SYNTECH

1. Core Structural Difference (Root of All Property Gaps)

Sodium Allyl Sulfonate SAS

Structure: CH₂​=CH−CH₂​−SO₃​Na

• Unsubstituted terminal double bond, no methyl branch
• Low steric hindrance around C=C bond, high polymerization reactivity

Sodium Methallyl Sulfonate SMAS

Structure: CH₂​=C(CH₃​)−CH₂​−SO₃​Na

• Extra methyl group attached to vinyl carbon
• Methyl creates strong steric hindrance, slows self-polymerization and chain transfer rate

2. Basic Chemical Identity Comparison

Item	SMAS	SAS
CAS No.	1561-92-8	2495-39-8
Molecular Formula	C4​H7​NaO3​S	C3​H5​NaO3​S
Molecular Weight	158.15	144.12
Double bond substitution	2-methyl substituted vinyl	Unsubstituted allyl vinyl
Steric hindrance	High	Low

3. Chemical & Polymerization Performance

1. Reactivity & Self-Polymerization Stability

• SAS: Highly reactive C=C; aqueous solution easily self-polymerizes under heating/UV; short shelf life for liquid grade
• SMAS: Methyl steric barrier suppresses spontaneous polymerization; liquid & powder storage far more stable, less gel risk

2. Chain Transfer Ability

• SAS: Strong chain transfer effect, drastically lowers polymer molecular weight
• SMAS: Moderate, controllable chain transfer; ideal for precise molecular weight regulation in polycarboxylate superplasticizer

3. Copolymer CompatibilitySAS suits acrylic fiber, electroplating additives; SMAS matches polycarboxylate, oilfield chemicals, latex emulsion

4. Physical & Industrial Specifications

Purity & Impurity

• SMAS premium powder: ≥99.5%, ultra-low chloride/sulfite (≤0.035% Cl⁻)
• SAS standard powder: 98–99%, slightly higher inorganic impurities allowed

Solubility & Thermal Decomposition

• SMAS decomposes ≥280℃; SAS decomposes ≥300℃
• Both fully water-soluble; SMAS slightly less soluble in short-chain alcohols

Commercial Forms

• SMAS: Mainly 99.5% anhydrous powder; small volume 35% liquid
• SAS: Dual mainstream: 35% liquid (electroplating dominant) + 98–99% powder

5. Separate Core Application Fields (Non-interchangeable)

Sodium Allyl Sulfonate SAS

1. Acid nickel electroplating primary brightener (largest consumption)
2. Acrylic fiber third monomer
3. Water treatment scale inhibitor, general emulsion auxiliary

Sodium Methallyl Sulfonate SMAS

1. Key co-monomer for polycarboxylate concrete superplasticizer (core exclusive use)
2. Oilfield fluid loss agent, high-performance dispersant
3. High-stability latex polymerization, textile antistatic agent
4. Long-distance export preferred (better storage stability)

6. Storage & Operation Difference

• SAS liquid: Prone to gelation, antifreeze required, shorter shelf life (18 months)
• SMAS liquid/powder: Resists gelling, wider temperature tolerance, powder shelf life up to 24 months
• SAS powder dust easier to auto-polymerize; SMAS dust has minimal self-reaction risk