Determination of ash content of polyvinyl alcohol resin

The ash content of polyvinyl alcohol resin refers to the percentage of the amount of inorganic matter remaining after burning off the organic matter in the sample at high temperature to the mass of the sample.

A common measurement method is described below:

• Experimental equipment and reagents:

• Oven: temperature controllable to 600°C, accuracy ±5°C

• Beaker: capacity about 50 mL, accuracy ±0.2 mL

• Potassium chromate (K2Cr2O7): purity ≥ 99.5%

• Sulfuric acid (H2SO4): purity ≥ 95%

• Deionized water

Experimental steps:

1. Adjust the oven temperature to 600 °C and wait at least 30 min for it to reach a steady state.

2. Weigh the dried polyvinyl alcohol resin sample and record its mass (m1).

3. Take a clean beaker, weigh about 3 g of sample, and record its net weight (m2).

4. Put the beaker into an oven that has been preheated to 600°C, and heat it until the sample is completely combusted and no longer emits smoke. Generally, it takes 3-4 hours to burn.

5. Turn off the oven and let it cool to room temperature.

6. Take out the beaker, add about 25 mL of deionized water, and dissolve the residue in the water with a magnetic stirrer.

7. Add 1 mL of concentrated sulfuric acid and 3 g of potassium chromate, and stir evenly with a magnetic stirrer for 2 min.

8. Let stand for 10 min to precipitate impurities.

9. The supernatant was filtered, washed with deionized water until neutralized, and the filtrate was collected.

10. Dry the filtrate in an oven until the quality no longer changes.

11. Take out the dried beaker and sample, and record its mass (m3).

12. Calculate the ash content: Ash content (%) = (m3 - m2)/m1 × 100%.

NBCHAO reminds you: During the operation, avoid contact between the sample and the dust in the air to avoid errors. At the same time, during the heating process, it is also necessary to avoid temperature gradients in the oven and try to maintain a uniform temperature distribution.