Risks of Synthesizing Water Treatment Copolymers with SMAS at Temperature Exceeding 100℃

Sodium Methallyl Sulfonate (SMAS) features allylic unsaturated double bonds and hydrophilic sulfonate side chains. When the polymerization system temperature rises above 100 °C, a series of irreversible monomer degradation, abnormal polymerization, finished product performance failure and safety hazards will occur, detailed as follows:

1. Thermal Degradation of SMAS Monomer, Loss of Sulfonate Functional Groups

• The C-S bond connecting the sulfonate group to the allyl skeleton is thermally unstable above 100 °C. Thermal cleavage generates free sulfate ions and unsaturated hydrocarbon fragments; the core anti-scale/dispersion sulfonate active segments are permanently lost.
• Degraded small hydrocarbon fragments form neutral hydrophobic impurities that cannot chelate Ca²⁺/Mg²⁺, directly reducing the salt tolerance and iron oxide dispersion capacity of the final copolymer.
• Decomposition produces trace acidic sulfonic acid byproducts, causing local pH collapse in the reaction kettle and accelerating side hydrolysis of acrylic acid.

2. Runaway Violent Exothermic Polymerization & Crosslinking Gelation

Persulfate thermal initiators decompose extremely rapidly over 100 °C, releasing massive free radicals in an instant:

• Ultra-high molecular weight cross-linked copolymer gels form in large quantities. The gel is water-insoluble, completely losing scale inhibition and dispersion functions, and cannot be used as water treatment agent.
• The polymerization reaction releases a large amount of latent heat; high temperature further accelerates radical chain growth, forming a positive feedback exothermic cycle, which may cause kettle material overflow, bumping and even pressure safety valve jumping, bringing major production safety risks.
• Severe gel agglomerates adhere to the reactor wall, stirring paddles and heat exchange coils, difficult to clean, and pollute subsequent batches of products.

3. Severe Side Reactions Reduce Monomer Conversion & Generate Mass Impurities

(1) Allyl double bond oxidation & homopolymerization

High temperature accelerates the oxidation of SMAS allylic groups by dissolved oxygen, generating aldehyde and ketone impurities. Meanwhile, SMAS self-homopolymerizes massively independent of acrylic acid; the homopolymer has poor calcium scale inhibition performance and increases finished product impurity content.

(2) Decarboxylation side reaction of acrylic acid

Temperatures above 100 °C trigger decarboxylation of acrylic acid monomers, releasing CO₂ bubbles, forming low-carbon alkane oligomers that cause persistent foaming in cooling water systems after dosing.

(3) Intermolecular dehydration crosslinking between copolymer chains

High temperature promotes dehydration condensation between carboxyl and sulfonate groups on polymer chains, forming internal crosslinking points. The copolymer turns turbid after dilution, precipitates under high-hardness circulating water, and blocks dosing pipelines and RO membrane pores.

4. Deteriorated Comprehensive Performance of Finished Water Treatment Copolymer

1. Weakened threshold scale inhibition: Loss of sulfonate groups reduces crystal lattice distortion ability, and the inhibition rate of calcium carbonate, calcium phosphate scale drops by more than 40%.
2. Poor metal ion dispersion: Cannot stably disperse iron oxide, manganese dioxide and silt; heat exchangers are prone to iron fouling and under-deposit corrosion.
3. Poor zinc salt stabilization: Unable to chelate zinc corrosion inhibitor components, forming zinc phosphate sludge and depositing on equipment surfaces.
4. Short shelf life & discoloration: High-temperature synthesized copolymers contain residual peroxide initiators and unsaturated degradation impurities; they turn dark yellow/brown within 1–2 months of storage, with continuous attenuation of activity.

5. Auxiliary Production & Equipment Hazards

1. Solvent volatilization loss: Aqueous reaction systems boil violently above 100 °C, a large amount of water vapor carries volatile organic impurities to the tail gas absorption system, increasing solvent consumption and waste gas treatment load.
2. Equipment corrosion acceleration: SMAS thermal decomposition produces weak acidic substances; long-term high-temperature acidic environment corrodes stainless steel reactor linings, flanges and heat exchange tubes, increasing metal ion contamination in products.
3. Difficult post-processing: Gelled materials block filter cloth and pipeline during filtration, greatly extending separation and washing time, raising production costs and reducing batch yield.