Delay addition

When a fiber is stressed, the instantaneous elongation that occurs is defined as instantaneous elastic deformation. The subsequent delayed additional elongation that occurs with increasing time is creep deformation. Upon stress removal, the instantaneous recovery that occurs is called instantaneous elastic recovery and is approximately equal to the instantaneous elastic deformation. If the subsequent creep recovery is 100%, ie, equal to the creep deformation, the specimen exhibits primary creep only and is thus completely elastic. In such a case, the specimen has probably not been extended beyond its yield point. If after loading and load removal, the specimen fails to recover to its original length, the portion of creep deformation that is recoverable is still called primary creep the portion that is nonrecoverable is called secondary creep. This nonrecoverable elongation is typically called permanent set. 

Impurities or the delayed addition of a catalyst causes inhibition or delayed initiation resulting in accumulation in the reactors. The major hazard from accumulation of the reactants is due to a potentially rapid reaction and consequent high heat output that occurs when the reaction finally starts. If the heat output is greater than the cooling capacity of the plant, the reaction will run away. The reaction might commence if an agitator is restarted after it has stopped, a catalyst is added suddenly, or because the desired reaction is slow to start. 

There are three important processes for preparing PVAc latexes in the presence of PVA as a protective colloid batch, semi-continuous, and delayed addition of monomer [10]. In this Chapter, the effects of the addition of VAc and initiators on the properties of PVAc latexes are discussed using the three methods under the same charge of ingredients for polymerization as shown in Fig. 1 [1,11]. 

Delayed Crosslinking Additives. Glyoxal [458,460,461] is effective as a delay additive within a certain pH range. It bonds chemically with both boric acid and the borate ions to limit the number of borate ions initially available in solution for subsequent crosslinking of a hydratable polysaccharide (e.g., galactomannan). The subsequent rate of crosslinking of the polysaccharide can be controlled by adjusting the pH of the solution. 

J. C. Dawson. Method for delaying the gellation of borated galactomannans with a delay additive such as glyoxal. Patent US 5160643,... 

Surfactants increase particle number and decrease particle size as their concentration in the initial reaction charge is increased. However, one can use delayed addition of surfactant after nucleation is complete to improve particle stability, without affecting the particle number, size, and size distribution. 

Catherall and coworkers studied the reaction kinetics of bis(pentachlorophenyl) oxalate and H2O2 catalyzed by salicylate in the presence of DBA and verified that the delayed addition of DPA did not alter the reaction kinetics. The authors also conducted several kinetic smdies on the peroxyoxalate system and proposed the participation of 4-hydroxy-4-(pentachlorophenoxy)-l,2-dioxetan-3-one (48, R=Cl5C60) as the HEI in the reaction ... 

Table 7.10 Physical properties of concrete with and without the delayed addition of water-reducing set-retarding admixture (Dodson)...

Agitator failure or restart of agitator after failure Contamination of reactants Additions too quickly Delayed addition... 

Bypassing of bubbles is compensated partially by diffusion between dense and bubble phases (i.e., by delayed addition of reactants). 

I, was oxidized with lead tetraacetate (LTA), the characteristic Diels-Alder adduct with tetracyclone (TC) could be obtained even when the diene was added following completion of N2 evolution, indicating that the polymer-bound intermediate had survived for tens of seconds. Secondly, while LTA oxidation of the monomeric aminotriazole I-a, affords the corresponding biphenylenes in high yield, the only products formed by I-b, in the absence of TC, were the aryl acetates II and III (combined yield of 80%). Monomeric o-benzyne is known to dimerize at the diffusion limited rate in the gas phase, therefore, formation of the Diels-Alder product following delayed addition of diene requires a substantially slower encounter process for the polymer-bound analog. 

The 2 hour pepsin incubation time was based on work reported by Narasinga Rao (11) and on literature reports on gastric emptying time (16,26). The slightly longer pancreatin Incubation time of 2 1/2 hours was chosen for two reasons. First, it was necessary to delay addition of the pancreatin-bile mixture for 30 minutes after the dialysis bag was added and the incubation begun. 

In a suitable solvent, solution polymerization involving the delayed addition of the monomer may be carried out. In this procedure, all of the solvent and 10-25% of the monomer are heated to reflux in the presence of an initiator. As the polymerization proceeds, additional monomer is gradually added. To complete the polymerization, the reaction solution is heated for a prolonged period after the monomer addition has been completed. Even so, the residual monomer content may be as high as 2% [95]. 

Delayed addition of surfactant and protective Increases particle size... 

Many variations on the delayed addition or gradual addition procedures are possible. Procedure 5-5 is a relatively simple example of the technique which produces a latex of high solids content with a low level of anionic surfactant and a modest level of protective colloid. 

The control of carrier gas composition is done by the detector unit at the end of the column. The course of time dependent concentration can be monitored via an amplifier and penwriter by the operator. The integrator calculates the area beneath the different peaks. The detection of concentration within the carrier gas has to be without any distortion or delay. Additionally it should be mentioned, that the detector volume should not exceed that carrier gas volume, referring to the characteristic width of the smallest peak. 

Inhibition or delayed initiation can be caused by external factors — for example, by impurities or the delayed addition of a catalyst—or they can be an inherent aspect of the process or reaction — for example, the Skraup reaction and the Grignard reaction. The desired reaction must be investigated in enough detail to identify such problems. 

From an appreciation of the reaction chemistry, and as the total heat change during the process is endothermic, over- or under-charging of the reactants will not lead to a higher temperature. The delayed addition of the acid catalyst has been simulated in the isothermal heat flow experiment. This showed that there is little accumulation of reactants and this maloperation will only lead... 

It allows one to determine the current if the applied voltage is known or the voltage (ohmic drop) when the current is flowing through the resistance. It also shows that current follows the potential without delay. Additionally, in electrical engineering, by convention, the current is positive when it flows from the positive... 

---