How to test the viscosity of hydroxypropyl methylcellulose?
Hydroxypropyl methyl cellulose for construction needs to avoid the infiltration of water into the wall, and the appropriate amount of water is retained in the mortar, which can make the cement fully produce good performance and perform the effect of water and water. Hydroxypropyl methyl cellulose The viscosity of the base cellulose in the mortar can be proportional, the higher the viscosity, the better the water retention of hydroxypropyl methylcellulose.
Once the water content of hydroxypropyl methylcellulose is too high, the water retention of hydroxypropyl methylcellulose will decrease, which will directly lead to a decrease in the construction efficiency of hydroxypropyl methylcellulose.
Apparent viscosity is an important indicator of hydroxypropyl methylcellulose. The usual measurement methods are rotational viscometry, capillary viscometry and fall viscometry.
Previously, the measurement method of hydroxypropyl methylcellulose was capillary viscometry, which used Ubbelohde viscometer. Usually the measurement solution is an aqueous solution of 2, and the formula is: V=Kdt. V is the viscosity, the unit is K is the constant of the viscometer, d is the density at constant temperature, t is the time from top to bottom through the viscometer, the unit is s. This method is cumbersome to operate. If there is insoluble matter, it is easy to cause errors, and it is difficult to identify the quality of hydroxypropyl methylcellulose.
The problem of building glue stratification is a big problem encountered by customers.
First of all, the construction glue stratification should consider the problem of raw materials. The main reasons for the construction glue stratification are polyvinyl alcohol (PVA) and hydroxypropyl methylcellulose (HPMC). caused by incompatibility. The second is because the stirring time is not enough; and the thickening performance of the construction glue is not good.
In construction glue, instant hydroxypropyl methyl cellulose (HPMC) must be used. Because hydroxypropyl methyl cellulose (HPMC) is only dispersed in water without real dissolution. After about 2 minutes, the viscosity of the liquid gradually increased, forming a transparent viscous colloid.
Hot-dissolving products, in the presence of cold water, can quickly disperse in hot water and disappear into hot water. When the temperature drops to a certain temperature. The viscosity slowly appears until a transparent viscous colloid is formed. The recommended dosage of hydroxypropyl methylcellulose (HPMC) in construction glue is 2-4kg.
Hydroxypropyl methylcellulose (HPMC) has stable chemical properties, mildew resistance and water retention in construction glue, and is not affected by pH changes. The viscosity can be used from 100,000 S to 200,000 S. However, in production, the higher the viscosity, the better. The viscosity is inversely proportional to the bond strength. The higher the viscosity, the smaller the strength. Generally, the viscosity of 100,000 S is appropriate.