The role of HPMC in putty powder

Propylmethylcellulose HPMC is a nonionic cellulose ether prepared by a series of chemical processing using natural polymer material cellulose as a raw material.They are an odorless, odorless, non-toxic white powder that swells in cold water into a clear or slightly turbid colloidal solution. It has the characteristics of thickening, bonding, dispersing, emulsifying, film forming, suspension, adsorption, gelation, surface activity, moisture retention and protective colloid. Hydroxypropyl methylcellulose HPMC chemical equation:

[C₆H₇O₂(OH)₃-m-n(OCH₃)m(OCH₂CH(OH)CH₃)n]x

In the putty powder, HPMC plays the role of WATER RETENTION ,THICKENING, CONSTRUCTION

Water retention: MPMC in putty powder can reduce the volatilization of water and assist the reaction of ash calcium under the action of water.

Thickening: HPMC cellulose can be thickened to suspend, keep the solution evenly uniform, and resist sag.

Construction: Cellulose has a lubricating effect, which can make the putty powder have good workability.

High quality HPMC, uniformity, its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain, which enhances the ability of oxygen atoms on hydroxyl and ether bonds to associate with water to form hydrogen bonds. The free water becomes the combined water, thereby effectively controlling the evaporation of water caused by the high temperature weather and achieving high water retention.

Under normal circumstances, the viscosity of HPMC in putty powder is 100,000, and the viscosity of mortar HPMC is 150,000. The most important role of HPMC is to retain water, followed by thickening. In the putty powder, as long as the water retention is good and the viscosity is less than 70-80,000, the required effect can also be achieved. Of course, the greater the viscosity of the putty powder, the better the relative water retention. If the viscosity exceeds 100,000, the effect of viscosity on water retention is not great.

Putty powder can not be used twice. Putty powder with water, on the wall, is a chemical reaction. Because of the formation of new substances, the putty powder on the wall is removed from the wall, ground into powder, and reused, it will not work, because a new substance has been formed (calcium carbonate). ). The main components of ash calcium powder are: Ca(OH)2, a mixture of CaO and a small amount of CaCO3, CaO+H2O=Ca(OH)2—Ca(OH)2+CO2=CaCO3↓+H2O ash calcium in water and air Under the action of CO2, calcium carbonate is formed, and HPMC only retains water, assists the better reaction of ash calcium, and does not participate in any reaction itself.