According to the application, Hydroxypropyl Methyl Cellulose (HPMC) can be divided into construction grade, food-grade, and medical grade. In construction, HPMC is mainly used in putty powder, accounting for 90% of the total.
In putty powder, Hydroxypropyl Methyl Cellulose (HPMC) products are mainly used as thickeners, water-retentioner, and lubricants.
Thickener: Hydroxypropyl Methyl Cellulose (HPMC) product can thicken putty powder to enhance its suspension ability, anti-sagging ability as well as keep the solution uniform.
Water–retentioner: HPMC can keep the putty powder in a moist state and make the auxiliary ash calcium react to underwater action.
Lubricant: Hydroxypropyl Methyl Cellulose (HPMC) has a lubricating effect, which can make the putty powder have good workability and keep it smooth during the construction process, saving manpower.
Hydroxypropyl Methyl Cellulose (HPMC) does not participate in any chemical reactions except as an auxiliary molecule. The process of adding water to putty powder is placed on the wall as a chemical reaction. In the process, a new substance (calcium carbonate) is formed.
The main components of ash calcium powder are: Ca(OH)2, a mixture of CaO, and a small amount of CaCO3. The reaction equation is as follows:
In this process, gray calcium will be transformed into calcium carbonate under the action of CO2 and water, while HPMC is only working as a water-retentioner to assist the reaction under the better condition without participating in the reaction.
The putty formula can be different according to different specifications. Therefore, the viscosity and the dosage of Hydroxypropyl Methyl Cellulose (HPMC) are also different. In practical applications, it is recommended to use HPMC products with lower viscosity in winter, which is more conducive to construction. Otherwise, when the temperature is low, the viscosity will increase, which may cause trouble for further applications.