S. H. Hamid

Comparative Study of Solvents for the Extraction of Aromatics from Naphtha

An experimental investigation was carried out to evaluate the efficiencies of different selective solvents used for the extraction of aromatic hydrocarbons from naphtha (boiling range IBP-200°C) distilled from Saudi Arabian light crude oil. The solvents used were 3-methoxypropionitrile, ethylene glycol, dimethylsulfoxide, sulfolane, phenol, and nitrobenzene. The parameters studied were operating temperature (range 20°-125°C), solvent-to-oil ratio (range 1:1-3:1), selectivity, and solvent capacity. The results indicate that sulfolane exhibits excellent extraction properties in comparison with other solvents. In addition, sulfolane has the advantage of having good solvent properties such as high density, low heat capacity, and appropriate boiling point, which helps simplify separation of the solvent from extract. Sulfolane is also commercially feasible as a solvent for aromatic extraction.

Weather-Induced Degradation of Linear Low-Density Polyethylene: Mechanical Properties

Abstract Plastics degrade through the influence of such factors as the suns radiation, temperature, humidity, rain, the oxygen content of the air, and atmospheric pollutants. The most deleterious of these effects is radiation, which is responsible for breaking up polymer chains. The sun emits a complete spectrum of energy radiation, with waves similar in physical structure but varying in length and therefore in photon energy. Wavelength has an inverse relationship to quantum energy, as shown in Fig. 1.

WEATHER INDUCED DEGRADATION OF LINEAR LOW DENSITY POLYETHYLENE (LLDPE): MECHANICAL PROPERTIES

Unstabilized LLDPE is exposed to the natural weather of Dhahran, Saudi Arabia, and changes in its mechanical properties have been studied. It has been shown that Dhahrans weather is more damaging to exposed polyethylenes than other exposure sites in the world

Application of Infrared Spectroscopy in Polymer Degradation

Abstract Infrared (IR) spectroscopy has become a powerful tool for chemical and physicochemical characterization of polymeric materials. The growth in IR spectroscopy after 1945 was provided by development of reliable electronic amplifiers and radiation detectors. More recently new innovations have been made in this field with the commercial introduction of the computer-controlled Fourier transform infrared (FTIR) spectrophotometer.

Ultraviolet-induced degradation of Ziegler-Natta and metallocene catalyzed polyethylenes

The metallocene revolution has aroused a storm of interest and associated questions regarding the performance and durability of polyolefins. This new technology has impacted the additives used to stabilize and process polymers. In this work, Ziegler-Natta and metallocene polyethylene (PE) samples were exposed to natural weather conditions under high doses of ultraviolet radiation, high temperature, and increased humidity. Weather-induced degradation of the two sets of PEs was studied using gel permeation chromatography, mechanical properties testing, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The gel permeation chromatography analysis indicated the change in molecular weight distribution and molecular weights of metallocene PE to be more stable than conventional Ziegler-Natta PE. The tensile properties of metallocene PE are known to have higher values than Ziegler-Natta PE. The former exhibited a lower drop rate in mechanical properties when exposed to natural weather. Formations of nonvolatile carbonyl oxidation products, which absorb in the infrared region with a maximum absorbance level at 1742 cm−1 were determined. This indicated a higher rate of photo-oxidative and thermal degradation of Ziegler-Natta PE as compared with metallocene PE. The ultraviolet stabilization of metallocene PE may require different doses and a new kind of stabilizer system that can impart a longer useful lifetime and are cost effective for PE used for outdoor purposes.

Studies on a terephthalic acid and dihydroxydiphenyl sulfone liquid crystalline copolymer and its composites with different thermoplastics

A liquid crystalline polymer (LCP) was synthesized by an interfacial polycondensation reaction at room temperature from terephthaloyl chloride and p,p′-dihydroxydiphenyl sulfone. The LCP synthesized was so stable and molecularly rigid that it did not show any phase transition until it degraded at about 320°C. Composites of the LCP with polycarbonate (PC), polystyrene (PS), and sulfonated polystyrene (SPS) were formed by compression molding at a temperature at which the thermoplastic matrix was in the melt state. They were thermally analyzed by differential scanning calorimetry. Tensile specimens were cut from the compression-molded plates, and mechanical tests were performed. The morphology of the material systems was studied by performing scanning electron microscopy analysis on cryogenically fractured specimens. For LCP/PS and LCP/SPS systems, a sharp two-phase morphology was formed, which suggested poor interfacial adhesion. The tensile strength of both systems decreased with LCP addition. The LCP/PC system also revealed a two-phase morphology; however, the interfaces between the LCP domains and the PC matrix were not so well defined, showing better interfacial adhesion than the two previous systems studied. Stronger bonding between the LCP and PC resulted in a significant improvement in the mechanical behavior of PC by LCP addition.

Weather-Induced Degradation of LLDPE: Calorimetric Analysis

Abstract Studies of polymer degradation over the past decade have increasingly been carried out using thermoanalytical methods. These methods involve the measurement of a convenient variable during a gradual, linear increase in temperature. The most widely used of these techniques are thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The morphology of a polymer sample (i.e., the crystallinity, shape and size of the crystals, the structure of the surface of the crystals, and the strain of amorphous regions) influences the heat content and its dependence on temperature. The latter can be satisfactorily investigated by calorimetry measurement in a differential scanning calorimeter.

Weather-Induced Degradation of Plastic Pipes

Abstract A number of plastic materials, such as unplasticized poly(viny1 chloride) (uPVC), acrylonitrile-butadiene-styrene (ABS), high-density polyethylene (HDPE), poly-(vinylidene fluoride) (PVDF), and chlorinated poly(viny1 chloride) (cPVC), are available for numerous applications. uPVC and HDPE pipes are used in pressurized piping systems in Saudi Arabia for industrial, agricultural, domestic, and general-purpose applications. Some studies have been carried out to investigate the causes of failure in plastic pipes, which is very high in the area. In this chapter an overview of the failure of plastic pipes is presented, with emphasis given to failure of pipes due to severe weather conditions in Saudi Arabia.

Effect of MTBE blending on the properties of gasoline

ABSTRACT The effect of blending MTBE in the gasoline was evaluated. MTBE effectively boost the octane numbers of gasoline without adversely effecting its other properties. However, MTBE is not as efficient as leadalkyl compounds as far as the specific octane number improvements are concerned. The addition of 5 to 30 volume percent MTBE increases 1.9 to 11.8 RON of a typical gasoline. MTBE addition also extends the volume of gasoline produces for a given crude by adding volume to the gasoline pool. MTBE provides much higher FEON to the gasoline in comparison with other gasoline components. A higher FEON increases the efficiency of the engine. MTBE is not affected by the lead level of the gasoline. For this reason, lost octane in future lead reductions of the gasoline in Saudi Arabia can be made up with MTBE. MTBE addition to the Saudi gasoline increases the RVP but within the specification of the gasoline. MTBE has favorable effect on the distillation characteristics of the gasoline. MTBE addition lowers t...

A study of the effect of polystyrene sulfonation on the performance of terephthaloyl chloride-dihydroxydiphenyl sulfone copolymer/polystyrene system

Thermal, morphological, and mechanical properties of composites of a liquid crystalline copolymer (LCP) poly(terephthaloyl chloride)-co-(p,p’-dihydroxydiphenyl sulfone) with polystyrene (PS) and sulfonated polystyrene (SPS) are presented and discussed. Sulfonation of polystyrene was expected to improve the interfacial adhesion by introducing hydrogen bonding in the LCP/PS system. The degree of sulfonation was 11 %. The incompatibility (lack of proper interfacial adhesion) of the LCP/PS system resulted in sharp decrease in the composite tensile strength with LCP addition. The performance of the system did not change when processed at a higher temperature (270 °C instead of 225 °C). While a composite plate of 25% LCP/PS could not be fabricated, it was possible for LCP/SPS (processed at 215 °C), indicating some improvement in interfacial bonding by sulfonation. Sulfonation of PS resulted in fracture with some degree of plastic deformation for pure SPS matrix and also the LCP/SPS system with the lowest LCP content (1 wt%), whereas plastic deformation was not observed for PS used as received. The strength of the LCP/SPS system also decreased with increase in LCP content, indicating that 11% sulfonation is not sufficient to introduce significant compatibility, but it was not as dramatic as that for LCP/PS. The performance of the LCP/SPS system was not affected significantly by heat treatment at the process temperature.