ABSTRACT:In this study, the heat-shrinkage property in polymer was induced by first compounding low-density polyethylene/poly(ethylene vinyl acetate) (LDPE/EVA) blends with various amounts of peroxide in a twin-screw extruder at about 130°C. The resulting granules were molded to shape and chemically crosslinked by compression molding. A process of heating-stretching-cooling was then performed on the samples while on a tensile machine. Shrinkability and effective parameters were also investigated using thermal mechanical analysis. The results showed that the gel fraction was higher for the sample of higher EVA content with the same amount of dicumyl peroxide (DCP). A decrease in the melting point and heat of fusion (⌬H f ), as determined from DSC, was observed with an increase in the DCP content. Studies on the heat shrinkability of the samples showed that samples stretched above the melting point had a higher shrinkage temperature than those stretched around the crystal transition temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. These could be attributed to the formation of new spherulites as well as changes in the amount and the size of crystals. Furthermore, in samples elongated at 120°C (above the melting point), the rate of stretching had no effect on the shrinkage temperature. The results showed that the extent of strain had no effect on the temperature of shrinkage, but rather on the ultimate shrinkage value.

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Absorption is one of the most established processes for CO2 capturing. However, the current technologies used in this process suffer from several drawbacks. Meanwhile, the ultrasound technique is proposed as a new alternative technology to assist the CO2 absorption process due to both its physical and chemical effects. Yet, the chemical effect is still under developments. Between all the influencing parameters, the ultrasonic power and the frequency are the vital key parameters to investigate sonochemical effects during the CO2    absorption process. The aim of this paper is to measure the ultrasonic power of an ultrasonic vessel. The total electrical power measured by using the voltage and the flow. Simultaneously, the ultrasonic power determined by using the calorimetric method. The measurements were done by using water with different volumes and repeated for three different frequencies. The results showed that almost 51% of the electrical power converted into the ultrasonic power and were independent of liquid volume.

Chemical absorption is the most matured and preferred separation process which is extensively used for CO 2 removal from natural gas. The current contactor systems used in the absorption process suffer from several drawbacks including excessive footprint, operating, and maintenance issues. Ultrasonic irradiation is a new alternative technique to assist the CO 2 absorption process without the aforementioned limitations. Thus, the aim of this paper is elucidating the potential of the ultrasonic-assisted CO 2 absorption system. To achieve this, the performance of the ultrasonic-assisted system was compared to that of the conventional stirring method. Two different solvents with dissimilar reaction mechanisms were chosen. The first part of the experiments was conducted in the ultrasonic-assisted batch vessel, while the second part was accomplished in the stirred batch cell. The parameters including ultrasonic power, ultrasonic frequency, stirring speed, and initial feed pressure were 18 W, 1.7 MHz, 500 rpm, and 11 bar, respectively. Besides, the operating temperature and the concentration were chosen based on the standard operating condition for each solvent. The mass transfer coefficient was calculated using the dynamic pressure-step method. The results revealed that in comparison with the stirring method, the ultrasonic-assisted absorption system significantly enhanced the CO 2 absorption process at similar operating conditions. By using ultrasonic irradiation, the volumetric absorption coefficient increased almost three times for MDEA and nearly six times for MEA. In the latter, this improvement can be related to the physical effect of the ultrasound. However, for the slow kinetic solvents, this improvement might be attributed to the chemical effect of the ultrasound.

Ultrasonic Irradiation (UI) is an emerging technology that is used to assist the CO2 absorption process. Even for the slow kinetic solvents without using any chemical promoter, high-frequency UI might enhance mass transfer during the absorption process. For this purpose, it is essential to study the performance of a high-frequency ultrasonic-assisted absorption system under varied operating conditions. The ultrasonic power is considered as one of the main parameters during the absorption of CO2. Thus, in this paper, the influence of ultrasonic power is presented using Methyl diethanolamine (MDEA) as a chemical solvent. The ultrasonic power has been varied from 0 to 15.3 W. The results tend to show a significant absorption rate enhancement for higher ultrasonic power. Moreover, they prove that the high-frequency ultrasonic absorption system has high potential to be utilized to enhance the absorption using promoter-free MDEA.