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Contemporary Machining Processes for New Materials
Published in E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan, Remanufacturing and Advanced Machining Processes for New Materials and Components, 2022
E. S. Gevorkyan, M. Rucki, V. P. Nerubatskyi, W. Żurowski, Z. Siemiątkowski, D. Morozow, A. G. Kharatyan
Physical blowing agents in a liquid or gaseous state under pressure are injected into a molten polymer, mainly inside a plasticating cylinder. The counterpressure in the cylinder prevents the mixture from bubbling, so that gas is solved in the polymer molt reducing its viscosity. It should be noted, however, that the effect on viscosity is dependent on many factors. It was demonstrated that mass fractions of blowing agents propane and carbon dioxide below 2 wt% had little to no effect in regard to viscosity reduction of a polypropylene melt, but a mass fraction of 3.5 wt% resulted in significantly decreased viscosity values (Vincent et al., 2020). Injected into a mold cavity, a polymer melt is foaming due to the lack of counterpressure, forming pores in the polymer. Usually, supercritical carbon dioxide (scCO2), nitrogen, and air, but also various ecological gas mixtures are applied as processing solvents. The Montreal Protocol and its subsequent amendments to the Vienna Convention for the Protection of the Ozone Layer have led to the introduction of “second-generation” blowing agents, such as hydrofluorocarbons (HFCs) or hydrocarbons. Zero ozone-depleting hydrocarbon blowing agents comprise n-pentane, isopentane, or cyclopentane (Höfer, 2012). Application of some other blowing agents, such as methylene chloride, becomes more and more limited under the air toxics legislation within various states considering it a suspected carcinogen (Kaufman and Overcash, 1993; Jimoda, 2011).
Theory of Radiation-Induced Cracking Reactions in Hydrocarbons
Published in Yuriy Zaikin, Raissa Zaikina, Petroleum Radiation Processing, 2013
The bar graph of cyclopentane derivative distribution in the RTC gasoline fraction (Figure 2.46) shows that the original oil contained a considerable amount of trimethyl-substituted cyclopentane (14.35%). Cyclopentane and methyl cyclopentane were absent in the original feedstock. Appearance of these compounds in the irradiation products testifies not only to the energetic breaks of C-C bonds in the long-chain structures but also to the dissociation of the C-C bonds of the alkyl substituents in the rings. The formation of such compounds as propyl-, i-propyl, methyl propyl-, butyl-, and methyl butyl cyclopentanes is also a result of radiation-induced cracking reactions. Formation of these compounds due to interactions of radicals,
Feedstock Composition and Properties
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Saturated cyclic hydrocarbon derivatives (cycloparaffins), also known as naphthenes, are also part of the hydrocarbon constituents of crude oils. The ratio, however, depends on the type of crude oil. The lower molecular weight members of naphthenes are cyclopentane, cyclohexane, and their monosubstituted compounds. They are normally present in the light and the heavy naphtha fractions. Cyclohexane derivatives, substituted cyclopentane derivatives, and substituted cyclohexane derivatives are important precursors for aromatic hydrocarbon derivatives. The higher-boiling petroleum fractions such as kerosene and gas oil may contain two or more cyclohexane rings fused through two vicinal carbon atoms (Speight, 2014a).
Progress in research on dispersants in gas hydrate control technology
Published in Journal of Dispersion Science and Technology, 2023
Yue Qin, Liyan Shang, Rencong Song, Li Zhou, Zhenbo Lv
A previous study[54] found that adding fumed nano-silica particles to a liquid cyclopentane (CP) system resulted in the formation of Pickering emulsions, which are emulsions dispersed only by particles. Moreover, it was found that when the particle concentration was less than 0.05 wt%, the particles were insufficiently covered on the oil-water interface; this hindered the formation of a stable emulsion. This is due to the Coulomb repulsion between the particles and the interface. Adding an appropriate amount of particles is sufficient for stabilizing the colloid, and a strong hydration reaction will occur due to the formation of an electric double-layer. However, Tcholakova et al.[103] found that adding salt to the oil-water system could provide an electrostatic barrier for particle adsorption, effectively shielding the electrostatic repulsion and hydration repulsion; thus, the particles could approach and eventually be adsorbed on the oil-water interface. At the same time, the addition of salt can promote flocculation or aggregation, which not only stabilizes the emulsion but also inhibits hydration.
Numerical and experimental investigation of liquid blowing agent and pentane blowing agent effects on the insulation of a household refrigerator
Published in Science and Technology for the Built Environment, 2021
Gizem Duru, Dilek Kumlutaş, Hasan Avci, Utku Alp Yücekaya, Özgün Özer
In the literature, the investigations on the blowing agents related with the heat transfer are generally made using experimental methods with polyurethane samples. Zhang et al. studied 5 PU samples formed by different blowing agents of CP (cyclopentane), CP + IP (cyclopentane + isopentane), CP + 245fa (cyclopenmettane + pentafluoropropane), CP + 245fa with lower gas pressure and CP + 245fa + LBA (cyclopenmettane + pentafluoropropane + liquid blowing agent) which are composed of HFC and HFO. Thermal conductivities were measured using a transient plane source method under various environmental conditions like long time storage, high & low temperature, and humidity. As a result of the study, the effects of all types of blowing agents' thermal performance on PU foam samples were revealed (Zhang et al. 2017).
Influence of lubricants on the performance of journal bearings – a review
Published in Tribology - Materials, Surfaces & Interfaces, 2020
Sunil Kumar, Vijay Kumar, Anoop Kumar Singh
Okaniwa and Hayama [117] compared ionic liquid lubricants with currently used space lubricants such as Perfluoropolyether (PFPE) and Multiplyalkylated-cyclopentane (MAC). Ionic liquids were proposed as possible base oil for space lubrication. Later on, Kobayashi [118] studied the antiwear performance of ionic liquid lubricants for space mechanisms and at −80°C and found similar to that of MAC and much better than that of PFPE. This mixture prevented metal to metal contact at a low temperature due to its high viscosity and high adsorption of molecules. The lubrication performance was evaluated with two types of vacuum tribometers; a reciprocating linear motion tribometer and unidirectional rotation tribometer. Ionic liquids possessed low vapour pressure and excellent thermal stability.