Mini-Encyclopedia of Papermaking Wet-End Chemistry
Additives and Ingredients, their Composition, Functions, Strategies for Use

POLYDIALLYLDIMETHYLAMMONIUM CHLORIDE (DADMAC)

Composition: The name of this chemical says it all. It is a linear homopolymer formed from a monomer that has a quaternary ammonium and two unsaturated -CH=CH2 functionalities. The monomer itself is formed by reacting two equivalents of allyl chloride with dimethylamine. Free-radical polymerization of the "DADMAC" monomers yields a structure in which the quaternary ammonium groups are on rings that are included in the backbone of the polymer chain. This composition means that the poly-DADMAC macromolecules tend to be quite stiff, having a longer persistence length than, for instance, polyamines. For this reason, poly-DADMAC is expected to have a more extended conformation in solution. The molecular weight of DADMAC is typically in the range of hundreds of thousands of grams per mole, and even up to a million for some products. DADMAC is usually delivered as a liquid concentrate having a solids level in the range of 10 to 50%.

Function: Pitch control; charge neutralization; promoter for anionic retention aids

Strategies for Use: Highly charged additives, including poly-DADMAC products, should be well diluted before use. A concentration of about 1% is likely to be a safe starting point in applications where there is no previous experience. When poly-DADMAC is used for pitch control, the best strategy is to add it near to the main source of the problem. The idea is to anchor the tacky particles onto the fibers before they have a chance to collide with each other and grow. Though poly-DADMAC is very effective as a charge-control additive, trials may be needed to justify its higher cost (usually) compared to polyamines, and especially alum. Poly-DADMAC is sometimes added to furnish that later will be treated with an anionic polyacrylamide (aPAM) retention aid. The cationic polymer forms patch-like cationic sites on the fibers and fines that can serve as anchoring points for an anionic polymer.

Cautions: Read the MSDS and follow procedures recommended by the manufacturer

   

PLEASE NOTE: Users of the information contained on these pages assume complete responsibility to make sure that their practices are safe and do not infringe upon an existing patent. There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives. Please send corrections if you find errors or points that need better clarification.


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This page is maintained by Martin Hubbe, Associate Professor of Wood and Paper Science, NC State University, m_hubbe@ncsu.edu .