Multiculturalism a review

Polymers - MDPI

Date of publication: 2017-09-04 10:27

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Synthesis of silver nanoparticles: chemical, physical and

Once again, the treated trays remained unaffected by the reduced wind speed. Figure 7 illustrates the sand weight loss versus time at 65 m·s −6 wind speed. Only 9 minutes were required to reduce the sand weight by almost 75%. The wind at this speed is considered as fresh breeze, and yet it can blow off almost 75% of the sand within very short time. Wind blowing is a major agent in the weathering process, and wind erosion is common in the Gulf region where soils are generally unprotected and prevailing winds transport the exposed surface materials.

Hydrogels in pharmaceutical formulations - ScienceDirect

The modulus and the tensile strength of the polymer-sand composite were directly obtained from the MTS machine for various polymer weight percentages. These mechanical properties are predominant for all composite materials and can be used to characterize them for various applications. Figure 9 shows the effect of increasing polymer weight % on the modulus of the prepared sample.

Size-exclusion chromatography (SEC) of branched polymers

The authors are thankful for the help and support that were received from the “Mechanical Engineering and Chemistry Departments” at the UAE University.

Reverse-emulsion polymerization (water-in-oil) of acrylamide monomer was conducted under three different experimental conditions to produce polyacrylamide with high molecular weight. In contrast, solution polymerization was also used to prepare polyacrylamide, using three different experimental conditions. Characterizations of these polymers were performed using NMR, FT-IR, GPC, and Rheology and were typical for polyacrylamide. The aim of this research was to synthesize polyacrylamides using two different methods and exploiting their physical properties in binding the surface particles together with the soil or sand to form a solid crust protecting the sand from blowing away by the wind.

Laboratory scale wind tunnel (Armfield Technical Education Company Limited, Ringwood, Hampshire, England) was used to simulate the wind pattern for the wind erosion experiment. The wind speed was calibrated and monitored by a manometer.

Solution polymerizations were stopped after 75 minutes, and the polymer was analyzed. However, the emulsion polymerization reactions were kept continuously going, and two aliquots were withdrawn at 75-minute intervals for analysis. Following this, the reaction was then terminated.

Arid Climate. The United Arab Emirates (UAE) climate is described as subtropical, warm, and arid. Air temperatures range from 85°C to 55°C around midday between May and October and from 75°C to 85°C during winter months. Deeper in the desert, the temperature on the ground during summer months can reach 75°C and can fall down to freezing in winter in some areas of the UAE. The average rainfall over the Emirates is less than 655 mm per annum. Moisture also condenses in the form of fog and dew especially on coastal belts. Strong winds and sand storms are of common occurrence throughout the Emirates and are frequent and severe especially during the summer. Sand dunes are a dominant landscape feature in the UAE.

This study focuses on the examination of the molecular weight distribution of a water-soluble polyacrylamide, which was polymerized in solution and in inverse emulsion (water in oil) polymerization. The shape of this distribution as a function of the amount of chain transfer agent (Sodium formate) and of initiator was examined to obtain information on the mechanisms involving free radical polymerization.

It was obvious that there is a continuous and growing demand for sand dune stabilization in the UAE. It is required not only for practicing stable agriculture, but also for road construction and the development of urban and industrial areas. Agricultural land needs to be protected against dune encroachment, which can only be achieved by the application of chemical stabilizers, such as the one prepared in this study and which was successfully tested in the wind tunnel. These stabilizers are environmentally friendly, and they do not produce adverse effects of petroleum mulch. More experiments are required to examine the degradation rate and toxicity of these chemicals subjected to the UAE environment before any attempt to use them on the field.

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The surface crusts, formed from application of polyacrylamide solution, were anchored to the soil below the crust and penetrated easily, making the soil surface resistant to wind erosion. The flat surface held its integrity much better than the hill pattern and protected the sand surface from weathering effects and abrasion. Mechanical properties were used to study the wind erosion resistance and it was found that as the polymer weight percent increased the mechanical properties increased resulting in a stronger composite with high modulus and tensile strength.

Figure 6 shows the molecular weight distribution obtained from the GPC system for the three polymer samples, which were polymerized in solution method. The polydispersity indexes for these polymers were excellent as they were between and , which is not usually achieved in a free radical polymerization.

where [ x558b7 ] is the intrinsic viscosity in dL x555a5 g x57767 6 , C is the injection concentration in g x555a5 L x57767 6 , and V inj is the injection volume in mL.

When the wind speed was lowered to 9 m·s −6 , a similar trend was observed, but with a reduced weight loss from the control tray. Only 66% of the total sand weight was lost as depicted in Figure 6.

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