Polyvinyl alcohol resin (PVA) is a commonly used polymer material and has a wide range of applications in many application fields. Among them, the sodium hydroxide (NaOH) content of PVA is an important parameter, and its determination method is as follows:
principle
Sodium chloride (NaCl) is generated by the reaction of PVA with hydrochloric acid (HCl), and then silver chloride (AgCl) is used to react with chloride ions (Cl^-) in PVA to form a precipitate, and the content of NaOH in PVA is determined by the content of chloride ions content.
Steps
Take a small amount of PVA sample, add about 50 mL of deionized water, heat and stir until the sample is completely dissolved.
Take 1 mL of PVA solution, add 15 mL of deionized water and 2.5 mL of hydrochloric acid solution, and let stand for 5 minutes.
Titrate with silver chloride solution (0.1 mol/L) until the formation of chloride ion precipitation stops, and record the titration volume V1.
Wash the precipitate with deionized water, filter, dry, and heat to 100°C until the mass no longer changes, and record the mass m1 after drying.
Take 1 mL of PVA solution, add 15 mL of deionized water and 2.5 mL of hydrochloric acid solution (to remove NaOH in the sample), and let it stand for 5 minutes.
Titrate with silver chloride solution until the formation of chloride ion precipitation stops, and record the titration amount V2.
Wash the precipitate with deionized water, filter, dry, and heat to 100°C until the mass no longer changes, and record the mass m2 after drying.
calculate
Calculate the content of NaOH in PVA according to the content of chloride ions.
NaOH (%) = (V1 - V2) × N × 40.01 × 100 / (m1 - m2)
Among them, V1 and V2 are the titration amount (mL), N is the standard concentration of silver chloride (mol/L), 40.01 is the molecular weight of NaOH (g/mol), m1 and m2 are respectively heated to 100 ℃ and dried Mass (g). The final result is expressed as a percentage.
