Low termination

The susceptibility of the polymerization of a given monomer to autoacceleration seems to depend primarily on the size of the polymer molecules produced. The high propagation and low termination constants for methyl acrylate as compared to those for other common monomers lead to an unusually large average degree of polymerization (>10 ), and this fact alone seems to account for the incidence of the decrease in A f at very low conversions in this case. 

For small particles Having a low terminal velocity, V01 Is usually taken aa VQs and v pX taken is ... 

When tetraphenyl orthocarbonate reacts with low terminal carboxyl PET, a small amount of diethylene glycol is formed by Side Reactions 27 and 28. 

Internal olefins are much less reactive than a-olefins in chain initiation and secondary hydrogenation reactions. The reactivity of added a-olefins in chain initiation reactions increased in the order ethylene > propylene s 1 -butene C5+ olefins it becomes almost independent of chain size for C5+ a-olefins. The higher reactivity of ethylene and propylene leads to C2 and C3 selectivity below those of the rest of the distribution in Flory plots (Fig. 5) and to the low termination probabilities measured for C2 and C3 surface chains (Fig. 8), as proposed previously by others (115). 

We ccmsider a polymerizing system with polymer particles per unit volume of latex. JVp is usually of the order 10 - 0 particles per liter of latex. Early in their life when polymer particles are relatively small lOO-1000 A) and when the polymer concentration is relatively low, termination with an entering radical will he affectively instantaneous. Thus, particles will contain either zero or one radical. Later in the polymerization particles may contain two or more radicals. The polymerization rate in a single particle with R free radicals is given by... 

A third way to influence the critical voltage is to play with the inter-electrode resistance. As seen in Equation (3.73), the higher the inter-electrode resistance, the higher will be the critical voltage. If low terminal voltages are desired for electrochemical discharges, attention has to be paid to the electrode geometry and the electrical conductivity of the electrolyte in order to minimise the inter-electrode resistance. 

According to the Mayo procedure [36], for polymerizations at low initiation and thus also at low termination levels, the inverse (average) degree of poly-... 

The anions that are preferred are mostly of low nucleophilicity, such as SbP6, AsFe, and PFe. These systems yield low termination rates, cure at room temperature, and exhibit considerable amounts of postcuring. There are some disadvantages to the use of initiators based on diazonium salts. They tend to gel, unless stored in the dark. The films also tend to be colored, further yellowing on ageing. Also, nitrogen evolution causes bubbles or pinholes in thicker films. 

Termination steps occur when two radicals encounter one another and combine. This eliminates both radicals and stops the growth of the polymer chain. If the number of radicals present is kept low, termination steps will be rare. 

Rice husks have very low bulk density (approximately 100 kg m ) and low terminal velocity (1.1 m s ) [11,85,86]. During the combustion of rice husks, the... 

If during cationic polymerization the impurity concentration is very low, termination reactions between the propagating cation and negatively charged species (e, M, M ) should also be considered ... 

The great drawback of LIBs with an LTD anode is their low terminal voltage, namely, 2.2-2.5 V with cathodes such as LCD, LiMn204 or LiNii/3Coi/3Mni/302, which means that the energy density of an LTD cell is considerably lower than that of conventional LIBs. 

Figure 10.3. Oscilloscope records obtained from system shown in Figure 10.2a. (a) Pulse generator connected to Hi terminals of SIU and preparation connected to Low terminals note tilt in top of pulse applied to preparation, (b) Pulse generator connected to Low terminals of SIU and preparation connected to Hi terminals note distortion in both wave forms, (c) Same conditions as (a) but with use of constant current source, (d) Same conditions as (b) but with use of constant current source. Note risetime improvement over lower trace in (b).

A higher rate CO conversion with same value of a would be possible when for very low termination rates the site of CO dissociation is different from that of chain growth. Previous quantum chemical calculations indicate the possibility of such a site [47]. Its kinetics we will discuss in the next subsection. 

---