Ilias Ali

A REVIEW OF THE APPLICATIONS OF NANOCARBON POLYMER COMPOSITES

Nanotechnology offers fundamentally new capabilities to architect a broad array of novel materials, composites and structures on a molecular scale. It is potentially capable of redefining the methods used for developing lighter, stronger, high-performance structures and processes with unique and nontraditional properties. This review summarizes different classes of nanocarbon-based polymer composites and their applications. Also, it highlights different ways to create smaller, cheaper, lighter and faster devices using nanocarbon-based polymer composites. The potential applications of such materials are in the fields of membrane, aviation, electronics, polymer composites, as well as the marine and transport industries. A detailed description of nanocarbon-based composite materials manufactured from PE, PP, PS, PS, PVC, PPS, ABS, PMMA, nitrile rubber, etc. is also reviewed. Some of the major applications of carbon-based polymer nanocomposites are in the tyre industry, semiconductors, and many more, which has brought about the new, developing and exciting research field called nanoscience.

Covering Materials Incorporating Radiation-Preventing Techniques to Meet Greenhouse Cooling Challenges in Arid Regions: A Review

Cooling greenhouses is essential to provide a suitable environment for plant growth in arid regions characterized by brackish water resources. However, using conventional cooling methods are facing many challenges. Filtering out near infra-red radiation (NIR) at the greenhouse cover can significantly reduce the heating load and can solve the overheating problem of the greenhouse air. This paper is to review (i) the problems of using conventional cooling methods and (ii) the advantages of greenhouse covers that incorporate NIR reflectors. This survey focuses on how the cover type affects the transmittance of photosynthetically active radiation (PAR), the reflectance or absorptance of NIR and the greenhouse air temperature. NIR-reflecting plastic films seem to be the most suitable, low cost and simple cover for greenhouses under arid conditions. Therefore, this review discusses how various additives should be incorporated in plastic film to increase its mechanical properties, durability and ability to stand up to extremely harsh weather. Presently, NIR-reflecting covers are able to reduce greenhouse air temperature by no more than 5°C. This reduction is not enough in regions where the ambient temperature may exceed 45°C in summer. There is a need to develop improved NIR-reflecting plastic film covers.

Thermotropic poly(azomethine-urethane)s with non linear optical properties: Synthesis and characterization

Two series of the thermotropic main chain poly(azomethine-urethane)s were synthesized by the polyaddition of azadiol, 1,8-octandiol with methylene bis(phenyl isocyanate) (MDI) and tolylene 2,4-diisocyanate (TDI) respectively. The mesomorphic properties and phase transition temperature of the polymers were characterized by differential scanning calorimetry and hot stage polarizing microscopy. These polymers showed nematic messophase. The non linear optical (NLO) activity of the polymers was also investigated.

Preparation and characterization of poly(lactic acid)/elastomer blends prepared by melt blending technique

Poly(lactic acid) (PLA) and biodegradable elastomer were melt blended and molded in an injection molding machine. The crystallinity, viscoelasticity, thermal and mechanical properties of the molded blend and annealed blend samples were studied. Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the melting temperature decreased as the amount of elastomer increased. Additionally, the presence of elastomer tended to increase the crystallinity of PLA at 10 and 20 wt%. The injection molding led to the diminishing of neat PLA crystallinity to be 20.79%; however, annealing could recover it to be 29.94%. This result was supported by x-ray diffraction and dynamic mechanical analysis tests. The complex viscosity and storage modulus of PLA melt decreased upon addition of elastomer. The elongation at break increased as the content of elastomer increased. However, the Young’s modulus and tensile strength decreased severely due to the addition of elastomer.

Different factors affecting the mechanical and thermo-mechanical properties of HDPE reinforced with micro-CaCO3:

In this study, we manufactured the HDPE/micro-calcium carbonate (CaCO3) composites. A twin screw extruder was used to melt blend different loadings of CaCO3 masterbatch, from 5% to 20%, with HDPE. Furthermore, injection-molded samples were manufactured using different molding conditions, namely pressure and cooling time. The presence of CaCO3 increased the viscosity and the stiffness of the composites. The viscoelastic analysis indicated that adding more than 15% on the CaCO3 masterbatch apparently affected the way the material behaves, as indicated by an abrupt change of some properties of the composite containing 20% masterbatch. As the molding pressure and cooling time increased, the shrinkage of the molded samples decreased. The tensile strength and the ductility of the composite decreased as the content of the CaCO3 increased and as the cooling time or the molding pressure decreased. The fracture surface of all samples had the characteristic dimples of polyethylene fracture; however, neat resin showed extensive fibrillation which was absent at high loadings of CaCO3.

Effects of aqueous extraction on the performance and properties of polypropylene/wood composites from Phoenix dactylifera and Acacia tortilis wood

Polypropylene/wood composites were prepared by melt blending technique using a twin screw extruder and subsequently ASTM samples were also prepared by injection molding technique. Untreated and pre-treated particles of Phoenix dactylifera and Acacia tortilis woods are used in this study to investigate the effect of pre-treatments on the different properties of polypropylene/wood composites. The tensile strength of the wood composites was evaluated by ASTMD-638 method and it was found to be higher than the neat polypropylene. The effect of incorporation of wood particles on the melting temperature (T m ), crystallization temperature (T c ) and relative crystallinity (X c ) was also studied and reported. The viscoelastic properties of the PP/wood composites were evaluated. The temperature sweep experiments reveals that the composites storage modulus (G′) has higher values than the neat polypropylene at elevated temperature. The water uptake test showed that the composite samples have improved water repletion properties. Water uptake of untreated PP/date palm composites increased from 0.042% after 2 h to 0.12% after 120 h of immersion time. Pre-treated date palm reduced water uptake to 0.077% after 120 h of immersion time. Similar trend was also observed for the composites prepared from A. tortilis wood. The interaction between the wood and the polymer matrix was characterized by Fourier transform infrared spectroscopy technique. The interfacial and the distribution of the wood particles in the polymer matrix were also investigated by scanning electron microscopy.

Improvements in barrier properties of poly(ethylene terephthalate) films using commercially available high barrier masterbatch additives via melt blend technique

Poly(ethylene terephthalate) films which contained commercially available masterbatch additives were prepared by melt processing. Three different commercially available additives were selected, of which two of them significantly improved the oxygen and water vapour barrier properties. The additives did not significantly alter the optical, crystallization and melt rheological properties. The diffusion mechanism of oxygen and carbon dioxide gases through the polymer matrix is also explained. This article discusses the improvements in barrier properties of poly(ethylene terephthalate) films which can be used for food packaging applications with emphasis on preparation, characterization, properties and diffusion mechanism.

Characterization of poly(lactic acid)/hydroxyapatite prepared by a solvent-blending technique Viscoelasticity and in vitro hydrolytic degradation

Poly(lactic acid) (PLA) was solvent blended in a chloroform solution using multiple weight fractions of hydroxyapatite (HAp) (5, 10, and 20 wt%). A miniature laboratory mixing extruder equipped with a ribbon die was used to produce thin ribbons of PLA/HAp biocomposites. The dynamic mechanical parameters (storage modulus (G′), loss modulus (G′′), complex viscosity (η*), and degree of crystallinity) increased with increasing HAp loading. In vitro hydrolytic degradation of the PLA biocomposites was conducted in a 0.01-M phosphate-buffered saline solution at 37°C. The presence of HAp tended to increase both the hydrolytic degradability of the PLA and the crystallinity, possibly resulting from the hydrophilicity of the HAp. The thermal stability of the PLA was slightly higher in the composites with HAp. Following hydrolytic degradation, several microholes and cracks appeared on the surface of these biocomposites, as observed by scanning electron microscopy. The Coats–Redfern method was used to evaluate the thermal degradation kinetics of the biocomposites with support from a chemical reaction model. From this evaluation, the activation energies of the biocomposites were found to exceed that of the neat PLA. These energies were observed to decrease after the hydrolytic degradation process.