The residual acetate ion in polyvinyl alcohol resin can be determined by acid-base titration, and the degree of alcoholysis of polyvinyl alcohol resin can be determined by colorimetry.
Determination method of polyvinyl alcohol resin residual acetate:
First, completely dissolve the polyvinyl alcohol resin sample in deionized water, take a part of it out and add enough hydrochloric acid solution, neutralize the sodium acetate in it into acetic acid, and titrate it with an indicator such as phenolphthalein, and record the titration volume.
According to the chemical equation of the reaction, the content of acetate in the sample can be calculated. The chemical equation for the reaction is:
NaOAc + HCl → CH3COOH + NaCl
Acetate content (%) = (titration volume × concentration × 82.03) / sample weight
Among them, 82.03 is the molar mass of sodium acetate, the unit of titration volume is mL, the unit of concentration is mol/L, and the unit of sample weight is g.
Determination method of alcoholysis degree of polyvinyl alcohol resin:
First dissolve the polyvinyl alcohol resin sample completely in water, take a certain amount of polyvinyl alcohol resin solution, add excess boric acid (or other borates) and mix well, then add sulfuric acid (or other sulfates) to make the concentration Reach 1mol/L.
Then, use the 1,3,5-trimethylbenzene comparison tube for colorimetry, and compare the alcoholysis degree of the polyvinyl alcohol resin with the colorimetric degree of the boric acid complex to calculate the value of the alcoholysis degree.
NBCHAO reminds you: During the operation, care should be taken to maintain the purity of the reagents and use precise measuring instruments to ensure the accuracy and repeatability of the measurement results.
