Kumho Petrochemical Co., Ltd.

In silica-reinforced passenger car tire tread compounds, solution-polymerized styrene–butadiene rubber supplied by Kumho Petrochemical Co., Ltd. is incorporated where the balance among wet traction, rolling resistance, and abrasion loss is governed by vinyl microstructure and styrene sequence distribution rather than by total styrene content alone. When the SSBR is specified with bound styrene content of 20–25 wt% and 1,2-vinyl concentration of 50–65 mol%, the macro-dispersed styrene sequence distribution typically yields a compound glass transition temperature between -35°C and -15°C, depending on extender oil loading and the ratio of high cis-butadiene rubber in the blend. Published data for the exact sequence distribution across every Kumho SSBR grade is limited, so factory approval routinely includes viscoelastic screening per ISO 4664-1 and ASTM D5992, with additional measurement of bound rubber after silanization to avoid releasing an under-characterized tread compound to production.Masterbatch processing is performed in an intermeshing internal mixer having a chamber volume of 320 L and fill factor 0.70–0.75. The first non-productive pass combines SSBR, high cis-butadiene rubber with cis-1,4 content above 96%, precipitated silica at 70–90 phr, bis-triethoxysilylpropyl tetrasulfide at 8.0–10.0 wt% relative to silica, zinc oxide at 2.5–3.0 phr, stearic acid at 1.0–2.0 phr, and hindered phenolic antioxidant at 1.0–2.0 phr. Dump temperature is limited to 150–160°C because the polysulfidic silane releases free sulfur above approximately 165°C, producing premature crosslinking in the non-productive stage. The remill pass holds the batch at 140–155°C for 4–8 min under controlled ram pressure so that ethoxy groups complete silanization at the silica surface; a rise in Mooney viscosity above 90 MU measured per ASTM D1646 after remill indicates incomplete silanization or filler dispersion failure, and the correction is made by adjusting rotor speed, batch weight, or cooling water flow rather than by increasing dump temperature.Curative addition is carried out on a two-roll mill with friction ratio 1:1.15 and nip gap 0.5–2.0 mm. Sulfur is limited to 1.2–1.8 phr, N-cyclohexyl-2-benzothiazolesulfenamide to 1.0–1.8 phr, and diphenylguanidine to 1.0–2.5 phr. The final batch temperature is not permitted to exceed 100°C, because premature crosslinking is observed as an increase in minimum torque during moving die rheometry per ASTM D5289. Vulcanizates are evaluated for tensile properties per ISO 37, tear strength per ASTM D624, hardness per ISO 48, and abrasion resistance per ISO 4649; a silica-filled SSBR/BR tread formulation of this class commonly exhibits tensile strength between 16 MPa and 21 MPa, with the exact value controlled by silane dispersion, silica surface area, and the glass transition spacing of the SSBR/BR blend.

How Does Acrylonitrile Content Govern NBR Compound Performance in Sealing Systems?

The selection of acrylonitrile-butadiene rubber for industrial seals, gaskets, fuel-contact parts, and oil-field components is controlled by bound ACN level because the polar nitrile group increases resistance to non-polar fluids while reducing low-temperature flexibility and increasing compound hardness. Kumho Petrochemical NBR grades with nominal ACN content from 28 wt% through 50 wt% are processed with sulfur-donor or peroxide cure systems, but the resulting volume swell, compression set, and low-temperature retraction values diverge sharply after immersion in ASTM reference fluids. A 28 wt% ACN grade shows a volume swell of 40–55% in IRM 903 after 70 h at 100°C per ASTM D471, while a 40 wt% ACN grade typically swells 10–18% under identical conditions, and a 50 wt% ACN grade may swell 5–8%. The same gradient reverses at low temperature: a 28 wt% ACN vulcanizate may show a TR10 temperature near -40°C per ASTM D1329, whereas a 50 wt% ACN vulcanizate commonly reaches TR10 near -10°C or higher.

Nominal ACN content	Volume swell in IRM 903 after 70 h/100°C per ASTM D471	Low-temperature TR10 per ASTM D1329	Compression set after 22 h/100°C per ASTM D395 Method B
28 wt%	40–55%	-40°C to -35°C	18–25%
35 wt%	20–30%	-30°C to -25°C	16–23%
40 wt%	10–18%	-25°C to -18°C	14–20%
50 wt%	5–8%	-10°C to -5°C	15–22%

Sulfur-donor cure systems for NBR are commonly built around tetramethylthiuram disulfide at 2.0–3.0 phr and 4,4-dithiodimorpholine at 0.8–1.5 phr, with sulfur held at or below 0.5 phr to limit bloom and improve heat-age resistance. Peroxide cure systems use dicumyl peroxide at 3.0–5.0 phr with a coagent such as trimethylolpropane trimethacrylate at 1.0–2.5 phr; the peroxide system is preferred for high-temperature oil-well and automotive under-hood seals because it produces carbon-carbon crosslinks with lower compression set after aging for 168 h at 150°C per ASTM D395. A process conflict occurs when acidic silica or acidic processing aids are added to peroxide-cured NBR: the acidic filler consumes the peroxide radical flux and reduces crosslink density, so silane-treated mineral fillers or neutral fillers are specified for peroxide formulations. Mixing is performed in an internal mixer with dump temperature below 110°C for sulfur-donor batches and below 100°C for peroxide batches to avoid scorch, and the final batch is dispersed on a two-roll mill with tight nip below 0.5 mm to eliminate undispersed coagent particles that act as flaws during pressure cycling.

Crosslinked SBS Networks in Bitumen Binder Modification

Styrene block copolymers supplied by Kumho Petrochemical for asphalt modification are linear or radial SBS grades with styrene content of 30–45 wt% and melt flow rates at 190°C/5 kg of 0.5–10 g/10 min, with the molecular architecture selected according to the base bitumen maltene content and the required low-temperature cracking resistance. The polymer is dispersed into bitumen at 170–190°C in a high-shear rotor–stator mill with tip speed above 20 m/s and gap clearance 0.3–1.0 mm. During swelling, the styrene domains remain physically crosslinked while the butadiene midblock absorbs maltenes; this phase morphology develops over 30–90 min of continuous milling, and the viscosity can rise from 0.5 Pa·s to 5–8 Pa·s at 135°C depending on SBS concentration. A typical formulation containing 4.5 wt% SBS in 60/70 pen bitumen increases the ring-and-ball softening point from 48–52°C to 80–90°C per ASTM D36 and reduces non-recoverable creep compliance at 64°C below 0.5 kPa⁻¹ per ASTM D7405.The principal processing conflict in SBS-modified bitumen is thermal and oxidative chain scission at the butadiene double bonds. Residence time above 200°C causes irreversible loss of polymer network, softening point reversion, and reduced elastic recovery. Localized hot spots in the high-shear mill accelerate this degradation, so the mill jacket temperature is controlled to keep bulk temperature under 190°C, and storage tanks are blanketed with nitrogen to reduce oxidative hardening. Storage stability of the modified binder is checked by the softening point difference between top and bottom samples after 3 days at 163°C per EN 13399; a difference above 5°C indicates insufficient dispersion or incompatibility between the base bitumen and the SBS midblock composition. Elastic recovery is measured per ASTM D6084, and low-temperature cracking tendency is evaluated through bending beam rheometer creep stiffness per ASTM D6648, with a creep stiffness below 300 MPa at the design temperature used as a boundary condition for polymer loading.

When ABS Melt Viscosity Must Remain Stable Through 260°C

Acrylonitrile-butadiene-styrene resin produced from Kumho Petrochemical styrene monomer, acrylonitrile, and polybutadiene latex is injection-molded into automotive interior substrates, instrument panel components, and electronic housings where the melt must remain thermally stable throughout the plastication and injection cycle. The resin is specified by melt flow index per ISO 1133-1:2022 at 220°C/10 kg, with values typically between 5 g/10 min and 30 g/10 min depending on rubber content and lubricant package. Before molding, granules are dried at 80°C for 3–4 h to reduce moisture below 0.05%; higher moisture produces splay, gate blushing, and surface roughness on molded substrates. The barrel temperature profile is set from 210°C at the feed throat to 230–250°C at the nozzle, with melt temperature not exceeding 260°C. Above 270°C, polybutadiene degradation releases volatile low-molecular-weight fragments, and melt index drifts upward with residence time, producing batch-to-batch viscosity instability during long production runs.Cavity filling is governed by injection speed and melt front stability. In thin-wall sections, injection speed below 50 mm/s produces short shots and flow marks, while speeds above 150 mm/s cause jetting, gate blush, and local shear heating above 270°C at the gate land. Clamp force is calculated from projected area using a cavity pressure range of 30–60 MPa, and hot-runner systems are operated with manifold temperatures within ±5°C of the nozzle set point to avoid drool or freeze-off. Finished parts are assessed for notched Izod impact per ISO 180, tensile properties per ASTM D638-14, heat deflection temperature per ISO 75-2, and flammability per UL 94 HB or V-0 after addition of halogen-free flame retardants where required. For automotive interior applications, residual acrylonitrile and styrene emissions are evaluated per VDA 278, and total volatile organic compounds in the molded part are measured per ISO 12219-2. The ABS should not be combined with undried polycarbonate regrind without plant-specific validation, because moisture-induced hydrolysis and transesterification at the ABS/PC interface reduce impact strength; published data for the exact Kumho ABS/PC regrind retention limit is limited, so trials are conducted at each regrind fraction.

Phenol-Derived Bisphenol A in Epoxy and Polycarbonate Streams

Bisphenol A produced from phenol and acetone within the Kumho Petrochemical value chain enters two distinct downstream streams: liquid epoxy resin for adhesives, coatings, and copper-clad laminates, and polycarbonate resin for optical and electronic components. The ketone condensation is operated with a phenol to acetone molar ratio between 4:1 and 8:1 over a sulfonated cation-exchange resin bed modified with a thiol promoter; the crude BPA is purified to polycarbonate-grade with 4,4′-bisphenol A content above 99.8 wt%, APHA color below 10, and iron content under 0.05 mg/kg.

Parameter	Test method	Polycarbonate-grade requirement
4,4′-BPA content	HPLC or GC derivatization	>99.8 wt%
APHA color, 50 g/100 mL methanol	ASTM D1209	<10
Iron content	ICP-OES	<0.05 mg/kg
Water content	Karl Fischer titration	<0.05 wt%

Epoxy resin derived from this BPA via reaction with epichlorohydrin is supplied as DGEBA with epoxide equivalent weight of 188–192 g/eq per ASTM D1652 and dynamic viscosity of 11–14 Pa·s at 25°C per ASTM D445. In copper-clad laminates, the resin is advanced with tetrabromobisphenol A and cured with dicyandiamide at 170–180°C for 60–90 min; glass transition temperature of the cured network is measured by differential scanning calorimetry per ASTM E1356, and peel strength is tested per IPC-TM-650. Residual alkali metal ions must remain below 1 mg/kg for electronic-grade epoxy because ionic contamination increases electrochemical migration in high-humidity biased testing per IPC-TM-650 method 2.6.3.7. Polycarbonate produced by interfacial phosgenation or melt transesterification from BPA requires moisture content below 0.02% before extrusion; the melt is processed at 280–310°C, and residence time above 320°C leads to color shift and molecular weight reduction measured by melt flow rate per ISO 1133-1:2022. Optical-grade polycarbonate is specified with light transmittance above 89–90% at 3 mm thickness per ISO 13468-1 and haze below 0.5%.Within unsaturated polyester resin operations, styrene monomer supplied by Kumho Petrochemical functions both as a crosslinking comonomer and as a viscosity-reducing diluent for resins used in pultrusion, filament winding, cast polymer manufacturing, and open-mold lamination. The resin is formulated with a styrene content between 35 wt% and 45 wt%, with the lower end selected for low-styrene-emission laminating grades and the upper end for filled casting compounds. Inhibitor content is maintained with 10–15 ppm of 4-tert-butylcatechol to prevent premature polymerization during storage, and the peroxide initiator is added at 1.0–2.0 phr of methyl ethyl ketone peroxide with 0.2–0.5 phr cobalt octoate accelerator. Gel time and exotherm peak are measured per ISO 2535, and the onset of the styrene crosslinking reaction is controlled by adjusting the cobalt-to-amine promoter ratio rather than by increasing peroxide concentration beyond 2.0 phr.Styrene storage and handling require bulk temperature below 25°C and exclusion of oxygen because the monomer forms peroxides that increase gel time drift and reduce batch-to-batch reproducibility in unsaturated polyester curing. During open-mold lamination, styrene vapor pressure at 20°C is approximately 0.6 kPa, so ventilation rates are set to keep airborne styrene below the occupational exposure limit, and low-styrene resin grades are selected where emission compliance is constrained. In expandable polystyrene production, a parallel styrene monomer stream is used for suspension polymerization with 5–7 wt% n-pentane as blowing agent; bead expansion is conducted at 95–115°C, and molded density is controlled between 15 g/L and 30 g/L per EN 1603. Residual styrene monomer in the molded polymer article is determined by gas chromatography per ASTM D2106, and the final expansion cycle is limited by steam pressure rather than by additional blowing agent loading to avoid cell rupture and density deviation.