Vitamin ether is the most commonly used additive in dry powder mortar. Hydroxypropyl methyl cellulose ether plays an important role in dry powder mortar. After the cellulose ether in the mortar is dissolved in water, the glue is guaranteed due to the surface activity. The coagulant material is effectively and evenly distributed in the system, and hydroxypropyl methylcellulose ether, as a protective colloid, “wraps” the solid particles and forms a layer of lubricating film on its outer surface, making the mortar system more stable and also Improve the fluidity of the mortar during the mixing process and the smoothness of the construction.
Due to its own molecular structure, the cellulose ether solution makes the water in the mortar not easy to lose, and gradually releases it over a long period of time, endowing the mortar with good water retention and workability. Water retention of hydroxypropyl methyl cellulose ether: It is the most important and basic indicator. Water retention refers to the amount of water that freshly mixed mortar can retain after capillary action on the absorbent base. The following test measures for water retention of cellulose ether are summarized for discussion.
Vacuum method
During the experiment, fill the Buchner funnel with the mortar mixed with water, place it on the suction filter bottle, start the vacuum pump, and perform suction filtration for 20 minutes under the negative pressure of (400±5) mm Hg. Then, according to the amount of water in the slurry before and after suction filtration, calculate the water retention rate as follows.
filter paper method
The water retention of cellulose ether is judged by the water absorption of filter paper. It is composed of a metal ring test mold with a certain height, filter paper and a glass support plate. There are 6 layers of filter paper under the test mold, of which the first layer is fast filter paper, and the other 5 layers are slow filter paper. Use a precision balance to first weigh the weight of the pallet and the 5 layers of slow filter paper, pour the mortar into the test mold after mixing and scrape it flat, and place it for 15 minutes: then weigh the weight of the pallet and the 5 layers of slow filter paper weight.