Processing and characterization of polyethylene-based composites

Thermoplastic matrix polymer composites have gained commercial success in the semistructural and structural applications. Polyethylene (PE) is one of the most versatile and widely used thermoplastics in the world because of its excellent properties like toughness, near-zero moisture absorption, excellent chemical inertness, low coefficient of friction, ease of processing and unusual electrical properties. This review is designed for comprehensive source of PE-based polymer composites research, including structure and classification of PE manufacturing/processing techniques for PE composites, and it also described different characterization methods for PE composites. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) characterization methods were used to describe the thermal properties of PE composites. Morphological studies were explained by using scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) techniques. Rheological properties and dynamic mechanical analysis (DMA) are also discussed in this review. X-ray diffraction (XRD) characterization was described in this review to explain crystallinity in PE composites. Hence, this review offers a comprehensive discussion on processing and characterization of PE-based composites

Biotechnological production process and life cycle assessment of graphene

The aim of this study is to compare the graphene produced using a biotechnological method (Escherichia coli) with the graphene produced by Hummers' method (a chemical method) and to study the effect on the energy consumption and environment. The results indicated that the chemical reduction process has higher energy consumption, approximately 1642 Wh, than the energy consumption of the biotechnological reduction process, which is 5 Wh. The potential of global warming (GWP 100) improved by 71% using the biotechnological route for the production of graphene. Abiotic depletion, the photochemical ozone creation potential, and marine aquatic ecotoxicity potential were improved when the biological route was employed, compared with the chemical route. The eutrophication potential, terrestrial ecotoxicity, and ozone depletion layer changed very little since the main variables involved in the production of graphene oxide and waste management are the same. The biotechnological method can be considered a green technique for the production of graphene, especially given the reduction in the negative effects on global warming, abiotic depletion, the photochemical ozone creation potential, and the marine aquatic ecotoxicity potential

Biotechnological production process and life cycle assessment of graphene

The aim of this study is to compare the graphene produced using a biotechnological method (Escherichia coli) with the graphene produced by Hummers' method (a chemical method) and to study the effect on the energy consumption and environment. The results indicated that the chemical reduction process has higher energy consumption, approximately 1642 Wh, than the energy consumption of the biotechnological reduction process, which is 5 Wh. The potential of global warming (GWP 100) improved by 71% using the biotechnological route for the production of graphene. Abiotic depletion, the photochemical ozone creation potential, and marine aquatic ecotoxicity potential were improved when the biological route was employed, compared with the chemical route. The eutrophication potential, terrestrial ecotoxicity, and ozone depletion layer changed very little since the main variables involved in the production of graphene oxide and waste management are the same. The biotechnological method can be considered a green technique for the production of graphene, especially given the reduction in the negative effects on global warming, abiotic depletion, the photochemical ozone creation potential, and the marine aquatic ecotoxicity potential

Melt processing and properties of linear low density polyethylene-graphene nanoplatelet composites

Composites of Linear Low Density Polyethylene (LLDPE) and Graphene Nanoplatelets (GNPs) were processed using a twin screw extruder under different extrusion conditions. The effects of screw speed, feeder speed and GNP content on the electrical, thermal and mechanical properties of composites were investigated. The inclusion of GNPs in the matrix improved the thermal stability and conductivity by 2.7% and 43%, respectively. The electrical conductivity improved from 10-11 to 10-5 S/m at 150 rpm due to the high thermal stability of the GNPs and the formation of phonon and charge carrier networks in the polymer matrix. Higher extruder speeds result in a better distribution of the GNPs in the matrix and a significant increase in thermal stability and thermal conductivity. However, this effect is not significant for the electrical conductivity and tensile strength. The addition of GNPs increased the viscosity of the polymer, which will lead to higher processing power requirements. Increasing the extruder speed led to a reduction in viscosity, which is due to thermal degradation and/or chain scission. Thus, while high speeds result in better dispersions, the speed needs to be optimized to prevent detrimental impacts on the properties.</p

Review of natural fibre-reinforced hybrid composites

Natural fibre-reinforced hybrid composites which contain one or more types of natural reinforcement are gaining increasing research interest. This paper presents a review of natural fibre-reinforced hybrid composites. Both thermoplastic and thermoset composites reinforced by hybrid/synthetic fibres or hybrid/hybrid fibres are reviewed. The properties of natural fibres, the properties and processing of composites are summarised

Biosynthesis and characterization of graphene by using non-toxic reducing agent from Allium Cepa extract: Anti-bacterial properties

Graphene based materials have attracted huge interest in recent years due to their outstanding properties and applications in various fields including bioengineering, electronics, nanotechnology, composite materials and many more. Despite numerous reports on synthesis of graphene, the mass production of high quality graphene in an inexpensive and eco-friendly method has remained as a challenge. In this work, we present a simple and green method for biosynthesis of graphene by using nontoxic reducing agent from Allium Cepa (onion) extracts. Modified Hummers' method was used to synthesis the Graphene oxide (G0) and extracts from Allium Cepa was used as reducing agent. The prepared graphene was analyzed by Raman spectroscopy, XRD, FTIR, SEM, TEM and XPS. The experimental results showed that GO was successfully reduced to graphene using onion extract. The Raman spectroscopy results, XPS results and XRD results confirmed the reduction of GO to graphene. The SEM and TEM results also reconfirmed the reduction of GO into graphene, where GO exhibited different morphologies, i.e. hexagonal larger sheets than graphene. The antibacterial properties of the graphene were studied against two gram-negative and gram-positive bacteria. Graphene inhibited cell growth, which proves that our prepared graphene can be useful as an antimicrobial agent against different microorganisms. This work thus reports the design of a novel, facile synthetic route for a new production method of grapheneThis article was made possible by the NPRP grant # ( NPRP9-144-3-021 ) from the Qatar National Research Fund (a member of the Qatar Foundation).Scopu

Improvement of ternary recycled polymer blend reinforced with date palm fibre

This paper investigates the study and preparation of date palm fibre reinforced recycled polymer blend composites. This is the first paper which describes the recycled polymer ternary blends of (1) recycled low density polyethylene (RLDPE), (2) recycled high density polyethylene (RHDPE) and (3) recycled polypropylene (RPP). The date palm fibre reinforced composites (CD00) were prepared by maintaining constant weight% of fibre of 20wt% without any fibre treatment. Maleic anhydride (MA) was used as the compatabilizer (1 and 2wt%) and the effect of compatabilizer on the blend matrix composites was studied. The mechanical, thermal, morphological properties, water absorption and chemical resistance properties were evaluated for these composites and also studied for pure blend matrix (C00). Date palm fibre improved the tensile strength and hardness of recycled polymer blend matrix. Further improvement was achieved with 1% MA (CD1), which showed that 1% MA treated composites (CD1) had higher tensile strength, modulus and hardness properties. Thermal stability and water absorption were improved by 1% MA. These improvements were demonstrated at the nanoscale level by the decrease in roughness appearing in Atomic Force Spectroscopic Microscopy analysis indicating that flow is better under this concentration. The SEM analysis also showed that the fibre matrix adhesion improved by adding 1wt% (CD1) of MA. The melting and crystallisation temperatures of the blends did not change with the addition of date palm fibre and MA, indicating that the additives did not influence the melting and crystallisation properties of the composites. The chemical resistance test results showed that these composites are resistance to all chemicals but more weight gain observed in solvents. 2wt% of MA (CD2) caused poor adhesion between the polymer chains and fibres as well as polymer chain scission

Effect of chain structure on the properties of Glass fibre/polyethylene composites

Three types of polyethylenes (low density: LDPE, medium density: MDPE, and high density: HDPE) were used to investigate the effect of chain branching on the dispersion and adhesion in Glass fibre reinforced polymer composites. The interaction between the polyethylene matrix and the Glass fibres was investigated in terms of differences in mechanical behaviour, morphological characteristics, rheological and thermal properties between the three polymer composites systems. Addition of Glass fibres enhanced the mechanical properties for all systems. The degree of enhancement, however, depended on the branching and crystallinity of each polymer. The long chain branching (LCB) in LDPE resulted in higher increases both in the Elastic (Young’s) modulus in the solid state and in the Storage modulus in the melt. The higher crystallinity of HDPE was responsible for higher increase in tensile strength and less fibre pull-out upon addition of Glass fibres. Rheological results also confirm the same observation for LCB. The addition of Glass fibres also resulted in improved thermal stability of the various polyethylene samples

Processing, characterization and modeling of recycled polypropylene/glass fibre/wood flour composites

Polypropylene (PP) is one of the most common thermoplastic materials in the world. There is a need to recycle the large amount of this used material. To overcome the environmental problems, related to the polymer waste, PP was recycled and used as a matrix material in different composites that can be used in high value applications. In this paper, composites made of recycled polypropylene (RPP) reinforced by glass fibres and/or wood flour of the palm tree were prepared, characterized and modeled. The mechanical and thermal properties of these recycled polymer matrix composites (RPMCs) were measured experimentally and modeled theoretically. The mechanical properties included tensile modulus, tensile strength and hardness, whereas thermal properties included thermal stability, melting and crystallinity percentage content were studied. In addition we applied the functionally graded materials concept, the elastic finite element analysis of a layered functionally graded pressurized pipe, which is one of the practical industrial applications, was accomplished in order to have some insight on the performance of such RPMCs. The results reveal that the desired mechanical and thermal properties met the requirements of a wide range of practical applications which can be attained by adding the considered fillers. Also, the proper selection of the layers of the pressurized pipe, which was made of RPMCs, led to decrease of the induced stresses and accordingly increased the operational safety.Qatar Science and Technology Park (QSTP), Center for Advanced MaterialsScopu

Improved flexible, controlled dielectric constant material from recycled LDPE polymer composites

In this study, recycled low density polyethylene (RLDPE) is developed with the addition of aluminum oxide (Al2O3) to have new polymer composites. The following wt% were used of the filler (1, 4 and 6 wt%). Tensile properties, Hardness, scanning electron microscopy (SEM) thermo gravimetric analysis, differential scanning calorimetry and dielectric properties were studied for these composites. 4 wt% Al2O3/RLDPE composites showed the optimum values of 15.52, 180.8 and 59.72 MPa for the tensile strength, tensile modulus and hardness were reported. Increasing the filler % decreased the mechanical properties of the composites due to agglomeration and poor surface contact with the polymer matrix. This is confirmed by SEM studies. Al2O3 filler increased the melting and crystallization temperature of RLDPE. Furthermore, it showed that Al2O3 filler improved the thermal stability of RLDPE with increasing the % of filler. Relative permittivity, dielectric loss factor and AC electrical conductivity were increased with increasing the amount of the AL2O3. The relative permittivity reached a value of 4.9 at 1 kHz frequency, which is a good value for a flexible composite prepared from recycled material and it can be used in electrical devices and electronic packaging.This work was made possible by NPRP Grant No. NPRP5-039-2-014 from the Qatar National Research Fund (A Member of The Qatar Foundation)