One-shot formation

One-shot formation process. The plates are formed in assembled batteries filled with... 

Lapresta-Femandez A, Huertas R, Melgosa M, Capitan-Vallvey LF (2009) Multianalyte imaging in one-shot format sensors for natural water. Anal Chim Acta 636 210-217... 

The more usual method of formation is to completely assemble the battery, fill it with electrolyte, and then apply the formation charge. This method is used for SLI and most stationary and traction batteries. A variety of formation conditions are used, similar to those for tank formation. The two major formation processes are the two-shot formation process (used for stationary and traction batteries) and the one-shot formation process (used for most SLI batteries). In the two-shot formation, the electrolyte is dumped to remove the low-density initial electrolyte and refilled with more concentrated electrolyte, chosen so that when this is mixed with the dilute initial acid residue which is absorbed in the elements or trapped in the case, the cell electrolyte will equilibrate at the desired density (Table 23.11). Typical values of the electrolyte specific gravity at full charge after formation are given in Table 23.12. 

Siroc [Silicate rock] Also known as the one-shot system. A chemical grouting system for hardening ground formations. Aqueous solutions of sodium silicate and formamide are mixed and injected into the ground the formamide slowly reacts with the silicate, precipitating hydrated silica, which binds the soil particles together. Invented in 1961 by the Diamond Alkali Company. See also Joosten. 

For Lewis acid promoted living polymerization of MMA with (TPP)AlMe (1,X= Me) as initiator, a photoinitiation prior to the addition of the Lewis acid is required. This is because (1) 1 (X=Me) without irradiation does not have the ability to initiate the polymerization even in the presence of Lewis acid, and (2) all-at-once polymerization by direct irradiation of a mixture of MMA, 1 (X=Me), and the Lewis acid results in the formation of a relatively broad MWD PMMA with Mn much higher than expected. In this sense, the procedure using 1 (X= Me) as initiator is not convenient for practical application. In this section, we report on aluminum porphyrins with various axial ligands which were tested as initiators in order to realize a more convenient, one-shot high-speed living polymerization of methyl methacrylate with no need for irradiation with visible light. 

One-shot method In this process, the entire polymer formation may be carried out simultaneously mixing together polyol, diisocyanate and chain extender (along with catalysts). The PU formation through this route is schematically represented in Figure 4.9. 

One-shot polyether foams were studied, using a variety of catalysts. The formula contained 100 parts by weight of poly(oxypropylene)triol of 3000 M.W., 38 parts of 80 20-TDI, 2.9 of water, 0.3 of 4-dimethyl-aminopyridine, 0.5 of lV,iV-dimethylbenzylamine, varying amounts of metal catalysts, and 0.1 part of X-520 siloxaneoxyalkylene copolymer. All of the gas was evolved from these systems within 60 sec after mixing. Viscosity measurements were not satisfactory due to fracture of the polymeric phase. Analysis of the reaction mixture at the end of 55 sec reaction time indicated the relative rate of formation of various products, as indicated in Table 22. The importance of selecting the proper catalyst to avoid undesirable side reactions is readily apparent. The results shown in Table 22 indicate that both tin catalysts promote the isocyanate/water reaction more than the isocyanate/hydroxyl reaction in the system studied. This is unusual, since other reports, though often of dilute solution studies, have shown the tin catalysts to promote the isocyanate/ hydroxyl reaction more [145,147,196]. 

Comparison of the rate of formation of various chemical species in one-shot polyether foams during the first 55 sec. of reaction... 

Manufacturing Process. Both prepolymer and one-shot processes are available, but the polymeric isocyanate-based one-shot process is used in preference because of the easy processing due to the low viscosity of the system, relatively low toxicity of polymeric isocyanates, and fewer environmental problems. However, a disadvantage of the one-shot process is a possible risk of shrunken-foam formation due to its higher closed-cell content. In contrast, the TDI-based prepolymer process has advantages including better in-mold flowability and higher open-cell content. 

It will be realized from Chapter 1 that in urethane elastomer formation from liquid components there is the possibility of several reactions occurring simultaneously during a prepolymer or one-shot process, and that the relative proportion of one to the other will affect the overall properties of the final polymer. Thermoplastic and millable urethanes are not, during their processing and fabrication stages, subjected to the type of catalysis discussed in this chapter during their polymer synthesis operations, however, reaction rate-structure considerations will apply. 

The primary isocyanate reactions discussed earlier in Chapter 1 are exothermic and proceed in principle without reaction accelerators. The extreme reaction rates required in many of today s sophisticated polyurethane products, however, necessitate the employment of suitable catalytic systems. This is particularly true for one-shot polyurethane RIM where not only do the reactions have to be very fast but also a proper balance has to be established between the simultaneous reactions, in particular the polymerization reactions (polyol/isocyanate) and the foaming reaction (water/isocyanate). This balance is of extreme importance for the production of foam without collapse, caused by insufficient polymer strength at the end of gas evolution, or crevassing, caused by too slow gas formation or too fast gelation. 

Freshly prepared SSC was used in a series of one shot polymerizations using both cationic and anionic initiators as shown in Table I. The first entry C50N is a control experiment that demonstrates formation of a stable latex form the cationic monomer, styrene, and VBC with no sulfonate monomer. The next two entries were designed to give approximately equal amounts of (+) and (-) charges after quaternization, but both latexes were unstable at the precursor stage, perhaps because of partial hydrolysis of the sulfonyl chloride. When potassium persulfate was... 

Moulded cushions tend to have slightly better fire retardancy and better resilience properties than slab-stock products. Hot-cure and, more recently, cold-cure moulding techniques have allowed better control of the side reactions (such as formation of isocyanurate and allophanate cross-links). One-shot processing with low-pressure dual-component dispensing equip-... 

The reasoning which led the author to make this first shot in the dark regarding the usefulness of combinations of solid compounds as ammonia catalysts was as follows If we assume that a labile iron nitride is an interminate in the catalytic ammonia synthesis, every addition to the iron which favors the formation of the iron nitride ought to be of advantage. In other words, the hypothesis was used that surface catalysis acts via the formation of intermediate compounds between the catalyst and one or more of the reactants. An experimental support for this theory was the fact that a stepwise synthesis via the formation and successive hydrogen reduction of nitrides had been carried out with calcium nitrides (Haber), and cerium nitrides (Lipski). Later, the author found molybdenum nitride as being the best intermediate for such a stepwise synthesis. 

Determination of residual stress of a failed component is one of the most important steps in failure analysis. The determination of residual stress is useful when failed components experience stress concentration, overload, distortion or the formation of cracks in the absence of applied loads, subjected to corrosive environments as in stress corrosion, mechanical or thermal fatigue due to cyclic loading, or when faults in processing such as shot peening, grinding, milling and improper heat treatment such as stress relief, induction hardening, thermal strains, exposure temperature are involved. 

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