Weigh 0.5g of the dry sample (accurately to 0.0002g) into a 500mL beaker, continue to heat up until the solution has just turned milky white, take 50ml of the hydroxypropyl methyl cellulose ether HPMC solution in 100ml. In the colorimetric tube, place the colorimetric tube in a 500mL beaker to heat it in a water bath, slowly increase the temperature and gently stir the sample, then place the beaker in an ice water bath to cool down, transfer the solution to a 250mL volumetric flask, and record the temperature as condensation Lower limit of glue temperature.
The temperature rise rate of HPMC aqueous solution of hydroxypropyl methylcellulose ether is 0.51℃ per minute. Shake well for later use. Stir fully to make it swell. The range is 50-100℃. Add 50mL of 80-90℃ hot water, when the solution appears milky white silky When gelling. Insert a 50-100℃ thermometer, carefully observe the change of the solution, dilute to the mark with distilled water, and record the temperature as the upper limit of the gel temperature.
The gel temperature of hydroxypropyl methyl cellulose ether HPMC is 60℃, 65℃, 75℃ and so on. The gel temperature directly affects the performance of the cellulose ether HPMC, so when choosing a product, you must make it clear to the salesperson to choose a suitable product.