Lubricant Additives - Amine Antioxidants Series: Nonylated Diphenylamine (NDPA) is the high-molecular-weight specialist of the Sinolook amine antioxidant range - differentiating from the broader Alkylated Diphenylamine grade (CAS 68411-46-1, C4–C12 mixed alkyl) by its specific C9 nonyl substituents (branched nonyl from propylene trimer) on the diphenylamine core. The C9 nonyl chain delivers a precisely optimised balance: longer than C4–C8 alkyl (→ lower volatility, higher MW ~350–393 g/mol, better high-temperature persistence in long-drain oils) but shorter and more branched than C12–C18 (→ better cold-flow and oil solubility across all base oil types). NDPA at MW ~393 (di-nonyl grade) is the amine antioxidant of choice for premium long-drain synthetics, aviation turbine oils (MIL-PRF-23699), and PAO/POE lubricants where maximum AO persistence with minimum volatility is required. SAPS-free (C/H/N only). Commercial equivalents: Naugalube 438L, VANLUBE 81, related grades. Sinolook Amine AO series: Alkylated DPA (CAS 68411-46-1) · Nonylated DPA - NDPA (this).
✅ SAPS-Free · High-MW Amine AO · C9 Nonyl Chain · MW ~350–393 g/mol · Superior Volatility vs General ADPA · Long-Drain Persistence · ACEA C1–C5 Compliant · PAO/POE/PAG Compatible · Aviation · Engine Oil · Turbine
Nonylated Diphenylamine (NDPA)
Nonyl DPA / Dinonyl Diphenylamine (DNPA) / Nonyl Dphenylamine / CAS 36878-20-3 (di-nonyl) / CAS 27177-41-9 (mono-nonyl mixture) / C₉ Alkyl Diarylamine / MW ~350–393 g/mol / Purity ≥95% / Amber Liquid
| CAS Numbers | 36878-20-3 (Dinonyl diphenylamine - di-nonyl grade, MW ~393) 27177-41-9 (Nonylated diphenylamine - mono-nonyl/mixture grade, MW ~350) |
| Structure | Diphenylamine core (Ph–NH–Ph) with C9 nonyl substituent(s) at para position(s) of the phenyl ring(s). Di-nonyl grade (CAS 36878-20-3): both phenyl rings carry a 4-nonyl group - structure is (4-C₉H₁₉–C₆H₄)₂NH, MW ~393. Mono-nonyl (within CAS 27177-41-9 mixture): one ring nonylated, MW ~351. The image shows the simplified notation C₉H₁₉–NH–C₆H₅ (representing the nonyl-aniline half of the molecule). The nonyl group (C₉H₁₉) is branched - sourced from propylene trimer (tri-propylene) alkylation, giving a branched isoC9 structure rather than linear n-nonyl. This branching is critical for low-temperature fluidity. |
| vs Alkylated DPA | Alkylated DPA (CAS 68411-46-1) is a broader mixture with C4–C12 alkyl chains of varying length. NDPA/DNPA is the C9-specific grade - higher than average MW vs the general alkylated DPA mixture, giving measurably lower volatility and better long-drain persistence. The C9 nonyl chain is the industry "sweet spot" - longer chain = lower volatility vs C4/C8, but the branched C9 maintains ambient-liquid form (no high-MP waxy solid issue of C12+ grades) and universal base oil solubility. |
| Trade equivalents | Naugalube 438L · VANLUBE 81 · BNX DLTDP-related amine grades · Antioxidant L06 (China) - NDPA is the generic equivalent of these commercial grades |
| ★ SAPS Status | ✅ Zero ash / sulphur / phosphorus / metals - C/H/N only
N is NOT a SAPS element. NDPA at any treat rate contributes zero to ASTM D482 (ash), D4951 (P), or D4294 (S). ACEA C1/C2/C3/C5 and API SP compliant unconditionally. |
| ★ MW Advantage |
Di-nonyl (CAS 36878-20-3): MW ~393 Mono-nonyl mixture: MW ~350
Higher MW vs general alkylated DPA (C8-based ~255–340) → lower vapour pressure → lower evaporative depletion rate in service → longer effective AO reserve. At RULER-measured 15,000 km, NDPA-grade retains measurably higher AO reserve vs lower-MW alkylated DPA grades. |
| Appearance | Clear to deep amber viscous liquid; characteristic phenylamine odour; fully liquid at ambient (>0°C); pour point <–5°C; soluble in all mineral and synthetic base oils. |
Why C9 Nonyl? - The Alkyl Chain Length Optimisation in Diarylamine Antioxidants
Nonylated Diphenylamine is the C9-specific member of the diarylamine antioxidant family - designed around the insight that alkyl chain length on the diphenylamine core is not a neutral variable but a critical parameter controlling volatility, oil solubility, cold-flow behaviour, and ultimately lubricant AO persistence. The diphenylamine core (Ph–NH–Ph) is the functional antioxidant group in all members of this family - the alkyl chains exist solely to control physical properties, not antioxidant chemistry. The selection of C9 (nonyl) as the alkyl chain length reflects a carefully optimised trade-off between three competing properties that change monotonically with chain length.
| Property | Short chain (C4–C6) | ★ C9 Nonyl (this) | Long chain (C12–C18) |
|---|---|---|---|
| Molecular weight | Low (~200–280) | ★ Moderate–high (~350–393) | High (~420–520+) |
| ★ Volatility @150°C | Higher - faster depletion | ★ Low - good persistence | Negligible |
| Cold flow / pour point | Good (low MP/PP) | ★ Excellent (liquid <–5°C) | Risk of high viscosity / solidification at low temp |
| Oil solubility (PAO/ester) | Moderate - risk of phase separation in high-PAO synthetics at low temp | ★ Excellent across all base oil types | Good in mineral, less reliable in high-PAO |
| AO activity/gram | Higher (lower MW dilution) | Moderate - acceptable efficiency/persistence ratio | Lower (high MW dilutes active N–H) |
| ★ Overall long-drain fit | Marginal for 15,000+ km | ★★ Best for 15,000–30,000 km + aviation | ★ Better for ultra-long industrial drain (transformer, 5yr+) |
Conclusion: C9 nonyl achieves the best combination of low volatility + cold-flow fluidity + universal oil solubility for automotive and industrial long-drain lubricant formulations. The branched nature of the commercial C9 (from propylene trimer alkylation rather than linear n-nonanol) further enhances low-temperature fluidity and Group IV/V synthetic oil solubility compared to linear C9.
NDPA operates by the identical partially-regenerating diarylamine radical mechanism as Alkylated DPA (CAS 68411-46-1): Step 1 - H-atom donation from N–H to ROO• (Ar₂N–H + ROO• → Ar₂N• + ROOH); Step 2 - aminyl radical scavenges second ROO• (Ar₂N• + ROO• → Ar₂N–OOR nitroxide); Step 3 - nitroxide reacts with ROOH to regenerate hydroxylamine (partial regeneration); Step 4 - final quinone-imine products. Net: 2–4 ROO• scavenged per molecule. The C9 nonyl chain does not participate in the antioxidant chemistry - it exists solely to control physical properties. The active site is identical to the alkylated DPA series - the Ph–NH–Ph nitrogen centre.
Lower vapour pressure of C9 (vs C4/C8) means less evaporative loss from the oil phase over time. At 150°C sustained oil temperature, the vapour pressure of a C9-alkylated DPA is approximately 3–5× lower than a C8-alkylated equivalent - directly translating to proportionally less loss from the lubricant per hour of operation. RULER depletion studies confirm that NDPA-grade amine AOs show 20–30% higher residual AO reserve at 15,000 km versus equivalent C8-based alkylated DPA at the same initial treat rate.
Optimal long-drain AO formulation: NDPA 0.2–0.4 wt% + L01/L57-type phenolic ester 0.3–0.5 wt% + ZDDP 0.7–1.2 wt%. NDPA replaces or supplements general alkylated DPA in this stack - the C9 nonyl's lower volatility means a slightly lower initial treat rate of NDPA achieves the same end-of-drain AO reserve vs a higher treat rate of lower-MW alkylated DPA. For ACEA C1/C5 (P ≤0.05%, restricting ZDDP) formulations: NDPA 0.4–0.5 wt% + L57-type 0.4–0.6 wt% as the SAPS-free AO stack fully compensating for reduced ZDDP AO contribution.
Both phenyl rings carry 4-nonyl groups. MW ~393, higher viscosity, slightly lower amine value/gram (more MW per N–H). Best for: aviation turbine oils, ultra-long-drain PAO/POE synthetics, industrial turbine oil >5000 hours. Specify for maximum volatility suppression.
One ring nonylated. MW ~350, slightly lower viscosity, slightly higher amine value/gram. Best for: long-drain PCMO engine oil (15,000–30,000 km), gear oil, compressor oil, general industrial lubricants. Better balance of AO activity/gram + volatility suppression for typical automotive drain intervals.
Sinolook supplies both grades. Specify application and drain interval for grade recommendation. Custom blends of di-nonyl + mono-nonyl at defined ratios available for OEM DI package development.
| Property | Di-nonyl (CAS 36878-20-3) | Mono-nonyl / Mixture (CAS 27177-41-9) |
|---|---|---|
| Appearance | Deep amber liquid | Amber liquid |
| ★ MW (g/mol) | ~393 | ~350 |
| Purity (GC) | ≥95% | ≥95% |
| Flash Point | ≥200°C | ≥200°C |
| Ash Content ✅ | 0% | 0% |
| Pour Point | <–5°C | <–5°C |
| KV @40°C (cSt) | ~600–2000 | ~400–1500 |
Technical Specification
Total active diarylamine content by GC. Di-nonyl (36878-20-3) grade: ≥95% di-nonyl DPA main component + minor mono-nonyl, all AO-active. ≥98% available on request.
Highest MW in the Sinolook amine AO range; directly translates to lowest volatility and best long-drain AO persistence vs CAS 68411-46-1 grade (MW ~255–340)
Same as alkylated DPA - non-flammable; no ADR Class 3; safe standard warehouse and IBC storage
✅ Truly ashless - C/H/N; zero metals, S, P; N ≠ SAPS; ACEA C1–C5 compliant unconditionally
| Parameter | Di-nonyl (CAS 36878-20-3) | Mono-nonyl/Mix (CAS 27177-41-9) | Test Method / Note |
|---|---|---|---|
| Appearance | Deep amber liquid | Clear to amber liquid | Visual - deep amber inherent to DPA chromophore; not an impurity indicator |
| Purity (GC) ★ | ≥ 95.0% | ≥ 95.0% | GC area %. Custom ≥98% on request. GC confirms di-nonyl vs mono-nonyl ratio in di-nonyl grade. |
| ★ Molecular Weight | ~393 g/mol | ~350 g/mol | MS / GPC - confirm vs CAS 68411-46-1 alkylated DPA (MW ~255–340 typical); higher MW = lower vapour pressure = slower evaporative depletion = better long-drain persistence |
| Amine Value | Grade dep. - reported per lot | Grade dep. - reported per lot | ASTM D2896. Note: mono-nonyl has slightly higher amine value/gram vs di-nonyl (lower MW dilution per N–H group) - relevant for AO efficiency per kg cost |
| Ash Content ✅ | 0% | 0% | ASTM D482. ✅ SAPS-free - C/H/N only; N ≠ SAPS element; zero impact on ACEA ash/P/S limits |
| Flash Point | ≥ 200°C | ≥ 200°C | ASTM D93. Non-flammable - safe standard transport and storage; no ADR Class 3 restrictions |
| KV @40°C (cSt) | ~600–2000 | ~400–1500 | ASTM D445. High viscosity liquid - IBC heating jacket recommended for efficient transfer; dissolves readily in warm base oil without settling |
| Water Content | ≤ 0.10% | ≤ 0.10% | Karl Fischer. Sealed storage essential; N₂ blanket for IBCs; 24-month shelf life sealed |
| Packaging | 25 kg pail · 200 kg drum · 1000 L IBC · Flexitank | 25 kg pail · 200 kg drum · 1000 L IBC · Flexitank | International transport standards; specify grade on order (di-nonyl CAS 36878-20-3 or mixture CAS 27177-41-9) |
Applications & Dosage Guidance
1. Long-Drain PCMO & HDEO Engine Oils
For passenger car motor oils (PCMO) at 15,000–30,000 km drain intervals and heavy-duty diesel engine oils (HDEO) at 60,000–100,000 km extended drain, NDPA mono-nonyl grade (CAS 27177-41-9) at 0.2–0.4 wt% provides the optimal balance of AO activity per gram and volatility suppression. In the standard three-component AO stack (NDPA 0.2–0.4 wt% + L01-type 0.3–0.5 wt% + ZDDP 0.7–1.2 wt%), NDPA's C9 nonyl grade demonstrates 20–30% better RULER-measured AO reserve at 15,000 km compared to a lower-MW alkylated DPA at the same initial treat rate. This enables lubricant formulators to either reduce the initial NDPA dose (cost saving) or extend the drain interval approval relative to formulations using shorter-chain alkylated DPA. For API SP-GF-6 and ACEA C3 OEM approvals, the three-component stack with NDPA is the industry best practice.
2. Aviation & Gas Turbine Lubricants
Aviation turbine lubricants (MIL-PRF-23699, MIL-PRF-7808, DEF STAN 91-101) and gas turbine oils (GEK-32568, Pratt & Whitney PWA 521/522) operate at continuous bulk oil temperatures of 150–200°C with peak hot-spot temperatures of 250°C+. At these temperatures, the di-nonyl grade (CAS 36878-20-3, MW ~393) is preferred over the mono-nonyl mixture: its higher MW means proportionally lower vapour pressure and longer AO persistence before the amine reserve is exhausted. In POE-based aviation turbine oils (di-pentaerythritol ester, tri-methylol propane ester), NDPA at 0.4–0.8 wt% combined with L57-type phenolic ester at 0.3–0.5 wt% achieves ASTM D2272 RPVOT >4000 minutes - the highest-tier benchmark for military and commercial aviation grade turbine oil oxidation stability.
3. PAO, POE & Ester Synthetic Lubricants
NDPA's branched C9 nonyl chain provides excellent compatibility with Group IV (PAO) and Group V (ester, PAG) synthetic base stocks - better than straight-chain C9 or C12+ alkyl DPA grades in terms of low-temperature homogeneity and dissolution rate. In PAO synthetics (commonly used in premium automotive and industrial gear oils, compressor oils, and engine oils), NDPA at 0.2–0.4 wt% remains fully dissolved at –40°C with no phase separation - a critical criterion for cold-start protection in synthetic lubricants used in cold climates. For POE-base aviation and refrigeration compressor oils, the NDPA / L57 combination is the standard AO approach - both components are fully compatible with polyol ester polarity. ASTM D2272 RPVOT results in Group IV PAO base oil blends: NDPA (0.3 wt%) + L57 (0.4 wt%) consistently achieves >3500 minutes, vs ~1500 minutes for the uninhibited PAO base oil.
4. Industrial Turbine, Compressor & Hydraulic Oils
In industrial steam and gas turbine oils (IEC 60296, DIN 51515, ASTM D3487) requiring 1000–8000+ hour TOST lives, NDPA mono-nonyl at 0.1–0.3 wt% combined with L01-type 0.1–0.2 wt% achieves ASTM D943 TOST values >5000 hours in Group III/IV base oils - exceeding the requirements of most OEM turbine oil approvals (GEK-32568 requires >3000 h, Alstom HTGD 90 117 requires >2000 h). For industrial hydraulic oils (DIN 51524-2/3 HLP, Denison HF-0/2, Vickers M-2950-S), NDPA at 0.1–0.2 wt% combined with HP-136-type (low viscosity phenolic ester) maintains RPVOT >1500 min while keeping finished oil KV within ISO VG specification. Compressor oil applications (DIN 51506 VDL, ISO 6521 VG 46–150) benefit from NDPA's high flash point and low volatility ensuring no carbonaceous deposits in compressor discharge valves - a common failure mode when using low-FP antioxidants in high-discharge-temperature compressors.
| Application | NDPA Grade | Treat Rate | Standard / vs ADPA |
|---|---|---|---|
| PCMO engine oil (15,000–30,000 km) | Mono-nonyl (27177-41-9) | 0.2–0.4 wt% | API SP, GF-6, ACEA C3; RULER confirms 20–30% better AO reserve vs C8-grade alkylated DPA at equal treat |
| Aviation turbine oil (MIL-PRF-23699) | Di-nonyl (36878-20-3) | 0.4–0.8 wt% | MIL-PRF-23699; ASTM D2272 >4000 min target; POE-compatible |
| Gas / steam turbine oil (IEC 60296) | Mono-nonyl (27177-41-9) | 0.1–0.3 wt% | IEC 60296, GEK-32568; ASTM D943 >5000 h target in Group III/IV |
| PAO/POE synthetic lubricant | Either grade | 0.2–0.5 wt% | ASTM D2272 >3500 min; confirmed cold-flow stability to –40°C; branched C9 ensures no phase separation |
| Industrial hydraulic oil (ISO VG 32–68) | Mono-nonyl (27177-41-9) | 0.1–0.2 wt% | DIN 51524-2/3; Denison HF-0/2; RPVOT >1500 min with HP-136 co-AO |
| Compressor oil (ISO VG 46–150) | Di-nonyl (36878-20-3) | 0.1–0.3 wt% | DIN 51506 VDL; high FP ≥200°C prevents deposit formation at discharge valve temperatures |
Frequently Asked Questions
Q: What is the quantitative difference in AO persistence between Nonylated DPA (NDPA) and the general Alkylated DPA (CAS 68411-46-1)?
The persistence advantage is primarily driven by the difference in vapour pressure at service temperatures - a consequence of the MW difference. NDPA di-nonyl (MW ~393) has approximately 3–5× lower vapour pressure at 150°C compared to a typical C8-alkylated DPA (MW ~255–280). In ASTM D5800 (Noack volatility test, 250°C/1h) applied to neat antioxidant samples, C8-grade loses roughly 15–25% mass, while C9 di-nonyl loses <5% mass. In formulated oil, the difference is less extreme because both compounds are dissolved in oil (reducing their volatility relative to the neat state) but the relative ranking is preserved. RULER voltammetry studies on used PCMO engine oil at 15,000 km consistently show: NDPA mono-nonyl retains ~55–65% initial amine AO reserve, while equivalent initial treat rate of general alkylated DPA retains ~35–45%. This 20-percentage-point difference in residual AO reserve translates directly to a meaningful extension of effective drain interval support - supporting drain intervals of 15,000 km vs ~10,000 km for the lower-MW grade at the same initial treat rate.
Q: Should I choose di-nonyl (CAS 36878-20-3) or mono-nonyl (CAS 27177-41-9) grade?
The choice depends primarily on the application temperature and drain interval: Di-nonyl (CAS 36878-20-3) is preferred for applications above 150°C continuous (aviation, gas turbine, high-temperature compressor) where maximum volatility suppression is required, and where the lower amine value/gram is acceptable given the high treat rate already used. Mono-nonyl/mixture (CAS 27177-41-9) provides a better cost-performance balance for automotive long-drain engine oils (PCMO, HDEO), industrial turbine oils at moderate temperatures, and PAO/POE synthetic lubricants - delivering most of the volatility advantage vs C8-grade ADPA at a slightly higher amine value/gram (better AO efficiency per mass of additive). For new formulation development, Sinolook recommends running RULER depletion studies at your target drain interval on both grades to confirm the cost-optimal choice. We can provide samples of both grades for this evaluation.
Q: Is NDPA compatible with Group IV PAO at low temperatures (–40°C cold-start conditions)?
Yes - the branched C9 nonyl chain (from propylene trimer alkylation) is specifically beneficial for Group IV PAO solubility at low temperatures. Linear alkyl diphenylamine grades (using n-dodecyl or stearyl substituents) can show marginal solubility / micro-crystallisation in high-PAO synthetic oils at temperatures below –20°C, especially at treat rates above 0.5 wt%. Branched C9 nonyl avoids this issue entirely - the branching disrupts crystalline packing and maintains full dissolution in PAO even at –40°C at treat rates up to 0.8 wt%. This is confirmed by ASTM D97 pour point and low-temperature homogeneity testing at –40°C on formulated synthetic engine oil containing NDPA 0.3 wt% + L57-type 0.4 wt% + ZDDP 0.8 wt% in PAO 4/6 base oil - no phase separation or viscosity anomalies detected. For cold-climate synthetic lubricant formulation (Arctic/Nordic SAE 0W-20/0W-30 grades), NDPA is the preferred amine AO grade over all linear alkyl DPA alternatives.
Technical & Regulatory References
GC (purity ≥95%) · MW confirmation (GPC/MS) · ASTM D2896 (amine value) · ASTM D482 (ash = 0%) · ASTM D93 (FP ≥200°C) · ASTM D445 (KV @40°C) · KFT (water ≤0.10%) · ASTM D2272 RPVOT (>3500 min for PAO, >4000 min for aviation POE) · ASTM D943 TOST (>5000 h target turbine oil) · ASTM D6186 PDSC (OIT screening) · ASTM D6971 RULER (AO reserve monitoring in used oil - primary tool for drain interval validation) · ASTM D5800 Noack (volatility comparison - neat AO) · ASTM D97 pour point (cold flow)
Engine oils: API SP/SN+ · ILSAC GF-6A/B · ACEA C1–C5 (SAPS-free ✅) · CK-4/FA-4 · VW 508/509 · BMW LL-04 · MB 229.5/229.71 · Aviation: MIL-PRF-23699 (Type II/IIIA) · MIL-PRF-7808 · DEF STAN 91-101 · Turbine (industrial): IEC 60296 · GEK-32568 · PWA 521/522 · Rolls-Royce OMAT · DIN 51515 L-TD/L-TG · Alstom HTGD 90 117 · Hydraulic: Denison HF-0/2 · DIN 51524-2/3 HLP · ISO 4406 · Compressor: DIN 51506 VDL · ISO 6521 · Synthetics (PAO/POE): Group IV (API basing) · Group V ester · Cold-climate performance (–40°C)
CAS 36878-20-3 (di-nonyl) · CAS 27177-41-9 (mono-nonyl/mixture) · EINECS registered · REACH compliant · TSCA listed · ✅ SAPS-free (ash 0%, S 0%, P 0% - N ≠ SAPS element) · FP ≥200°C - non-flammable (no ADR Class 3) · GHS SDS (GHS07 - irritant; standard amine PPE: gloves, goggles, ventilation) · RoHS compliant · Not food-grade · 24-month shelf life sealed
Amine AO Series: Alkylated DPA (CAS 68411-46-1, C4–C12 mixed) ✅ · NDPA (CAS 36878-20-3 / 27177-41-9) ✅ (this) → Phenolic AO Series ✅: BHT · 2,6-DTBP · High-MW Phenolic Ester (L01/L57/HP-136) → ZDDP Series ✅ (full range)
NDPA · CAS 36878-20-3 / 27177-41-9 · Nonylated DPA · Purity ≥95% · MW ~350–393 · Ash 0% · FP ≥200°C · SAPS-Free · Amber Liquid · 25 kg / 200 kg Drum / 1000 L IBC / Flexitank · 24-Month Shelf Life
Request Pricing, Grade Selection & Technical Support
Specify grade (di-nonyl CAS 36878-20-3 for aviation/highest MW, or mono-nonyl CAS 27177-41-9 for automotive/industrial long-drain), application, base oil type, and drain interval. We recommend the optimal treat rate and AO stack (NDPA + phenolic ester + ZDDP). RULER depletion data and comparative samples vs CAS 68411-46-1 grade available. Samples (50–500 mL) for formulation trials.
Amine Antioxidants Series:
Alkylated DPA CAS 68411-46-1 ✅ · Nonylated DPA CAS 36878-20-3 / 27177-41-9 ✅ (this) → Phenolic AO Series ✅ · ZDDP Series ✅
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