When 4–6 wt% Linear SBS YH-791 Is Sheared into 170–190 °C Bitumen

YH-791 is introduced into straight-run bitumen at 4–6 wt% based on bitumen mass, with the 4 wt% lower boundary applicable to intermediate course binders and the 6 wt% upper boundary reserved for stone mastic asphalt and porous wearing courses where elastic recovery and high-temperature rutting resistance govern. The dispersion stage is conducted in a jacketed vertical tank fitted with a rotor-stator high-shear mill operating at tip speeds of 15–25 m·s⁻¹; the bitumen phase is held at 170–190 °C because temperatures below 170 °C leave undispersed SBS domains that later coalesce, while temperatures above 190 °C accelerate oxidative chain scission in the polybutadiene midblock and produce a torque-independent viscosity drift. After 30–60 min of high-shear dispersion, the blend is transferred to a low-shear maturation vessel at 160–170 °C for 2–4 h to allow polystyrene end-block network formation. A production-scale bottleneck occurs at the binder transfer pump: PMB viscosity at 135 °C should remain below 3 Pa·s, but blends approaching 6 wt% YH-791 can reach 2.5–3.5 Pa·s, requiring jacketed transfer lines to be held at 160 °C rather than the conventional 150 °C used for unmodified bitumen.

Compliance for this application is evaluated against EN 14023:2010 and, in jurisdictions where used, ASTM D5976-22. Storage stability is measured according to EN 13399:2017 after 48 h at 163 °C; PMB grades intended for high-temperature climates typically specify a top-to-bottom softening-point difference no greater than 5 °C, while storage-stable grades with tighter specification commonly require ≤2.5 °C. Low-temperature cracking resistance is assessed with EN 12593:2015 Fraass breaking point, and elastic recovery is quantified by EN 13587:2017 force ductility. The downstream asphalt mixtures fall under EN 13108-5:2016 for stone mastic asphalt and EN 13108-7:2016 for porous asphalt. Terminal product types include highway wearing courses, airport taxiway overlays, bridge deck asphalt, and polymer-modified tack coats used in maintenance paving. Pellets stored at ambient humidity above 60% RH should be pre-dried at 60 °C for 2 h before feeding the high-shear mixer; residual moisture causes foaming at the mill intake and creates binder volume expansion that destabilizes the rotor-stator hydraulic load.

Hot-Melt Pressure-Sensitive Adhesive Formulation Limits with C5 Tackifier Systems

YH-791 is formulated into hot-melt pressure-sensitive adhesives at 20–35 wt% of the finished adhesive compound; the recommended starting formula for a general-purpose packaging tape is 100 phr YH-791, 80–120 phr hydrogenated C5 aliphatic tackifier, 40–80 phr naphthenic process oil, and 1–2 phr hindered phenolic antioxidant. The tackifier is selected for compatibility with the polybutadiene midblock rather than the polystyrene end-block; hydrogenated C5 or hydrogenated rosin ester resins produce a broad plateau in the dynamic mechanical loss tangent between −20 °C and 40 °C, which correlates with peel adhesion. Mixing is performed in a jacketed Z-blade kneader at 150–170 °C under a nitrogen blanket at 0.2–0.4 kPa positive pressure. YH-791 pellets are combined with half of the oil first to reduce elastomer viscosity, followed by incremental tackifier addition; adding tackifier before oil produces a high-melt-viscosity elastomer phase that overloads the kneader drive torque. If melt temperature is held above 175 °C for more than 30 min, the unsaturated polybutadiene segment undergoes thermal-oxidative chain scission, observed on the production floor as falling agitator torque and reduced PSTC 101 peel force; published grade-specific degradation kinetics for YH-791 in this configuration are limited, but the boundary is consistent with linear SBS unsaturation behavior.

Compliance for pressure-sensitive applications is governed by PSTC 101 for 180° peel adhesion, PSTC 107 for static shear adhesion, and ISO 29862:2018 for self-adhesive tape peel properties. For adhesives in food packaging, FDA 21 CFR 175.105 permits indirect contact within good manufacturing practice limits, but formulators must verify that the tackifier, oil, and antioxidant each carry their own food-contact authorization because YH-791 alone does not grant full adhesive compliance. Terminal product types include carton sealing tapes, label stock, hygiene elastic attachment adhesives, and protective film laminates. The final adhesive is applied by slot-die coating at 150–165 °C; viscosity at the coating die should be maintained between 5,000 mPa·s and 20,000 mPa·s to avoid ribbing defects below the lower limit and die-lip char above the upper limit.

Does a 25 phr SBS YH-791 Dose Shift DIN Abrasion Loss Below 150 mm³ in Shoe Soles?

In vulcanized footwear compounds, YH-791 is added at 20–50 phr to an SBR/NR premasticated base, with the 20–30 phr range used for solid outsoles and the 40–50 phr range used for lightweight midsoles where density reduction is more important than tensile strength. The material participates in sulfur vulcanization through the unsaturated polybutadiene midblock, but cure rate lag relative to natural rubber requires accelerator adjustment rather than a sulfur increase above 2.2 phr; the preferred cure system is 1.8–2.2 phr sulfur with 1.2–1.8 phr N-cyclohexyl-2-benzothiazolesulfenamide and 0.2–0.5 phr diphenylguanidine. Mixing is executed in a tangential rotor internal mixer of 50–70 L net chamber volume with a fill factor of 0.70–0.80, dropping the batch at 120–140 °C to prevent scorch; the batch is then sheeted on a two-roll mill at 60–80 °C before being fed to multi-station rotary injection machines with clamp force 1,500–4,000 kN. Above 30 phr YH-791, tensile strength measured to ISO 37:2017 decreases monotonically, while tear strength and flex-crack resistance remain stable if the compound contains 2–4 phr UV stabilizer and 1–2 phr microcrystalline wax for external part use.

Test standards for the finished sole are ISO 37:2017 for tensile stress-strain, ISO 868:2003 or ISO 48-4:2018 for Shore A hardness, ISO 4649:2017 for rotating-drum abrasion, and ISO 17707:2005 for outsole flex resistance; the question of abrasion loss below 150 mm³ depends more on filler type than on YH-791 dose. A compound with 25 phr YH-791, 40 phr N220 carbon black, and 10 phr precipitated silica typically reaches 120–170 mm³ abrasion loss under ISO 4649:2017, but grade-specific published data for YH-791 in this exact filler matrix is limited. Terminal products are casual shoe outsoles, lightweight midsoles, slipper soles, and safety footwear side components. Pre-drying is unnecessary for ambient-stored pellets below 60% RH, but moisture exposure above that threshold requires 60 °C drying for 2 h to avoid porosity in injection-molded soles.

In the manufacture of torch-applied SBS-modified bitumen roofing membranes, YH-791 is compounded into fluxed bitumen at 8–15 wt% to create a low-temperature-flexible waterproofing compound that retains dimensional stability under roof thermal loads. This addition window is higher than road-paving PMB because membrane compounds must pass cold-bending tests at −5 °C to −20 °C without forming surface cracks, and because the compound is subsequently loaded with mineral filler. The mixing system is a vertical high-torque blender at 180–200 °C; after SBS digestion, 20–30 wt% ground calcium carbonate or talc is added to control cost, fire resistance, and slump during torch application. The filler boundary is critical: above 30 wt% filler, melt viscosity at 180 °C can exceed 20 Pa·s, and the compound no longer penetrates the polyester or glass-fiber carrier mat, producing strike-through defects and delamination at the selvage. The impregnated mat is calendered at 160–180 °C and cooled under tension below 30 °C before sand or slate surface treatment.

Compliance is evaluated against EN 13707:2013 for reinforced bitumen sheets for roof waterproofing and EN 13969:2013 for bitumen damp proofing sheets, with ASTM D6164/D6164M-21 used in North American specifications for SBS-modified polyester-reinforced sheets. The relevant mechanical test clauses are cold bending at specified temperatures, tensile strength of the sheet, and dimensional stability after 80 °C aging; the production laboratory typically uses EN 1109:2013 for flow resistance to confirm that the membrane does not slump at 70 °C under inclined service. Terminal product types include torch-applied roof waterproofing membranes, bridge deck membranes, basement tanking sheets, and self-adhesive roofing underlayments. YH-791 must be protected from outdoor UV exposure in the finished membrane by mineral surfacing or pigmented coatings; unsaturated polybutadiene segments otherwise undergo cross-linking embrittlement and surface cracking during prolonged light exposure.

Melt-Phase Compatibilization Shifts Notched Impact Response in PS Compounds

YH-791 is used at 5–20 wt% as a drop-in impact modifier for general-purpose polystyrene and high-impact polystyrene compounds; the 5–10 wt% range is applied to packaging and disposable articles, while the 15–20 wt% range is used in appliance housings where notched impact strength measured to ISO 180:2019 is the primary specification. Compounding is carried out on a co-rotating twin-screw extruder with an L/D ratio of 40:1 and barrel temperatures from 160 °C at the feed throat to 200 °C at the die. The polystyrene end-blocks of YH-791 mix with the PS matrix without additional coupling agent, but the polybutadiene midblock remains phase-separated; at 15–20 wt% SBS loading the morphology shifts from discrete dispersed elastomer droplets to a co-continuous or highly interconnected structure, which creates a stepwise gain in notched Izod impact but simultaneously reduces tensile modulus measured to ISO 527-1:2019. Molders observe that injection molding pressure drop increases with SBS content because melt viscosity rises; thin-wall parts require melt temperature 200–230 °C and hydraulic clamp force 800–2,500 kN depending on projected area.

The compound must comply with RoHS 2011/65/EU for electrical enclosures and REACH SVHC restrictions for consumer goods; melt mass-flow rate is controlled according to ISO 1133-1:2022 to maintain filling consistency. For outdoor or UV-exposed parts, 0.2–0.5 wt% hindered amine light stabilizer and 1–2 wt% carbon black are required because the polybutadiene midblock of YH-791 is unsaturated and will otherwise embrittle under light. Terminal products include appliance housings, electrical switch covers, toy components, cosmetic packaging, and extruded sheet for thermoformed packaging. The processing boundary is set by the die temperature: above 210 °C the risk of polybutadiene thermal degradation rises, generating gel specks in transparent blends and reducing notched impact performance.

Compounding oil-extended SBS-type thermoplastic elastomers based on YH-791 for injection-molded grips requires the elastomer to be present at 25–40 wt% of the final TPE compound, with a typical starting formula of 100 phr YH-791, 50–120 phr paraffinic or naphthenic oil, 20–50 phr polypropylene, and 0–20 phr mineral filler. The twin-screw extruder is operated at 170–200 °C, and process oil is injected downstream through a gear pump into the melt after the primary kneading blocks; injecting the full oil dosage at the feed throat causes phase inversion and a gritty surface, because the oil preferentially swells the polybutadiene midblock before the polystyrene end-blocks are dispersed in the polypropylene phase. The compound is pelletized underwater at 30–40 °C to prevent pellet agglomeration. Injection molding is conducted at 180–210 °C with a screw L/D of 20–22 and back pressure 0.5–1.5 MPa; clamp force requirements for multi-cavity grip tools typically fall between 500 kN and 1,500 kN. Pellets stored above 60% RH are dried at 60 °C for 2 h before molding to prevent surface splay and weld-line weakness.

Material classification follows ISO 18064:2022 as a styrenic block copolymer thermoplastic elastomer, with hardness tested to ISO 48-4:2018 and compression set tested to ISO 815-1:2019 after 22 h at 70 °C; unfilled grades commonly exhibit compression set of 40–60%, while mineral-filled grades may fall below 35% depending on oil and polypropylene ratio. Terminal product types include soft-touch power tool grips, appliance knobs, sealing gaskets, anti-slip floor pads, and cable strain-relief boots. High-aromatic process oils should be avoided above 20 phr because they plasticize the polystyrene end-blocks, leading to Shore A hardness collapse and increased compression set; amine-based additives are not recommended in this compound because they can generate discoloration at 190–200 °C melt temperatures.