| Feed preparation | Diallyldimethylammonium chloride (DADMAC) aqueous feed | Commercial aqueous monomer feeds are commonly about 60 wt% DADMAC; the polymerization feed is often diluted to a grade- and equipment-dependent concentration. | Confirm feed assay and calculate the batch charge on an active-monomer basis. Use compatible, corrosion-resistant equipment. |
| Feed preparation | Solution pH and water quality | A mildly acidic to near-neutral feed, approximately pH 4–7, is a practical screening window; the validated product specification takes precedence. | Record pH and water conductivity. Keep feed composition consistent because salts and contaminants can affect polymerization and viscosity. |
| Reactor preparation | Oxygen control | Reduce oxygen exposure before initiation; maintain an appropriate inert-gas blanket during the reaction. | Oxygen can inhibit free-radical polymerization. Record the purge procedure and verify reliable venting and pressure control. |
| Initiation | Water-soluble radical initiator | Ammonium persulfate is one established initiator option. A preliminary screening range is about 0.05–0.30 wt% active initiator on active monomer. | The appropriate initiator system and dosage depend on the target molecular weight, solids, and reactor scale. Follow the validated formulation and chemical-handling procedures. |
| Polymerization | Reaction temperature | A representative development window is about 55–70 °C, selected according to the initiator system and heat-removal capacity. | Use a calibrated reactor-temperature probe and trend the temperature throughout the batch. Scale-up requires reaction-calorimetry and cooling-capacity review. |
| Polymerization | Mixing and heat removal | Maintain effective agitation as viscosity rises; no single impeller speed is transferable across reactor sizes or geometries. | Trend temperature, agitator load, and cooling response. Establish operating limits and an approved response for temperature excursions before running a batch. |
| Conversion tracking | Residual DADMAC sampling | Take representative samples at defined intervals, for example at 0, 1, 2, and 4 hours during process development. | Use a validated method such as HPLC or ion chromatography to quantify residual monomer. Quench or prepare samples using the validated analytical procedure. |
| Conversion tracking | Conversion calculation | Conversion (%) = 100 × (initial DADMAC amount − residual DADMAC amount) ÷ initial DADMAC amount. | Correct for sample dilution and use consistent mass or mole units. Set the batch endpoint from the applicable product specification rather than a universal conversion value. |
| Viscosity tracking | Sample conditioning and test method | Compare samples at a fixed temperature, concentration, and equilibration time; 25 °C is a common laboratory test temperature. | Specify the viscometer, spindle or geometry, speed or shear rate, and sample concentration. Report viscosity in mPa·s (cP) with the full test conditions. |
| Viscosity tracking | Interpretation of viscosity trend | Viscosity commonly increases as polymer forms, but it is not a direct measure of conversion and is strongly affected by molecular weight, solids, salts, and test conditions. | Use residual-monomer analysis for conversion decisions and viscosity as a separate process and product-quality trend. |
| Finishing and release | Cooling, dilution, and final checks | Cool and adjust the product to the specified solids and handling viscosity; final concentration depends on the intended grade. | Check appearance, solids, pH, viscosity under the specified method, and residual monomer against the approved product specification. |