redispersible latex powder RDP for tile adhesivesDecember 7th 2023
Application principle of hpmc in inner wall insulation mortar
In the recent research on the composition of the internal wall insulation mortar, it is not difficult to find that there is a kind of hpmc that is very common in our lives. Let’s not look at its economic benefits for the time being. First of all, this type of raw material for internal wall insulation mortar has the effect of strengthening the product. So what is hpmc and what is the working principle of product response:
(1) hpmc is calcium hydroxide, the molecular formula is Ca(OH)2, which is a commonly used inorganic bonding powder material. It is made by selecting, calcining, aging and crushing limestone with a certain amount of cold water. It mainly acts as a bonding agent in putty powder and thermal insulation mortar, and can achieve waterproof and water-resistant effects. As the hpmc reacts with CO2 in the air, CaCO3, which is insoluble in water, is generated, thereby achieving the effect of waterproof and water resistance. On the other hand: after mixing and stacking together, hpmc can be modified, and in practice it is neutralized and denatured. The modified interior wall putty does not turn yellow when scratched to the wall, there is no blooming phenomenon after the latex paint is used, the tempered porcelain imitation paint does not change color, and the exterior wall putty and external thermal insulation powder materials are not easy to alkalize. The more calcium oxide content in hpmc, the greater the activity. The consumption of putty is likely to cause the latex paint to bloom, the consumption of external thermal insulation adhesives is prone to efflorescence, the consumption of tempered paint cannot be stored, and it is easy to cause the ultramarine discoloration and yellowing of the wall. It is the high content of calcium oxide in hpmc. We here provide a way to modify hpmc to make hpmc activity inert. The method is to add aluminum sulfate in the proportion of 4% of the hpmc addition, and alum, which is potassium aluminum sulfate, can also be used.
(2) Hardening principle of hpmc:
First: dry and hardening: hpmc evaporates a large amount of water in the squeegee, so that a large amount of the same pore network is formed in the slurry, and the free water remaining in the pores, due to the surface tension of the water, generates capillary pressure, causing The hpmc particles are becoming tighter, so they gain strength, and when the slurry becomes more dry, this effect is also enhanced.
Second: Charcoal hardening: The slurry absorbs CO2 gas from the air to form calcium carbonate that is practically insoluble in water. This process is called the carbonation of the slurry. The total response is as follows: Ca(oH)2+CO2+H2O→CaCO3+(n+1)H2O.