Primary cycle

When characterizing polymer networks, the following definitions are typically applied [150] and are illustrated in Fig. 7. When a radical on a polymer chain propagates through a pendant double (i.e. a double bond from a monomer with one double bond already reacted), a crosslink, secondary cycle, or primary cycle can be formed. A crosslink forms when the radical reacts with a pendant... 

Fig. 10. Kinetic gelation model prediction of the relative fraction of crosslinks, primary cycles, and secondary cycles as a function of double bond conversion for the polymerization of a multifunctional monomer...

Figure 9.4 Different types of crosslinkages (a) intermolecular, (b) intramolecular, yielding a primary cycle, and (c) intramolecular, yielding a secondary cycle.

W48 W49 62% W50 38% Primary cycle time, sec Seen ergonomics video Any ergonomics changes to workplace or methods... 

In conjunction with this benchmark data to determine supply chain potential, additional insights are gained through the understanding of supply chain cycles. In the supply chain, time is often money. There are 10 primary cycles to map ... 

The product of this primary cycle is the polymer hydroperoxide ROOH. Under use conditions, these are imstable and decompose to yield new radicals, which initiate new chains. Thus, a chain reaction that regenerates its own initiator is started and the result is autoacceleration. Typically, there is an indnction period of slow reaction, followed by rapid oxidation, as illustrated in Fignre 4, which shows some data for accelerated aging of polypropylene (PP). In some cases, eg, PP, the formation of peroxides may be faster than their decomposition (depending on the temperatnre), so that they accumulate in the polymer. In other cases the peroxides are so imstable that they decompose as soon as they are formed. 

It is recommended that broadcasters send populated EITs covering at least three days. The primary cycle time guidelines are illustrated in Figure 16.55. 

This chapter covers corrosion and corrosion testing for the water side and steam side of utility and industrial steam generation, fossil fuel, and nuclear units. It does not cover primary cycles of nuclear units, fire side in fossil fuel fired steam generators, gas turbines, and cooHng water systems. 

With a few exceptions, coatings and linings are not used on the water and steam sides. In an EPRI project, about 50 turbine blade coatings have been evaluated, but none of these are being routinely applied. To reduce steam side oxidation in reheaters and superheaters, chromizing and chromating have been developed but these treatments are also not routinely applied. There is little use of composite materials with the exception of condenser tube sheets, which could be made of explosively clad stainless steel or titanium on carbon steel, and of the surfaces in the primary cycles of nuclear units where carbon or low alloy steels are protected by weld-deposited stainless steels. In pulp mill black liquor recovery boilers, stainless steel clad boiler tubes are often used. 

The product of this primary cycle is the polymer hydroperoxide ROOH. Under use conditions, these are unstable and decompose to yield new radicals, which initiate... 

The primary cycle is inorganic, in which phosphate rock formation, mainly from diagenesis of P-enriched sediments in marine and fresh waters, takes place over very long periods of time (ca. 10 -10 y M. ... 

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