Adhesion Mechanism of Sodium Hexametaphosphate (SHMP) in Coatings. Since 2018, both foreign and domestic famous coating enterprises have adjusted their strategies and implemented price increases. This upsurge of price increase is driven by cost. It is also an opportunity for manufacturers of sodium hexametaphosphate used in coating addition. Sodium hexametaphosphate can play a very good role in dispersing coatings, complexing calcium, magnesium and other metal ions in coatings, and making the color and drip performance of coatings better.
Next, let us talk about the main bonding mechanism of sodium hexametaphosphate: sodium hexametaphosphate is sticky after absorbing water, which is closely related to the properties of sodium hexametaphosphate itself. The molecular formula of sodium hexametaphosphate is (NaPO3)6, which belongs to a kind of polyphosphate with uncertain composition. The anions of sodium hexametaphosphate have high molecular weight, and generally contain 30-90 PO3 genes and form a long chain.
With the addition of water glass and other alkaline substances, an alkaline environment with PH value of 10-10.5 was prepared. That is to say, the concentration of OH- ions in the coating is large, and the reaction proceeds to the right, which is conducive to the further decomposition of H3PO4 and also promotes the conversion of sodium hexametaphosphate to orthophosphate. At this time, phosphate will undergo condensation of multiple phosphate functional groups, especially at high temperature, the molecular groups of sodium hexametaphosphate will condense. After condensation, the molecular groups are combined with the three-dimensional network bentonite molecular groups in the coating, which effectively plays a bonding role.
With the increase of the content of sodium hexametaphosphate, it has more obvious influence on the brushing property. When the content of sodium hexametaphosphate is 2%, the coating is thin, with good fluidity but serious flow. After coating, there are obvious flow marks, and the effect is poor. When the content of sodium hexametaphosphate in the coating rises to about 6%, the coating can be saturated and brushed briskly and smoothly. After coating, the coating will be automatically leveled for a period of time without leaving any trace, and the viscosity will be restored at the same time. The drip of the coating with this content is very low and the coating after coating can keep its inherent shape under the action of gravity.
Video of SHMP: https://youtu.be/X_X0cCp_8O4
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