Most people who search for polyDADMAC are trying to solve one of two problems. Either a jar test showed that adding polymer alone will not drop the turbidity, or a supplier quoted "polyDADMAC" against an enquiry for flocculant and the two words got treated as interchangeable. They are not. PolyDADMAC is a coagulant, polyacrylamide is a flocculant, and on most plants they do different jobs in sequence rather than competing for the same dosing point. This guide explains what polyDADMAC actually is, the duties where it earns its cost, how it is dosed, and how it pairs with a polymer flocculant.
We should be straightforward about our own position first, because it changes how you should read the rest of this page. ChinaPAM manufactures polyacrylamide flocculants at our Xinxiang, Henan factory, with 100,000 t/yr documented capacity. We do not supply coagulants — not polyDADMAC, not polyamine, not PAC. That means we have nothing to sell you on the coagulant side of this decision, so what follows is written to help you specify it correctly with whoever does supply it, and to get the flocculant half of the pair right, which is the part we can genuinely help with.
What PolyDADMAC Is
PolyDADMAC is short for poly(diallyldimethylammonium chloride). It is a synthetic cationic polyelectrolyte built from a quaternary ammonium monomer, which means every repeating unit on the chain carries a fixed positive charge. That charge does not depend on pH. A quaternary ammonium group stays positive whether the water sits at pH 4 or pH 9, which is the single most useful property polyDADMAC has and the reason it holds up in duties where other cationic chemistries fade.
Two numbers describe a commercial grade. The first is charge density, which for polyDADMAC is inherently very high because every unit is charged. The second is molecular weight, which is low by polymer standards — typically in the tens of thousands to low hundreds of thousands of daltons, against 5 to 20 million for a flocculant-grade polyacrylamide. That combination, high charge and short chain, is what makes it a coagulant rather than a flocculant. It ships as a clear to pale yellow aqueous solution, commonly at 20%, 40%, or 50% active content, and it is already dissolved, so no make-up ageing is required.
It is worth knowing that polyDADMAC has a second life outside water treatment as a conditioner ingredient in shampoos and personal care, listed as Polyquaternium-6. That is the same chemistry, and it explains why the raw material has a broad supply base independent of the water treatment market.
Coagulant or Flocculant: The Distinction That Decides Your Dose
This is the confusion worth clearing up before anything else, because getting it wrong wastes chemical and produces water that never clarifies properly no matter how much you add.
A coagulant destabilises. Fine particles in raw water and most effluents carry a negative surface charge, and because like charges repel, the particles stay suspended and refuse to come together. They are stable, and stability is the problem. A coagulant supplies positive charge that cancels this repulsion. The particles can now approach each other and form very small, loose clusters called microflocs. Coagulant dose is set by how much charge the water demands, not by how much solid is present.
A flocculant bridges. Once particles are destabilised, they still need to be assembled into flocs large and strong enough to settle in a clarifier or release water on a filter belt. A high molecular weight polyacrylamide does that by adsorbing at several points along its very long chain and physically tying microflocs together. Flocculant dose is set by solids loading.
Sequence matters. Coagulant goes in first, at the point of highest mixing energy, because charge neutralisation needs rapid and complete dispersion within seconds. Flocculant goes in second, under gentle mixing, because the long chains that do the bridging are fragile and vigorous agitation shears them. Reverse the order, or dose both at the same point, and you generally get a worse result than dosing either one alone.
How Charge Neutralisation Actually Works
A suspended particle carries a surface charge, and the measurable proxy for it is zeta potential, reported in millivolts. Raw surface water typically sits somewhere around −15 to −30 mV. The more negative that figure, the more strongly particles repel one another and the more stable the suspension.
Adding a cationic coagulant moves zeta potential toward zero. The practical target is a small band near zero rather than an exact value, because at zero net charge there is nothing left to hold particles apart and they aggregate readily. This is why zeta potential or streaming current measurement is a far better dose control tool than turbidity alone: turbidity tells you the outcome after the fact, whereas charge tells you whether the dose is right now.
The consequence that catches people out is what happens past the optimum. Keep adding cationic coagulant beyond the neutral point and zeta potential crosses zero and climbs positive. The particles are now mutually repulsive again, this time because they are all positively charged, and the suspension restabilises. Turbidity climbs back up. An operator who reads rising turbidity as "not enough chemical" and increases the dose makes it worse with every increment. PolyDADMAC is especially prone to this because its charge density is so high that the window between underdose and overdose is narrow.
Charge demand also is not constant. It tracks the negative colloid and dissolved organic load in the water, so it moves with rainfall, season, and upstream process changes. A dose that was correct in dry weather is usually wrong after a storm. This is the argument for measuring rather than fixing the dose.
Charge density is the property doing the work here, and it behaves as an axis independent of molecular weight — a point that matters just as much when selecting the polymer that follows. Our explainer on what charge density means and how to read it on a spec sheet sets out how the two axes trade off against each other.
Where PolyDADMAC Earns Its Cost
PolyDADMAC costs considerably more per tonne than an inorganic coagulant like aluminium sulphate or polyaluminium chloride. It earns that premium in specific situations, and outside them the inorganic option is usually the better commercial choice.
Sludge volume matters. This is the main one. An inorganic coagulant works partly by precipitating metal hydroxide, and that precipitate becomes sludge you must then dewater and dispose of. PolyDADMAC contributes essentially no precipitated solids of its own, so for the same clarification duty the sludge volume is meaningfully lower. Where sludge disposal is expensive or capacity-limited, that saving can outweigh the higher chemical price on its own.
Alkalinity is limited. Alum and ferric coagulants consume alkalinity and drive pH down, which on soft or low-alkalinity water forces you to dose lime or caustic to compensate — a second chemical, a second dosing system, and a second cost. PolyDADMAC does not consume alkalinity and barely shifts pH.
The pH window is wide or unstable. Metal coagulants have a fairly narrow effective pH band, and outside it performance drops sharply. A fixed quaternary ammonium charge does not care, so polyDADMAC holds performance across a wide range and tolerates pH swings that would defeat alum.
Residual metal is unacceptable. Some duties cannot tolerate residual aluminium or iron in the treated water, whether for regulatory reasons, downstream process sensitivity, or product quality. An organic coagulant introduces no metal.
The common duties that follow from this are municipal drinking water clarification, oily wastewater and emulsion breaking, paper mill white water and pitch control, textile dye effluent where the dye itself is anionic, laundry and car wash recycling, and swimming pool clarification. It is also widely used as a partial replacement, where a reduced inorganic dose is combined with a small polyDADMAC dose to cut sludge volume without paying full organic coagulant cost.
Dosing PolyDADMAC
Because polyDADMAC ships as a solution, there is no dissolution step and none of the ageing discipline a powder polyacrylamide demands. That removes the most common source of field failure, but it introduces a different one: the neat product is viscous, and if it is injected without dilution it disperses poorly and you get localised overdose alongside untreated water. Dilute in-line to roughly 0.5% to 2% before the injection point, and inject where mixing energy is highest.
The dose figures below are representative ranges compiled from typical process practice, expressed as active polymer. They exist to size a jar test, not to replace one, because charge demand is water-specific and moves with conditions.
| Duty | Typical dose (mg/L active) | Notes |
|---|---|---|
| Drinking water clarification | 0.5–5 | Regulated duty; approval status must be confirmed for the jurisdiction |
| Municipal wastewater, primary | 2–15 | Often paired with reduced inorganic dose rather than replacing it |
| Oily wastewater / emulsion breaking | 10–50 | Higher demand; stable emulsions may need heat or pH adjustment as well |
| Paper mill white water | 2–20 | Also used for anionic trash and pitch control |
| Textile dye effluent | 20–100 | Demand tracks dye load; reactive dyes are the hardest case |
| Pool and recreational water | 0.5–3 | Sold retail as pool clarifier, usually at low active content |
One arithmetic trap is worth naming, because it produces both wrong doses and misleading price comparisons. PolyDADMAC is quoted at active contents ranging from 20% to 50%. A quote for 20% product at half the price of a 50% product is not a bargain, it is the same money for the same active polymer plus more freight for the water. Normalise every quote and every dose to active basis before comparing anything.
PolyDADMAC, Polyamine, or PAC
These three get quoted against each other constantly, and they are not equivalent. The comparison below is the one worth having before you commit to a chemistry.
| Property | PolyDADMAC | Polyamine | PAC (inorganic) |
|---|---|---|---|
| Charge type | Quaternary, pH-independent | Mostly secondary/tertiary amine, pH-sensitive | Hydrolysing metal species |
| Effective pH range | Wide | Narrower, weakens as pH rises | Narrow band, duty-specific |
| Sludge produced | Minimal | Minimal | Significant metal hydroxide |
| Alkalinity consumed | None | None | Yes, pH correction often needed |
| Cost per tonne | High | Moderate to high | Low |
| Dose required | Low (mg/L) | Low to moderate | High (tens of mg/L) |
Polyamine is the closest substitute and often the cheaper organic option, but its charge comes from amine groups that lose protonation as pH rises, so it fades in alkaline water where polyDADMAC holds. Polyamine also tends to perform better on emulsion breaking and oily duties, so the choice is genuinely application-specific rather than one being simply better. PAC remains the default for high-turbidity surface water where its sludge penalty is acceptable and its low cost dominates, and the frequent best answer on municipal plants is a reduced PAC dose plus a small organic coagulant dose rather than either alone.
Pairing a Coagulant With a Polymer Flocculant
On most plants that use polyDADMAC, it is one half of a two-chemical programme. The coagulant destabilises and the flocculant assembles, and the plant that runs both correctly uses less of each than a plant trying to do the whole job with one.
The practical arrangement is a rapid-mix zone where the diluted coagulant is injected and dispersed within seconds, then a flocculation zone with gentle tapered mixing where the polymer is added and flocs are allowed to grow without being sheared apart. Contact time between the two matters: dose the polymer too soon and it competes with charge neutralisation that has not finished, too late and the microflocs have already begun to settle unevenly.
Which polymer to pair depends on what the coagulant has left you with. After a cationic coagulant has neutralised the negative surface charge, an anionic polyacrylamide is usually the correct bridging flocculant, because the now near-neutral or slightly positive microflocs give an anionic chain good adsorption sites. This is the standard municipal and industrial clarification pairing. Where the solids are strongly organic and the duty is sludge dewatering rather than clarification, a cationic polyacrylamide often does both jobs adequately on its own and the separate coagulant becomes unnecessary. If you are unsure which polymer family fits the duty at all, our flocculant selection page sets out the four classes and where each one belongs.
The most common mistake in a paired programme is optimising the two chemicals separately. Charge demand and bridging demand interact: raise the coagulant dose and the optimum polymer dose usually falls, and vice versa. Jar testing should vary both together in a small grid rather than fixing one and tuning the other, or you will land on a combination that works but costs more than it needs to.
Potable Water and Regulated Duties
If the treated water is destined for human consumption, the chemistry question becomes a compliance question, and the answer is jurisdiction-specific rather than universal.
In North America the relevant framework is NSF/ANSI/CAN 60, the standard covering drinking water treatment chemicals, which is administered through certification bodies rather than being something a manufacturer can self-declare. The critical detail buyers miss is that certification attaches to a specific product from a specific production site, not to a chemical class. "PolyDADMAC is approved for potable water" is not a meaningful statement. The only meaningful question is whether the exact grade you are buying, from the exact plant producing it, holds a current listing — and that is verifiable, because certification bodies publish searchable listings. Ask for the certificate and check the listing yourself rather than accepting a general assurance.
In the European Union, chemicals placed on the market fall under REACH registration obligations, and drinking water contact materials are additionally governed by national and EU-level provisions that continue to evolve. Note that REACH registration is held by the EU importer or an appointed only-representative, not by a Chinese manufacturer — a supplier in China can provide safety data and composition information to support your filing, but cannot hold the registration for you. Treat any claim otherwise as a sign the supplier does not understand the regime.
Two residual concerns are specific to organic coagulants in potable duty. For polyDADMAC, unreacted DADMAC monomer is the parameter that matters, and certified grades carry limits on it. For polyamine chemistries, the relevant residuals relate to epichlorohydrin and its reaction products. Both are the reason potable-grade material costs more than industrial grade, and both are reasons not to substitute an industrial grade into a drinking water plant because the price looked better.
The same logic applies to the polymer side. Residual acrylamide monomer is the gating parameter for polyacrylamide in potable and food-contact duty, and it is the first thing to specify at enquiry rather than something to discover on arrival. Our guide to polyacrylamide in municipal drinking water covers what to require on the COA and how the regulated duties differ from industrial ones.
Storage and Handling
PolyDADMAC solution is chemically stable and undemanding compared with a powder polymer, but four practical points cause most of the field problems.
It freezes. The product is an aqueous solution, so it will freeze in an unheated store in winter. Freezing does not usually destroy the polymer, but it can cause separation, and partially thawed material dosed from the top of a drum delivers the wrong concentration. Thaw fully and mix before use, and store above freezing where you can.
It corrodes carbon steel. A concentrated quaternary ammonium chloride solution is aggressive to carbon steel. Dosing systems should be polyethylene, polypropylene, PVC, PVDF, or an appropriate stainless grade. This catches plants retrofitting an organic coagulant into pipework that was sized and specified for something else.
Spills are a slip hazard, not just a mess. Polymer solution on a wet floor is genuinely dangerous, and the instinct to hose it down makes it worse because water spreads it and increases the slipperiness. Contain and absorb with an inert absorbent, then remove the absorbent.
Shelf life is finite. Sealed drums typically hold for around one to two years depending on grade and storage temperature. Confirm the figure with your supplier and rotate stock rather than assuming indefinite stability.
Frequently Asked Questions
Is polyDADMAC the same as polyacrylamide?
No, and the difference is functional rather than cosmetic. PolyDADMAC is a low molecular weight, very high charge density cationic coagulant that destabilises particles by neutralising surface charge. Polyacrylamide is a high molecular weight flocculant that bridges already-destabilised particles into large flocs. They do sequential jobs, and on many plants both are dosed. Our comparison of anionic versus cationic polyacrylamide covers how the polymer families differ from each other once you get to the flocculant stage.
Can polyDADMAC replace my polyacrylamide?
Generally not, because its chains are far too short to bridge particles into settleable flocs. There is one partial exception: on strongly organic sludge in a dewatering duty, a high charge density cationic polyacrylamide can sometimes handle both charge neutralisation and bridging on its own, which removes the need for a separate coagulant. That is a case of the polymer replacing the coagulant, not the reverse.
Why did my water get cloudier when I increased the dose?
You have most likely passed the charge neutralisation optimum and restabilised the suspension. Past the optimum, particle surfaces carry net positive charge and repel one another again, so turbidity rises. The corrective action is counterintuitive: reduce the dose and retest in small decrements. PolyDADMAC is more prone to this than inorganic coagulants because its charge density is so high that the usable window is narrow.
How do I compare quotes at different active contents?
Normalise everything to active polymer before comparing. A 20% solution at half the price of a 50% solution is not cheaper per unit of active polymer, and you also pay freight on the extra water. Ask for price per tonne of active content and dose in mg/L active, then compare.
What should I ask a coagulant supplier for?
Active content and how it was determined, charge density, molecular weight class, viscosity at supply concentration, freezing point, recommended dilution range, materials compatibility, shelf life, and for potable duty the specific certificate with a listing you can verify independently. If a supplier cannot produce a batch COA, that is the answer to the question.
Do you sell polyDADMAC?
No. We manufacture polyacrylamide flocculants only, so we do not supply polyDADMAC, polyamine, or PAC. We can help you specify the flocculant that pairs with whichever coagulant you select, and we would rather tell you that plainly than quote you something we do not make.
Getting the flocculant half right
If you have the coagulant sorted and need the bridging polymer to match it, tell us the duty, the water or sludge characteristics, the equipment downstream, and the coagulant you are dosing. We will recommend a grade and send samples so you can jar test the pairing before committing to a container. Trial MOQ is 500 kg with free samples first, TDS, COA and SDS supplied per batch, and lead time on common grades runs 7 to 10 days after order confirmation.
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