In the construction industry, HPMC is often put into neutral water, and the HPMC product is dissolved alone to judge the dissolution rate.
After being placed in neutral water alone, the product that quickly clumps without dispersing is a product without surface treatment; after being placed in neutral water alone, the product that can disperse and not clump together is a product with surface treatment.
When the untreated HPMC product is dissolved alone, its single particle dissolves rapidly and forms a film quickly, which makes it impossible for water to enter other particles, resulting in agglomeration and agglomeration. It is called instant product on the market at present. The characteristics of untreated HPMC are: individual particles dissolve very quickly in neutral, alkaline, and acidic states, but cannot disperse between particles in liquid, resulting in agglomeration and clustering. In actual operation, after physical dispersion of this series of products and solid particles such as rubber powder, cement, sand, etc., the dissolution rate is very fast, and there is no agglomeration or agglomeration. When it is necessary to dissolve HPMC products separately, this series of products should be used with caution, because it will agglomerate and form lumps. If it is necessary to dissolve the untreated HPMC product separately, it needs to be uniformly dispersed with 95°C hot water, and then cooled to dissolve.
Surface-treated HPMC product particles, in neutral water, individual particles can be dispersed without agglomeration, but will not immediately produce viscosity. After soaking for a certain period of time, the chemical structure of the surface treatment is destroyed, and the water can dissolve the HPMC particles. At this time, the product particles have been fully dispersed and absorbed enough water, so the product will not agglomerate or agglomerate after dissolution. Dispersion speed and dissolution speed depend on the degree of surface treatment. If the surface treatment is slight, the dispersion speed is relatively slow and the sticking speed is fast; while the product with deep surface treatment has fast dispersion speed and slow sticking speed. If you want to make this series of products dissolve quickly in this state, you can drop a small amount of alkaline substances when they are dissolved alone. The current market is usually referred to as slow-dissolving products. The characteristics of surface-treated HPMC products are: in aqueous solution, the particles can disperse with each other, can dissolve quickly in alkaline state, and dissolve slowly in neutral and acidic state.
In actual production operation, this series of products often dissolve after being dispersed with other solid particle materials under alkaline conditions, and its dissolution rate is no different from that of untreated products. It is also suitable for use in products that are dissolved alone, without caking or lumps. The specific model of the product can be selected according to the dissolution rate required by the construction.
During the construction process, whether it is cement mortar or gypsum-based slurry, most of them are alkaline systems, and the amount of HPMC added is very small, which can be evenly dispersed among these particles. When water is added, HPMC will quickly dissolve. Only real hydroxypropyl methylcellulose can withstand the test of the four seasons: the reaction process is precisely controlled to produce HPMC, and its substitution is complete and the uniformity is very good. Its aqueous solution is clear and transparent, with few free fibers. The compatibility with rubber powder, cement, lime and other main materials is particularly strong, which can make the main materials play the best performance. However, HPMC with poor reaction has many free fibers, uneven distribution of substituents, poor water retention and other properties, resulting in a large amount of water evaporation in high temperature weather. However, the so-called HPMC with a large amount of additives is difficult to coordinate with each other, so the performance of water retention is even worse. When poor-quality HPMC is used, problems such as low slurry strength, short opening time, powdering, cracking, hollowing and shedding will be caused, which will increase the difficulty of construction and greatly reduce the quality of the building. The same is cellulose ether, can have completely different results.