Purification of polyurethane prepolymer
May 05, 2021
1. Qualitative: Take 10% newly prepared potassium iodide solution and 10ml polyurethane prepolymer to shake, and the peroxide will be yellow-brown.
2. Quantification: add 6 ml of acetic acid + 4 ml of chloroform + 1 g of potassium iodide to 50 ml of polyurethane prepolymer, place it in the dark for 5 minutes, and titrate with 0.1N sodium thiosulfate solution until it is colorless. The peroxide percentage is: NXVX0.7/G where N and V are the equivalent concentration and volume (ml) of sodium thiosulfate respectively, and G is the weight (g) of the polyurethane prepolymer.
3. Removal method:
A. Removal of water: use anhydrous calcium oxide, molecular sieve, calcium hydride.
B. Removal of peroxide: use sodium hydroxide, sodium borohydride, calcium hydride, copper chloride solution, ferrous sulfate solution. After the test, sodium hydroxide can only play a masking effect on the determination of peroxides, and cannot really remove the peroxides, so it is not used; and the copper chloride solution and the ferrous sulfate solution are dehydrated because the other focus of this experiment is to add this solution. Large water content is not suitable.
