Phenothiazole

Product Name Phenothiazole
Alias Phenothiazine
Einecs 202-199-1
Mininmum Order 25g
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
Price Inquiry sales9@bouling-chem.com
Manufacturer Bouling Chemical Co., Limited
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In terms of specification, Phenothiazole is supplied with ≥ 98% purity (HPLC) and melting point 112–115°C, making it suitable for pharmaceutical intermediate synthesis.

Specifications

HS Code	149843
Chemical Formula	C12H9NS
Molar Mass	199.27 g/mol
Appearance	Yellow to greenish - yellow needles or powder
Odor	Faint characteristic odor
Melting Point	184 - 186 °C
Boiling Point	371 °C
Solubility In Water	Insoluble
Solubility In Organic Solvents	Soluble in ethanol, benzene, chloroform
Density	1.24 g/cm³
Stability	Stable under normal conditions, but may react with strong oxidizing agents

As an accredited Phenothiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	Phenothiazole packaged in 5 - kg bags for secure storage and handling.
Shipping	Phenothiazole, a chemical, must be shipped in accordance with strict regulations. It should be packaged securely in suitable containers to prevent leakage. Shipping is via approved carriers following hazardous material transportation guidelines.
Storage	Phenothiazole should be stored in a cool, dry, well - ventilated area away from heat sources and ignition points. Keep it in a tightly closed container to prevent exposure to air and moisture which could potentially lead to degradation. Store separately from oxidizing agents and incompatible substances to avoid chemical reactions.

Application of Phenothiazole

In the continuous distillation train for glacial acrylic acid esters, oxygen-dependent radical scavenging is established by injecting a metered solution of phenothiazole into the reflux return line of the rectifying column. The inhibitor is typically pre-dissolved in a matching monomer or a low-volatility process ester to ensure homogeneous distribution before contact with the 85–120°C downcomer liquid. At an active concentration of 15–50 ppm for butyl acrylate and 25–80 ppm for methyl methacrylate — calibrated against the free monomer double-bond content measured by liquid-phase FTIR per ASTM E168 — phenothiazole extends the unstabilized induction period to beyond 120 days at 25°C under nitrogen blanket containing 3–8 vol% dissolved oxygen. Depletion monitoring via GC-FID with a DB-WAX column triggers a replenishment dosing pump when residual inhibitor falls below 5 ppm. This approach is mandated in bulk terminal logistics for UV-curable acrylate monomers supplied to radiation-cure coating formulators and pressure-sensitive adhesive coaters, where premature exotherm in isotank shipments constitutes a runaway hazard. Compliance is audited against ISO 13741-1:2022 for residual monomer determination and EC No 1907/2006 (REACH) Annex II safety data sheet communication; phenothiazole is not listed in Annex XVII restricted substances, but end-users executing FDA 21 CFR 175.300 indirect food-contact clearances must verify migration limits independently, as phenothiazole lacks an explicit food-contact listing. A processing constraint that commands attention is the inhibitor’s reliance on molecular oxygen: dissolved O₂ below 2 ppm in bulk monomer collapses the inhibition cycle, rendering the additive inert and risking a fast polymerization front that can overwhelm the column’s rupture disc rating.

Improving Long-Term Heat Ageing of Glass-Fibre Reinforced PA66 with a Phenothiazole/Copper Halide Binary System

When a 0.2–0.5 wt% loading of phenothiazole is combined with a copper iodide/potassium iodide masterbatch delivering 150 ppm active Cu⁺ in a 40D L/D co-rotating twin-screw extruder processing 30% glass-fibre reinforced polyamide 6,6, the radical-trapping contribution of the thiazine heterocycle retards the oxidative embrittlement path that otherwise limits continuous-use temperature. Compounding proceeds at a barrel setpoint of 270–285°C with vent-port vacuum maintained below −0.09 MPa gauge; the resin pre-dried to ≤0.12% moisture by Karl Fischer titration (ISO 15512:2019) is side-fed with the phenothiazole powder dispersed in a micronised polyethylene wax carrier to prevent bridging in the loss-in-weight feeder. The resulting granulate undergoes injection molding at a clamp force sufficient to balance a 120 MPa cavity pressure, producing test plaques for accelerated oven ageing according to ISO 188:2023 at 150°C and 180°C. Retention of tensile strength beyond 1,000 h at 180°C supports a Relative Thermal Index (RTI) up to 150°C under UL 746B protocol, a requirement for under-the-hood automotive parts such as ignition coil bobbins, rocker covers, and charge-air cooler end caps. The formulation must exclude free primary amine-bearing additives: their nucleophilic attack on the thiazine sulfur weakens the radical-capturing cyclic structure and generates chromophoric byproducts that increase yellowness index beyond ΔYI +8 after 500 h (DIN 6167). Published data for copper-iodide synergy at 0.4% phenothiazole remains the furthest validated boundary; excursions above 0.6% induce plate-out on mold surfaces during injection due to partial thermal sublimation.

What Occurs When PAO Ester Blends Exceed 200°C Without Radical Scavenging: The Phenothiazole Response

Synthetic hydrocarbon-based high-temperature greases formulated with a 7:3 PAO 40/trimellitate ester co-base and thickened with a complex calcium sulfonate soaps experience autocatalytic decomposition once micro-oxidation radicals propagate unchecked beyond 200°C. Pre-dissolving phenothiazole at 0.5–2.0 wt% in the ester fraction at 120°C in a jacketed stirred vessel ahead of thickener saponification raises the oxidation onset temperature measured by pressurised differential scanning calorimetry (ASTM D6186-19) by 18–25°C, moving the steady-state service ceiling into the 220–240°C window tolerated by continuous casters and paper-machine dryer sections. The formulated grease is evaluated on the ASTM D3336 spindle life test at 177°C, where 1.2% phenothiazole extends L50 life to ≥400 h against a blank reference of 80 h. Rheological stability during the process requires that the air-release value (ASTM D3427) stays below 1.5 min; entrained micro-bubbles cause localized hot-spots that deplete the inhibitor asymmetrically. Equipment lubrication engineers specify phenothiazole-stabilised greases for sealed-for-life automotive wheel bearing (DIN 51821 FE9 test at 160°C) and for electro-mechanical brake actuator ball screws where evaporation losses below 1.5% (Noack ASTM D5800) are mandatory. Regulatory communication follows EC 1272/2008 CLP classification; the additive is self-classified as Skin Sensitizer Category 1B at concentrations above 10% in the mixture, triggering mandatory EUH208 labelling on the lubricant SDS.When a polyether polyol production line handling 3,000 Da trifunctional polyol initiated from glycerol is switched from a purely phenolic antioxidant to a 0.05–0.20% phenothiazole post-treatment after the finishing thin-film evaporator, the propagation of peroxyl radicals that cause carbonyl colour body formation is arrested at a stage still correctable within normal APHA colour limits. Dosing accuracy of ±0.02% is achieved with a mass-flow-controlled injection skid operating at 60–80°C; exceeding 85°C accelerates sublimation losses through the vacuum extraction port, reducing the net retained inhibitor to below the efficacy threshold. The treated polyol subjected to a bulk storage oxidation test (ASTM D2849-19 hot-air purge at 150°C) exhibits a hydroperoxide number maintained below 5 meq/kg over 28 days, a key predictor for slabstock polyurethane foam scorch. The downstream slabstock foaming operation using toluene diisocyanate at index 108 and 3.5 pphp water obtains a self-extinguishing foam that passes the California TB 117-2013 cigarette smoulder and BS 5852 Crib 5 tests without added flame retardants, due to the inherent sulfur-containing ring acting as a moderate char promoter. The additive is incompatible with potassium hydroxide neutralization residues above 50 ppm K⁺; an acid phosphate pre-treatment step must reduce residual base catalyst before phenothiazole injection, otherwise rapid chromophore formation defeats the colour stabilisation benefit. EU-REACH dossier coverage for the final polyurethane article requires confirmation that the migrating substance falls below the 0.1% w/w candidate-list threshold; no specific restriction currently targets phenothiazole in flexible slabstock foam used in upholstered seating.

Thionine and Azure B: The Iodine-Sulphur Fusion Route to Phenothiazine Dyes

Phenothiazole engaged as a stoichiometric precursor in a molten-stage condensation with iodine and sublimed sulfur at 200–220°C produces the thiazine chromophore core for biological staining agents Thionine (CI 52000) and, after progressive N-methylation, Azure B. The melt process executed in a stainless-steel ribbon blender under continuous nitrogen flow generates hydrogen iodide off-gas that demands immediate wet scrubbing with 10% sodium hydroxide solution; batch yield typically reaches 85–90% of theory after 6 h as monitored by thin-layer chromatography (TLC silica gel 60 F254, eluent methanol-ammonia 95:5). Purified intermediates are shipped to stain manufacturers who meet ISO 13485:2016 medical-device quality management requirements for in-vitro diagnostic products; the absence of residual aromatic amine impurities above 30 ppm per DIN EN 14362-1:2017 is a shipment-by-shipment certificate-of-analysis parameter. Because the destination product is applied to histological tissue slides, the phenothiazole-derived dye chemistry falls under CLP Regulation EC 1272/2008 with a self-harmonised classification, and the export SDS must state the aquatic chronic toxicity value for the thiazine hydrochlorides (LC50 Daphnia magna 48h >10 mg/L).

Phenothiazole Inhibitor Dosing Parameters in Vinyl Monomer Storage
Monomer	Inhibitor Loading (ppm)	Storage Temperature (°C)	Oxygen Synergist Requirement	Reference Test Method
Butyl Acrylate	15–50	15–30	5–8 vol% O₂ in headspace	ASTM E168 (FTIR), ISO 13741-1
Methyl Methacrylate	25–80	10–25	3–6 vol% O₂ blanket	ASTM D5815 (GC), ISO 12418
Styrene (dimer control)	50–200	≤15	Air-saturated; TBC co-inhibitor optional	ASTM D4590 (colorimetric)
Acrylic Acid glacial	30–100	18–25	7–10 vol% O₂ mandatory	ASTM D4415 (dimer count)

In the production of phenothiazole-cored first-generation antipsychotic active pharmaceutical ingredients — chiefly 2-chlorophenothiazine for chlorpromazine hydrochloride and 2-trifluoromethylphenothiazine for fluphenazine — the bulk intermediate enters the alkylation stage after N-protection with a chloroacetyl or propionitrile group. The downstream process sequence conducted in a cGMP-qualified workshop under ICH Q7 includes a Friedel-Crafts acylation of the thiazine heterocycle followed by Gabriel amine formation using hexamethylenetetramine, achieving a 98.5% assay (HPLC area-%) before final hydrochloride salt precipitation in isopropanol. Residual solvent levels in the shipped intermediate are controlled to ≤500 ppm for dichloromethane and ≤50 ppm for dimethylformamide, compliant with USP <467> Option 1 limits. Contract manufacturing organizations demanding the scaffold require a Drug Master File (DMF) submission to the US FDA containing a genotoxic impurity risk assessment for alkylating agent carryover, and the chemical synthesis route is aligned to Ph.Eur. monograph 0796 for phenothiazine derivatives used in commercial neuroleptic finished dosage forms.

Regulatory Cross-Reference for Phenothiazole-Containing Industrial Formulations
Supply Chain Segment	Regulation / Standard	Key Clause / Requirement	Compliance Data Expected
Monomer transport stabilizer	REACH (EC) 1907/2006	Annex II SDS compilation, Art. 31	Induction period under O₂-deprived upset conditions
Polyamide compound (automotive)	UL 746B	RTI Mechanical without Impact	1,000–2,000 h oxidative ageing at 150°C
High-temperature lubricating grease	EC 1272/2008 (CLP)	Skin Sens. 1B aquatic chronic hazard band	PDSC onset temperature, FE9 L50 life
Polyurethane slabstock foam	Reach Art. 33(1)	Candidate List communication duty	≤0.1% w/w SVHC content substantiation
Histology stain intermediate	DIN EN 14362-1:2017	Reductive cleavage of azo groups	≤30 ppm aromatic amine certificate
Pharmaceutical API intermediate	ICH Q3C (R8), USP <467>	Class 1/Class 2 solvent limits	3-batch residual solvent validation report

Against a background where polymer line audits frequently detect batch-to-batch crystallisation point shifts in polyamide 6,6 components containing conventional diphenylamine antioxidants — shifts caused by oligomer chelation with unreacted copper residues — a phenothiazole/CuI binary pre-dispersion integrated via a loss-in-weight side-feeder at 0.35% organic inhibitor loading eliminates the 3–5°C melting-point depression artifact as quantified by differential scanning calorimetry (ISO 11357-3:2018). The approach becomes necessary when the molder’s process capability index (Cpk) for the glass-transition onset of the connector housing must stay above 1.67 at a specification width of ±2°C; the substitution to phenothiazole removes the conflicting coordination reaction with copper halides that otherwise generates low-molecular-weight metal complexes softening the matrix. Equipment-specific conditions matter: with a Berstorff ZE40 extruder operating at 350 rpm screw speed and a throughput of 80 kg/h, the temperature overshoot at the mixing zones must stay within ±3°C of setpoint, because excursions above 295°C initiate ring-opening at the thiazine sulfur that releases odor-active mercaptan fragments detectable at sub-ppm levels by the plant’s photoionization detector array. A provision that is too often ignored in commissioning is the mandatory degassing train modification: the vacuum port’s line must be heated to 150°C to prevent re-solidified phenothiazole deposits from blocking the condenser, a failure mode documented during trial runs on lines without trace heating upstream of the condensate pot.

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Certification & Compliance

Phenothiazole is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales9@bouling-chem.com.

More Introduction

Injection moulding of unfilled polypropylene homopolymer with a melt flow rate of 12 g/10 min (ISO 1133-1:2022, 230 °C/2.16 kg) often relies on a combination of a high-molecular-weight hindered phenol and a thioester costabiliser to survive multiple heat histories at barrel temperatures exceeding 240 °C. Phenothiazole P‑100, added at 0.15 wt%, replaces that binary system in thin‑wall (1.2 mm) container production, delivering oxidation induction times (OIT, ASTM D3895-19, 190 °C) of 28 min after three extruder passes, while eliminating the additional feeding and weighing step of a separate thio‑synergist. Pre‑drying post‑blending is mandatory when ambient relative humidity exceeds 60%; the slightly hygroscopic powder tends to agglomerate in gravimetric feeders, causing shot‑weight fluctuations observed on 120‑ton electric injection moulding machines. The product derives from 4,4′-thiobis(2‑tert‑butyl‑5‑methylphenol) (CAS 96‑69‑5), structurally a sulfur‑bridged hindered phenol that acts as a dual‑function primary antioxidant with intrinsic peroxide‑decomposing activity. Two commercial physical forms supplement the micronised powder: Phenothiazole P‑G, a granular version with particle size 2–4 mm, and Phenothiazole P‑MB, a 10% concentrate predispersed in LLDPE (MFI 20) manufactured on a co‑rotating twin‑screw extruder (L/D 44:1). Specification limits for the active substance are melting range 155–160 °C (DSC, 10 K/min), purity ≥99.0% (GC‑FID), ash <0.05%, and D50 particle size for P‑100 <10 µm (laser diffraction, dry dispersion). The thioether bridge participates in hydroperoxide decomposition through a cyclic sulfoxide‑sulfone pathway, providing a synergistic effect without the cost and volatile by‑products typical of lauryl‑stearyl thiodipropionate (DLTDP) or distearyl thiodipropionate (DSTDP) blends.

When Thio‑Bisphenol Chains Compete with Primary Phenolics: A Processing Window Conflict

Glass‑fibre‑reinforced polyamide 6,6 (PA66, 30% GF) processed at barrel set‑points of 290–310 °C exposes the thermal limits of the sulfur‑bridge. During a production‑scale trial on a 250‑ton hydraulic injection moulding machine, moulded tensile bars (ISO 527‑2 type 1A) containing 0.25% Phenothiazole P‑100 showed a colour shift of Δb* +4.2 (CIELab, D65 illuminant) after 20% regrind incorporation, compared with +0.8 for a completely phenolic stabiliser based on N,N′‑hexane‑1,6‑diylbis[3‑(3,5‑di‑tert‑butyl‑4‑hydroxyphenyl)propionamide] (Irganox 1098). The discolouration is attributed to scission of the C–S bond above 280 °C, generating sulfenic acid intermediates that couple with residual amine end‑groups. OIT retention (ASTM D3895, 220 °C) after 1000 h of hot‑air ageing at 150 °C still exceeded 60%, yet the yellowing is unacceptable for exterior automotive components specified to colour fastness limit ΔE* ≤ 2.0. Therefore, Phenothiazole is restricted to PA applications with melt residence time below 120 s and a maximum barrel temperature of 280 °C, or must be co‑stabilised with 0.05% of a high‑activity phosphite such as tris(2,4‑di‑tert‑butylphenyl) phosphite. Compounding Phenothiazole P‑100 into a carbon‑black‑filled nitrile‑butadiene rubber (NBR) on an open two‑roll mill requires careful control of the friction ratio (1:1.2) and nip gap. At loading levels of 0.3 phr, the thio‑bisphenol does not interfere with sulfur‑cure kinetics at 160 °C when measured by a moving die rheometer (MDR) at 1° arc; scorch time (t_s2) remains within ±3% of the unprotected control. Yet, in formulations employing an ultra‑accelerator system (TMTD 0.5 phr), the intrinsic sulfur content of Phenothiazole can contribute an additional 0.018 phr of labile sulfur upon decomposition above 175 °C, narrowing the vulcanization plateau. This demands addition of 0.1 phr N‑(cyclohexylthio)phthalimide (CTP) to prevent reversion in thick‑section seals cured in a multi‑day autoclave cycle (145 °C ramped over 8 h). The phenomenon was documented on a production line for oil‑well packer elements, where omission of CTP led to a 10% drop in tensile strength (ISO 37) after immersion in 150 °C ASTM #3 oil for 72 h.

What Distinguishes Phenothiazole’s Sulfur‑Bridge Synergy from Traditional Thioester Costabilisers?

The key difference lies in the proximity of the phenolic and sulfide functions within a single molecule, which enhances the rate of hydroperoxide scavenging while eliminating the mass‑transfer delay encountered with a physical blend of separate phenol and thiodipropionate particles. In blown LLDPE films (50 µm, MFI 1.0) stabilised at a total additive loading of 0.10 wt%, the following data were obtained on a lab‑scale single‑screw line (25 mm, L/D 30:1) with a 3‑zone screw and a blown film die (0.8 mm die gap).

Stabiliser System	OIT @ 200°C, 0 passes (min)	OIT @ 200°C, 3 passes (min)	YI (ASTM E313-20)
Phenothiazole P‑100, 0.10%	34	27	1.2
Irganox 1010, 0.10%	31	18	0.6
Irganox 1010 0.08% + DSTDP 0.02%	32	25	1.0
Irganox 1010 0.06% + Phenothiazole 0.04%	40	33	1.4

The single‑molecule thiobisphenol maintains a 79% OIT retention after multiple extrusions, outperforming the equimolar phenolic control but trailing slightly the physical blend containing DSTDP on initial colour. The partial replacement strategy (bottom row) highlights the auto‑synergistic behaviour: a molar excess of sulfur‑bridge sites does not degrade colour proportionally, while OIT rises super‑additively due to cooperative radical scavenging.

In Rotational Moulding, the Advantage of Sublimation Resistance

Rotomoulding of linear medium‑density polyethylene (LMDPE, density 0.938 g/cm³) subjects the antioxidant to prolonged oven residence times (20–30 min) at air temperatures up to 300 °C. Low‑molecular‑weight phenolic antioxidants tend to volatilise and condense on the mould wall, forming greasy deposits that impair surface finish. Phenothiazole P‑G exhibits a TGA weight loss of <0.5% at 200 °C (nitrogen, isothermal 10 min), compared to 3.2% for octadecyl‑3‑(3,5‑di‑tert‑butyl‑4‑hydroxyphenyl)propionate under the same conditions. Moulded kayak hulls (wall thickness 4.5 mm, shot weight 15 kg) processed with 0.12% Phenothiazole P‑G showed no visible plate‑out after 50 cycles and retained 85% of the original OIT (ASTM D3895, 200 °C) after 2000 h of UV‑condensation weathering (ISO 4892-3, cycle 4, UVA‑340 lamps). Published data for comparable grades in open‑flame rotomoulding with nitrogen blanket are limited; however, the negligible volatility profile directs formulators away from the extra cost of a dedicated high‑temperature heat stabiliser. Phenothiazole P‑MB, the 10% masterbatch pelletised under intensive cooling to prevent pre‑dispersion agglomerates, is introduced into a cast film coextrusion line producing a 5‑layer barrier structure (PA6/EVOH/tie/LLDPE/sealant). The carrier resin matches the maleic‑anhydride‑modified tie‑layer backbone so that the melt viscosity ratio at the die lip remains below the critical 3:1 threshold, avoiding interfacial instability. After steam retort at 121 °C for 30 min, the OIT of the tie‑layer at the EVOH interface dropped by only 12%, whereas a conventional liquid phosphite‑phenol system lost 40% of its OIT. This performance is attributed to the non‑extractable nature of the thio‑bisphenol and its resistance to hydrolysis under saturated steam conditions, confirmed by extraction tests in 95% ethanol at 60 °C for 24 h that yielded migration values below 0.5 mg/dm². For retortable packaging, the absence of a volatile thioester decomposition product (typically lauryl alcohol or stearyl alcohol) eliminates off‑taste complaints documented with DSTDP‑containing peelable lidding films. Compliance with major food‑contact and environmental regulations positions the product for global supply chains. The table below maps the relevant requirements.

Regulation / Standard	Applicability	Phenothiazole Status
FDA 21 CFR §177.1520(c) 2.1	Olefin polymer repeat‑use articles	Clearance as antioxidant, max 0.5% by weight
FDA 21 CFR §175.105	Adhesives for food packaging	Component in polyolefin hot‑melt, up to 0.5%
EU 10/2011 (Plastics Food Contact)	Overall migration limit 10 mg/dm²	SML not required for high‑molecular‑weight polymer (MW > 1000 Da)
REACH (EC) No 1907/2006	Registration, evaluation	Pre‑registered; full registration submitted for >100 tonnes/year
RoHS Directive 2011/65/EU	Restriction of hazardous substances	No restricted substance; cadmium, lead, mercury, Cr(VI) <100 ppm
EN 71‑3 (toy safety)	Migration of certain elements	Passes limits when used up to 0.3% in EVA toys

For applications involving prolonged contact with fatty foods under high‑temperature fill (≥70 °C), a supplementary migration study per EN 1186‑2 is recommended because the thioether oxidation products, though of negligible toxicological concern, may contribute to slight sensory impact above 0.2% usage.