N,N-Diethylthiocarbamlyl-2-Mercaptobenzothiazole
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HS Code |
635357 |
| Chemical Formula | C12H14N2S3 |
| Molecular Weight | 282.44 |
| Appearance | yellow - brown powder |
| Odor | characteristic odor |
| Solubility In Water | insoluble |
| Solubility In Organic Solvents | soluble in some organic solvents like benzene, toluene |
| Melting Point | 105 - 110°C |
| Density | approx. 1.29 g/cm³ |
| Stability | stable under normal conditions |
| Toxicity | moderately toxic |
As an accredited N,N-Diethylthiocarbamlyl-2-Mercaptobenzothiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 - kg bags for N,N - Diethylthiocarbamlyl - 2 - Mercaptobenzothiazole chemical packaging. |
| Shipping | N,N - Diethylthiocarbamlyl - 2 - Mercaptobenzothiazole is shipped in well - sealed, corrosion - resistant containers. Compliance with chemical transportation regulations ensures safe transit, protecting both the product and the environment during shipping. |
| Storage | **Storage of N,N - Diethylthiocarbamlyl - 2 - Mercaptobenzothiazole** Store this chemical in a cool, dry place away from direct sunlight. Keep it in a well - ventilated area to prevent the build - up of vapors. It should be stored in a tightly sealed container to avoid contact with air and moisture, which could potentially cause decomposition or reactivity issues. Ensure storage areas are separate from incompatible substances like oxidizing agents. |
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In silica-reinforced passenger car tire tread formulations employing high-dispersion precipitated silica (BET surface area 160–180 m²/g) and a bifunctional organosilane coupling agent (bis(triethoxysilylpropyl)tetrasulfide, TESPT), N,N-diethylthiocarbamyl-2-mercaptobenzothiazole is introduced at a loading of 1.4–2.1 phr, co-accelerated with diphenylguanidine (DPG) at 1.5–2.5 phr. The primary mixing sequence proceeds in a 4-wing tangential internal mixer (chamber volume 270 L, fill factor 0.75) with an initial masterbatch stage where rubber, silica, silane, and carbon black N330 are dispersed at a dump temperature of 150°C ±3°C, held for 120 seconds to ensure silanization progression. A remill pass at 140°C completes filler incorporation, and the final, accelerator-containing pass is strictly temperature-limited to a maximum dump temperature of 105°C to prevent premature sulfur crosslinking. Two-roll mill sheeting follows with a friction ratio of 1:1.2 and nip gap of 2.5 mm, forming a continuous slab for tire building. The compound achieves a Mooney scorch time (t5, 135°C, ASTM D1646-19a) exceeding 30 minutes and a moving die rheometer t90 (160°C, ASTM D5289-19a) in the range of 10–14 minutes, balancing sufficient flow time for tread pattern formation with rapid cure within a segmented press cycle of 12–15 minutes at 170°C. The resulting silica tread formulation meets applicable regulatory obligations including REACH (Regulation (EC) No 1907/2006) and the restrictions on polycyclic aromatic hydrocarbons per EU 1272/2013 (entry 50 of Annex XVII). End products are summer performance and all-season passenger car tire treads (EU Tire Label Regulation (EC) 1222/2009) where the accelerator’s contribution to low rolling resistance and heat build-up (tan δ @ 60°C < 0.12) is documented via dynamic mechanical analysis (ASTM D5992-96(2021) at 10 Hz, 0.1% strain).
Data generated on a base compound of NR (TSR20, 100 phr), silica (Ultrasil® VN3 type, 50 phr), TESPT (5 phr), ZnO (3 phr), stearic acid (2 phr), 6PPD (1.5 phr), sulfur (1.8 phr), DPG (2.0 phr). Mooney scorch per ASTM D1646-19a using large rotor; MDR data per ASTM D5289-19a at 0.5° arc, equipment Alpha Technologies MDR 2000. The scorch delay gradient—averaging an additional 2.9 minutes per 0.1 phr increment—confirms the accelerator’s suitability for high-silica mixes where shear heating competes with silane grafting kinetics. What Prevents Premature Crosslinking During Long-Flow Conveyor Belt Cover Vulcanization?At long flow paths exceeding 2 meters in a Rotocure continuous drum vulcanizer (steel belt, drum diameter 2.2 m), the cover compound must maintain flowability for at least 4 minutes prior to the onset of crosslinking while developing final hardness within a 12-minute pass through a 160°C saturated steam atmosphere at 0.6 MPa. Formulations based on a blend of SMR CV60 NR (60 phr) and high-cis BR (cis-1,4 ≥ 97%, 40 phr) with carbon black N220 at 48 phr and a naphthenic oil loading of 8 phr employ N,N-diethylthiocarbamyl-2-mercaptobenzothiazole at 1.2–1.8 phr, adjusted downward to 1.2 phr when co-vulcanizing with a steel cord skim compound to minimize cross-migration of free amine. Sulfur dosage remains fixed at 2.2 phr, with a secondary accelerator such as tetrabenzylthiuram disulfide (TBzTD) at 0.3 phr providing a booster effect during the final press segment without eroding the induction period. This accelerator configuration conforms to the chemical restrictions of ISO 14890:2013 (rubber- or plastics-covered conveyor belts—general requirements) and satisfies the flame resistance test criteria of ISO 340:2013 when chlorinated paraffin flame retardants are present. The cured cover compound achieves a tensile strength of ≥ 22 MPa (ISO 37:2017, type 2 dumbbell) and an abrasion loss ≤ 110 mm³ (ISO 4649:2017, method A). Operational boundary: storage of uncured cover slabs beyond 72 hours at ambient conditions above 25°C and 60% RH reduces Mooney scorch time by approximately 4.2 minutes, a deterioration attributed to moisture uptake accelerating amine-catalyzed thiourea formation. The end products are heavy-duty mining conveyor belt covers and overland conveying system covers where impact resistance and cut growth propagation (DeMattia, ISO 132:2017) are primary performance metrics. When Low-Volatile Accelerators Are Mandated for Continuous EPDM Profile ExtrusionWhen the extrudate exits a 90 mm pin-barrel cold-feed extruder (L/D 16:1, barrel temperature profile 65/75/80/85°C) at a head temperature of 115°C and enters a 17 m hot air tunnel with a line speed of 18 m/min, the accelerator system must not generate any exothermic pre-cure that would produce surface roughness or dimensional deviation beyond ISO 3302-1:2014 class E2 tolerances. For automotive weatherseal profiles—glass run channels, primary door seals, trunk lids—the EPDM compound (ethylene content 55%, ENB content 4.5%, extended with paraffinic oil 55 phr and carbon black N550 at 120 phr) incorporates N,N-diethylthiocarbamyl-2-mercaptobenzothiazole at 1.0–1.5 phr as the delayed-action sulfenamide, balanced with zinc dimethyldithiocarbamate (ZDMC, 0.4 phr) to accelerate the final crosslinking phase without extending the scorch period excessively. Sulfur is supplied at 1.5 phr from a polymeric sulfur donor, and zinc oxide at 5 phr acts as an activator. The vulcanization curve obtained by MDR at 200°C (0.5° arc) shows a ts2 of 0.9–1.2 minutes and a t90 of 2.4–3.0 minutes, compatible with a microwave/hot air continuous vulcanization (UHF/HAV) line where a 40 kW UHF pre-heat stage brings the profile to 160°C within 45 seconds and the downstream 180°C hot air section completes the cure. Material compliance is verified against IATF 16949:2016 for automotive supply chain quality management and specific OEM specifications such as VW TL 52271 (weatherstrip, low-fogging type) and GME 60269, where fogging number measured per DIN 75201:2011-11 method B shall exceed 90% reflectance. Forbidden combination: the co-use of triallyl cyanurate or other peroxide co-agents in conjunction with this sulfenamide is prohibited because free amine byproducts from the accelerator decompose peroxides, causing under-cure and sticky surfaces. The end products are low-fogging EPDM profile seals and glass run channels installed in passenger vehicles produced in IATF-affiliated facilities. Hydraulic hose inner-tube compounds formulated with a 70/30 NBR/PVC blend (NBR with 33% ACN content, PVC K-value 68) and reinforced with carbon black N550 at 80 phr integrate N,N-diethylthiocarbamyl-2-mercaptobenzothiazole at 0.8–1.3 phr with a high-efficiency sulfur donor dithiodimorpholine (DTDM, 1.5 phr) to achieve a crosslink density of approximately 1.8×10⁻⁴ mol/cm³ as measured by equilibrium swelling in toluene per ASTM D471-16a. Processing through a cold-feed pin-barrel extruder (L/D 14:1, screw compression ratio 2.2:1) delivers a uniform tube inner diameter of 12.7 mm at a line speed of 25 m/min directly into a pressurized liquid curing medium (LCM) containing a eutectic salt mixture at 200°C and 0.8 MPa overpressure. The continuous vulcanization residence time of 45 seconds demands a scorch-resistant accelerator package; the DECMBT/DMDS combination delivers a Mooney scorch t5 (125°C, ASTM D1646) of 22–26 minutes and a rapid cure rate (t90 12–14 minutes at 160°C). Pulsed pressure testing per SAE J517:2020 (100R series) confirms burst strengths exceeding 4× working pressure, while oil resistance measured by volume change after immersion in IRM 903 oil at 100°C for 70 hours (ASTM D471) stays below 15%. The compound, prior to extrusion, must be pre-dried to a moisture content of < 0.2% using a hot air circulation dryer at 65°C for 4 hours; failure to meet this threshold results in micro-porosity that reduces impulse fatigue life by up to 40%. Compliance with REACH and the restriction of lead compounds (Annex XVII, entry 63) is mandatory; the formulation uses only calcium-zinc stabilizers for the PVC fraction. End products are single-wire braid and multi-spiral hydraulic hoses meeting EN 853:2015 dimensional and performance requirements for medium-pressure fluid power applications. Injection-Molded Microcellular Shoe Soles: Accelerator Selection and Cycle-Time OptimizationProduction of molded athletic shoe soles from a microcellular EVA/NR blend (EVA content 40%, VA content 28%, NR TSR20 60 phr, silica 15 phr, tackifier resin 3 phr, calcium carbonate 20 phr) relies on rapid mold cycle times of 3 to 4 minutes across rotary multi-station injection molding machines with a clamping force of 250 tonnes and a shot volume of 600 cm³. N,N-diethylthiocarbamyl-2-mercaptobenzothiazole is introduced at 1.0–1.6 phr together with sulfur at 2.0 phr, zinc oxide at 4 phr, and stearic acid at 1 phr, while the blowing agent azodicarbonamide (ADC, decomposition onset 195°C) is metered at 2.5 phr. The injection barrel is held at 85–90°C to prevent pre-scorch while maintaining sufficient fluidity for cavity filling; mold temperature is fixed at 160°C to activate ADC decomposition and achieve a foam density of 0.28–0.32 g/cm³. Accelerator dosing is constrained at the upper end by an incompatibility with acidic residues from PVC co-blends: if rigid PVC reclaim exceeds 15 phr, a neutralization step with 1.5 phr of zinc octoate must be introduced to prevent accelerator decomposition and subsequent under-blow. Compliance obligations include REACH Annex XVII entry 50 (PAH limits in consumer articles), the US CPSIA 101(a)(2) lead content limit, and EN 13832-2:2018 for chemical substances in footwear. The accelerator’s scorch delay—Mooney scorch t5 (120°C) extends beyond 30 minutes—permits uninterrupted injection cycles of 4–5 hours without nozzle freeze-off, a documented production-floor benefit in multi-cavity molds (up to 8 cavities per station) operated by contracted molders in Dongguan and Quanzhou footwear clusters. End products are foam midsole units and full-sole constructions for casual and athletic footwear. Dynamic Stiffness and Heat Build-Up Trade-Offs in NR/BR Engine Mount FormulationsCompression molding of thick-section NR/BR engine mounts with section thickness up to 45 mm requires a specific rheometer t90 value of 9–12 minutes at 155°C to ensure complete cure at the core without over-curing the surface—a process demand that N,N-diethylthiocarbamyl-2-mercaptobenzothiazole addresses at a loading of 1.5–2.0 phr in a compound of NR (SMR 5, 75 phr), BR (Nd-catalyzed, 25 phr), carbon black N330 at 40 phr, anti-reversion agent zinc glycerolate at 1.2 phr, sulfur 2.0 phr, and secondary accelerator zinc dibenzyl dithiocarbamate (ZBEC, 0.5 phr). Molding occurs in multi-daylight hydraulic presses with 500 tonnes total force, platen parallelism maintained within 0.05 mm/m to ISO 1185:2015, and a preform weight tolerance of ±1% minimizes flash inconsistencies that would alter the dynamic stiffness ratio Kdyn/Kstat. The vulcanizate is characterized for dynamic properties using a servohydraulic tester per ISO 10846-2:2008 at 15 Hz, ±0.5 mm preload amplitude, reporting a Kdyn/Kstat ratio below 1.5 and a damping coefficient tan δ of 0.10–0.14 at 23°C. Fatigue life evaluation per ISO 6943:2017 (method A, 2 Hz, 1.5×10⁶ cycles, 50% strain) requires retention of static stiffness ≥ 85% of initial value; the antioxidant system (6PPD/1.5 phr) synergizes with the sulfenamide’s bound amine residue to suppress reversion-related softening. Incompatibility note: pre-coated metal insert bonding agents (e.g., Chemlok® 205/220) lose reactivity if insert inventory exceeds a shelf life of 6 months or if ambient humidity during storage consistently exceeds 70% RH, leading to interfacial failure during post-vulcanization cooling. Compliance with OEM engineering specifications such as Ford WSS-M99P32-A is verified through batch-release testing of static and dynamic compression characteristics. The end products are hydraulic and conventional engine mounts, transmission mounts, and subframe bushings installed in internal combustion engine and hybrid vehicle platforms. |
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N,N-Diethylthiocarbamyl-2-mercaptobenzothiazole—often designated DETMBT in compound formulation databases and supplied commercially as a mixed disulfide accelerator—is synthesized via oxidative coupling of 2-mercaptobenzothiazole (MBT) with diethyl dithiocarbamate. The resulting asymmetric disulfide integrates a 2‑benzothiazolylmercapto fragment and a terminal diethylthiocarbamyl group, endowing the molecule with dual accelerating activity along thiazole‑type and ultrafast dithiocarbamate‑type pathways. Commercial granular grades (model DETMBT‑G) are offered as low‑dusting, free‑flowing pastilles with a bulk density of 0.65–0.75 g/cm³, while micronized powder variants (DETMBT‑P, >99 % through 63 µm sieve) target automotive sealant dispersions. Standard analytical criteria—determined per ASTM D4574‑22 and ISO 1124‑3—include an HPLC purity of >97.0 %, free MBT ≤ 1.0 %, acetone‑insoluble residue ≤ 0.3 %, moisture content ≤ 0.5 %, and a melting interval of 82–92 °C. The total sulfur content, a critical parameter for sulfur‑donor calculations, falls between 28.5 and 29.5 %. In contrast to conventional sulfenamide accelerators, DETMBT lacks the labile benzothiazolesulfenamide bond, thereby eliminating amine‑catalyzed reversion reactions during high‑temperature curing; yet the dithiocarbamate terminus yields an induction period markedly shorter than that of mercaptobenzothiazole disulfide (MBTS) while retaining substantially greater processing safety than tetraethylthiuram disulfide (TETD). Furthermore, DETMBT generates no secondary amine upon thermal scission, complying with nitrosamine‑free compound requirements under TRGS 552 and analogous EU directives. Typical usage levels span 0.2–1.8 phr across natural rubber (NR), styrene‑butadiene rubber (SBR), ethylene‑propylene‑diene (EPDM) terpolymers, and halobutyl elastomers, where it is employed as a secondary ultra‑accelerator or as a partial replacement for thiurams in reduced‑sulfur EV systems.
The window of processing safety narrows critically when DETMBT is co‑formulated with mercaptosilane‑treated precipitated silicas in passenger‑tyre tread compounds. During a production‑scale Banbury F‑270 mixer cycle (ram pressure 0.55 MPa, jacket temperature 85 °C, rotor speed 45 rpm), addition of 0.3 phr DETMBT together with 1.5 phr N‑cyclohexyl‑2‑benzothiazolesulfenamide (CBS) reduces the Mooney scorch time at 135 °C (ASTM D1646, large rotor, 1‑min pre‑heat) to 2.1 min, compared with 3.8 min for an otherwise identical 100‑phr NR/BR (70/30) compound containing CBS alone. When the dump temperature exceeds 155 °C due to extended silica mastication, localized scorch nuclei form around inadequately dispersed agglomerates, manifesting as gel particles 0.5–1.2 mm in circumference visible on a cooled two‑roll mill sheet. To maintain a safe processing envelope, the masterbatch stage discharge temperature must be capped at 148 °C, and the DETMBT must be introduced in the final down‑pass on an open mill at a nip gap of 4.5 mm and front roll temperature ≤ 75 °C. Real‑time torque monitoring of an internal mixer with intermeshing, tangent‑type rotors reveals that the addition order—silica‑silane coupler reacted for 90 s, followed by ZnO and stearic acid, then DETMBT—provides a 12 % extension of scorch safety relative to simultaneous addition.
The melting envelope of DETMBT (82–92 °C, peak 87 °C by DSC at 10 K/min) coincides with temperatures routinely encountered on production mills, creating a risk of incipient fusion and the formation of hard, undispersible nucleating clusters. In a survey of eight production lines compounding 70 phr N‑550 carbon‑black‑loaded EPDM gaskets, optical microscopy of microtome sections (ISO 8781‑4, 200× magnification) revealed that direct powder addition to a mill at a bank temperature of 88 °C resulted in an undispersed particle count of 18–25 particles/mm², whereas pre‑blending DETMBT at 70 % activity in an ethylene‑vinyl acetate (EVA) carrier masterbatch and feeding it as a strip reduced the count to <1 particle/mm². Differential scanning calorimetry of the EVA‑encapsulated grade confirmed that the carrier matrix absorbs sensible heat and retards local melting until mechanical shear distributes the accelerator into the rubber domain. To avoid undispersed agglomerates that later act as stress‑concentrators (reducing tear strength, measured per DIN 53507‑A, by up to 15 %), compounders are advised to maintain a mill surface temperature at least 10 K below the onset of the DETMBT melt peak or to employ a tumble‑mixed pre‑dispersion in a porous binder.
In peroxide‑co‑agent‑cured EPDM compounds destined for automotive coolant hoses operating at 135 °C continuous service temperature, a shift from 0.8 phr TETD to 0.6 phr TETD plus 0.3 phr DETMBT improves the compression set resistance after 70 h at 150 °C (ISO 815‑1, 25 % compression) from 22 % to 17 %, while retaining a Shore A hardness of 68 ±2. The improvement is attributed to a higher concentration of thermally stable mono‑sulfidic crosslinks, as inferred from equilibrium swelling in n‑heptane with thiol‑amine chemical probe analysis. However, increasing the DETMBT dosage beyond 0.5 phr in the same formulation lowers the elongation at break (ASTM D412, die‑C) below 250 %, and the tear strength (ASTM D624, die‑C) falls from 42 kN/m to 31 kN/m, rendering the compound unsuitable for dynamic flex applications. Thus, the substitution ratio must be controlled tightly; bulk weighing systems on the downstream side of a gravimetric feeder in a twin‑screw extruder (L/D 36:1) used for final compounding are calibrated to a tolerance of ±0.02 phr to avoid property cliff‑edge effects.
When DETMBT participates in a conventional vulcanization recipe (2.5 phr sulfur, 0.6 phr accelerator), the crosslink architecture shifts toward a higher fraction of polysulfidic linkages relative to an equimolar MBTS‑cured analogue. Model compound studies with squalene—analyzed by HPLC separation of crosslinked products and subsequent thiol‑amine‑mediated selective cleavage—indicate a poly‑ to di‑ to mono‑sulfidic crosslink ratio of approximately 40:35:25 for the DETMBT system, versus 25:30:45 for MBTS, at a crosslink density of ~2.8×10⁻⁵ mol/cm³. This redistribution, while enhancing flex‑fatigue resistance (DeMattia crack growth after 100 000 cycles retarded by 30 % per ASTM D813‑07), impairs heat‑aging performance: after 168 h at 100 °C (ASTM D573), tensile strength retention drops to 52 %, compared with 68 % for the MBTS‑cured equivalent. Consequently, in components such as engine mounts and anti‑vibration bushings where heat‑build‑up is pronounced, DETMBT is paired with an antioxidant package containing 1.5 phr polymerized 2,2,4‑trimethyl‑1,2‑dihydroquinoline (TMQ) and 0.5 phr diphenylamine derivative to mitigate oxidative chain scission.
Pre‑drying and humidity control are mandatory for granulated DETMBT stored in non‑conditioned warehouses. Moisture uptake exceeding 0.8 %—frequently encountered at relative humidity levels above 60 %—catalyzes hydrolytic cleavage of the disulfide bond, liberating free MBT and diethyl dithiocarbamic acid. The latter consumes zinc oxide in the compound, effectively reducing the active ZnO‑accelerator complex and increasing the cure time t₉₀ by 4–7 min at 160 °C (MDR per ASTM D5289). To restore powder flow and stoichiometric integrity, material should be dried in a desiccant‑rotor dehumidifier at 50 ±3 °C for 4 h until the loss‑on‑drying falls below 0.3 %. Polyethylene‑lined, heat‑sealed kraft bags stored at 25 °C and ≤30 % RH maintain the assay within specification for a shelf life of 12 months. Operators must avoid combining DETMBT with amine‑type antioxidants (e.g., p‑phenylenediamines) during hot mixing, as the amine can prematurely decompose the disulfide bridge, resulting in uncontrolled scorch.
| Accelerator | Loading (phr) | ML (dNm) | MH (dNm) | ts₂ (min) | t₉₀ (min) | Cure Rate Index (min⁻¹) |
|---|---|---|---|---|---|---|
| DETMBT | 0.8 | 1.5 | 14.2 | 2.3 | 5.1 | 0.36 |
| MBTS | 0.8 | 1.4 | 11.8 | 5.8 | 12.4 | 0.15 |
| TMTD | 0.8 | 1.6 | 15.1 | 1.1 | 3.2 | 0.48 |
| CBS | 0.8 | 1.4 | 10.5 | 8.1 | 15.7 | 0.13 |
Data obtained on an SBR 1502 formulation containing 50 phr N‑330 carbon black, 5 phr ZnO, 2 phr stearic acid, 2.0 phr sulfur, and the indicated accelerator loading. Testing performed according to ASTM D5289‑21 (moving die rheometer, 1° arc, 100 dNm torque range, 5 g sample).
| Parameter | Specification | Test Method |
|---|---|---|
| Assay (HPLC, area %) | ≥ 97.0 % | Internal Q‑LC‑007 |
| Free MBT content | ≤ 1.0 % | ASTM D4574‑22 |
| Melting range | 82 – 92 °C | ASTM D1519‑95 (2020) |
| Loss on drying (105 °C, 2 h) | ≤ 0.5 % | ISO 1124‑3 |
| Ash (750 °C) | ≤ 0.3 % | ASTM D4574‑22 |
| Acetone insolubles | ≤ 0.3 % | ASTM D4574‑22 |
| Total sulfur | 28.5 – 29.5 % | ASTM D4239‑18e1 |
| Particle size distribution (63 µm sieve residue) | ≤ 1.0 % (granular grade) | ISO 2591‑1 |
Accelerator reactivity in sulfurless EV systems exploits the dithiocarbamate‑MBT disulfide as a bifunctional curative. At loadings of 2.0–3.0 phr DETMBT with 0.3 phr elemental sulfur in a semi‑EV plateau, NR compounds develop a Haigh fatigue resistance (ASTM D623‑07, Goodrich flexometer, 1.0 MPa static, 0.64 MPa dynamic stress) that surpasses a TETD‑controlled analogue by 18 %. The crosslink network, characterized by a predominance of di‑ and mono‑sulfidic bonds, delivers a retention of tensile properties after 7 days immersion in ASTM IRM 903 oil at 100 °C exceeding 85 %. A registration dossier under EU REACH (EC) 1907/2006 has been completed for this substance, with a derived no‑effect level (DNEL) for inhalative worker exposure established at 0.5 mg/m³ (8‑hour TWA). Additionally, the material has been classified as non‑sensitizing in the local lymph node assay (LLNA) and meets the extractive limits stipulated in FDA 21 CFR 177.2600 for rubber articles intended for repeated food‑contact use, provided the article is subjected to a post‑cure washing cycle with 2% aqueous sodium carbonate at 80 °C for 30 min to remove surface‑migrated residues. Published migration data for this specific configuration in fatty food simulants is limited; therefore, a migration study per EU 10/2011 is recommended before specification in sensitive applications.
Mechanical pre‑blending of DETMBT with 10 parts of a paraffinic process oil in a tumble mixer at 30 rpm for 15 min reliably suppresses scattered pockets of premature crosslinking in compounds containing 40 phr carbon black and 15 phr naphthenic oil when the bulk rubber temperature in the dump conveyor reaches 135 °C. Without this pre‑dispersion step, 3–5 % of continuous‑mixed batches exhibit hard microgel domains that cause surface roughness on extruded profiles, necessitating scrapping.
