| I. simple method for distinguishing the quality of hydroxypropyl methylcellulose HPMC: (1) first look at the whiteness of hydroxypropyl methyl cellulose, the appearance of color is white, uniform color, there is no more black spots under the microscope; poor color slants gray, black spots more. Look at the shape and liquidity of the particles, the cotton as the starting material for the use of long strip, poor mobility, the use of lignocellulose as the starting material of the particles near the cube, good liquidity. (2) followed by fineness and particle size distribution, the best size of hydroxypropyl methylcellulose is homogeneous, small particle size, granular and liquid; the opposite is not good. Hydroxypropyl methyl cellulose fineness generally has 80 eyes and 100 mesh, 120 less purpose, Hebei produces hydroxypropyl methyl cellulose mostly 80 mesh, the finer the fineness, in general, the better. (3) transmittance: the hydroxypropyl methyl cellulose HPMC into the water, forming transparent colloid, to see its transmittance, transmittance of the greater the better, indicating that less insoluble substances. The vertical reactor generally has good transmittance, but the horizontal reactor is a little worse, but it can not be explained that the quality of the kettle is better than that of the still kettle, and the quality of the product is determined by many factors. (4) proportion: the heavier the proportion, the heavier the better. Than in general, usually because of the high content of hydroxypropyl, hydroxypropyl content is high, then water conservation is better. Ⅱ, Adulterate hydroxypropyl methyl cellulose (HPMC) is distinguished from pure propyl methyl cellulose (HPMC) 1. appearance: pure hydroxy propyl methyl cellulose HPMC look fluffy, smaller bulk density, the scope is: 0.3-0.4g/ml; HPMC hydroxypropyl methyl cellulose better liquidity adulterated, feel more heavy, there exist obvious differences in appearance and quality. 2.: pure hydroxy propyl methyl cellulose HPMC powders are fibrous in a microscope or magnifying glass; and hydroxypropyl methyl cellulose HPMC adulterated can be observed under microscope or magnifying glass or granular solid crystal. 3. odor: pure hydroxyl propyl methyl cellulose HPMC, can not smell ammonia, starch and alcohol flavor; adulterate hydroxypropyl methyl cellulose HPMC can smell all kinds of flavor, even if tasteless, it will feel heavier. 4.: pure aqueous solution of hydroxypropyl methyl cellulose HPMC solution clarification, high transmittance, water retention rate is more than 97%; the adulteration of hydroxypropyl methyl cellulose HPMC solution is turbid, water retention rate of 80% is difficult to achieve. Ⅲ, hydroxypropyl methyl cellulose HPMC water retention, to distinguish between good and bad: The water retention property of methyl cellulose ether in high temperature is an important index to distinguish the quality of methyl cellulose ether. Factors such as air temperature, temperature and air pressure velocity affect the volatilization rate of water in cement mortar and gypsum based products. Therefore, in different seasons, adding HPMC same amount of products has some differences in water retention effect. In the concrete construction, the water retention effect of slurry can be adjusted by increasing the amount of added HPMC. The excellent hydroxypropyl methyl cellulose HPMC can effectively solve the water retention problem at high temperature. High quality cellulose can be uniformly and effectively dispersed in cement mortar and gypsum products, and wrapped all the solid particles, and the formation of a layer of membrane wetting, medium water gradually released in quite a long time, hydration and inorganic cementitious materials, so as to ensure the material bonding strength and compressive strength. Hydroxypropyl methyl cellulose HPMC high quality, its uniformity is very good, the methoxy and hydroxypropoxy group along the cellulose chain distribution, it can improve the hydroxyl and ether bond on the oxygen atom and water molecules capable of forming hydrogen bonds, free water into a combination of water, so as to effectively control the evaporation of water at high temperature due to the weather, achieve high water retention. So, in the construction of high temperature in summer, in order to achieve the effect of water conservation should be in accordance with the formula adding enough high-quality HPMC products, otherwise, there will be excessive drying caused by water is not enough, strength reduction, cracking, hollowing and loss and other quality problems, but also increase the difficulty of construction workers. With the decrease of temperature, the amount of HPMC can be reduced gradually, and the same water retention effect can be achieved. Ⅳ, Determination of solubility of hydroxypropyl methylcellulose HPMC In the construction industry, hydroxypropyl methyl cellulose HPMC is often placed in neutral water, and HPMC products are dissolved separately to determine dissolution rate. Separate into neutral water, quickly hold together, not dispersed products, is not surface treatment products; separate into neutral water, can disperse non Baotuan products, is the surface treatment products. When alone dissolved the unmodified HPMC hydroxypropyl methyl cellulose, the single particle dissolves quickly, quickly into the film, resulting in water cannot enter other particles, resulting in aggregation, caking, currently on the market called slow dissolving products. Surface treated hydroxypropyl methylcellulose HPMC product particles in neutral water, individual particles can be dispersed without agglomeration, but not immediately product viscosity. After a period of immersion, chemical structure, surface treatment has been destroyed, the water can be dissolved in HPMC particles, while the product particles has been fully dispersed, absorb enough water, so the product dissolved without agglomeration, agglomeration. The dispersion speed and dissolution rate depends on the extent of surface treatment, surface treatment of mild, dispersed relatively slow speed glue; surface treatment products and deep, high dispersion speed, slow speed glue. If the product is rapidly dissolved in this state, a small amount of alkaline substance may be dropped when dissolved alone. At present, the market is often called instant products. The surface treatment of HPMC products is characterized by: in aqueous solution, particles can be dispersed between each other, in the alkaline state can dissolve quickly, in the neutral and acidic state dissolved slowly. The characteristics of hydroxypropyl methyl cellulose HPMC untreated is: a single particle in acidic, alkaline and neutral state dissolving speed is very fast, but between the particles in the liquid and the particles can not be dispersed, resulting in Baotuan and agglomeration. In practice, the series of products and rubber powder, cement, sand and other solid particles dispersed in physics, the dissolution rate is very fast, there is no agglomeration, agglomeration phenomenon. In the need to separate dissolved HPMC products, this series of products should be used with caution, it will agglomerate, baotuan. If the surface treated hydroxypropyl methylcellulose HPMC product must be dissolved separately, it should be dispersed evenly at 95 DEG C and then cooled down. In the actual production process, the series of products are often dissolved in alkaline conditions and other solid particles dispersed, and its dissolution rate and untreated products are not different. Also suitable for individual dissolved products, not caking, can not afford mass. According to the construction needs of the dissolution rate, select the specific model of the product. In the construction process, whether cement mortar or gypsum slurry, most of them are alkaline system, and the amount of HPMC is very small, can be uniformly dispersed in these particles, when water is added fast dissolving HPMC. |
