- Hydration performance. At room temperature, stpp chemical is quite stable, and it will slowly undergo hydrolysis in humid air, eventually producing sodium orthophosphate. Under the same conditions, the high-temperature type hydration generates high heat quickly and is prone to agglomeration when dissolved in water. This is due to the presence of sodium ions of the quadridentate ligand, which has a strong affinity for water. On the contrary, the low-temperature type forms hexahydrate at a low speed in water.
- Chelating ability to metal ions. The heavy metal ions, such as, Ca2 and Mg2 in water are combined with detergent molecules to form insoluble salts in the washing process, which will reduce the washing ability and even lose its effect completely. So it is necessary to add a substance that can make the heavy metal ions contained in the washing water harmless to the detergents. Sodium tripolyphosphate is such a builder, which has strong chelation effects on heavy metal ions, seal them up and eliminate their negative effects on washing. STPP in detergent has complexation action with metal ions, such as, calcium, magnesium and Fe dissolved in water to form soluble complexes. The complexing capacity of sodium tripolyphosphate is generally expressed by calcium value, that is, the grams of calcium ions complexed by 100g phosphate. The theoretical value is 13.4. In addition, it can also capture various types of metal components in the dirt and play the role to dissociate dirt during washing.
- Buffer effect. The aqueous solution of STPP is weakly alkaline. It forms a suspension liquid in water with the PH value ranging from 4.3 to 14. This is its dispersion effect. In addition, it can also make the liquid and solid particles better soluble in the liquid medium, so that the appearance of the solution is completely transparent, just like the real solution, this is its solubilization effect. As an auxiliary agent of synthetic detergent, sodium tripolyphosphate can keep the PH value of detergents around 8.4 and promote the removal of acidic dirt.
This is precisely because of its unique properties that make stpp powder an important ideal raw material in washing powder and detergents.