TSRC Corporation

Silica-Filled SSBR/BR Tread Compound Design under WLTP Rolling Resistance Targets

In passenger car radial tire tread compounds, the replacement of partial or full emulsion SBR with TSRC Corporation Taipol solution-polymerized styrene-butadiene rubber grades having bound styrene between 15% and 25% and vinyl content between 30% and 45% can shift the dynamic glass transition toward the −20 °C to 0 °C range where wet grip indices are evaluated under tyre labelling protocols. A silica-reinforced tread formulation is typically compounded with 55–80 phr SSBR and 20–45 phr TSRC neodymium-catalyzed polybutadiene having cis-1,4 content above 96%, plus 50–95 phr highly dispersible silica, an organosilane coupling agent at 6–10 wt% of the silica mass, and 5–15 phr paraffinic or treated distillate aromatic extract oil. The rubber-silica mixture is processed in an intermeshing rotor internal mixer with ram pressure between 0.5 MPa and 0.8 MPa, because the silanization reaction requires a sustained non-productive stage temperature of 145–155 °C for 3–5 min; if the dump temperature exceeds 160 °C, pre-scorch and re-agglomeration of silica particles can occur. The cured tread is tested under ISO 37:2017 for tensile stress at 300% strain, ISO 28580:2018 for rolling resistance coefficient, and DIN 53516 for abrasion loss, while the uncured compound Mooney viscosity is checked against ISO 289-1:2018 before extrusion. Compliance validation for European market release is based on Regulation (EU) 2020/740 for tyre labelling and ECE R117 Rev. 04 for rolling sound, wet grip, and rolling resistance thresholds. Production lines that calendar these compounds into tread profiles operate extruder barrel temperatures from 70 °C at the feed throat to 110 °C at the die, and cooling water on the two-roll mill is maintained below 40 °C to prevent sulfur bloom on the slab. Terminal products include silica-filled passenger car tire treads, light truck tire treads, sidewall compounds for low-rolling-resistance summer tires, and pre-cured retread strips; the SSBR/BR ratio in sidewalls is shifted toward 40–60 phr BR to improve flex crack resistance under cyclic deformation. The primary operational boundary is residual moisture in silica: if the silica moisture content exceeds 2%, a pre-drying step at 105 °C for 2 h or an additional purge cycle in the internal mixer is required to avoid void formation and coupling agent hydrolysis.

On a 270-L intermeshing rotor internal mixer, the first non-productive stage is filled to 70–75% chamber volume; rotor speed is held at 40–60 min⁻¹ until the silanization plateau, then reduced to 30–40 min⁻¹ for silica dispersion. Batch-to-batch variance in SSBR Mooney viscosity above ±3 MU under ISO 289-1:2018 shifts power draw by 5–10%, so mill operators adjust the first-stage fill factor rather than increasing temperature. If the compound is subsequently processed through a cold-feed pin barrel extruder for tread profiling, screw speed is capped at 40–60 min⁻¹ to prevent excessive shear heating and scorch; head temperature is kept below 110 °C and die swell is monitored by laser diameter measurement. In some silica tread systems, a silane coupling agent dosage reduction to 4–6 wt% can be achieved with specialized SSBR grades, but published data for this specific configuration is limited.

At a polymer-modified bitumen membrane line using TSRC Corporation Globalprene SBS radial grades, the blending vessel is operated with a rotor-stator high-shear mixer at 3,000–4,000 min⁻¹ while the asphalt phase is held between 180 °C and 190 °C; under these conditions the SBS domains swell and form a continuous polymer network only after the polymer loading exceeds 6 wt% for a 60/70 penetration-grade bitumen. In paving-grade PMB, the formulation addition ratio is 3–8 wt% SBS, with sulfur crosslinking at 0.05–0.15 wt% to suppress phase separation; waterproofing membrane compounds use 10–15 wt% SBS, extending the service temperature range and increasing softening point from 48 °C to 85 °C or higher when measured by ASTM D36. The production process is a two-stage dispersion: high-shear wetting for 1–2 h, followed by low-shear maturation for 2–4 h to stabilize the network before the PMB is discharged to a holding tank with a stirrer operating below 100 min⁻¹. Compliance is reviewed against EN 14023:2010 for polymer-modified binders, EN 13399:2017 for storage stability, ASTM D5976-00 for polymer content and type, and EN 13707:2017 for reinforced bitumen sheets used in roof waterproofing. Terminal products include airport runway joint sealants, bridge deck waterproofing membranes, self-adhesive roofing membranes, and low-noise poroelastic road surfaces. The operational boundary is storage temperature: the product must not exceed 200 °C during storage to prevent SBS thermal degradation; viscosity build is monitored by ASTM D4402 rotational viscosity at 160 °C.

Failure modes reported on production-scale PMB lines include phase separation in the holding tank when the sulfur dosage is mistimed by more than 0.02 wt%, softening point drift above 5 °C in the EN 13399:2017 storage stability test, and viscosity inversion when the radial SBS level is increased too rapidly. For waterproofing membrane compounds, the final blend is calendered or cast onto a polyester or glass-fibre carrier at 130–160 °C; the cooling drum below 20 °C prevents blocking of the self-adhesive surfaces.

What Controls SBS Diblock Content in Hot-Melt PSA Viscosity Curves and Spray Pattern Uniformity?

Hot-melt pressure-sensitive adhesive compounding with TSRC Corporation Globalprene SBS or SIS grades depends on the diblock-to-triblock ratio because low diblock fractions below 10 wt% increase shear holding power but make piston pump delivery difficult, while diblock fractions above 20 wt% reduce viscosity and improve nozzle wet-out at the cost of cohesive strength. For a general-purpose packaging adhesive, the compound is formulated with 20–35 wt% SBS or SIS, 40–55 wt% C5/C9 tackifier resin, 15–25 wt% naphthenic or paraffinic oil, and 0.5–1.0 wt% hindered phenolic antioxidant. The downstream process uses a heated melt reservoir at 150–170 °C, a gear or piston pump with adjustable stroke, and either slot-die coating, bead deposition, or spiral spray application; viscosity is monitored by ASTM D3236-15 with a Brookfield thermosel spindle 27 at 160 °C, and the target range for spray-grade PSA is 500–1,500 mPa·s. Common terminal products are clear label stocks, polypropylene tape backings, general carton closure adhesives, and diaper elastic attachment lines. Compliance anchors include FDA 21 CFR 175.105 for adhesives used indirectly in food packaging, REACH Annex XVII for restricted substances, and RoHS Directive 2011/65/EU for electrical and electronic goods packaging that may be integrated into final articles. Because SBS retains unsaturation from the butadiene midblock, the melt reservoir must be blanketed with nitrogen and the residence time at 160 °C should not exceed 4 h; if a line pause exceeds 30 min, the applicator head should be cooled to below 100 °C to prevent charring at the nozzle. For continuous high-temperature application above 180 °C, SEBS-based grades are substituted at similar addition ratios, but the tackifier system must be adjusted from C5 to hydrogenated hydrocarbon resins to maintain clarity.

In a continuous label coating line, adhesive transfer is controlled by the hot-melt pump speed and the die lip gap of 0.15–0.30 mm; the coated weight is held at 15–25 g/m² for general paper labels. Because diblock content changes zero-shear viscosity, the operator records pump back pressure at the start of each batch and adjusts the temperature setpoint in 5 °C increments to maintain 1,000–1,200 mPa·s at the nozzle. If back pressure exceeds 7 MPa, the formulation may require a higher diblock grade or a reduction in tackifier softening point.

Compounds based on TSRC Corporation Globalprene SEBS hydrogenated styrenic block copolymers for medical tubing are dry-blended with polypropylene homopolymer or random copolymer in a co-rotating twin-screw extruder having a 40:1 L/D ratio and a 12-barrel temperature profile from 190 °C to 230 °C. The formulation addition ratio falls between 30–60 wt% SEBS, 30–60 wt% PP, 5–15 wt% medical white oil, and 0.1–0.3 wt% antioxidant; the PP phase is used to reduce tack and raise heat distortion for autoclave exposure at 121 °C for 30 min. Downstream tubing extrusion is run through a single-screw extruder with a barrel profile of 180–210 °C, a die temperature of 190–210 °C, and a vacuum sizing tank held at 20–40 °C to lock the outer diameter before reel winding. The material is evaluated under ISO 10993-5:2009 for cytotoxicity, ISO 10993-4:2017 for hemocompatibility when the tubing contacts blood, USP Class VI protocols, and FDA 21 CFR 177.2600 for repeated-use rubber articles; final device documentation follows EU MDR 2017/745 and REACH Regulation (EC) No 1907/2006. Terminal products include IV infusion tubing, drip chambers, syringe plungers, and reusable medical device connector components. The operational boundary is sterilization dose: gamma sterilization up to 40 kGy is typically acceptable, but electron beam doses above 50 kGy can cause surface tack; if the compound absorbs more than 0.1% moisture during storage, a dryer at 80 °C for 2 h is required before extrusion.

Failure modes on production-scale medical tubing lines include surging from unmolten PP pellets in the feed zone, gel specks from degraded SEBS that remains in dead spots behind the screw tip, and ovality above 0.05 mm when the vacuum sizing tank water temperature is not controlled. After tubing is extruded, it is cut to length, assembled into drip chambers by butt welding, and sealed in pouches before sterilization. The operator verifies extractables by ISO 10993-12:2021 sample preparation and monitors changeover between SEBS-based compounds and PVC by purging with PP at 230 °C to avoid cross-contamination.

When Low-Cis Polybutadiene Enters HIPS Polymerization: Morphology, Gel Content, and Izod Swing

High-impact polystyrene production using TSRC Corporation low-cis polybutadiene rubber depends on rubber solution viscosity and gel content after prepolymerization. The rubber is dissolved in styrene monomer at 5–8 wt% in the final HIPS, and the low-cis grade is selected with Mooney viscosity ML 1+4 at 100 °C between 40 and 60, vinyl content 10–20%, and solution viscosity low enough to maintain pump discharge pressure within the continuous prepolymeriser. During the first-stage reactor, phase inversion occurs at 10–15% styrene conversion; the continuous phase changes from rubber-in-styrene to styrene-rubber droplets, producing the salami morphology that governs toughness. After prepolymerization at 120–140 °C, the syrup is transferred to a devolatilizing extruder with a vacuum of 20–50 mbar to strip residual styrene below 100 ppm for food-grade grades. Impact performance is measured by ASTM D256-10 Izod notched impact and ISO 180:2019, while melt flow rate is determined under ISO 1133-1:2022 at 200 °C with 5 kg. The compliance anchor for food-contact refrigerator liners and trays is FDA 21 CFR 177.1640 for rubber-modified polystyrene, with EU 10/2011 as the European framework for plastic food contact materials. Terminal products include refrigerator inner liners, single-use food packaging trays, appliance housings, and disposable cutlery. The deep-dive process conflict is gel specification: if gel content falls below 20%, the impact strength drops sharply; if gel content exceeds 35%, the surface gloss and processability decline, requiring the operator to adjust agitator speed in the prepolymeriser or to change the transfer line temperature.

On a continuous HIPS line with two prepolymerizers and a devolatilizing extruder, the viscosity of the rubber-styrene syrup changes from 0.1 Pa·s to above 100 Pa·s as conversion rises from 10% to 80%; the screw speed of the devolatilizing extruder is set between 120 and 180 min⁻¹ to avoid excessive shear heating above 240 °C, which would degrade the polybutadiene phase and reduce Izod impact. The low-cis BR grade from TSRC must also exhibit a solution viscosity below 50 mPa·s in 5 wt% styrene solution at 25 °C to avoid pump cavitation in the monomer recovery system. If the gel content specification is met but the swelling index drops below 10, the rubber crosslinking density is too high, producing hard, glossy but brittle HIPS; in this case the line operator reduces the prepolymerizer temperature by 3–5 °C to restore a more open rubber network.

Where a two-shot injection moulding line produces soft-touch overmoulded handles on PP substrates, the TSRC Corporation SEBS-based compound is dried to less than 0.05% moisture at 70–80 °C for 2–4 h before the second barrel. The formulation uses 25–45 wt% SEBS, 30–50 wt% PP homopolymer, 10–25 wt% paraffinic white oil, and 0.1–0.5 wt% antioxidant to reach hardness between 30 Shore A and 70 Shore A depending on the tool grip requirement. Processing parameters include a melt temperature of 190–230 °C, a mould temperature of 30–60 °C, and a rotating platen index time of 4–8 s; the substrate surface is pre-heated above 80 °C and must be free of mould release agent to avoid delamination at the interface. Compliance tests include EN 71-3:2019+A1:2021 for migration of elements for toys, FDA 21 CFR 177.1810 for styrene block copolymers intended for food-contact articles, EU 10/2011 for overall migration, and RoHS 2011/65/EU for restricted substances when used in electronic accessories. Terminal products include kitchen utensil handles, manual tool grips, toy grips, toothbrush handles, and overmoulded lids for small appliances. The operational boundary is repeated hot-water contact: formulations containing plasticizer oil above 20 wt% exhibit increasing surface leaching and are not specified for continuous use above 80 °C; in those cases plasticizer-free SEBS grades with higher styrene content are selected.

In practice, overmoulding failures on two-shot lines are often traced to substrate moisture, mould temperature below the PP recrystallization threshold, or excessive oil migration to the interface when the SEBS compound is injected at 230 °C and held at pressure above 50 MPa. For toys and utensils, the moulded parts are conditioned at 23 °C and 50% relative humidity for 24 h before extraction testing, and the total colour difference after UV exposure is measured to confirm that the hydrogenated midblock resists yellowing under indoor lighting. The use of plasticizer-free SEBS grades with higher melt viscosity can be substituted when the application requires dishwasher exposure above 65 °C; however, this substitution reduces flow length and may require a 20–30% increase in injection pressure.