1-Phenyl-1H-Pyrrole-2,5-Dione
|
HS Code |
671630 |
| Chemical Formula | C10H7NO2 |
| Molar Mass | 173.17 g/mol |
| Appearance | Yellow - orange solid |
| Melting Point | 119 - 123 °C |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, chloroform |
| Odor | Odorless |
| Stability | Stable under normal conditions |
| Reactivity | Can react with nucleophiles at the carbonyl groups |
As an accredited 1-Phenyl-1H-Pyrrole-2,5-Dione factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 1 - Phenyl - 1H - Pyrrole - 2,5 - Dione packaged in a sealed chemical - grade bottle. |
| Shipping | 1 - Phenyl - 1H - Pyrrole - 2,5 - Dione is shipped in accordance with strict chemical transport regulations. Packed securely in suitable containers, it's transported by approved carriers to ensure safe and compliant delivery. |
| Storage | 1 - Phenyl - 1H - Pyrrole - 2,5 - Dione should be stored in a cool, dry, and well - ventilated area. Keep it away from sources of heat, ignition, and direct sunlight. Store it in a tightly - sealed container to prevent moisture absorption and contact with air, which could potentially lead to chemical reactions or degradation. Store separately from incompatible substances to avoid dangerous interactions. |
When a 15% HDT Uplift Triggers a 40% Notched Izod Collapse in ABS CompoundingIncorporation of 1-Phenyl-1H-Pyrrole-2,5-Dione into acrylonitrile–butadiene–styrene matrices proceeds via reactive extrusion on co-rotating twin-screw lines—typically 40:1 to 48:1 L/D ratio, segmented screw profiles with distributive kneading blocks positioned downstream of the side-feeder—where the monomer grafts onto the styrene-acrylonitrile copolymer backbone at melt temperatures maintained between 195°C and 235°C. A processing window narrower than ±5°C near the upper boundary exists: exceeding 240°C initiates retro-Diels–Alder cleavage of any transient adducts formed with residual butadiene unsaturation, liberating free maleimide that sublimates onto vacuum vent ports and downstream pelletizer die faces, causing progressive die-lip fouling that escalates backpressure drift by 0.8–1.5 bar/h on ZSK-class machines. Pre-drying at 70°C under -0.095 MPa vacuum for a minimum of 4 h drives moisture content below 0.08 wt%; residual water at 0.15 wt% or above catalyzes ring-opening hydrolysis to N-phenylmaleamic acid, a species that decarboxylates at processing temperatures and generates intra-melt microbubbles visible as silver streaking in injection-molded plaques.The property trade-off manifests sharply when the phenylmaleimide comonomer fraction surpasses 12–14 wt% relative to the SAN phase. Heat deflection temperature measured per ISO 75-2:2013 (Method A, 1.80 MPa flexural stress, flatwise orientation) rises from a baseline of 89–94°C to 108–117°C—a gain commercially significant for automotive interior components requiring ≥105°C short-term thermal resistance in instrument panel top surfaces. Simultaneously, notched Izod impact strength determined under ISO 180:2023 (Type 1 specimen, notch A, edgewise impact) degrades from 22–28 kJ/m² to as low as 8–12 kJ/m², a drop attributable to the suppression of rubber-phase cavitation by a stiffened SAN graft shell that raises the glass transition of the interfacial layer above the dilatational yielding threshold. On manufacturing floors, operators running 1500–2500 kN clamp force injection presses observe that mold-fill analysis must be re-benchmarked after each 2 wt% N-PMI increment: melt volume-flow rate drops nonlinearly, with MVR (220°C, 10 kg) shifting from 18–22 cm³/10 min to 6–9 cm³/10 min at 18 wt% incorporation. Gate blush and jetting become more prevalent in multi-cavity hot-runner tools unless melt temperature is raised by 8–12°C, which then narrows the thermal degradation margin. Published data for the long-term thermal oxidative stability of these specific N-PMI-grafted ABS grades under ISO 188:2023 air-oven aging at 120°C beyond 500 h remains limited; embrittlement onset time varies by over 300% depending on antioxidant package selection, with lactone-based processing stabilizers outperforming hindered phenolic systems by a factor of 1.8–2.3 in yellowness-index retention per ASTM E313.---On a suspension-polymerized polyvinyl chloride dry-blend compounding floor, the substitution of a fraction of conventional tin mercaptide stabilizer with 1-Phenyl-1H-Pyrrole-2,5-Dione at 0.8–2.2 phr introduces a parallel Diels–Alder trapping mechanism directed at the conjugated polyene sequences that propagate during early-stage dehydrochlorination. The maleimide dienophile reacts preferentially with cis-configured double bonds in the 4–7 conjugated-unit oligoene range—before the chromophore length reaches the 8–10 double-bond threshold at which visible discoloration becomes perceptible under D65 illuminant—effectively capping the polyene propagation and shifting the reflectance spectrum toward shorter wavelengths. Static heat stability trials conducted on a two-roll mill with a 190°C front roll and 0.8 mm nip gap show that Congo Red indicator paper discoloration time extends from 34 min to 51–58 min at 1.5 phr loading, provided the formulation excludes basic metal soaps; combination with calcium stearate above 0.3 phr triggers N-phenylmaleamic acid salt precipitation that manifests as white exudate on the calendered sheet surface within 72 h of ambient storage. The operational boundary is pH-dependent: PVC formulations buffered above pH 6.2 in the melt phase accelerate imide ring-opening, negating the stabilization gain. Off-gas analysis via Draeger tube sampling above the mill bank at 200°C detects 2–5 ppm of free aniline—generated through thermal scission of the N–phenyl bond—a concentration below the 10 ppm occupational exposure limit but sufficient to require enhanced local exhaust ventilation airflow of ≥0.5 m/s face velocity at the operator station per ISO 14123-1:2015.Optical-Grade Styrenic Copolymers and the Refractive Index–Abbe Number Tightrope at High N-PMI LoadingsTransparent molding compounds for ophthalmic lenses and light-guide plates derive their optical performance from terpolymerization of styrene, methyl methacrylate, and 1-Phenyl-1H-Pyrrole-2,5-Dione, conducted via continuous bulk polymerization in a multi-stage stirred-tank reactor cascade with residence time distribution tightly controlled within 3.5–5.0 h total. The N-phenylmaleimide repeat unit contributes a molar refraction increment that raises the refractive index nD (589 nm) by approximately 0.0025–0.0032 per weight percent comonomer incorporated, enabling lens designers to target nD 1.56–1.59 without resorting to brominated or sulfur-containing aromatic monomers that degrade Abbe number below 31. At 25–30 wt% N-PMI in the terpolymer, nD reaches 1.575–1.585 while the Abbe number (νD) holds at 32–34, measured per ISO 489:2022 Method A on polished 2 mm plaques. The processing hazard that limits further N-PMI incorporation is not optical but rheological: zero-shear viscosity at 230°C climbs past 12,000 Pa·s when the N-PMI fraction exceeds 32 wt%, exceeding the plastication capacity of standard 35 mm reciprocating-screw injection units and requiring barrel temperature profiling that approaches the ceiling imposed by monomer thermal stability. Residual volatile N-PMI monomer in the pelletized resin must remain below 250 ppm (quantified by headspace GC–MS per ISO 6401:2022) to prevent mold-deposit formation on polished SPI A-1 finish cavity surfaces; vapor-phase monomer re-deposits as a crystalline film that nucleates haze patches after 150–200 injection cycles on 8-cavity lens molds.Why Does the BMI Prepreg Tack–Outlife Relationship Depend on Phenylmaleimide Copolymer Fraction?In bismaleimide resin formulations for carbon-fiber prepreg destined for aerospace secondary structure (service temperature ceiling 230–260°C), 1-Phenyl-1H-Pyrrole-2,5-Dione functions not as the primary matrix monomer but as a reactive diluent and crosslink-density modifier blended at 10–25 parts per hundred parts of 4,4′-bismaleimidodiphenylmethane (BMI-1). The phenylmaleimide comonomer depresses the melt viscosity of the blended resin at 120°C from approximately 8–15 Pa·s to 1.5–4 Pa·s, a reduction that enables hot-melt film impregnation on 300–400 mm wide reverse-roll coaters running at 3–6 m/min line speed without exceeding a 130°C resin bath temperature—critical because the differential scanning calorimetry exotherm onset (Tonset) of an uncatalyzed BMI-1/N-PMI blend lies at 165–175°C, and any localized over-temperature in the coater pan precipitates microgel particles that translate into dry spots in the prepreg. The outlife at 23°C and 50% RH, defined as the interval over which tack retention measured by the probe-tack method (ASTM D2979-16) remains above 70% of the initial value, shortens from 21–28 days for unmodified BMI-1 to 12–16 days at 20 phr N-PMI loading because the monofunctional phenylmaleimide introduces chain termini that plasticize the partially advanced resin and accelerate ambient-temperature physical aging of the tackified surface.Autoclave cure cycle design must accommodate the altered cure kinetics. The N-PMI component copolymerizes through a radical-mediated mechanism that operates concurrently with the thermal ene–Diels–Alder sequence of the difunctional BMI, producing a dual-cure exotherm profile with a first peak at 195–210°C and a second at 240–255°C in dynamic DSC scans at 5°C/min ramp rate (ISO 11357-1:2023). If the autoclave heat-up rate between these two exotherms falls below 1.5°C/min, the evolving network vitrifies prematurely and traps unreacted maleimide termini; these residual groups undergo post-cure crosslinking during the first 50–100 h of service at 230°C, driving a Tg increase of 8–15°C that embrittles the matrix and reduces open-hole compressive strength (ASTM D6484/D6484M-23) by 12–18% relative to specimens subjected to an optimized stepped post-cure. Void content measured by optical microscopy of polished cross-sections per ASTM E2534-20 must remain under 0.5 vol% for primary-structure qualification; N-PMI volatilization at the 180–200°C vacuum hold stage can contribute 0.1–0.3 vol% additional voidage if the vacuum bag pleating configuration fails to maintain ≤5 mbar absolute pressure at the laminate edge bleeder.---On rubber processing lines manufacturing peroxide-cured ethylene–propylene–diene terpolymer profiles for automotive weatherseal and coolant hose applications, the partial replacement of triallyl cyanurate coagent with 1-Phenyl-1H-Pyrrole-2,5-Dione at 1.0–3.5 phr alters the crosslinking network topology in a manner that is not captured by standard moving-die rheometer torque differentials alone. At 180°C cure temperature, the scorch safety margin (ts2) on an MDR 2000-type instrument operated at 0.5° arc amplitude per ISO 6502-3:2023 extends by 0.4–0.9 min relative to the TAC-coagent control, while the cure rate index (tc90 − ts2) remains statistically unchanged—an asymmetric response that cannot be explained by a simple radical-scavenging model and instead reflects the preferential addition of EPDM macro-radicals to the maleimide double bond rather than to allylic coagent unsaturation. The practical consequence emerges at the extrusion die: compound containing N-PMI at 2.0 phr exhibits a 15–22% reduction in die swell (annular die, L/D 10:1, 40 mm mandrel diameter, 1.2 mm gap) measured by in-line laser micrometer, permitting tighter dimensional tolerances on the vulcanized profile without a compensatory draw-down ratio adjustment. The limitation demanding process-engineering attention is the fume condensation pattern in the continuous hot-air vulcanization tunnel: N-PMI sublimate deposits on the 220–250°C zone heat-exchanger fins and, over 72–96 h of continuous operation, forms a thermally insulating coating that drops the tunnel heat-transfer coefficient by 8–12%, necessitating a scheduled cleaning cycle that coincides with every third compound changeover.
Semiconductor Epoxy Mold Compound: Low-Warpage Formulations and the Maleimide–Epoxy Cure Mismatch ProblemEpoxy mold compounds formulated for fine-pitch ball-grid-array packages with die-to-mold-cap clearances below 150 μm incorporate 1-Phenyl-1H-Pyrrole-2,5-Dione—pre-reacted into a styrene–maleimide oligomer backbone with Mn 1500–3500 Da—as a high-Tg modifier blended at 8–15 wt% relative to the ortho-cresol novolac epoxy base resin. The maleimide-functional oligomer phase-separates during transfer molding at 175°C into dispersed domains with an average diameter of 80–200 nm (characterized by tapping-mode atomic force microscopy on cryo-microtomed cross-sections), and these domains pin the epoxy network shrinkage during post-mold cure at 175°C for 6 h, reducing in-plane mold shrinkage from 0.35–0.45% to 0.18–0.25% as determined by thermomechanical analysis on 5 mm × 5 mm × 0.8 mm specimens per ISO 11359-2:2021. Warpage measured on a 12 mm × 12 mm PBGA substrate with 0.4 mm pitch after post-mold cure and JEDEC Level 3 moisture preconditioning decreases from 85–110 μm to 40–60 μm coplanarity deviation. The catch, well-documented on production-floor molding presses equipped with 200–350 kN clamp systems and multi-plunger transfer pots, is that the N-PMI oligomer raises the spiral flow length requirement by 15–25% for complete cavity fill; molding compound suppliers compensate by reducing the fused silica filler loading from 88 wt% to 84–86 wt%, a shift that increases the coefficient of thermal expansion below Tg (α1) from 8–10 ppm/K to 12–15 ppm/K—partially offsetting the warpage benefit and introducing a wire-sweep risk during encapsulation of 25 μm diameter gold bonding wires when filler content drops below 85 wt%. At the qualification stage, the formulation must satisfy UL 94 V-0 flammability at 0.8 mm thickness and pass biased highly accelerated stress testing (130°C, 85% RH, 3.7 V bias, 96 h) without intermetallic corrosion at the ball-bond interface; chloride ion contamination originating from residual N-phenylmaleamic acid in the oligomer must therefore be held below 5 ppm by ion chromatography extraction per IPC-TM-650, Method 2.3.28.1. |
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1-Phenyl-1H-pyrrole-2,5-dione (CAS 941-69-5; N-phenylmaleimide, NPMI) is a five-membered cyclic imide with molecular formula C10H7NO2 and molar mass 173.17 g/mol. The monomer is supplied as pale yellow crystalline flakes exhibiting a melting endotherm between 82 and 86°C (ASTM D3418, differential scanning calorimetry at 10 K/min) and a mass purity ≥98% by gas chromatography–flame ionization detection. Its electron-deficient double bond undergoes rapid free-radical addition, copolymerisation with styrenics and acrylates, and Diels–Alder cycloaddition, allowing NPMI to function as both a high-temperature-resistant comonomer and a sacrificial co-agent in radical curing. Unlike N-alkyl maleimides such as N-ethylmaleimide, the phenyl substituent raises the ceiling temperature and retards thermal homopolymerisation, pushing the decomposition onset to approximately 220°C (thermogravimetric analysis, N2, 10 K/min). When compared with difunctional bismaleimides (e.g., 4,4′-bismaleimidodiphenylmethane), NPMI does not generate an insoluble network on its own; this monofunctionality preserves melt processability while still enabling molecular weight build-up via graft or coupling chemistry. A typical specification summary appears below.
| Property | Value | Method |
|---|---|---|
| Purity | ≥98.5 % | GC-FID |
| Melting range | 82–86 °C | ASTM D3418 |
| Ash content | ≤0.1 % | ISO 3451-1 |
| Moisture (Karl Fischer) | ≤0.3 % | ISO 15512 |
| Colour (APHA, 10 % acetone) | ≤50 | ASTM D1209 |
| Storage stability (sealed, 5°C) | 12 months | Proprietary |
Unopened NPMI remains stable for at least twelve months under refrigeration; however, the imide ring is susceptible to hydrolytic opening in the presence of moisture, yielding maleanilic acid that acts as an acidic catalyst and accelerates further degradation. When packaging is exposed to ambient relative humidity exceeding 40% RH for more than 30 minutes, enough surface moisture can adsorb to initiate ring-opening during subsequent thermal processing. This hydrolysis pathway manifests as an off-specification melting endotherm broadening and a colour shift beyond 100 APHA. In twin-screw compounding operations, hydrolysed monomer generates volatile maleic anhydride at melt temperatures above 200°C, corroding downstream vacuum venting components and causing inconsistent grafting yields. For this reason, pre-drying in a vacuum oven at 60°C and ≤10 mbar for 4–6 h is mandatory when the resin has been stored in unsealed liners for more than 24 h at ambient shop-floor humidity. Desiccant-wheel dryers with a dew point below -40°C are adequate for continuous conveying, provided residence time in the hopper does not exceed 4 h. Melt-compounding trials on a co-rotating twin-screw extruder (L/D = 40, D = 27 mm) with vent vacuum below 50 mbar showed that skipping the drying step at 65% RH ambient conditions led to a 15–20% reduction in grafted NPMI content, as quantified by Fourier-transform infrared spectroscopy of purified polymer isolates.
Twin-screw compounding of acrylonitrile-butadiene-styrene (ABS) with 1-phenyl-1H-pyrrole-2,5-dione at loadings from 2.5 to 7.5 wt% is employed to raise the heat deflection temperature under load (HDT/A, 1.82 MPa, ASTM D648) by up to 18°C relative to unmodified resin. The NPMI molecule grafts onto the styrene-acrylonitrile matrix during peroxide-initiated or thermally induced radical transfer, increasing the glass transition temperature (Tg) of the continuous phase. Table 1 illustrates the trade-off between thermal resistance, impact strength, and flowability on a production-scale 40 mm co-rotating twin-screw line running at 250 kg/h.
| NPMI loading (wt%) | HDT/A (°C) ASTM D648 | Notched Izod (J/m) ASTM D256 | MFR (g/10 min) 220°C/10 kg ISO 1133 | Tensile strength (MPa) ASTM D638 |
|---|---|---|---|---|
| 0 | 84 | 210 | 24 | 43 |
| 2.5 | 92 | 175 | 16 | 46 |
| 5.0 | 99 | 130 | 10 | 50 |
| 7.5 | 105 | 85 | 5 | 54 |
The processing window narrows noticeably above 5 wt% NPMI because the onset of maleimide homopolymerisation accelerates at local hot spots above 215°C, generating microgels that produce surface defects in injection-moulded parts. Barrel zones downstream of the melting section must be held at or below 210°C, and the screw configuration must favour distributive mixing over aggressive kneading blocks to limit dissipative temperature overshoot. Production experience indicates that nitrogen blanketing of the feed throat and the side-stuffer port reduces oxidative discolouration, especially when the base ABS contains high butadiene rubber levels. Avoid combining NPMI with amine-based antioxidants in the same concentrate because exothermic Michael addition at the maleimide double bond can trigger gelation inside the side-feeder.
In unplasticised poly(vinyl chloride) (PVC-U) dry blends processed on counter-rotating conical twin-screw extruders (45/90 mm, throughput 80–120 kg/h), the incorporation of 1–3 phr 1-phenyl-1H-pyrrole-2,5-dione through a solid-state grafting approach raises the Vicat softening temperature (VST/B50, ISO 306) by 6–10°C. The maleimide ring is activated by the dehydrochlorination intermediates generated during the early stages of melt processing; radical species attach NPMI to the PVC backbone, forming a rigid pendant that hinders chain segmental motion. This grafting is accompanied by a steep increase in melt viscosity: torque rheometry tests at 190°C and 40 rpm show that the fusion torque climbs from a baseline of 18–20 N·m to 28–32 N·m at 3 phr NPMI. Processors therefore throttle the extruder throughput and open the die gap by 0.2–0.3 mm to avoid excessive melt pressure. Calcium-zinc stabiliser packages, particularly those containing high levels of zinc stearate, catalyse the homopolymerisation of NPMI during the dwell time in the holding section, generating brown specks and early colour shift; tin-based stabilisers show better colour hold. Published data for long-term heat stability under 200°C oven ageing per ISO 305 is limited, but commercial experience suggests that NPMI-modified PVC-U pipes extruded with 1.5 phr maleimide meet DIN 16892 Vicat requirements for hot-water piping while retaining K-value above 64.
In peroxide-cured ethylene-propylene-diene monomer (EPDM) formulations, 1-phenyl-1H-pyrrole-2,5-dione functions as a coaggregating agent that mitigates main-chain scission during free-radical crosslinking. A dosage of 2–4 phr NPMI, co-fed with dicumyl peroxide (DCP 40% active, 6 phr), raises the maximum rheometer torque (MH) by 15–25% in a moving die rheometer at 170°C, 0.5° arc (ISO 6502). The resulting vulcanisates exhibit compression set (22 h/150°C, ASTM D395 method B) values below 18%, compared to 28–32% for the peroxide-only control, while elongation at break (ISO 37) remains above 350%. NPMI is monofunctional; it grafts pendant phenylmaleimide adducts that do not create the dense, rigid crosslink clusters characteristic of bismaleimide co-agents, preserving the rubbery plateau modulus without embrittlement. Processing safety demands strict segregation from amine-type antioxidants in the masterbatch because the rapid Michael addition releases sufficient exothermic heat to initiate scorch in an internal mixer. Zinc oxide, a common EPDM activator, promotes imide ring opening at mixing temperatures above 120°C; therefore, a ZnO-free or low-ZnO (≤1 phr) formulation is recommended when NPMI is added upstream.
Hydrogenated nitrile butadiene rubber (HNBR) sealing elements exposed to H2S-containing crude oil at 150°C demand maximum crosslink density and minimal compression set. A co-agent system using 3 phr NPMI together with 1.5 phr triallyl isocyanurate (TAIC) and 7 phr 1,3-bis(tert-butylperoxyisopropyl)benzene (40% on silica) yields after press cure (170°C/20 min) and post-cure (150°C/4 h) a crosslink density, determined by equilibrium swelling in methyl ethyl ketone (Flory-Rehner), of 8.2×10-5 mol/cm³. The compound displays a Shore A hardness of 78 (ASTM D2240) and retains 85% of its initial tensile strength after 168 h ageing in IRM 903 oil at 150°C. Because NPMI has a solubility parameter closer to the nitrile matrix than alternative bismaleimides, bloom was not observed up to 5 phr loading; however, above that threshold, surface frost appears after 72 h storage at 23°C/50% RH. Production-scale injection moulding of HNBR stator elements with internal heating channels requires a mould temperature of 185°C and a cure time extended by 30 s relative to TAIC-only recipes to ensure complete consumption of the maleimide double bond, confirmed by residual exotherm absence in DSC scans of cured skins.
The architectural divergence between monofunctional NPMI and difunctional bismaleimides (BMI) dictates their respective processing and performance profiles. NPMI possesses a single reactive double bond; thus, it cannot form a macroscopic network by itself but instead couples pendant maleimide groups onto polymer chains or participates in copolymerisation as a monomer unit. This characteristic enables precise control over molecular architecture without inducing gelation in a twin-screw compounding line, whereas BMI monomers such as 4,4′-bismaleimidodiphenylmethane form crosslinked domains whose size depends on shear and dispersion. The melt point of NPMI (82–86°C) falls within the feeding and plastication zones of a standard extruder, promoting rapid dissolution into a styrenic or acrylic melt pool, while the melt point of unmodified aromatic BMI (155–160°C) places it late in the plastication sequence, risking undispersed particles. During the cure of rubber compounds, NPMI addition raises the scorch time (ts2) relative to BMI at iso-concentration because the absence of a second reactive terminus reduces premature crosslink build-up; yet the overall state of cure is lower, reflected in a delta torque about 30–40% of that achieved with an equimolar olefinic bond content of BMI. On thermal ageing, NPMI-modified ABS exhibits a slower embrittlement rate in hot-air ovens at 120°C (ISO 188) due to the absence of hydrolytically vulnerable ester or amide linkages that form in some BMI crosslinked networks.
