TSSC (also known as p-Toluenesulfonyl semicarbazide, RA/TSSC, PTSS) with CAS number 10396-10-8 is a specialty organic chemical widely known for its use as a high-temperature blowing (foaming) agent in polymer processing.

Because of its dual identity as both a reagent (in organic synthesis) and a functional additive (in plastics/foaming), a comprehensive discussion must cover its structure, properties, synthesis, decomposition/foaming behavior, compatibility with polymers, safety and handling, regulatory/tariff aspects, and technical challenges in its use.

Chemical Identity, Structure & Physical Properties

Chemical Identity & Synonyms

• IUPAC / systematic name: 2-[(4-methylphenyl)sulfonyl]hydrazinecarboxamide (or in some sources “(4-methylbenzenesulfonic acid, 2-(aminocarbonyl)hydrazide”)

• Common synonyms: TSSC, p-Toluenesulfonyl semicarbazide, PTSS, RA (when marketed as a blowing agent)

• CAS number: 10396-10-8

• Molecular formula: C₈H₁₁N₃O₃S

• Molecular weight: ~ 229.26 g/mol

• InChIKey: VRFNYSYURHAPFL-UHFFFAOYSA-N

• SMILES: CC1=CC=C(C=C1)S(=O)(=O)NNC(N)=O

Physical Properties

• Appearance: off-white, free-flowing powder (fine crystalline)

• Density: ~ 1.381 g/cm³

• Melting point: ~ 236 °C

• Thermal stability / decomposition: begins to decompose at elevated temperatures (above ~200 °C)

Solubility:

• Insoluble or very sparingly soluble in water, acetone, many non-polar solvents.

• Some polar organic solvents may dissolve it to limited extent, but it is generally considered insoluble in most common solvents.

• Odor: odorless (no significant smell)

Other Properties & Derived Data

• Predicted pKa: ~ 8.92 ± 0.43 (calculated estimate)

• Ash content (residue after decomposition) and moisture content limits (e.g. water ≤0.5%) are typical in technical specs from manufacturers.

• Gas evolution (upon decomposition) in air: about 140–150 mL/g (as marketed spec for RA/TSSC)

• Decomposition temperature (5 °C/min in air): ≥ 228 °C (a quality spec)

Synthesis & Manufacturing Routes

The synthesis of TSSC is typically achieved via reaction of p-toluenesulfonyl chloride (tosyl chloride) with semicarbazide (or a semicarbazide salt) under suitable conditions.

General Reaction Scheme

• A simplified synthetic route: p-Toluenesulfonyl chloride + semicarbazide → p-Toluenesulfonyl semicarbazide + byproducts

More concretely:

• Semicarbazide (e.g. hydrazinecarboxamide) is used, perhaps in a base or neutral medium.

• Tosyl chloride (4-methylbenzenesulfonyl chloride) is slowly added under controlled temperature.

• Reaction is allowed to proceed, precipitate is filtered, washed, and purified.

Some suppliers and references mention two upstream routes:

• One route using hydrazinecarboximidic acid + tosyl chloride toward TSSC.

• Another route via related intermediates (e.g. using other reagents that ultimately yield the semicarbazide moiety).

Downstream, TSSC can be further reacted (for example, as a reagent in organic synthesis, or modified) but its main commercial route is the blowing agent form (RA/TSSC).

Purification & Quality Control

Key purification steps include:

• Washing to remove unreacted tosyl chloride, residual acid (HCl), and other inorganic salts.

• Recrystallization or filtration to improve purity.

• Drying under vacuum, possibly at moderate temperature to avoid decomposition.

• Quality control by HPLC, melting point, moisture content, ash, and gas yield (for blowing agent use) specification.

Commercial products often are offered with ≥ 98% purity, low water content, and defined decomposition/gas yield behavior.

Functional Role as a Blowing / Foaming Agent & Decomposition Behavior

One of the principal industrial uses of TSSC is as a chemical blowing (foaming) agent in polymer processing — particularly for structural foams in thermoplastic or thermosetting materials processed at high temperatures.

Mechanism of Gas Generation & Decomposition

The basic idea is that at elevated temperature, TSSC thermally decomposes, liberating gaseous products (e.g. N₂, CO, CO₂) that create a cellular foam structure.

Detailed aspects:

• The decomposition is not instantaneous; below ~200 °C, decomposition is slow, but above ~200–230 °C it becomes appreciable.

• In fire or overheating, decomposition is rapid and can be hazardous.

• Decomposition products can include nitrogen oxides, CO, CO₂, and sulfur oxides (SO₂) and possibly other volatile fragments.

• The “gas volume in air” is a standard metric for blowing agents — for RA/TSSC typical values are 140–150 mL/g.

• The decomposition temperature onset (for 5 K/min heating) is specified ≥ 228 °C.

Application Temperature Window

Because of its decomposition kinetics, TSSC is suited for polymers processed at high temperatures (≈200–240 °C). Many plastics such as ABS, nylon (PA), polycarbonate, high‐temperature PVC, and engineering thermoplastics qualify.

If used in lower temperature polymers, it may not decompose properly (insufficient gas generation) or cause foaming issues (premature decomposition).

Advantages & Limitations

Advantages:

• High thermal stability before decomposition (limits premature foaming)

• Relatively predictable gas release

• Compatibility with many high-temperature polymers

Limitations & technical issues:

• At even moderate overload or poor temperature control, premature decomposition or degradation may occur

• The presence of catalysts, residual acids, bases, or other additives may influence decomposition behavior (rate, gas yield)

• Gas generation may be insufficient in some matrix or require synergists/activators

• The foaming process needs careful balance: too much gas leads to cell rupture; too little, poor expansion

• Distribution and dispersion within the polymer matrix is a challenge — uneven dispersion leads to nonuniform cell structure

Compatibility with Polymers & Processing Considerations

When incorporating TSSC into polymer systems, various factors must be carefully managed.

Dispersion & Mixing

• TSSC must be uniformly dispersed in feed resin to prevent local overdosing and defects.

• Micro-pelletizing or masterbatch dilution may be used to facilitate handling.

• It must also remain stable during compounding before reaching the decomposition temperature.

Influence of Additives & Catalysts

• Additives such as stabilizers, fillers, antioxidants, inorganic salts, acid scavengers, and processing aids may interact with TSSC, modifying its decomposition kinetics.

• Residual acid or base in the system can catalyze or accelerate decomposition, potentially prematurely.

• Catalysts or accelerators specifically added to tune foaming behavior may help control cell nucleation and expansion.

Pressure, Mold Design & Temperature Profile

• Because TSSC evolves gas, the mold / die system must accommodate internal pressure control.

• Temperature gradient and dwell time must be designed to allow controlled decomposition and foam growth without rupturing the cell walls.

• Cooling rate, venting, and pressure release must be optimized to lock cellular structure.

Impact on Mechanical Properties

• The cellular structure (cell size, uniformity, density) dictates mechanical properties (strength, stiffness, impact resistance).

• Over-foaming (too high gas per volume) reduces structural integrity.

• Under-foaming yields low density and inefficient use of material.

Post-Processing Stability

• After foaming, the product must remain dimensionally stable.

• Residual decomposition or slow ongoing reactions could lead to gas evolution or shrinkage over time — so selecting the right grade and stabilizers is essential.

Safety, Handling, & Stability Considerations

When dealing with TSSC, a range of safety and stability concerns arise.

Hazard Classification & Regulatory Safety Data

• According to the MSDS, TSSC is considered not hazardous under 2012 OSHA HazCom standard (29 CFR 1910.1200) in some jurisdictions, though this may reflect specific concentration or packaged form disclaimers.

• In older or other MSDS sources, TSSC (or the form MIKROFINE TSSC) is classified as Class 4.1 (flammable solid), packaging group II.

• It may have hazard risk phrases R10 (flammable), R22 (harmful if swallowed), R42/43 (sensitizing by inhalation or skin contact).

• In many supplier datasheets, hazard statements include: H228 (flammable solid), H302 (harmful if swallowed), H317 (skin sensitizer), H319 (eye irritation), H341 (suspected of causing genetic defects), H351 (suspected of causing cancer).

• Precautionary statements often include P280 (wear protective gloves/eye protection), P210 (keep away from heat/ignition), P240 (use explosion-proof equipment), P264 (wash hands), P270 (do not eat), P301+P310 (if swallowed, call poison center), P370+P378 (in fire, use extinguishing media), among others.

Thermal Decomposition Risks & Explosion Potential

• As noted, TSSC decomposes quickly above ~200 °C, and at higher temps rapidly.

• In fire conditions, dense fumes and toxic gases (CO, CO₂, NOx, SOx) may evolve.

• There is a possibility of dust-air explosion if fine particles come into contact with ignition sources.

• Incompatible materials (strong oxidizers, strong acids or bases) can trigger hazardous reactions.

First Aid & Exposure Control

• Eye contact: Flush with copious water; seek medical attention.

• Skin contact: Wash thoroughly; if irritation persists, get medical attention.

• Inhalation: Move to fresh air; consult physician if symptoms.

Engineering controls and PPE:

• Use fume hoods, local exhaust ventilation.

• Wear protective gloves, safety goggles, lab coat.

• Work away from ignition sources; control electrostatic discharge.

• Storage in cool, dark, inert atmosphere (or under inert gas) is recommended. Some vendor spec suggests storage under –20 °C.

Stability & Shelf Life

• Over time, TSSC may slowly decompose, especially if stored above ambient or under moisture or impurities.

• Exposure to humidity, metals, acids, or catalytic impurities may accelerate degradation.

• Storage under dry inert atmosphere, in sealed containers, in cool environments, is critical.

Regulatory, Tariff & Import Classification

Because TSSC is used industrially, import, export, and tariff classification are relevant for users in cross-border trade.

• In a U.S. Customs ruling, Mikrofine TSSC (CAS 10396-10-8) is classified under HTSUS subheading **2935.00.7500** (sulfonamides: other) with a duty rate of 9.3% ad valorem.

• TSSC’s classification as a sulfonamide for tariff purposes (rather than an azo or diazo compound) is noteworthy.

Beyond tariffs, depending on jurisdiction:

• Regulatory registration (e.g. REACH in Europe) may require substance registration and safety dossiers.

• In many jurisdictions, due to its potential hazard and use in polymer applications, environmental discharge, waste handling, and disposal must comply with local legislation.

• Transportation classification: being a flammable solid (Class 4.1) in some MSDS, shipping must follow appropriate hazardous materials (HAZMAT) regulations.

Technical Challenges & Best Practices in Application

When using TSSC in industrial polymer/foam systems, several technical issues commonly arise; understanding and mitigating them is essential.

Premature or Uncontrolled Decomposition

• Impurities, residual acid/base, moisture, or catalysts may trigger early decomposition, leading to foaming during extrusion or insufficient control.

• Pre-drying of polymer resin and all ingredients is critical.

• The addition of stabilizers or inhibitors (radical scavengers, scavenging acids/bases) may help suppress premature decomposition.

Gas Yield Variability & Consistency

• Differences in batch purity, particle size, or additive interactions may reduce gas yield or change gas-evolution profiles.

• Quality control in manufacturing (COA, gas yield testing) is critical to consistency.

Cell Uniformity, Nucleation & Growth Control

• The number, size, and distribution of cells depend on nucleation sites, local supersaturation, and melt viscosity.

• Nucleating agents, processing temperature profile, pressure ramping, and cooling control can be tuned to optimize cell structure.

• If the gas generation is too fast relative to melt strength, cell rupture or coalescence may occur.

Compatibility & Interference with Other Additives

• Some polymer additives (e.g., residual catalysts, pigments, metal salts) may catalyze or inhibit TSSC decomposition.

• In composite systems (filled polymers, fiber reinforcements, etc.), the presence of fillers or reinforcers may affect local heat transfer and hence decomposition kinetics.

Thermal & Mechanical Stress in Processing Equipment

• Because decomposition is an exothermic process, local hot spots may accelerate decomposition.

• Equipment (extruders, mixers) must have uniform temperature control and shear profiles to prevent localized runaway reactions.

Scale-Up & Reliability

• Lab-scale results may not translate directly to industrial scale; residence time, mixing, thermal gradients, and mold geometry all differ.

• Real-time monitoring (e.g. pressure, temperature, gas generation) and feedback control may be necessary in large-scale processes.

Post-Foaming Stability & Aging

• Any residual decomposable material may continue to evolve gas slowly, causing dimension changes or internal stress.

• Over time, diffusion of gas or collapse of microstructures (e.g. coarsening) may alter foam properties.

• Aging studies and accelerated testing should be part of product qualification.