Application of hydroxypropyl methyl cellulose in putty powder
Hydroxypropyl methylcellulose has three main roles in putty powder: thickening, water retention and construction.
Thickening: Cellulose thickens the putty and helps to suspend it, to keep it in a homogeneous solution and to resist sagging.
Water retention: It makes the putty powder dry more slowly and assists the reaction of calcium grey under the action of water.
Construction: Cellulose has a lubricating effect and allows the putty powder to have a good workability.
Hydroxypropyl methylcellulose HPMC does not take part in any chemical reaction, but only plays an auxiliary role. The main components of ash calcium powder are: Ca(OH)2, CaO and a small amount of CaCO3 mixture, CaO + H2O = Ca(OH)2 - Ca(OH)2 + CO2 = CaCO3↓ + H2O, ash calcium forms calcium carbonate in the presence of water and CO2 in the air, whereas HPMC only retains water and assists the grey calcium to react better, it is not involved in any reaction itself.
The most important role of HPMC is water retention, followed by thickening. In putty powder, as long as the water retention is good, a lower viscosity (70-80,000) is possible.