The Chemistry of Building Materials
Commercial-grade cellulose ethers cover a wide range of product types and differ in terms of substituents, substitution level, molecular weight (viscosity), and particle size. Predominant cellulose ether types are:
Those derivatives of HEC with alkyl side-chains containing more than two C-atoms are so-called hydrophob modified HEC (hmHEC or HMHEC).
A lot of those cellulose ethers used in building industry (generally knows as "modified cellulose ether") are blends with other additives. Their function may be to improve desired properties, to reduce or wholly suppress undesirable properties, or to add new properties:
The components may be physically blended or chemically bonded. Examples for both alternatives as well as for the intermediate are listed below:
Die meisten Additive werden getrennt hergestellt und vermahlen und erst dann mit dem Celluloseether gemischt. Die wichtigsten Modifizierungsmittel für Celluloseether sind die Stärkeether und die Polyacrylamide.
In principle modified cellulose ethers may contain each thinkable mortar additive, but in practice they are limited to those, whose action is almost independent of the binder system. Set retarder and accelerators are an example for less suitable candidates for blending because of their individual interaction with different binders.
The additive may be linked to the cellulose ether molecule, for example:
This group includes coated cellulose ethers and solid solutions:
Some additives shall not influence any properties of the mortar. The reason for their use is to improve properties like shelf-live, handling and/or transportability: