: ethanolamine (denoted eth), Jeffamine M2070 (m27) and Jeffamine XTJ502 (xtj). The interface strength was identified through the morphology observation such as X-ray diffraction and scanning electron microscopy of fracture surface, in which later are correlated with various mechanical properties of nanocomposites

A facile approach to fabricate highly sensitive, flexible strain sensor based on elastomeric/graphene platelet composite film

This work developed a facile approach to fabricate highly sensitive and flexible polyurethane/graphene platelets composite film for wearable strain sensor. The composite film was fabricated via layer-by-layer laminating method which is simple and cost-effective; it exhibited outstanding electrical conductivity of 1430 ± 50 S/cm and high sensitivity to strain (the gauge factor is up to 150). In the sensor application test, the flexible strain sensor achieves real-time monitoring accurately for five bio-signals such as pulse movement, finger movement, and cheek movement giving a great potential as wearable-sensing device. In addition, the developed strain sensor shows response to pressure and temperature in a certain region. A multifaceted comparison between reported flexible strain sensors and our strain sensor was made highlighting the advantages of the current work in terms of (1) high sensitivity (gauge factor) and flexibility, (2) facile approach of fabrication, and (3) accurate monitoring for body motions

Organic Food and Farming in Egypt

Description of the organic Food and farm sector in Egypt, production and farmstructure, historical development, institutional set-up, certificiers, market trends for the domestic as well as export and future prospects for growth