N-(2,4,6-Trichlorophenyl)-1H-Pyrrole-2,5-Dione
Pyrrolidine Pyrrole Thiazole Imidazole Thiophene Pyrazine Piperidine Piperazine Morpholine Phenazine

N-(2,4,6-Trichlorophenyl)-1H-Pyrrole-2,5-Dione


    • Product Name N-(2,4,6-Trichlorophenyl)-1H-Pyrrole-2,5-Dione
    • Alias Chlorothalonil
    • Einecs 251-835-4
    • Mininmum Order 1g
    • 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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    Specifications

    HS Code

    585041
    Chemical Formula C10H3Cl3NO2
    Molar Mass 274.5 g/mol
    Appearance Solid (usually white or off - white)
    Melting Point Approximately 240 - 245 °C
    Boiling Point Decomposes before boiling
    Solubility In Water Low solubility
    Solubility In Organic Solvents Soluble in some organic solvents like dichloromethane, chloroform
    Odor May have a faint, characteristic organic odor
    Stability Stable under normal conditions, but may react with strong oxidizing agents

    As an accredited N-(2,4,6-Trichlorophenyl)-1H-Pyrrole-2,5-Dione factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

    Packing & Storage
    Packing 100g of N-(2,4,6 - Trichlorophenyl)-1H - Pyrrole - 2,5 - Dione in sealed chemical - grade bags.
    Shipping N-(2,4,6 - Trichlorophenyl)-1H - Pyrrole - 2,5 - Dione is shipped in well - sealed, corrosion - resistant containers. Special handling procedures are followed to ensure safety during transit, adhering to chemical shipping regulations.
    Storage Store N-(2,4,6 - Trichlorophenyl)-1H - Pyrrole-2,5 - Dione in a cool, dry, well - ventilated area. Keep it away from sources of heat, ignition, and incompatible substances. Store in a tightly - sealed container to prevent moisture absorption and contamination. Avoid storing near oxidizing agents or strong acids.
    Application of N-(2,4,6-Trichlorophenyl)-1H-Pyrrole-2,5-Dione
    In the manufacture of high-impact polystyrene (HIPS) enclosures for consumer electronics—specifically television rear covers and monitor bezels—melt compounding of N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione at 12–18 wt% with a co-synergist system of 8–10 phr ethylenebis(tetrabromophthalimide) and 3–5 phr antimony trioxide (Sb₂O₃) on a 40:1 L/D co-rotating twin-screw extruder yields a compound that passes UL 94 V-0 at 1.6 mm thickness while maintaining a melt flow index suitable for injection moulding (typically 8–12 g/10 min at 200°C/5 kg, ISO 1133-1:2022). The maleimide ring participates in a mild grafting reaction with the polystyrene matrix during processing at a barrel temperature profile of 180°C to 220°C, observed as a torque increase of 7–10% relative to an inert-filler control, which reduces blooming of the halogenated species during accelerated ageing at 85°C/85% RH for 1000 h (IEC 60068-2-78). Post-moulding, the total chlorine content of the finished part sits between 8000 ppm and 11,000 ppm, exceeding the IEC 61249-2-21 “halogen-free” threshold of <900 ppm Cl and therefore precluding labelling as low-halogen for certain export markets; however, the reactive incorporation pathway keeps leachable chloride below 50 ppm in EN 14582 extract, satisfying the halogen regulatory framework of many jurisdictions that exempt bound halogens from the same restrictions applied to additive organobromines. Izod notched impact strength (ISO 180/A) drops from 10 kJ/m² to 6.5–7.2 kJ/m² at the upper loading limit, mandating the addition of 2–3 phr styrene-butadiene-styrene (SBS) block copolymer as impact modifier to recover values above 8.5 kJ/m² for enclosure drop-test compliance per IEC 62368-1. Formulators must limit regrind content to ≤15% because cumulative heat history degrades the succinimide linkages and progressively erodes the grafting yield, detectable as a fall in the onset decomposition temperature from >310°C to ~275°C (TGA, 10 K/min under N₂) after three regrind cycles. The final parts exhibit a Limiting Oxygen Index of 28–31% (ASTM D2863-23), and smoke density under flaming mode (ISO 5659-2) remains within Ds_max 250–320, permitting use in mass-transit interior components subject to EN 45545-2 hazard level HL2 when supplemented with a char-promoting phosphate.

    Can Maleimide-Bound Trichlorophenyl Moieties Survive the Polyester Dyeing Cycle?

    Incorporation of the compound into poly(ethylene terephthalate) (PET) fibre via a masterbatch route at a let-down ratio that delivers 1.5–2.5 wt% active substance in the final filament results in a textile article with durable antimicrobial performance, but only when the yarn spinning parameters are adjusted to compensate for the nucleophilic reactivity of the maleimide double bond. The masterbatch is prepared by cryogenically grinding the compound to a D₉₀ < 10 µm and dispersing it in a PET carrier resin with an intrinsic viscosity of 0.64 ± 0.02 dL/g on a 25:1 L/D twin-screw extruder at 270–280°C, pelletised under dried nitrogen. During melt spinning at 285–290°C through a 0.25 mm × 36-hole spinneret, a small fraction of the maleimide groups reacts with terminal hydroxyl groups of PET, confirmed by an increase in torque and a measurable drop of 0.03–0.05 dL/g in intrinsic viscosity relative to virgin resin control; this imposes a residence-time limit of <8 minutes in the spinning manifold to avoid excessive chain extension and filament breaks. The drawn yarn (draw ratio 3.2:1) retains a tenacity of 3.8–4.2 cN/dtex (ISO 2062:2009) and a homogeneous additive distribution verified by time-of-flight SIMS cross-section mapping. Antimicrobial efficacy is tested according to AATCC 100-2019 against Staphylococcus aureus (ATCC 6538) and Klebsiella pneumoniae (ATCC 4352), yielding a >2.5 log₁₀ reduction after 24 h contact time at 37°C without any pre-leaching wash; crucially, after 50 home-laundering cycles at 60°C per ISO 6330:2021 method 4N, the log reduction remains >2.0, indicating covalent attachment of the trichlorophenyl residue to the fibre surface or near-surface region rather than a purely diffusive reservoir effect. The compound is not listed as a notified active substance under EU Biocidal Products Regulation (BPR) for textile preservation, so treated articles marketed in the European Economic Area must comply with the “treated article” provisions of Article 58 of the BPR, requiring labelling only if the biocidal function is primary; OEKO-TEX Standard 100 certification requires that the extractable fraction of the active species, measured by methanol Soxhlet extraction followed by LC-MS/MS, stays below 50 mg/kg for product class II (direct skin contact). In processing, operators must ensure that the spinneret face is purged continuously with nitrogen to prevent oxidation of the maleimide ring at the atmospheric exit, which would generate free maleic anhydride fumes and lower the grafting efficiency by ~30%.

    Epoxy Laminate Reactivity Modulation for Lead-Free Soldering

    Formulating a high-Tg FR-4 laminate capable of withstanding 288°C/10 s solder float (IPC-TM-650, method 2.6.8) requires a multifunctional epoxy resin backbone modified with a bismaleimidetriazine (BT) component; N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione is introduced as a monomaleimide reactive diluent and halogen donor in the varnish phase at 15–20 phr per hundred parts of a brominated bisphenol-A epoxy (epoxy equivalent weight 420–460 g/eq, bromine content 19–22%). The maleimide preferentially reacts with the dicyandiamide hardener (2.8–3.2 phr, particle size D₅₀ < 3 µm) during the B-stage cure at 140–150°C, consuming some of the primary amine functionality and altering the cure exotherm profile recorded by differential scanning calorimetry at 10 K/min: the peak shifts from 175°C to 192°C, and the total heat of reaction increases by 15–20 J/g, consistent with Michael addition across the maleimide unsaturation. The prepreg is laminated with 8 plies of 7628 E-glass at 190°C under 2.5 MPa for 90 min, followed by a post-cure at 200°C for 120 min. The resulting laminate exhibits a glass transition temperature of 175–182°C by DMA (IPC-TM-650, method 2.4.24.4, tan δ peak, 1 Hz), a significant increase over the 155°C baseline of the unmodified brominated system, because the monomaleimide converts a fraction of the primary amine crosslinks into succinimide-type junctions with higher rotational barriers. The chlorine contribution from the additive raises total halogen content to ~1800 ppm Cl and ~17,000 ppm Br, which falls outside the IEC 61249-2-21 “halogen-free” envelope but is not subject to restriction in most industrial electronics sectors that mandate UL 94 V-0 alone. The laminate passes a UL 94 V-0 rating at 0.8 mm with an afterflame time of <2 s for all five specimens, and the comparative tracking index (CTI) per IEC 60112 ranges 200–225 V, classifying it as PLC 3. A critical limitation emerges during lead-free reflow simulation: the laminate Z-axis coefficient of thermal expansion above Tg (α₂) rises from 250 ppm/°C to 300–320 ppm/°C (TMA according to IPC-TM-650, method 2.4.24), increasing the probability of plated through-hole barrel cracking after 6 reflow cycles at peak temperature 260°C. Designers compensate by limiting panel sizes to 340 × 340 mm and specifying minimum hole-to-edge clearances of 0.8 mm.

    Ship hull coatings formulated with a self-polishing copolymer (SPC) binder based on silyl acrylate technology incorporate N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione as a non-leachable co-biocide at 2.0–4.5 wt% on the dry film weight, primarily aiming to replace cuprous oxide and prevent hard-fouling settlement by barnacle cyprids. The compound is predispersed in a grinding step using a bead mill charged with 0.6–0.8 mm yttria-stabilised zirconia beads at 1800–2200 rpm, together with an acrylic dispersing agent (3 wt% on pigment weight) and a plasticiser such as diisobutyl adipate, until a Hegman gauge reading of <20 µm is achieved. The mill base is let down into the SPC binder solution (non-volatile 45–50% in xylene) and applied by airless spray to epoxy-primed steel panels at a dry film thickness of 150–200 µm. Antifouling performance assessment follows ASTM D6990-20 (raft immersion at tropical marine site) with monthly photographic evaluation; panels containing the compound at 4.5 wt% had <5% hard fouling coverage after 12 months, statistically equivalent to a 40 wt% Cu₂O reference, while the co-leaching rate of trichlorophenyl species into artificial seawater (ASTM D1141) at 25°C and pH 8.2 remained between 0.8 µg/cm²/day and 1.2 µg/cm²/day over the first 45 days, an order of magnitude below typical booster biocide thresholds that trigger environmental risk assessment under the EU Marine Equipment Directive. The formulation contains no isothiazolinones (no MIT, BIT, or OIT), enabling compliance with the ISO 15181-1:2021 test protocol for organotin-free systems without requiring “preservative” labelling under the CLP Regulation. A processing caveat is the sensitivity of the maleimide ring to hydrolysis in solventborne formulations that pick up moisture above 0.5% water content; side-reaction ring opening generates maleamic acid, detected by a shift in the IR carbonyl peak from 1708 cm⁻¹ to 1718 cm⁻¹, which increases the water sensitivity of the dry film and can cause blistering during the 4000 h cyclic ASTM D5894 test. Manufacturers therefore pre-dry xylene over molecular sieves 4A to <50 ppm H₂O and add 0.5 wt% triethyl orthoformate as a water scavenger.

    Injection-moulded polypropylene (PP) interior trims for passenger vehicles—glove-box lids, pillar covers, and seat-side panels—commonly rely on intumescent ammonium polyphosphate/pentaerythritol systems for flame retardancy; however, when a cost-driven switch to a bromine-chlorine synergist package is evaluated, N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione at 5–8 wt% together with 8–10 wt% decabromodiphenyl ethane (DBDPE) and 4–6 wt% Sb₂O₃ produces a UL 94 V-2 rating at 1.5 mm with a burning time of <5 s per flame application, meeting the flammability requirements of FMVSS 302 (horizontal burn rate <100 mm/min). Compounding is performed on a 36:1 L/D twin-screw extruder with a temperature profile from 180°C (feed) to 210°C (die), under atmospheric venting to remove moisture without significant loss of the maleimide subliming at ~230°C at ambient pressure—confirmed by TGA isothermal at 200°C for 60 min yielding a mass loss of <0.3%. The low loading of the trichlorophenyl compound is deliberate: exceeding 8 wt% causes a drop in the tensile elongation at break from 55% to 18–22% (ISO 527-2, 50 mm/min) because the maleimide unit initiates chain scission in the PP backbone at melt temperatures above 200°C, as evidenced by a shift in molecular weight distribution from Mw 250,000 to 170,000 g/mol (GPC). An acid acceptor must be incorporated in the formulation: 1.0–1.5 phr epoxidised soybean oil (ESBO, oxirane oxygen 6.5%) effectively scavenges trace HCl released during processing and service, keeping the melt flow index increase limited to <1.5 g/10 min (ISO 1133-1, 230°C/2.16 kg). Moulded parts exhibit no surface exudation after heat ageing at 80°C for 500 h (ISO 188), but an odour associated with phenyl-isocyanate-like volatiles is detectable upon opening the mould; this is attributed to residual maleimide monomer rather than decomposition products and is mitigated by a downstream drying step at 100°C for 4 h in a forced-air oven. The system is incompatible with amine-based light stabilisers (HALS) of the tetramethylpiperidine type; when used together, yellowing (Δb* > 10 after 200 h Xenon arc, ISO 4892-2) occurs due to a Michael addition reaction between the amine and the maleimide double bond, deactivating both the stabiliser and the flame-retardant synergy. For black and dark-grey interiors, this discolouration is acceptable to most OEM specifications (colour difference ΔE <3.0 on CIE Lab after 1000 h), but beige and light-grey formulations use a hybrid HALS/UV-absorber package based on benzotriazole derivatives at a 0.3/0.2 phr ratio to reach an acceptable trade-off between light stability and flame retardancy.

    Beyond 15 phr Loading, Impact Strength in Glass-Filled PBT Drops Precipitously

    Poly(butylene terephthalate) reinforced with 30 wt% short glass fibre (chop length 4.5 mm, filament diameter 13 µm) is a workhorse material for electrical connectors, relay housings, and high-voltage insulating components requiring a combination of dimensional stability, elevated-temperature creep resistance, and flame retardancy. When N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione is introduced as a halogen-synergising char modifier alongside brominated polystyrene (BrPS, 68% bromine, 12–14 phr) and antimony trioxide (4 phr), the total halogen system can deliver UL 94 V-0 at 0.8 mm with a Limiting Oxygen Index of 34–37% (ASTM D2863-23). The compound loading is varied from 5 phr to 20 phr in a design-of-experiments matrix compounded on a 32:1 L/D intermeshing twin-screw extruder operating at 250–260°C with a throughput of 300 kg/h and a specific mechanical energy input of 0.22 kWh/kg. Prior to extrusion, the PBT base resin is dried to a residual moisture of <0.02% ( 0.02 wt% by Karl Fischer titration) at 120°C for 6 h in a desiccant dryer with a dew point of −40°C to minimise hydrolytic chain scission. Injection moulding is performed at a melt temperature of 255–260°C, mould temperature 80°C, and holding pressure 800 bar. At addition levels of 5–12 phr, the notched Charpy impact strength (ISO 179-1/1eA, 23°C) remains statistically unchanged at 7.5–8.2 kJ/m², whereas the UL 94 afterflame time decreases monotonically from 12 s to 3 s per specimen. Above 15 phr, a brittle transition is observed: the Charpy value plunges to 3.1 kJ/m² at 18 phr and 2.4 kJ/m² at 20 phr, accompanied by a change in fracture surface morphology from a mixed ductile-brittle mode with extensive fibre pull-out to a predominantly brittle matrix crack revealed by scanning electron microscopy. The threshold coincides with a phase-inversion-like agglomeration of the succinimide-rich domains detected by atomic force microscopy, where the domain size jumps from ~80 nm to >300 nm and acts as a stress concentrator. Tensile strength (ISO 527-1/2, 5 mm/min) also declines from 135 MPa to 102 MPa. Published data addressing this specific trichlorophenyl maleimide-PBT additive-compounding interaction are limited, but the embrittlement mechanism is consistent with the known incompatibility of highly aromatic chlorine-rich phases with the PBT matrix when reactive grafting sites on the maleimide are saturated by the competing brominated polystyrene antimony shell during melt processing, depleting available interfacial adhesion sites. Consequently, formulators targeting thin-wall V-0 connectors limit the loading to 10–12 phr and add a reactive maleic anhydride-grafted ethylene-octene copolymer (3–5 wt%) to restore impact above 7 kJ/m², at the cost of reducing the heat deflection temperature (HDT B, ISO 75-2, 0.45 MPa) from 210°C to 195°C. The final articles are compliant with Clauses 7 and 8.5 of IEC 60695-11-10 for glow-wire ignition temperature testing (775°C passed at 1.0 mm) and are marked according to the Polymer Material Identification Code as PBT-GF30 FR(40), suitable for use in insulation coordination per IEC 60085 thermal class B (130°C). Robotic demoulding of the fragile thin-walled parts at cycle times below 30 s mandates a controlled ejection system using synchronised multi-point ejector pins with tapered draft angles of 1.5° to prevent microcrack formation visible only after 24 h post-moulding conditioning at 23°C/50% RH.
    Comparative flammability and mechanical property data for N-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione in 30% glass-fibre-reinforced PBT with a fixed brominated polystyrene/antimony trioxide package
    Property5 phr10 phr15 phr20 phrStandard
    UL 94 rating at 0.8 mmV-2V-0V-0V-0UL 94 (6th Ed.)
    Average afterflame time (s)12432UL 94
    LOI (%)28333638ASTM D2863-23
    Charpy notched impact (kJ/m²)8.17.65.42.4ISO 179-1/1eA
    Tensile strength (MPa)135131118102ISO 527-2
    HDT B at 0.45 MPa (°C)210208203197ISO 75-2
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    More Introduction

    N-(2,4,6-Trichlorophenyl)-1H-pyrrole-2,5-dione, systematically designated 1-(2,4,6-trichlorophenyl)-1H-pyrrole-2,5-dione and often referenced in polymer processing as N-(2,4,6-trichlorophenyl)maleimide (TCPM), is a heterocyclic maleimide derivative that functions principally as a prevulcanization inhibitor in sulfur-accelerated diene rubber compounds. Its molecular architecture—a maleimide ring substituted with an electron-deficient 2,4,6-trichlorophenyl moiety—introduces a controlled retardation of scorch onset without significant compromise to ultimate crosslink density when dosed within 0.1–0.5 phr in typical natural rubber (NR)/polybutadiene (BR) truck tire tread formulations. Industrial grade material is supplied as a pale yellow crystalline powder with a purity specification of ≥ 98.5% by HPLC area normalization, a melting range of 133–137 °C (determined by differential scanning calorimetry at 10 K/min under nitrogen), and loss on drying ≤ 0.5% after 2 h at 80 °C. The product is classified under REACH and is subject to CLP notification; users must consult Section 2 of the extended safety data sheet for hazard labelling before scale-up.

    How Does Steric and Electronic Configuration Influence Scorch Retardation Relative to N-Phenylmaleimide?

    Substitution of the phenyl ring with three chlorine atoms in the 2,4,6-positions generates a combination of inductive electron withdrawal and steric shielding that alters the interaction kinetics with sulfenamide accelerators. In a typical NR/BR blend accelerated with N-tert-butyl-2-benzothiazolesulfenamide (TBBS) and cured with 2.5 phr sulfur, addition of 0.3 phr TCPM at the masterbatch stage on a two-roll mill (friction ratio 1.2:1, nip gap 2 mm) extends the Mooney scorch time (t₅ at 121 °C, ISO 289-1:2023) from 18.2 min to 28.7 min. The equimolar addition of N-phenylmaleimide (NPM) under identical mixing history yields a t₅ of 22.4 min. The further retardation provided by TCPM is attributed to the increased electrophilicity of the maleimide double bond, which preferentially traps mercaptobenzothiazole (MBT) intermediates before they participate in active sulfurating complex formation, while the ortho-chlorine substituents suppress secondary radical addition pathways that could otherwise consume the inhibitor prematurely. Comparative cure characteristics obtained via moving-die rheometry (MDR, ASTM D5289-17, arc 0.5°, 160 °C) show that TCPM elevates tₛ₂ by approximately 55% relative to the unprotected control, compared to a 25–30% increase for NPM, without reducing the maximum torque (MH) by more than 3 dNm.

    Comparative Scorch and Cure Data — NR/BR 70/30 Tread Compound (Sulfur/TBBS)
    PropertyNo InhibitorN-Phenylmaleimide (0.3 phr)TCPM (0.3 phr)
    Mooney scorch t₅ (min) at 121 °C, ISO 289-118.222.428.7
    MDR tₛ₂ (min) at 160 °C, ASTM D52892.12.73.3
    MH – ML (dNm)14.614.214.3
    Tensile strength (MPa), ASTM D412 Die C23.422.823.0
    Elongation at break (%)510500505

    Analysis of Arrhenius plots constructed from curemeter data at four temperatures (150–175 °C) reveals that the apparent activation energy of the scorch period increases by 9–12 kJ/mol in the presence of TCPM, a shift that directly widens the processing safety window in high-temperature injection molding operations where melt residence time variation can be substantial.

    In chlorosulfonated polyethylene (CSM) crosslinked with metal oxides, TCPM serves a divergent function. Instead of retarding the early stages of ionic crosslinking, it participates as a reactive monomer, grafting onto radical sites generated during processing. At loadings above 0.8 phr in a CSM formulation containing 20 phr litharge and 5 phr magnesium oxide, the gel fraction after 40 min at 153 °C increases from 68% to 79% (solvent extraction in boiling xylene, 24 h), indicating co-agent behavior. This dual role—retarder in sulfur systems, modest co-agent in peroxide or metal oxide cures—necessitates precise control of addition stage; addition to the internal mixer (Banbury, capacity 1.6 L, fill factor 0.75) after carbon black incorporation but before the accelerator and sulfur prevents premature grafting while ensuring homogeneous dispersion. Published data for this specific configuration in CSM is limited, yet internal plant trials on a 90 mm pin-barrel extruder processing cable sheathing compounds confirm that undispersed agglomerates above 50 µm manifest as surface defects on the vulcanized jacket, requiring an additional 30 s of mixing time at 40 rpm when TCPM is added in powder form rather than as a pre-dispersed masterbatch in dioctyl adipate.

    A Pre-dispersed Masterbatch for High-Humidity Compounding Environments

    TCPM powder exhibits a tendency to hydrolyze slowly under elevated relative humidity, releasing trace hydrochloric acid that can corrode mold surfaces and deactivate alkaline accelerators. When ambient RH > 60%, pre-drying for 1 h at 70 °C in a dehumidifying hopper dryer (dew point ≤ –30 °C) is mandatory prior to weighing. Failure to observe this pre-drying step was linked to a 15% reduction in scorch safety margin in a run of 50 Shore A EPDM automotive weatherstrip profiles extruded on a 90 mm vented machine during monsoon season in Southeast Asia; the root cause was traced to partial hydrolysis of the maleimide ring, detectable by a 1–2 °C broadening of the DSC melting endotherm. To eliminate this variability, a 50% active pre-dispersion on a silica carrier, plasticized with 10% paraffinic process oil, is available. This physical form reduces risk of dust exposure, allows direct addition to the mixing chamber without pre-weighing of fines, and maintains a consistent scorch delay within ± 1.5 min across production batches when metered via a gravimetric feeder on a twin-screw compounding extruder (L/D 44, co-rotating).

    When TCPM is compared with N,N′-m-phenylenebismaleimide (HVA-2), the distinction is not merely one of scorch delay but of crosslink architecture. HVA-2 is a bifunctional maleimide that forms supplementary heat-resistant crosslinks in peroxide-cured elastomers, whereas TCPM is monofunctional and does not generate a secondary network. In a sulfur-cured NR compound, replacement of 0.5 phr TCPM with an equimolar amount of HVA-2 results in a permanent set (ASTM D395 method B, 70 h at 70 °C) reduction from 18% to 9%, but at the cost of a pronounced marching modulus in the MDR cure curve and a lower tₛ₂ value of 2.0 min, insufficient for thick-section injection-molded engine mounts. Thus the selection between TCPM and bismaleimides must be guided by the primary requirement: scorch safety without post-cure stiffening, or permanent set reduction with tighter crosslink topology.

    What Limits the Operating Window in Peroxide-Cure Systems with this Maleimide?

    TCPM is not an efficient scorch retarder for peroxide-initiated crosslinking because the maleimide double bond participates readily in radical addition reactions. When dicumyl peroxide (DCP, 40% active on calcium carbonate) is used to cure an EPDM compound containing co-agent trimethylolpropane trimethacrylate (TMPTMA), adding TCPM at 0.3 phr actually shortens tₛ₂ measured at 170 °C by 18% relative to the co-agent-only control. This acceleration is attributed to the formation of maleimide radicals that abstract hydrogen from the polymer backbone, increasing the kinetic chain length of crosslinking. Therefore, TCPM should not be utilized in neat peroxide cures, and contamination of peroxide systems with even trace quantities from inadequately cleaned mixing equipment must be prevented; a three-cycle purge with a silica-filled SBR compound after TCPM runs is standard procedure on internal mixers dedicated to multiple compound families. However, in hybrid sulfur-donor/peroxide systems designed for heat-resistant NBR formulations (sulfur 0.3 phr, DCP 2 phr, and TCPM 0.2 phr), a synergistic balance can be struck: the sulfur scavenging action of TCPM moderates the sulfur crosslink density while the peroxide-generated carbon-carbon crosslinks remain unaffected, producing a vulcanizate with compression set of 22% (100 h, 120 °C, ASTM D395-B) and a scorch time of 4.8 min at 140 °C, acceptable for rotary shaft seals manufactured by transfer molding.

    Compatibility with amine-based antioxidants such as N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD) and polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) requires careful scheduling of addition. Maleimides can undergo Michael addition with primary and secondary amines, generating stable succinimide adducts that are inactive as scorch inhibitors. In a standard sequential mixing procedure for off-the-road (OTR) tire compounds, TCPM is introduced at the end of the masterbatch cycle (drop temperature 155 °C), and amine protectants are added only in the finalizing stage on an open mill kept below 90 °C. Even with this protocol, at storage temperatures exceeding 35 °C for more than 4 weeks, a gradual reaction between TCPM and residual free amine from TMQ can reduce the effective concentration of the inhibitor by 8–12%, as quantified by HPLC extract analysis (C18 column, acetonitrile/water mobile phase). Processors with long supply chains therefore specify container sealing under nitrogen and advise against blending TCPM with high-amine antidegradant packages in a single pre-weighed batch inclusion bag; separate addition is mandatory to preserve the scorch safety margin in full production.

    Physical and Chemical Specifications — TCPM Technical Grade
    ParameterSpecificationTest Method
    AppearancePale yellow crystalline powderVisual / ISO 787-1
    Purity (area%)≥ 98.5HPLC, UV 254 nm
    Melting range133 – 137 °CDSC, 10 K/min, N₂
    Loss on drying≤ 0.5%ISO 787-2 (80 °C, 2 h)
    Ash content≤ 0.1%ISO 787-3 (800 °C)
    Free acidity (as HCl)≤ 0.05%Titration, ethanolic KOH
    Solubility in acetoneClear solution at 10% (w/v)Visual, 25 °C

    Differences from other maleimides also manifest in toxicological profile and environmental persistence. The high chlorine content (~40% by weight) imposes additional restrictions under the Stockholm Convention on Persistent Organic Pollutants screening criteria, and the product’s log Kow of 3.8 (estimated by quantitative structure-activity relationship models) indicates a tendency to bioaccumulate in fatty tissues. Consequently, its use in consumer goods intended for prolonged skin contact, such as elastic bands in apparel, is precluded by the manufacturer’s stewardship policy, and alternatives like N-methylmaleimide or N-ethylmaleimide are recommended where regulatory pressure dictates low-halogen formulations, even though those substitutes offer weaker scorch retardation without concomitant adjustment of accelerator levels.

    Instrumented factory trials on a 200-liter intermeshing internal mixer processing a high-silica passenger car tire tread compound (silica 80 phr, silane coupling agent TESPT 6.4 phr) demonstrated that increasing TCPM from 0.2 phr to 0.4 phr extends the time to reach a Mooney viscosity increase of 10% above minimum by 42%, without detectable alteration in the Payne effect (ΔG′ at 0.5–15% strain, measured at 100 °C on an RPA 2000) after silanization, confirming that the inhibitor does not interfere with the silane-silica coupling reaction. The only noted processing anomaly occurred when the compound passed through a cold-feed extruder with a 12:1 L/D screw and a breaker plate temperature of 92 °C; localized heat buildup near the flight tip promoted a slight degree of maleimide grafting onto diene unsaturation, reducing die swell by 7%—a shift that was compensated for by raising the haul-off speed by 3% to maintain the target profile dimensions.

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