Method of Analysis (MOA) For Water Soluble Polyester (WSP) Resin

Method of Analysis (MOA) for Water-Soluble Polyester (WSP) Resin

1. Intrinsic viscosity

Capillary viscometer method

1.1 Summary

The flow times of a pure solvent and a specimen solution at a concentration of 0.005 g/mL are measured at 25 ℃. The intrinsic viscosity value is calculated from the measured flow time and the concentration of the specimen solution. Choose these capillary viscometers, which meet the requirement that their kinetic energy correction term is unnecessary to be considered, such as type 1B capillary viscometers.

1.2 Apparatuses

1.2.1 Thermostatic bath, capable of being maintained at (25.00±0.05)℃

1.2.2 Ubbelohde viscometer, Gas-supported liquid column Ubbelohde viscometer type 1B as specified in lS0 3105. Other types of viscometers listed in lS0 3105 may be used, provided equivalent results are obtained. In the event of a dispute, Ubbelohde viscometers shall be used.

1.2.3 Conical flask, of capacity 100 mL, fitted with a ground-glass stopper.

1.2.4 Pipette or liquid adder, of capacity 25 mL.

1.2.5 Analytical balance, of accuracy 0.1 mg.

1.2.6 Filter, stainless-steel filter screening, with a nominal aperture size of [70,120] μm or corresponding sintered-glass funnel.

1.2.7 Timer, of accuracy 0.01 s.

1.2.8 Heating device, of accuracy 2℃.

1.2.9 Vacuum dryer, capable of being maintained at (105 ± 5)℃, with pressure less than 133.3 Pa.

1.3 Reagents

1.3.1 Phenol/1,1,2,2-tetrachloroethane(mass ratio 50 :50)

The two solvents are well mixed in a 50:50 mass ratio, and the weighing accuracy is at least 1%. The density range is(1.280±0.003)g/cm³ at (25.00±0.02)℃.

1.3.2 Phenol/1,1,2,2-tetrachloroethane (mass ratio 60:40)

The two solvents are well mixed in a 60:40 mass ratio, and the weighing accuracy is at least 1%. The density range is (1.235+0.003)g/cm³ at(25.00±0.02)℃.

1.4 Test specimen

1.4.1 Weigh (0.125 +0.005)g of test specimen(accurate to 0.1 mg) into a conical flask. If the moisture content is higher than 0.5%, dry the test specimen in a vacuum dryer at 105℃ for 3 h, with the pressure lower than 133.5 Pa. Cool the test specimen to room temperature in a desiccator. The test specimen may also be washed with acetone to remove surface moisture, and the residual acetone is then evaporated in the oven at 80℃ for 15-20 min.

1.4.2 The weighing mass is calculated according to Formula(1).

where

m    is the mass of the test specimen, expressed in grams(g);

W_i   is the content of inorganic materials in the test specimen, expressed in percentage;

w₀   is the content of other additives in the test specimen, expressed in percentage

When the contents of inorganic materials or other additives of the test specimen exceed 0.5%, the mass shall be corrected.

1.5 Preparation of solution

Keep the solvent temperature at (25 ± 2)℃. Add 25 mL of the solvent into the flask. Stopper the flask and warm on the heating device. Place the test specimen in the oven. The water-soluble polyester resin is heated at (50±5)°C under vacuum for 4 hours to remove surface moisture without melting. Take out the test specimen and cool it to room temperature. Grind and continuously sieve the test specimen through sieves with openings of 833 µm and 350 µm. Collect the residue on the 350-µm sieve.

The concentration (c) of the specimen in solution is calculated according to Formula (2), expressed in grams per 100 mL (g/100 mL).

1.6 Testing procedure

1.6.1 Filter the solvent into the Ubbelohde viscometer. Fill the viscometer to a level between the filling mark lines.

1.6.2 Mount the Ubbelohde viscometer in the thermostatic bath at(25.00± 0.05)℃. Ensure that the viscometer is vertical and that the upper timing mark line is at least 30 mm below the surface of the bath liquid. Allow at least 15 min for the solvent temperature in the viscometer to reach equilibrium. Determine the flow time of the solvent five times; the values should not differ from each other by more than 0.1 s. The mean value is the flow time of solvent(t₀). Clean the viscometer if two successive determinations of the mean flow time differ by more than 0.4 s.

1.6.3 Determine the flow time of solution in the same viscometer and in the same manner. Repeat the measurements three times; the values should not differ by more than 0.2 s. The mean value is the flow time of solution(t₁).

1.7  Result calculation

1.7.1 Calculate the relative viscosity(ŋ_r) and specific viscosity(ŋ_sp)  according to Formula(3) and Formula(4):

where

ŋ_r    is relative viscosity;

t₀     is the flow time of solution, expressed in seconds(s);

ŋ_sp    is the flow time of solvent, expressed in seconds(s);

t₁     is specific viscosity.

1.7.2 When using phenol/1,1,2,2-tetrachloroethane solvent (mass ratio 50 : 50)(5.1.1.3.1), calculate the intrinsic viscosity([ŋ])according to Formula(5).

When using phenol/1,1,2,2-tetrachloroethane solvent(mass ratio 60 : 40)(5.1.1.3.2), calculate the intrinsic viscosity([ŋ])according to Formula(6).

where

ŋ_r         is relative viscosity;

ŋ_sp        is specific viscosity;

[ŋ]     is intrinsic viscosity, expressed in deciliters per gram(dL/g);

c      is the concentration of the specimen solution, expressed in grams per 100 mL(g/100 mL).

1.7.3 The viscosity of the dilute solution of polyester resin may also be expressed by viscosity number( I ), which is calculated according to Formula(7), expressed in milliliters per gram(mL/g).

1.8 Expression of results

The intrinsic viscosity is expressed as the mean of two parallel tests and rounded to the third decimal place in accordance with GB/T 8170.

Annex A gives the numerical relationship between the intrinsic viscosity measured in two different proportional solvents.

1.9 Precision

1.9.1 Repeatability

When the intrinsic viscosity is [0.630,0.720]dL/g, the absolute difference between two independent single test results obtained under repeatability conditions will not be greater than the repeatability limit (0.006 dL/g)in more than 5% of cases.

1.9.2 Reproducibility

When the intrinsic viscosity is [0.630,0.720] dL/g, the absolute difference between two single test results obtained under reproducibility conditions will not be greater than the reproducibility limit(0.006 dL/g)in more than 5% of cases.

2. Color

Dry-grinding method

2.1 Summary

After drying and grinding, the color of the test specimen is measured by an automatic colorimeter. The result is expressed in the HunterLab color system L, a, b.

NOTE: Comparisons of color measurements can only be made if the material is the same; the pellet cut, size, and shape of chips are essentially the same; the test instrument has the same geometrical structure and approximate observation port.

2.2 Apparatuses

2.2.1 Colorimeter, illumination of D65, 10° viewing angle, 0/45 or 45/0 directional geometry.

HunterLab color system, recommended ports [45,52]mm.

2.2.2 Specimen cell, in quartz glass.

2.2.3 Oven.

2.2.4Specimen sieve, with a nominal aperture size of 833 um and 350μm.

2.3 Testing procedure

2.3.1 Place the test specimen in the oven. The polyester resin is heated at(140±5)℃ for 60 min. Take out the test specimen and cool it to room temperature. Grind and continuously sieve the test specimen through sieves with openings of 833 µm and 350 µm. Collect the residue on the 350-µm sieve.

2.3.2 Pack the test specimen particles tightly in the specimen cell. Place the specimen cell on the measuring port. Measure the color(values of L, a, b )at each 120°rotation for a total of three times.

2.4 Expression of results

The result is expressed as the mean of three 120° rotations and rounded to the first decimal place in accordance with GB/T 8170.

2.5 Precision

When the L value is [75.0,95.0], the b value is [- 1.0, 6.0], the a value is [-2.0,2.0], the absolute difference between the two independent single test results obtained under repeatability conditions will not be greater than the repeatability limit(2.0)for L value, (0.6)for b value, (0.4) for a value in more than 5% of cases.

3. Solubility

Weigh approximately 20 g of the test specimen in the dried weighing bottle, accurate to 0.1 mg. Return the weighing bottle to the oven and heat at 120°C for another 2 hours to dry the specimen to a constant weight.

4. Moisture content

Gravimetric method

4.1 Summary

Heat the test specimen to evaporate moisture. Determine the moisture content according to the mass loss of the test specimen after drying.

4.2 Apparatuses

4.2.1 Analytical balance, of accuracy 0.1 mg.

4.2.2 Vacuum dryer oven or ventilating oven or electric heating blast dryer, temperature range [20,200]℃

4.2.3 Weighing bottle, 65 mm in diameter and 5 mm in height.

4.2.4 Desiccator.

4.3 Testing procedure

4.3.1 Put the weighing bottle in the oven (if a vacuum dryer oven is used, ensure the residual pressure is lower than 400 Pa). Heat at 120 ℃ for 2 h. Open the oven (or remove the vacuum from the dryer, if applicable) and promptly transfer the weighing bottle into a desiccator to cool for 30 min. Weigh the mass to an accuracy of 0.1 mg.

4.3.2 Weigh approximately 20 g of the test specimen in the dried weighing bottle, accurate to 0.1 mg. The further procedure is the same as 5.7.1.3.1.

4.4 Result calculation

Calculate the moisture content according to Formula(11).

where

X₄      is the moisture content of the test specimen, expressed in percentage;

m₁     is the mass of the test specimen with the weighing bottle before drying, expressed in grams (g);

m₂    is the mass of the test specimen with the weighing bottle after drying, expressed in grams(g);

m      is the mass of the test specimen, expressed in grams(g).

4.5 Expression of results

The result is expressed as the mean of two parallel tests and rounded to the second decimal place in accordance with GB/T 8170.

4.6 Precision

When the moisture content is [0.10%, 0.40%], the absolute difference between two independent single test results obtained under repeatability conditions will not exceed the repeatability limit (0.05%) in more than 5% of cases.

5. Glass Transition Temperature(Tg)

5.1. Scope of Application

This method applies to fiber-grade, bottle-grade, and film-grade polyester resin. The glass transition temperature (Tg) is determined using a Differential Scanning Calorimeter (DSC).

5.2. Instruments and Materials

5.2.1 Differential Scanning Calorimeter (DSC), with aluminum crucibles, crucible lids, and sample press

5.2.2 Analytical balance (accuracy: 0.01 mg)

5.2.3 Forced-air drying oven and desiccator

5.2.4 High-purity nitrogen gas (purity ≥ 99.99%)

5.3. Sample Preparation and Pre-treatment

5.3.1 Sampling: Randomly collect representative polyester chips and remove any impurities or discolored particles.

5.3.2 Drying: Place the sample in a vacuum drying oven at (50±5)°C for 12 hours. Immediately transfer to a desiccator upon removal and allow to cool to room temperature before use.

5.3.3 Sample Loading: Weigh 5–10 mg of sample and place into a standard aluminum crucible. Seal with a lid and press firmly, ensuring the sample is evenly spread with no voids and no risk of spattering.

5.4. Instrument Parameter Settings

5.4.1 Atmosphere: High-purity nitrogen, flow rate 20–50 mL/min

5.4.2 Heating Rate: 10°C/min (standard rate; must not be altered)

5.4.3 Temperature Program:

Initial temperature: room temperature

Final temperature: 300°C

5.4.4 Reference: Empty aluminum crucible

5.5. Test Procedure

5.5.1 Instrument Warm-up: Switch on the DSC unit, cooling system, and gas lines in advance. Purge the lines with nitrogen for at least 5 minutes.

5.5.2 Sample Placement: Place the loaded crucible in the sample position and an empty crucible in the reference position. Close the furnace.

5.5.3 Start Test: Enter the sample ID and name, then run the pre-set temperature program.

5.5.4 After Test: Once the program is complete, remove the crucibles, clean the furnace chamber, and save the raw curve and data.

5.6. Data Reading and Result Evaluation

5.6.1 The Tg value is taken as the midpoint temperature of the glass transition step on the DSC curve.

5.6.2 Run 2 parallel tests. If the difference between the two results is ≤ 1.0°C, report the average as the final result. If the difference exceeds this limit, repeat the test.

5.6.3 Reference range for standard polyester resin: 70–80°C.

5.7. Precautions

5.7.1 Moisture significantly lowers Tg. Samples must be thoroughly dried, and contact with air during cooling must be strictly avoided to prevent moisture absorption.

5.7.2 Crucibles must be properly sealed to prevent sample volatilization or decomposition at high temperatures, which may affect the curve.

5.7.3 Calibrate the instrument regularly using certified reference materials (e.g., indium, tin) for both temperature and enthalpy.

5.7.4 If a cold crystallization peak is present in the sample, it does not affect Tg reading — the transition step remains the basis for determination.

5.7.5 For samples from the same batch, keep sample weight, heating rate, and gas flow parameters consistent to ensure data comparability.

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Q: How do you test water-soluble polyester resin quality?
A: We evaluate IV, color, solubility, moisture content, and Tg through standardized laboratory testing procedures.

If you are looking for a stable water-soluble polyester resin supplier or need technical support for your specific application, please feel free to contact us. We are ready to provide professional solutions tailored to your requirements.

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