Self-retardation

During this phase the initial self-retarding calcium silicate hydrate layer appears to break down, allowing further hydration products from the C3S and C2S phases to be formed. These appear to be produced in three... 

It is surprising to realize how often the undercure produced by vitrification is completely ignored when performing the thermosetting polymerization by irradiation (UV, EB, X-ray) at room temperature. As there is no external heat source, once vitrification sets in conversion may only increase through the continuation of reaction in the glassy state. However, as we have discussed in Chapter 5, polymerization in the glassy state is a self-retarded and very slow process. 

Fig. 4. Etch rate vs. time shows reaction to be self-retarding.

The self-retarding character of the process causes the reaction to continue at a rate below the limit of detection by the DSC, but changes still show up in the mechanical properties, notably in T(tan the temperature of maximum mechanical loss. This can be seen when the experiments shown in Fig. 16 are repeated under slightly different conditions. In Fig. 17, the irradiations at the lower intensities have been continued until equal doses were applied in all cases... 

The behavior of 2-furyl vinyl ketone is similar to that of 2-vinylfuran, in which the monomer is activated in the normal fashion by the primary radical (addition onto the vinylic bond), but the formed polymer chains act as radical traps through their pendant furan ring. Thus at a critical polymer concentration practically all primary radicals are quenched to form stable furyl radicals, and normal initiation cannot take place. This phenomenon of self-retarding is also responsible for the low molecular weight [353]. 

What is the role of admixture on concrete properties State the difference between water reducing, self-retarding and set accelerating admixture. 

At deep stages of hydrocarbon oxidation, the self-retardation of the process is often observed, which is caused by the following facts. 

Very often all four factors act simultaneously, which results in the self-retardation of autoxidation at degrees of conversion of 40-50%. 

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