Hydroxypropyl methyl cellulose is a kind of additive widely used in different kinds of dry mortar product.
Normally, Dry mix mortar product consists of three parts: Binder, filler and additives.
Hereby, we will give you some examples of some normal materials which is used in dry mortar.
Binders: Cement, Gypsum, Lime, Redispersible polymer powder(RDP) etc.
Fillers: Fly ash, sand, Perlite powder, EPS granule etc.
Additives: Cellulose ether (Hydroxypropyl methyl cellulose-HPMC, Methyl hydroxyethyl cellulose-MHEC), Calcium Formate, Retarder, Defoamer, Water reducing agent, water repellent etc.
Cellulose ether-HPMC is normally used in all types of dry-mix mortar products as a basic additive in the formulation to provide the water retention. Water is a very important index in the whole formulation, not only provide enough water for cement hydration, but also provide water for other materials to show their different functions.
Hereby, we will analysis the detailed functions of HPMC based on our own product-Hydroxypropyl methyl cellulose.
Particle size of HPMC and its water retention performance:
Normally, we all know that the particle size is smaller, the time to reach the highest point of water retention will be shorter. But is there any differences of the highest water retention based on different particle size? Actually, it is different. Normally, we suggest to choose the particle size below 180µm(80mesh). It could reach over 90%-95% water retention when the particle size is smaller than 180µm. But based on the particle size 300µm, it only can reach 80%-90%.
(please note, it is all based on all other items all the same, same temperature, same dosage etc, viscosity 150000cps test method: NDJ-1,2% solution, 20℃).
Our standard hydroxypropyl methyl cellulose is 98% pass 80 mesh(180µm) suitable for dry mix mortar industry to provide good performance in water retention.
Dosage of HPMC and its water retention performance:
The water retention rate is positively correlated with the dosage. Water retention increase obviously when increase the dosage of HPMC. Normally, the water retention rate reach the highest point when the dosage reach 0.3%. When the dosage is over 0.3%, there is almost no changes in water retention.
Please note, it is all based on all other items all the same, same temperature(20℃), viscosity 150000cps test method: NDJ-1,2% solution, 20℃.
Viscosity of HPMC and its water retention performance:
The water retention rate is positively correlated with the viscosity. When the viscosity increase, the water retention grow accordingly. Our product could reach the best performance when the viscosity reach 100000cps, over that, there is no big changes even increase the viscosity to 150000 or 200000cps.
Temperature and its water retention performance:
For HPMC, its water retention will drop down when the temperature get higher. Normally, when the temperature get over 40℃, there will be a obviously drop and will lost viscosity according to the different gelation temperature. Based on the Methoxy content 19.0-24.0% and Hydroxypropoxy content 4.0-12%, Mailose MP-hydroxypropyl methyl cellulose could reach over 70℃ gelation temperature to provide more stability in high temperature environment. However, we still suggest to increase the dosage in summer.
Other functions of HPMC in dry mix mortar:
Hydroxypropyl methyl cellulose-HPMC also make contribution to the consistency, workability, setting time and bonding strength of mortar. It is important to choose right specification according to different formulation of products. hydroxypropyl methyl cellulose provide various specifications for different applications.