Poly(diallyl dimethyl ammonium chloride) – PDADMAC to most of us, Quaternium-40 to the INCI crowd – shows up on safety data sheets as CAS 26062-79-3 and in everyday plant talk as “the workhorse polymer with the built-in charge.” Whether you label it PDAC, PolyDMDAAC, or simply the 261 series, this linear cationic polyelectrolyte stays the same: a positively charged backbone that grabs anionic nasties and refuses to let go.

What’s in the jug – and why it matters

At a glance, the formula reads C₈H₁₆N and the molecular mass tips the scale at 126.2 g mol⁻¹, but the magic lies in the repeating quaternary nitrogens. Dissolve the beads or the 20 % syrup and you’ll see 1.09 g cm⁻³, a flash point north of 100 °C, and a near-instant formation of crystal-clear stock liquor. Operators appreciate that the residual monomer stays low (we’re talking parts per million), which keeps toxicological scores slim and regulators calm.

Chemistry that performs in real streams

Pour it into a dyehouse effluent coloured like melted Skittles and something remarkable happens: the chroma collapses. Acid, reactive, even disperse dyes don’t stand much chance once the polymer’s cationic claws wrap around their sulfonate groups. The same mechanism binds clays, silica fines, and the odd spec of iron oxide, knitting them into dense, fast-settling flocs. Next to alum or PAC, you’ll need a lighter dose and you’ll haul away less sludge. When the river runs chocolate-brown after a summer thunderstorm, the plant that feeds PDADMAC (in grades cleverly tagged e261, 261LV, or cp261LV) still ships water that meets turbidity targets.

Beyond the dewatering station

Head down the hall to the paper machine and you’ll find the polymer again – this time reinforcing sheets and tightening surfaces without bringing formaldehyde along for the ride. Over in textiles it fixes dyes under slightly acidic liquor, giving deeper shades and better wash-fastness minus aldehyde odor headaches. Extrude polyester filament? A whisper of PDADMAC in the spin finish kills static so fibers slide past each other instead of hugging every speck of lint.

Bottom line

PDADMAC, PolyDADMAC, Quaternium-40 – call it what you will – delivers charge where you need it, performance you can measure, and a greener footprint than yesterday’s coagulants. If you’re wrestling with colour, fines, or electrostatic headaches, this polymer wants the job. Need titration curves, residue specs, or on-site dosage advice? Our lab coat brigade likes nothing better than a fresh challenge – drop us a line.