Continue: Quality Identification of Hydroxypropyl Methyl Cellulose(HPMC)
Ⅲ. Hydroxypropyl methyl cellulose HPMC dissolution
In the construction industry, hydroxypropyl methyl cellulose HPMC is often put into neutral water and dissolved separately to judge the dissolution speed of HPMC products. After being put into neutral water alone, the product that is rapidly clumped and not dispersed is the product without surface treatment. After being put into neutral water alone, the product that can be dispersed and not clumped is the product with surface treatment. When untreated hydroxypropyl methyl cellulose (HPMC) is dissolved alone, the individual particles dissolve rapidly and form a film quickly. As a result, water cannot re-enter other particles. Causing agglomerates and lumps, which are currently marketed as slow dissolving products.
Surface treated hydroxypropyl methyl cellulose (HPMC) product particles, in neutral water, individual particles can be dispersed without agglomeration. But it will not immediately product viscosity. Through a certain period of immersion, the chemical structure of the surface treatment is destroyed before the water can dissolve the HPMC particles. At this point the particles have been fully dispersed and have absorbed enough water. So that the product does not clump or agglomerate after dissolution.
The speed of dispersion and dissolution depends on the depth of the surface treatment. If the surface treatment is light, the dispersion speed is relatively slow and the tacking speed is fast. While if the surface treatment is deep, the dispersion speed is fast and the tacking speed is slow. If the product is to dissolve quickly in this state. A small amount of alkaline substance can be added to the product by drops as it dissolves on its own. This is now commonly referred to as a fast dissolving product.
Surface treated HPMC products are characterised by the ability of the particles to disperse from each other in an aqueous solution. In the alkaline state, it dissolves quickly. In the neutral and acidic state, dissolution is slow.
Untreated HPMC with hydroxypropyl methylcellulose is characterised by the fact that the individual particles dissolve very quickly in the acidic, alkaline and neutral states. However, it cannot be dispersed from particle to particle in liquids and leads to clumping and agglomeration. In practice, after physical dispersion of the product series and solid particles such as gum powder, cement and sand. The dissolution rate is very fast and there is no lumping or agglomeration. This product should be used with caution when dissolving HPMC products alone, as it will agglomerate and clump. If it is necessary to dissolve untreated HPMC alone, the product should be dispersed with hot water at 95°C and then cooled down to dissolve.
In practice, the product is often dissolved under alkaline conditions after dispersion with other solid granular materials. There is no difference between the dissolution rate of the product and that of the untreated product. It is also suitable for use in individually dissolved products without lumping or agglomeration. The specific type of product can be selected according to the dissolution speed required for the construction.
During construction, they are mostly alkaline systems, whether they are cement mortars or gypsum-based slurries. HPMC is added in small quantities and can be evenly dispersed among these particles. When water is added HPMC will dissolve quickly.
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