The CD is always a polymer. It has strong anionic functional groups, normally carboxylic, distributed in specific distances from each other.

Few of them are participating to the crystal growing, taking strategic places into the growing surface, replacing normal scale anions. By this procedure the polymer molecule becomes part of the growing crystal.

The remaining anion groups are floating to the crystal surrounding, disturbing further crystal increase, and repulsing normal anions to reach and to participate to the deposit formation.

The important factors for the cd activity are:

• the type of the polymer,
• the charge density,
• the molecular weight and
• even more important the molecular weight distribution.

The same polymeric matrix, p.e. the polyacrylic acid, according to the molecular weight increase, can act as:

• sequestrant       (mw <800),
• CD,                   (mw 1300-8000)
• flocculent or as (mw 30.000 -1500000)
• a plastic to paint the walls. (mw >35M)

As long as the polymer is produced through a polymerization process, it is very difficult (and expensive) to have a precise and strict molecular weight distribution.

But it is mandatory. The actions of sequestrant and flocculant are competitive to crystal distortion.

• A flocculant present into the solution will agglomerate and precipitate the distorted crystals and will promote deposition.
• A sequestrant will capture round it ion clouds, preventing its participation onto a crystal growing procedure. But it easily liberates them at the heating surfaces as to make deposition in situ.

Our CD containing products are not acting as a sequestrant. It remains into the solution, waiting for crystallites to start to grow.

And this is separating the best from the rest.

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