Polyacrylamide (PAM) physical and chemical properties

Polyacrylamide (PAM)

[Structural formula]

The chain extension of polyacrylamide is linear and has a hydrophilic amido group (-CONH ₂ ), so it can be dissolved in water

[Physical and chemical properties] White powder or translucent beads and flakes

[Preparation method] There are many preparation methods of polyacrylamide.

(1) Aqueous polymerization method

Aqueous solution polymerization is a polymerization reaction in which monomer acrylamide and initiator are dissolved in water.

Example: Preparation method of polyacrylamide emulsion

①Put deionized water into the container, add acrylamide, ammonium sulfate, dispersant, acryloyloxyethyl dimethyl benzyl ammonium chloride at a stirring speed of 40 ~ 70r/min, and dissolve uniformly to make a raw material liquid Standby

②Pump the raw material liquid into the reactor, ventilate nitrogen to remove oxygen, and heat up to 20-50°C, add 20-100 parts of seed emulsion, and stir at a speed of 50-60r/min

③After dissolving the initiator and reducing agent in water, add them to the raw material liquid and react for 10-20h at a stirring speed of 40-60r/min

④ Add anhydrous sodium sulfate and continue stirring for 30 minutes

⑤Add acetic acid and continue stirring for 30 minutes to discharge, then the product is obtained

(2) Inverse emulsion polymerization method

Inverse emulsion polymerization refers to the polymerization of water-soluble monomers dispersed in non-polar organic solvents under the action of emulsifiers and initiated by oil-soluble or water-soluble initiators

However, the process of this method is difficult to control.

Li Xiaolan and others studied the influence of initiator, oil-water ratio and feeding method on the synthesis of ultra-high molecular weight polyacrylamide

In patent USP6686417, Reekmas uses amphiphilic polymer low HLB value block polymerized butyl stearate as emulsifier and vegetable oil as continuous phase to prepare polyacrylamide

(3) Precipitation polymerization method

The so-called precipitation polymerization method refers to the use of appropriate solvents and additives on the basis of solution polymerization to dissolve the monomers in the medium, and the resulting polymer is insoluble in the medium and precipitates, and granular products can be directly obtained.

The advantages of the precipitation polymerization method are: the heat of polymerization is easy to dissipate, and the viscosity of the system is small, which greatly improves the ease of operation of the polymerization process; the remaining monomers in the later stage of the reaction can still diffuse freely, which is beneficial to increase the conversion rate and increase the molecular weight; The molecular weight distribution of the polymerization product is narrow, and most of the residual monomers are retained in the solvent, which is beneficial to obtain high-purity and low-toxic products; the reaction materials can be pumped, the product can be separated or filtered, and the airflow dried to obtain a loose powdery product, which simplifies the post-processing process

(4) Radiation polymerization method

The method of radiation polymerization is to add an aqueous solution of acrylamide into a container, then vacuumize, fill with nitrogen, close the container, and irradiate ⁶⁰ Co gamma rays at a certain temperature to cause polymerization reaction to obtain the product

[Technical index] GB 17514-1998 water treatment agent polyacrylamide

[Application] Polyacrylamide is used as a scale inhibitor in industrial cooling water systems.
In most cases, it needs to be used in combination with other scale inhibitors and requires a relative molecular mass in the range of 8000～10000.
High molecular weight polyacrylamide is generally used.
Used as a flocculant
.
Polyacrylamide with a relative molecular mass in the range of 10 ⁵ to 10 ⁶ can peel off sludge when used in conjunction with other scale inhibitors
.