I. Adulterated hydroxypropyl methyl cellulose (HPMC) and pure hydroxypropyl methyl cellulose (HPMC) difference
1. Appearance: pure hydroxypropyl methyl cellulose HPMC looks fluffy and has a small bulk density, ranging from 0.3-0.4g/ml; adulterated hydroxypropyl methyl cellulose HPMC has better fluidity and a sunken feel, with obvious differences in appearance from the genuine product.
2. State: pure hydroxypropyl methyl cellulose HPMC powder is fibrous under microscope or magnifying glass; while adulterated hydroxypropyl methyl cellulose HPMC can be observed as granular solid or crystal under microscope or magnifying glass.
3. smell: pure hydroxypropyl methylcellulose HPMC can not smell to ammonia, starch and alcohol; adulterated hydroxypropyl methylcellulose HPMC can smell all kinds of taste, even if odorless, will feel heavy in the hand.
4. aqueous solution: pure hydroxypropyl methyl cellulose HPMC aqueous solution clarity, high light transmission rate, water retention rate of ≥ 97%; adulterated hydroxypropyl methyl cellulose HPMC aqueous solution is more turbid, water retention rate is difficult to reach 80%.
Second, the water retention of hydroxypropyl methyl cellulose HPMC, distinguishing between superior and inferior.
The water retention of methyl cellulose ether under high temperature conditions is an important indicator to distinguish the quality of methyl cellulose ether. Air temperature, temperature and wind pressure speed and other factors will affect the evaporation rate of water in cement mortar and gypsum-based products. So there are some differences in the water retention effect of products with the same amount of HPMC added in different seasons. The water retention effect of the slurry can be adjusted by increasing or decreasing the amount of HPMC added in the specific construction. Excellent hydroxypropyl methylcellulose HPMC products can effectively solve the problem of water retention at high temperatures.
High quality methyl cellulose is evenly and effectively dispersed in cement mortars and gypsum based products and envelops all solid particles and forms a wetting film. The water in the base is gradually released over a considerable period of time and reacts with the inorganic cementitious material to ensure the bond and compressive strength of the material. High-quality hydroxypropyl methylcellulose HPMC, which has a very good homogeneity. Its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain. It improves the ability of the oxygen atoms on the hydroxyl and ether bonds to form hydrogen bonds with water, turning free water into bound water. This effectively controls the evaporation of water caused by hot weather and achieves high water retention.
Therefore, in order to achieve water retention in hot summer construction, high quality HPMC products need to be added in sufficient quantity according to the formula. Otherwise, there will be quality problems such as insufficient hydration, reduced strength, cracking, hollow drums and peeling caused by too fast drying. It also increases the difficulty of construction for workers. As the temperature decreases, the amount of HPMC added can be gradually reduced and the same water retention effect can be achieved.
Landcel specialises in the production of high purity, high quality HPMC, which is sold worldwide.