Hydroxypropyl methylcellulose (hereinafter referred to as HPMC) can be divided into instant type and slow-soluble type. Instant hydroxypropyl methylcellulose HPMC refers to the surface treatment using cross-linking agent during the production process, so that HPMC can be dissolved in cold water. It is quickly dispersed in the medium, but it is not really dissolved. Through uniform stirring, the viscosity slowly rises before it is dissolved; slow-dissolving HPMC can also be called a hot-melt product. It clumps together in cold water and can be dissolved in warm water (the water temperature should not exceed 60℃), quickly disperse in hot water, stir evenly, and when the temperature of the solution drops to a certain temperature, the viscosity will slowly appear until a transparent viscous colloid is formed.
The physical and chemical indicators of instant-soluble and slow-soluble HPMC are the same, but they differ in the scope of application. Slow-dissolving HPMC is mainly used in dry-mixed mortars such as mortar and putty. After even dry mixing, HPMC is separated by other materials. After adding water, the viscosity will appear immediately and will not clump; when making glue and paint, clumps will occur. Phenomenon, it must be dissolved with warm water or thorough stirring.
Instant-dissolving HPMC has a wider application range than slow-dissolving HPMC. It can be used in lime-calcium-based putty and cement-based mortar, as well as glue and paint. Under alkaline conditions, instant-dissolving HPMC quickly reaches the calibrated viscosity; in gypsum-based In mortar, due to the acidic pH value of gypsum, instant HPMC is slow to stick out, and the initial setting of building gypsum is ≥3 minutes and final setting is ≤30 minutes. Although a certain amount of retarder is added to gypsum-based mortar to delay its setting time, but its operating time is still not as good as cement-based and gypsum-based products, so some alkaline substances must be added to improve the sticking time of HPMC.
Post time: Oct-07-2023