Quality Parameters Covered
Appearance
Checks the physical condition, uniformity and cleanliness of the supplied polymer.
Relative Molecular Mass
Uses dilute-solution viscometry to evaluate the polymer-chain characteristics of the PAM grade.
Solid Content
Determines the mass remaining after controlled drying to constant mass.
Anionic Degree
Measures the anionic functionality of applicable grades by a standardized colloid-titration procedure.
Dissolution Time
Tracks conductivity during controlled dissolution and records the time required to reach a stable endpoint.
Particle Size Distribution
Uses controlled mechanical sieving to quantify coarse and fine fractions.
Water-Insoluble Matter
Separates, dries and weighs material that remains after extended dissolution.
1. Sampling and Sample Preparation
Reliable results begin with a representative sample. For solid PAM, sampling points are distributed across the selected packaging units. The sampler is inserted vertically into the material so that product is collected from below the surface rather than only from the top layer. The increments are combined, mixed and reduced by quartering to obtain the laboratory sample.
The final sample is placed in clean, dry and tightly sealed containers. Each container is identified with the product name, grade, batch number, sampling date and sampler. One portion is used for testing and a separately sealed portion is retained for traceability. PAM is hygroscopic, so unnecessary exposure to ambient humidity is avoided during sampling, weighing and storage.
Laboratory control: All mass-based calculations use the actual test-portion mass and, where required, the measured solid-content fraction. Instruments are verified before use, and reagent blanks or duplicate determinations are included when specified by the method.
2. Appearance Inspection
A representative portion is spread in a clean, dry tray and inspected under uniform lighting. The analyst records the physical form, color uniformity, particle consistency, visible agglomeration, foreign material and any sign of moisture pickup or package contamination.
Appearance inspection is not used as a substitute for laboratory measurement. It is an initial identity and handling check that helps identify abnormal storage, damaged packaging or cross-contamination before instrumental testing begins.
3. Relative Molecular Mass by Dilute-Solution Viscometry
Method principle
PAM increases the flow time of a dilute sodium chloride solution through an Ubbelohde viscometer. The solvent flow time and polymer-solution flow time are used to calculate relative viscosity, specific viscosity and intrinsic viscosity. Relative molecular mass is then derived from the validated Mark-Houwink relationship for the method.
Main equipment and solution
Ubbelohde viscometer with a working capillary internal diameter of approximately 0.58 mm.
Constant-temperature bath controlled at 30.0 °C ± 0.1 °C.
Stopwatch readable to 0.1 s.
Acid-resistant filtration funnel and volumetric glassware.
1.0 mol/L sodium chloride solution used as the solvent.
Solvent flow-time check
The clean, dry viscometer is placed vertically in the constant-temperature bath with the measuring bulb immersed. Filtered sodium chloride solution is introduced to the specified filling marks and allowed to equilibrate for 10-15 min. The liquid is drawn above the upper timing mark and released. The time required for the meniscus to pass between the timing marks is measured three times. Closely agreeing readings are averaged to obtain the solvent flow time, t0.
Polymer solution preparation
A test portion equivalent to about 0.02 g on a dry basis is weighed to 0.2 mg in a dry beaker. It is dissolved with sodium chloride solution without introducing undissolved fisheyes, transferred quantitatively to a 100 mL volumetric flask, diluted to volume with the same solvent and mixed thoroughly. The concentration is adjusted so that the polymer-to-solvent flow-time ratio is between 1.2 and 2.0, keeping the measurement within the method's working interval.
Measurement and calculation
The polymer solution is equilibrated and measured using the same viscometer procedure to obtain t1. The relative viscosity and specific viscosity are calculated as follows:
In these equations, c is the dry-basis polymer concentration in g/dL, [η] is intrinsic viscosity, M is relative molecular mass, and K and α are the constants specified in the approved method. Duplicate results are reviewed for repeatability before the value is reported.
4. Solid Content by Oven Drying
Method principle
A known mass of PAM is dried under controlled conditions until constant mass is reached. The remaining dry mass is expressed as a percentage of the original test portion.
Procedure
Step 1: Dry a clean weighing bottle at 120 °C ± 2 °C, cool it in a desiccator and record its constant mass as m0.
Step 2: Add approximately 1 g of sample and weigh the test portion to 0.2 mg. Record the sample mass as m.
Step 3: Place the open weighing bottle in the oven at 120 °C ± 2 °C and dry to constant mass.
Step 4: Cool the covered bottle in a desiccator and record the mass of the bottle plus dried sample as m1.
Parallel determinations are performed, and the arithmetic mean is reported after the repeatability check is satisfied.
5. Anionic Degree by Colloid Titration
Method principle
The anionic groups in a dissolved PAM sample react with a known amount of methyl glycol chitosan under alkaline conditions. The excess cationic reagent is titrated with standardized potassium polyvinyl sulfate solution using toluidine blue as the endpoint indicator. A reagent blank is tested in parallel, and the blank-corrected titrant consumption is used to calculate the anionic degree.
Reagents and equipment
Magnetic stirrer and suitable volumetric glassware.
Sodium hydroxide solution, hydrochloric acid solution and purified water.
Standardized methyl glycol chitosan solution.
Standardized potassium polyvinyl sulfate titrant.
Toluidine blue indicator.
Titrant standardization
The potassium polyvinyl sulfate titrant is standardized against a accurately weighed cetylpyridinium chloride reference solution. An aliquot of the reference solution is diluted, adjusted to pH 3.5-4.5 and treated with toluidine blue. The titration proceeds to the specified blue-to-purple endpoint. A blank is run under the same conditions, and the blank correction is included when calculating the exact titrant concentration.
Sample solution
Water is placed in a 500 mL beaker and stirred until a stable vortex forms. Approximately 1 g of PAM is added slowly and uniformly into the vortex to prevent agglomeration. Stirring continues until the polymer is completely dissolved and the total prepared solution mass is recorded.
Titration
A weighed portion of the prepared PAM solution is transferred to a 250 mL conical flask and diluted with 100 mL water. The pH is adjusted to 10.4-10.6. A 5 mL aliquot of methyl glycol chitosan solution and three drops of toluidine blue indicator are added. The mixture is titrated with standardized potassium polyvinyl sulfate until the solution changes from blue to purple. A blank determination is performed at the same time.
The anionic degree is calculated from the blank-corrected titrant volume, the exact titrant concentration, sample-solution mass, total prepared mass, measured solid fraction and the stoichiometric relationship defined in the approved calculation sheet. Duplicate determinations and endpoint consistency are reviewed before reporting.
6. Dissolution Time by Conductivity Monitoring
Method principle
The conductivity of water increases as PAM dissolves. When the polymer has fully dissolved under controlled mixing and temperature conditions, the conductivity reaches a stable value. The elapsed time from sample addition to a stable conductivity reading is recorded as the dissolution time.
Procedure
Step 1: Add 100 mL water to a 200 mL beaker and place it in a temperature-controlled bath.
Step 2: Position the conductivity probe 5-10 mm from the beaker wall with an immersion depth of approximately 20 mm.
Step 3: Start stirring and adjust the speed to form a vortex approximately 20 mm deep.
Step 4: Bring the bath to 30 °C ± 1 °C and allow the system to equilibrate for 10-15 min.
Step 5: Weigh 0.040 g ± 0.002 g of PAM and add it through the upper part of the vortex in a controlled manner.
Step 6: Record conductivity continuously. Stop the test when the reading shows no change for 3 min.
The time from sample addition to the stable endpoint is reported in minutes. The analyst also records any fisheyes, floating agglomerates, wall deposits or abnormal solution behavior observed during the test.
7. Particle Size Distribution by Mechanical Sieving
Equipment
A 200 mm diameter sieve assembly is prepared with a receiving pan, a 180 µm sieve and a 1.00 mm sieve. The sieves are clean, dry and pre-weighed. A mechanical sieve shaker operating at approximately 350 cycles per minute is used.
Procedure
Step 1: Assemble the pan, 180 µm sieve and 1.00 mm sieve from bottom to top.
Step 2: Weigh approximately 200 g of sample to the nearest 1 g and place it on the upper sieve.
Step 3: Secure the lid and operate the sieve shaker for 20 min.
Step 4: Carefully brush the underside of each sieve, keeping the released particles with the correct fraction.
Step 5: Weigh each sieve with its retained material and weigh the receiving pan fraction as required.
Separate results are recorded for the material retained on the 1.00 mm sieve and the material retained on the 180 µm sieve.
8. Water-Insoluble Matter
Method principle
A known mass of PAM is dissolved for an extended period under controlled stirring. The solution is passed through a pre-cleaned and pre-weighed stainless-steel screen. The retained material is washed, dried to constant mass and weighed.
Procedure
Step 1: Clean a 0.11 mm opening stainless-steel screen with acetone, dry it to constant mass and record the screen mass as m1.
Step 2: Add 1,000 mL water to a beaker and start stirring to form a vortex approximately 4 cm deep.
Step 3: Weigh approximately 0.4 g of PAM to 0.2 mg and add it slowly to the vortex.
Step 4: Continue stirring at room temperature for 6 h.
Step 5: Filter the solution through the prepared stainless-steel screen without losing retained material.
Step 6: Dry the screen and retained material at 120 °C ± 2 °C to constant mass, cool in a desiccator and record the combined mass as m2.
Here, m0 is the original sample mass. Parallel determinations are completed and reviewed before the result is entered in the batch record.
9. Data Review and Batch Release
Each test record includes the sample identity, batch number, test date, analyst, instrument identification, calibration status, reagent identity, raw observations, calculations and duplicate-test review. Unexpected results trigger a documented investigation and, when appropriate, resampling and retesting under the approved procedure.
The laboratory result is reviewed against the applicable Bluwat product specification, purchase contract and customer-specific requirements. Only reviewed data are used for batch disposition and the final Certificate of Analysis.
10. Laboratory Safety and Good Testing Practice
Analysts wear the required laboratory coat, gloves and eye protection and follow the current safety data sheets for all reagents.
Volatile solvents are handled with suitable ventilation and kept away from ignition sources.
Glassware and screens are cleaned, dried and protected from contamination before weighing.
PAM is added slowly to moving water to prevent fisheyes and uneven wetting.
Balances, ovens, temperature baths, conductivity meters and timing devices are maintained under the laboratory calibration program.
Controlled work instructions and current approved forms take precedence over this public method overview.
Frequently Asked Questions
Why is PAM tested on a dry basis?
Moisture affects the apparent concentration of active polymer. Dry-basis calculations allow test results to be compared consistently between samples and batches.
Why is sodium chloride used in the viscometry method?
The controlled ionic-strength medium reduces variability caused by electrostatic expansion of charged polymer chains and supports a more reproducible viscosity measurement.
Why is conductivity used to determine dissolution time?
Conductivity provides a continuous, instrument-based signal as the polymer hydrates and dissolves. A stable reading under fixed temperature and mixing conditions provides a consistent endpoint.
Can one test result describe PAM performance in every wastewater?
No. Laboratory quality tests confirm product consistency, while treatment performance also depends on wastewater chemistry, pH, suspended solids, mixing conditions and dosage. A jar test with the actual water is recommended for grade selection and process optimization.
Are the same methods used for every PAM grade?
The core principles are consistent, but the applicable test set and calculation details depend on whether the product is anionic or nonionic and on the agreed grade specification. The laboratory follows the approved inspection plan for the batch being tested.
Reference and Scope
This article is a practical overview of Bluwat Chemicals' quality-control approach for anionic and nonionic water-treatment polyacrylamide, developed with reference to GB/T 17514-2017. It is intended to explain the testing workflow and does not replace the full standard, a controlled laboratory SOP, a product specification or a customer contract.
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