Naphthalene formaldehyde sulfonates effect

The effect of the interaction between two types of SPs (naphthalene formaldehyde sulfonates-NFS and melamine formaldehyde sulfonate-MFS) and the VEA on the fluidity of mortar is seen in Fig. 7.46. In the case of NFS, the mortar flow decreases with increasing addition of the VEA. This result indicates an appreciable interaction between NFS and the VEA. On the other hand, the fluidity of the mortar containing the MFS does not change. Measured amounts of the SPs showed that there was good correlation between the amount of SP adsorbed and observed fluidity. 

Figure 11. Effect of sulfonated naphthalene formaldehyde on viscosity of cement paste.

The material is produced from naphthalene by oleum or sulfur trioxide sulfonation under conditions conducive to the formation of the h sulfonate. Subsequent reaction with formaldehyde leads to polymerization and the sulfonic acid is neutralized with sodium hydroxide [17] or lime. The process is illustrated in Fig. 2.2. The value of n is typically low but conditions are chosen to get a proportion of higher-molecular-weight product as it is believed to be more effective [18]. The quantity of sodium sulfate by-product formed by the neutralization of excess sulfonating reagent will vary depending on the process used, but can be reduced by a subsequent precipitation process using lime [19]. 

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