Thermal Pyrolysis of Polystyrene Aided by a Nitroxide End-Functionality Improved Process and Modeling of the Full Molecular Weight Distribution

A significantly improved thermal pyrolysis process for polystyrene (PS) is reported and mathematically modeled, including the description of the time evolution of the full molecular weight distribution of the polymer during its degradation by direct integration of the balance equations without simplifications. The process improves the styrene yield from 28–39%, reached in our previous report, to 58–75% by optimizing the heating ramp during the initial stage of the pyrolysis process. The process was tested at 390 and 420 °C on samples of conventional PS synthesized via free-radical polymerization (FRP) and PS with a nitroxide end-functionality synthesized via nitroxide mediated polymerization (NMP) with three levels of the nitroxide to initiator (N/I) molar ratio: 0.9, 1.1 and 1.3. The NMP-PS produced with N/I = 1.3 generates the highest styrene yield (75.2 ± 6.7%) with respect to the best FRP-PS yield (64.9 ± 1.2%), confirming the trends observed in our previous study. The mathematical model corrects some problems of a previous model that was based on assumptions that led to significant errors in the predictions; this is achieved by solving the full molecular weight distribution (MWD) without assumptions. The model provides further insight into the initial stages of the pyrolysis process which seem to be crucial to determine the chemical paths of the process and the styrene yield, as well as the influences of the initial heating ramp used and the presence of a nitroxide end-functionality in the polymer.

Design and Development of Microcontroller Based Electromagnetic Induction Injera Mitad Prototype

Injera is flat, thin, soft, usually circular bread like staple food for most Ethiopians. Its cooking process islong and sensitive to environmental conditions. Injera baking requires temperature ranging from 150oC to 180oC. To generate this temperature, most people use biomass products, whereas thosehaving access to grid connection use locally manufactured traditional electric injera mitad which uses Nickel–Chrome resister as heat source. This electric clay mitad consumesat an average 3 – 3.5 KWand has low efficiency. To improve power consumption and efficiency of injera cooking mitad, the author developed Electromagnetic Induction Injera Mitad prototype. The prototype operation is based on laws of electromagnetic induction. After complete assembly of the components, a series of lab and field tests were conducted and it was observed that, for a similar injera quality, the initial heating up time was reduced to 45%, the power consumption was reduced to 50%, and the efficiency was increased around 30% comparedto that of traditional electric injera mitad.

Synthesis of Gold Nanoparticles by using Batch Method and Study its Antibacterial Activity

The research involves preparing gold nanoparticles (AuNPs) and studying the factors that influence the shape, sizes and distribution ratio of the prepared particles according to Turkevich method. These factors include (reaction temperature, initial heating, concentration of gold ions, concentration and quantity of added citrate, reaction time and order of reactant addition). Gold nanoparticles prepared were characterized by the following measurements: UV-Visible spectroscopy, X-ray diffraction and scanning electron microscopy. The average size of gold nanoparticles was formed in the range (20 -35) nm. The amount of added citrate was changed and studied. In addition, the concentration of added gold ions was changed and the calibration curve was calculated used to estimate Au ions in different samples. The effectiveness of gold nanoparticles prepared according to Turkevich method was studied as antibacterial agents against E. coli bacteria. The minimum inhibition concentration of gold nanoparticles that inhibit bacterial growth was calculated using the broth dilution method, which is based on several dilutions to determine the inhibition concentration.

Material-dependent ultrasonic heating behavior during the reshaping of dry paper webs

The use of ultrasonic tools during the reshaping of dry paper webs results in a temperature increase. This work aimed to determine the influence of the material and the ultrasonic process parameters of amplitude, ultrasonic duration, and static process pressure on the heating behavior of paperboard during ultrasonic-assisted reshaping. The results showed that the initial process pressure, the ultrasonic amplitude, and the compression resistance of the material noticeably influenced the heating rate. Materials with low compression resistance tended to reach higher initial heating rates during ultrasonic treatment. In addition, coating the paperboard led to an even temperature distribution in the paperboard during the ultrasonic process.

ТЕХНОЛОГИЯ, КИНЕТИКА ТВЕРДЕНИЯ, ПРОЧНОСТЬ И СВОЙСТВА ТЯЖЕЛОГО БЕТОНА С ПОЛИФУНКЦИОНАЛЬНОЙ КОМПЛЕКСНОЙ ДОБАВКОЙ

В материале статьи приведены результаты исследований влияния на кинетику твердения и свойства тяжелого бетона разрабатываемой полифункциональной комплексной добавки, содержащей пластификатор, ультрадисперсный микрокремнезем (УДМК) и ускоряюще-уплотняющий компонент, с целью повышения темпа роста и уровня прочности бетона на основе формирования более плотной структуры цементного камня и зон его контакта с поверхностью зерен заполнителя. Экспериментально подтверждена эффективность предлагаемой добавки при ее применении как в высокопрочном, так и в рядовом по прочности бетоне с целью повышения темпа и уровня роста прочности, снижения энергетических затрат в технологии производства бетонных и железобетонных изделий и монолитном строительстве, повышения плотности и непроницаемости, а на этой основе качественных характеристик бетона водонепроницаемости, морозостойкости и защитной способности по отношению к стальной арматуре. Показана возможность значительного снижения энергетических затрат на прогрев бетона с полифункциональной комплексной добавкой за счет использования термосного режима его твердения с начальным разогревом до 30...35 С и последующей выдержки в тепловом устройстве без подвода тепла. В этих условиях бетон с полифункциональной комплексной добавкой при прогреве по режиму 2 ч. предварительной выдержки, 2 ч. подъема температуры и 12 ч. выдержки в тепловом устройстве набирает прочность на уровне 80...90 от проектной (28 суточной), что достаточно не только для передачи преднапряжения арматуры на бетон, но и для отпуска изделий потребителю. В исследованиях использовали стандартизованные методики оценки прочности и эксплуатационных свойств бетона.The article presents the results of studies on the kinetics of hardening and the properties of heavy concrete being developed by a multifunctional complex additive containing a plasticizer, ultradispersed microsilica (UDMS) and an accelerating compaction component in order to increase the growth rate and level of concrete strength based on the formation of a more dense cement stone structure and zones of its contact with the surface of the aggregate grains. The effectiveness of the proposed additive was experimentally confirmed in its application both in high-strength and ordinary concrete in terms of strength in order to increase the rate and level of strength growth, reduce energy costs in the production technology of concrete and reinforced concrete products and monolithic construction, increase density and impermeability, and on this basis, the quality characteristics of concrete - water resistance, frost resistance and protective ability in relation to steel reinforcement. The possibility of a significant reduction in energy costs for heating concrete with a multifunctional complex additive is shown, due to the use of the thermos mode of its hardening with initial heating to 35 ... 40 C and subsequent aging in a thermal device without heat supply. Under these conditions, concrete with a multifunctional complex additive during heating according to the mode: 2 hours of preliminary exposure, 2 hours of temperature rise, and 12 hours of exposure in a thermal device gains strength at 80 ... 90 of the design (28 days), which is not only enough for transferring prestressing of reinforcement to concrete, but also for dispensing products to the consumer. The studies used standardized methods for assessing the strength and performance properties of concrete.

Powder interlayer bonding of geometrically complex Ti-6Al-4V parts

Powder interlayer bonding (PIB) is a novel joining technique, which has been developed to facilitate high-integrity repairs of aerospace components, manufactured from commonly used titanium alloys. The PIB technique utilises an interlayer between complex geometric components which are mated under pressure and a highly localised heating source. In this study, induction heating enabled bonding in an inert fusion zone by use of an oxygen-displacing shielding gas, with particular attention to the initial heating and pressure application. These early stages proved crucial to the elimination of pores and consolidation of the alloy powder, with porosity volume fraction reduced to just 0.5% after just 20 sec at the bonding force. The technique has produced high-integrity bonds in alloys such as Ti-6Al-4V, retaining approximately 90% of the alloy strength in previous studies, offering advantages over established joining methods such as tungsten inert gas (TIG) and plasma arc (PA) welding due to a more highly localised heating and fusion zone. It is believed that powder interlayer bonding can compete against these techniques, providing a more time and cost-effective repair route for net shape components manufactured from a range of alloys with minimal post-processing.

ANALYSIS OF THE COMBINED HEAT PUMP HEATING SCHEMES USING THE HEAT OF ATMOSPHERIC AIR AND HOUSE SEWAGE

The method of analysis of the system of heat pump heating using the heat of sewage of the building and atmospheric air as sources of heat is outlined in this article. A thermodynamic analysis of the heating circuit was made, in which a dependence was obtained for determining the ratio of the thermal flow introduced into the evaporator with atmospheric air to the total heat consumption for heating. It is shown that the scheme of heat pump system with the use of additional heat of sewage is more effective than the initial heating scheme. The correlation for determining the total specific energy expenditure for the heat pump system using the heat of atmospheric air and sewage is obtained. It is determined that when using this scheme at the stage of design of the system of heat pump heating it is possible to significantly reduce capital and operating costs. The use of obtained dependencies in the development of heat pump systems will ensure the maximum energy efficiency of their operation. Bibl. 7, Fig. 4.

Identification of the influence of the heating upon the heat transfer during pyrolysis process used for End-of-Life tires treatment

End-of-Life tires (EOLT) are waste that does not practically decompose in nature and because of this their sound treatment is needed for environment protection. One of the possible methods for such a treatment is pyrolysis process. Globally, around 23% of all EOLT are processed through pyrolysis, whereas in the Republic of Bulgaria only 5% are processed by pyrolysis. This shows that for Bulgaria this method pyrolysis still has a good potential for development and further research. In our previous paper [1], an adequate mathematical model of non-stationary heat transfer during pyrolysis used for the treatment of end-of-life tires has been developed. A numerical algorithm has been also developed in MATLAB to solve the respective mathematical initial and boundary value problems. In this study on the base of the previously developed model we examine the temperature regimes in the pyrolysis station with three cameras and their strong dependence upon the characteristics of the initial heating. Results for the temperature fields, temperature isolines and gradients for different kind of initial heating of the process are presented and commented.