Exothermic peak retarders

Furthermore, the addition of 1.1%) retarding polycarboxylic-acid SP to the 25% FA mix resulted in not only a large decrease of the release rate and quality of hydration heat, but also a great delay of the occurrence time of exothermic peak, especially a significant reduce of... 

There was a decrease in hydration heat at all ages for all the HPC mixes with SCMs, and FA was more pronounced in decreasing the hydration heat than GGBS. In addition, the inclusion of set retarding-type polycarboxylate superplasticizer further decreased the hydration heat release rate and could delay the occurrence time of exothermic peak. 

Another family of flame retardant additives is phosphazene derivatives. The addition of hexamethoxycyclotriphosphazene (HMPN) in 1 M LiPF /EC + DMC (50 50 wt%) depressed exothermic peaks in a differential scanning calorimeter (DSC) and self-heat rate in ARC at elevated temperature due to the passivation layer formed by this additive. 

With a fixed ITA content raising the MA content increases the temperature of the exotherm peak, whilst A/f falls. The thermograms in air when MA is introduction into the system has the initial effect of permitting the oxidation reaction to proceed at a lower temperatures, albeit with smaller overall heat evolution, but at greater additions the reaction is retarded and the heat evolution becomes even less. 

The difference between our quaternary and binary systems is attributed to the presence of butanol in system B. Alcohol molecules participate in retarding the crystallization of, presumably, surfactant headgroups, thus leading to a lower temperature exothermic peak in the quaternary system. 

The effect of 0, 1,2, and 4% SMF on the hydration of C3A + 25% gypsum may be followed by conduction calorimetry (Fig. 4).Iri An exothermic peak appears at 20 hours with 1 % SMF, at about 23 hours with 2% SMF, and at about 15 hours with 4% SMF. A continuous hump is registered for the sample containing no admixture. The retardation effect of C3A-ettringite reaction to produce low sulfoaluminate may be caused by the adsorption of SMF on the hydrating C3A surface. 

Superplasticizing admixtures are used widely in high performance concrete production. Not only do they influence the rheological parameters, but also the setting characteristics. These effects depend on the type and dosage of the admixture. In Fig. 17, the role ofthree types of superplasticizers, viz., 0.5% Ca-SNF, commercial SMF, or Na-SNF on the hydration of slag cements is examined. Addition of the superplasticizer results in the retardation in terms of the time of appearance of the exothermal peak and also a decrease of the peak intensity. Na-SNF retards most of the superplasticizers studied. 

Some linear carbonates (Figure 9.17) are nonflammable and can be used in lithium-ion batteries. If the hydrogen atoms of these carboxylates are replaced with fluorine, the carbonates can be used as flame retardants, which can significantly improve the thermal stability of the electrolyte. For example, when LiPFg solution in difluoroacetyl methyl carbonate reacts with lithium or Lio.5Co02, the exothermic peak is increased to about 300°C. The cycling efficiency for lithium metal is also good. 

DTA of inorganic fire retardants run in oxygen may shift the peak position temperature or the amount of heat released. Sodium tetraborate reduced the volatile products exotherm considerably, increased the glowing exotherm, and stimulated the appearance of a second glowing peak around 510 °C, as seen in Figure 14. Sodium chloride also reduced the first exotherm, increased the size of the second, but did not produce a second glowing exotherm as did the... 

All fillers will increase the viscosity of resins most fillers also influence the gel time. Gelation is normally retarded, but alumina and some types of china clay have the reverse effect. It is difficult to predict the precise effect on gel time of particular filler and this should be determined by experiment in each case. Fillers also reduce the volumetric shrinkage of resins when curing, as well as peak exothermic temperature. 

It can be concluded that polyvinyl alcohol incorporated in nylon 6,6 reduces the rate of heat release and increases the char yield. Cone calorimetry data for permanganate-oxidized polyvinyl alcohol indicate an improvement in peak rate of heat release compared with polyvinyl alcohol alone, but the smouldering process is exothermic. Silicon/stannic chloride systems act as ecologically friendly flame retardants for both nylon 6,6 and polypropylene. 

The rate of hydration of cement-fly ash also depends on the particle size of fly ash. Conduction calorimetric curves have been obtained for cements containing 30% fly ash of surface areas of200,450, and 650 m /kg. These mixtures are designated PFA-0, PFA-1, and PFA-2 respectively in Fig. 4. The fly ash cements exhibited sharper peaks at earlier times at 11-12 hours compared to the reference cement. These peaks become sharper as the surface area of fly ash increases. The peak effects are associated with the hydration of C3A after the depletion of gypsum in the system. The initial exothermal effect due to alite hydration is retarded by the fly ashes. 

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