Overview: HPMC(hydroxypropyl methyl cellulose) is one of the most important additives in dry mix mortar. HPMC is very important in the dry mortar formulation. HPMC solution has its own molecular structure characteristics, so that the water in the mortar is not easy to lose, and is gradually released over a long period of time, giving the mortar good water retention and workability. Water retention is the most important index and the basic standard of HPMC. Water retention rate refers to the amount of water retained by the freshly mixed mortar on the absorption substrate.
Normally, we have two ways to test it.
1.Vacuum method
-Moisture in the mortar after suction filtration
-Moisture in the mortar before suction filtration
Refer to JC/T517-2005 ＆ JISA 6904-1976.
Fill the Buchner funnel with the stirred mortar, place it on the suction filter bottle, start the vacuum pump, and filter under the negative pressure of 400±5mm pump column for 20 minutes, and then calculate according to the following formula according to the water volume in the mortar before and after the suction filter Water retention rate：
Water retention(%) = Moisture in the mortar after suction filtration/Moisture in the mortar before suction filtration ×100
This method need to professional equipment, the cost is high. But the test result is more accurate.
2.Filter paper method
1) Test equipment: Mortar mixer, Electronic balance
2) Material: filter paper, standard sand, cement, sypsum
3) Mothed:
The filter paper method judges the water retention of HPMC by the water absorption of the filter paper.
Composed of a certain height of metal ring experiment mold, filter paper and glass pallet.Below the experimental mold are 6 layers of filter paper, the first layer is fast filter paper, and the remaining 5 layers are slow filter paper. Use a balance to weigh the glass pallet and 5 layers of slow filter paper, pour the mortar into the experimental mold and scrape it flat, place the experimental mold upside down on the filter paper for 15 minutes, and finally weigh the pallet and 5 layers. Calculated according to the following formula:
M=(M1-M2)/S
M: water loss g/mm²
M1: The weight of pallet and 5 layers filter paper
M2: The weight of pallet and 5 layers filter paper after 15 minutes
S: Experimental mold area mm²
By this method, could see the Water absorption of filter paper directly. The lower filter paper water absorption, the water retention is better.
Jinan maissen new material co.,ltd is the professional HPMC manufacturer for dry mix mortar industry.
If there is any inquiry, please contact with us
info@mailose.com
website: www.maissen-hpmc.com
