How to determine the acid resistance of surfactants

(1) Method overview

Acid has hydrolysis effect on some surfactant textile auxiliaries, and the solubility of the hydrolyzed products is different from the original auxiliaries, so the acid resistance of the auxiliaries in acidic aqueous solution can be judged from the change of the appearance of the solution.

(2) Instruments and reagents

(1) Round bottom flask 250ml.

(2) Spherical condenser 300ml.

(3) Pipette 2ml.

(4) Measuring cylinder 250ml, 500ml.

(5) Volume bottle 1000ml.

(6) Beaker l50ml, 600ml.

(7) Electric thermostatic water bath constant temperature range of 37 ~ 100℃, temperature fluctuation ±l℃, Hy31 type or the same effect of constant temperature water bath.

(8) Sulfuric acid (GB 625) is chemically pure.

(9) Formic acid (HG-3-1296) is chemically pure.

(3) Operation procedures

1. Preparation of sample solution

(1) Weigh the sample 2g(accurate to 0.1g) and dissolve it in 1000ml distilled water.

(2) Weigh the sample 5g(accurate to O.1g) and dissolve it in 1000ml distilled water.

2. Test method

(1) 200ml of the first sample solution (2g/L) was added to the three 250ml round-bottom flask, and then 0.4g sulfuric acid (0.22m1) and 0.4g formic acid (0.34m1) were added to the first flask; 1.Og sulfuric acid (0.55 m1) and 1.0g formic acid (0.85 m1) were added to the second flask. In the third flask, 2.0g sulfuric acid (1.1m1) and 2.0g formic acid (1.70m1) were added. After adding acid, first visually test the appearance of the solution, and then heat to boil, reflux. Starting from reflux, the time was measured visually for 3 times at 30min, 60min and 120min, and the appearance of the solution was recorded. Remove from heat and leave overnight. The next day, visual inspection again l times. If there is turbidity or precipitation, then temperature rise to 60℃ after visual measurement l times. The result of the secondary test prevails.

(2) The acid resistance of the second test solution (5g/L) was determined with the same operation steps.

(4) Results

1. Look at the rating criteria

Grade 1 - the solution is completely clarified;

Grade 1 ~ 2 - the solution is milky white to slightly cloudy;

Grade 2 - the solution is cloudy but no flocculent;

Grade 2 to 3 - the solution is very cloudy but no flocculent or oil is separated;

Grade 3 - whether the solution is clear or cloudy, flocculent or oil is separated.

2. assess

After the acid test of three concentrations of surfactants, the acid resistance grade of the surfactants is assessed according to the first rating standard, which can be divided into the highest acid resistance grade, acid resistance grade, conditional acid resistance grade and non-acid resistance grade. Specific provisions are as follows:

Highest acid resistance grade - tested with 3 concentrations of acid. Results reached l grade or reached 1 ~ 2 grade after standing overnight;

Acid resistance grade - after testing with a medium concentration of acid, reaching grade 1 or Grade L-2 in the rating;

Conditional acid resistance grade - after testing at moderate concentrations of acid. Achieving level 2 or 2-3 in the rating and level 2 after acid testing at low concentrations;

Non-acid-resistant grade - Grade 3 after testing with the lowest concentration of acid.