Cellulosic HPMC a versatile excipient in pharmaceutical formulations.
1、Hydroxypropyl methyl cellulose can provide viscosity and can be used as anti-settlement additive.
2、Hydroxypropyl methylcellulose can enhance the flowability and pumpability, thus improving the floor efficiency.
3、Hydroxypropylmethylcellulose can control water holding capacity, thus greatly reducing cracking and shrinkage.
Generally, three principle working mechanisms for water retention can come into place whenever a cement paste is subject to filtration on a substrate. These potential mechanisms have been proposed in earlier works by Desbrières and are as follows [20], [21]: (a) Water retention as a result of increased viscosity: increased dynamic filtrate viscosity can decelerate the filtration rate. (b) Water retention as a result of adsorption: anionic polymers may adsorb onto hydrating cement particles and obstruct filter cake pores either by polymer segments which freely protrude into the pore space or even bridge cement particles. Through this mechanism, filter cake permeability is reduced. (c) Water retention as a result of physical pore plugging: polymers may plug pores in the cementitious matrix through formation of polymer films (e.g. latexes), or through large polymer associates which form a 3D network, or through simple swelling and expansion caused by the uptake of an enormous amount of water into the inner sphere and hydrate shells of polymers. This process leads to the formation of large microgel particles. Through this mechanism, a large portion of the mixing water is physically bound and cannot leak-off into a porous substrate. The enormous water-binding capacity of polysaccharides has been described in an earlier study. By using a sorption balance and a microcalorimeter it was found that at the saturation level, neutral polysaccharides (amylose and amylopectin) can bind up to four water molecules per anhydroglucose unit [22].
These features collectively make Methyl Hydroxyethyl Cellulose (MHEC) a valuable and versatile additive, offering numerous benefits in various industries such as construction, personal care, pharmaceuticals, coatings, and more.
Here, an attempt was made to establish the working mechanism of MHEC. For this purpose, its water retention effectiveness in cement paste and its dynamic viscosity in cement pore solution were measured. Furthermore, its potential adsorption on cement was probed via a specifically designed static filtration test. Finally, concentration-dependent hydrodynamic diameters of solved MHEC molecules, and their surface tension in cement pore solution were measured to establish the mechanism underlying the effectiveness of MHEC as water retention agent.