Physicochemical properties of hydroxypropyl methylcellulose
Hydroxypropyl methylcellulose (HPMC) is an organic macromolecule compound commonly used as a water-soluble film-coating agent with good chemical stability. Appearance: White or almost white fibrous or granular powder Stability: Solid is flammable and incompatible with potent oxidizing agents. Particle size; 100 mesh pass rate greater than 98.5%; The pass rate of 80 mesh is 100%. Particular specifications with a particle size of 40-60 mesh. Carbonization temperature: 280-300 ℃. Apparent density: 0.25-0.70g/cm3 (usually around 0.5g/cm3), specific gravity 1.26-1.31. Color change temperature: 190-200 ℃. Surface tension: 42-56dyne/cm in a 2% aqueous solution.
Solubility: Soluble in water and some solvents, such as appropriate proportions of ethanol/water, propanol/water, etc. Aqueous solutions have surface activity: high transparency, and stable performance. The gel temperature of products of different specifications differs, and the solubility changes with viscosity. The lower the density, the more excellent the solubility. The performance of HPMC of other specifications is different, and the dissolution of HPMC in water is not affected by pH value. With the decrease of methoxy content, the increase of gel point, the reduction of water solubility, and the decline of surface activity of HPMC. HPMC also has thickening ability, low salt resistance, pH stability, water retention, dimensional stability, excellent film-forming power, extensive enzyme resistance, dispersibility, and adhesion. Dissolution method: Dry mixing can add all models to the material. It is best to use a cold water dispersion type when it is necessary to add it to a room-temperature aqueous solution directly. After adding it, it usually takes 10 to 90 minutes to thicken. The ordinary model is first dispersed by stirring with hot water and then cooled by adding cold water to dissolve. If clumping and wrapping occur during dissolution, it is due to insufficient stirring or the direct addition of ordinary models to cold water. In this case, rapid stirring should be carried out. If bubbles are generated during dissolution, they can be removed by standing for 2 to 12 hours (the specific time depends on the consistency of the solution), vacuuming, pressurizing, or adding an appropriate amount of defoamer. If you are looking for high quality, high purity and cost-effective zinc sulfide, or if you require the latest price of zinc sulfide, please feel free to email contact mis-asia.