SINOPEC Maoming SBS F675 is a linear styrene-butadiene-styrene block copolymer supplied as solid granules. Manufacturer certificates of analysis for this grade commonly report bound styrene content in the range 38–42 wt%, volatile matter below 0.5 wt%, and ash below 0.8 wt%. Tensile properties are determined at 500 mm/min using dumbbell specimens according to ISO 37:2017; typical lot values for tensile strength fall between 16–20 MPa and elongation at break between 600–800%. Melt flow rate is measured under ISO 1133-1:2022. F675 is a high molecular weight linear SBS with low diblock content, and its processing behavior is dominated by styrenic end-block association and butadienic mid-block elasticity. If pellets are exposed to condensation or storage humidity above 60% RH, drying at 60–70°C for 2 h is required before melt processing. The downstream scenarios below are limited to applications where linear SBS grades of this styrene content are commercially specified; published data for this specific configuration in any given end-use should be verified against the current certificate of analysis before production qualification.

When a PG 70-22 binder specification forces SBS loadings between 4.5 and 5.5 wt% in dense-graded wearing courses

In bituminous pavement modification, SINOPEC Maoming SBS F675 is introduced at 4.0–6.0 wt% of the base bitumen mass, with the narrower 4.5–5.5 wt% range typically required to reach PG 70-22 or PG 76-22 performance under ASTM D5976-96(2021) and EN 14023:2010. The exact addition threshold is governed by the maltene-to-asphaltene ratio of the base binder; waxy or highly aromatic sources may require the upper end of the range, while low-penetration naphthenic binders may achieve continuous network formation at lower dosage. At addition levels near 5 wt%, the SBS absorbs light fractions and forms a continuous network through styrenic end-block association, producing a large increase in elastic recovery and an inflection point in softening point. Dosage must be selected before blending because excess SBS above 7 wt% in unmodified paving bitumen can raise mixing viscosity into a range where the high-shear dispersion step becomes equipment-limited. Compliance testing follows EN 14023:2010 for framework specification of polymer-modified bitumen, ASTM D5976-96(2021) for Type I polymer-modified asphalt for pavement construction, and JTG E20-2011 for Chinese highway binder test methods. Critical test designations include softening point EN 1427 or ASTM D36, elastic recovery EN 13398, force ductility EN 13589, storage stability EN 13399, and multiple stress creep recovery ASTM D7405. For heavy traffic PG 70-22 acceptance, MSCR Jnr at 3.2 kPa is commonly specified below 4.5 kPa⁻¹ with percent recovery above 30%, although project specifications vary.

Downstream production of polymer-modified bitumen is carried out in a jacketed high-shear mixer using a rotor-stator head or colloid mill. Base bitumen is heated to 175–190°C; F675 granules are added gradually under high-shear mixing at 5000–10000 rpm. Dispersion time is typically 45–60 min, with batch temperature held below 200°C. The critical processing window is narrower than general SBS modification because prolonged residence above 210°C accelerates oxidative chain scission of the butadiene midblock, while temperatures below 170°C do not allow sufficient bitumen fluidity for network development. When European or Chinese storage stability requirements apply, sulfur or a sulfur donor may be added at 0.05–0.15 wt% of the binder. Sulfur addition induces controlled crosslinking between butadiene segments and available unsaturated sites; maturation is carried out at 180°C for 2–4 h with slow agitation. Batch-to-batch variance is observed when the base bitumen contains more than 2 wt% wax; the wax fraction competes with the SBS for light oil absorption and can delay phase inversion by 0.5–1.0 wt% SBS dosage. On production-scale units, this is monitored by torque rise, UV fluorescence microscopy dispersion checks, and asphalt binder separation tubes according to EN 13399.

The formulation gradient in the following table gives representative values for linear SBS of 38–42 wt% styrene in 70/100 penetration bitumen, not a substitute for plant qualification.

Under EN 13707:2013 reinforced bitumen sheet production, F675 is introduced at 8–12 wt% of the binder fraction, corresponding to 6–9 wt% of the total compound after limestone filler addition. The addition ratio is higher than paving modification because a roofing membrane must retain flexibility at temperatures below −20°C and resist flow at 70–100°C under installed roof exposure. In this application, the SBS network is supplemented by a reinforcing polyester or glass-fibre mat; the compound is tested according to EN 1109 for low-temperature flexibility, EN 1110 for high-temperature dimensional stability, EN 12311-1 for tensile strength and elongation, and ASTM D5147-18 for bituminous sheet material evaluation. Formulation compliance is generally established under EN 13707:2013 for mineral-surfaced and metal-faced roofing sheets, with additional national requirements where pre-applied waterproofing membranes are specified.

Production of SBS-modified bitumen sheets is executed in heated vertical or horizontal mixing vessels with low-speed agitators followed by in-line rotor-stator refining. The binder compound is heated to 165–185°C; F675 and antioxidant are added before filler to avoid encapsulating polymer granules in limestone. After polymer dispersion, filler is introduced at 20–30 wt% to control coat weight and flame penetration resistance. The finished compound is coated onto a pre-heated reinforcement carrier at 1.0–1.5 m/min line speed and calibrated to 3–5 mm thickness. Excessive filler above 30 wt% reduces the continuous polymer network and results in low elongation at low temperature, while filler below 15 wt% increases cost and causes dimensional instability during torch application. Terminal products include torch-applied mineral-surfaced roofing membranes, self-adhesive bituminous sheets, and cold-applied bridge deck waterproofing membranes. For torch-applied systems, the polymer network must survive brief surface temperatures of 800–1000°C at the flame without losing dimensional stability; this is evaluated by EN 1110 after heat exposure.

Does a linear SBS with 38–42 wt% bound styrene require higher tackifier loading than SIS in hot-melt PSA compounding?

In hot-melt pressure-sensitive adhesives, F675 is formulated at 20–30 wt% rubber, 45–55 wt% C5 aliphatic hydrocarbon tackifier, 15–25 wt% naphthenic process oil, and 0.5–1.0 phr hindered phenolic antioxidant. Compared with SIS, the linear SBS tends to require a moderately higher total tackifier content when the same loop tack value is targeted because the butadiene midblock has a lower solubility parameter than isoprene and the styrenic end-blocks contribute physical crosslinks that must be selectively solvated by the resin. Hydrogenated C5 tackifier with softening point 100–115°C is preferred; rosin ester or aromatic resin addition above 10 wt% of the tackifier phase can penetrate the styrene domains and reduce shear adhesion failure temperature. The F675 high molecular weight linear architecture produces a higher cohesive plateau than SIS and allows permanent label and tape formulations to pass ASTM D3654 static shear at 1 kg loading for more than 100 h when coating weight is controlled at 15–40 g/m². Compliance references include FDA 21 CFR 175.125 for pressure-sensitive adhesives used in food packaging, REACH 1907/2006 Annex XVII restrictions, and RoHS 2011/65/EU for electronic tape applications.

Melt compounding is executed in a sigma-blade mixer or co-rotating twin-screw extruder with a melt temperature of 150–175°C. The extruder is preferred for continuous slot-die coating lines because it provides a residence time distribution below 5 min and limits cumulative thermal exposure that causes butadiene crosslinking. In sigma-blade mixers, nitrogen blanketing is recommended at temperatures above 165°C; without blanketing, viscosity rise from oxidative gelation can exceed 15% after 24 h at 180°C. Adhesive melt is pumped through a heated filter assembly of 100–150 µm mesh and applied through a slot die at 160–175°C. Test methods for PSA performance include loop tack ASTM D6195, 180° peel adhesion ASTM D3330, static shear ASTM D3654, and rolling ball tack PSTC-6. Terminal product types include permanent paper labels, double-sided mounting tapes, duct tape, and protective surface films where removable performance is adjusted by reducing tackifier content toward 40–45 wt%.

Solvent-borne contact adhesives: viscosity build, open-time thresholds and domain-selective solvent limits

F675 is dissolved in aromatic/aliphatic solvent blends at 15–25 wt% solids for brush and roll-applied contact adhesives. The base formulation on dry solids comprises 100 phr F675, 40–80 phr C9 aromatic hydrocarbon resin, 10–20 phr rosin ester, and 1 phr antioxidant. Solvent composition is adjusted to Hansen solubility parameters; a typical blend of toluene and cyclohexane in a 70:30 mass ratio dissolves the rubber phase quickly, while acetone or ethyl acetate is added up to 20 wt% to reduce viscosity and flash-off time. Aromatic solvents above 30 wt% of the solvent blend can swell the styrene end-blocks and reduce cohesive strength of the dried film, so the blend is formulated to solvate the butadiene midblock preferentially. Compliance is established under REACH 1907/2006 Annex XVII for restricted solvents, 2010/75/EU for solvent emissions, and ASTM D413-98(2019) for peel adhesion of rubber-to-substrate assemblies. The adhesive film is tested for green strength, open time, and final peel; wet tack is not characteristic of this system because bond formation occurs after solvent flash.

Manufacturing involves charging the solvent blend into an explosion-proof high-speed dissolver, then adding F675 granules gradually at 20–35°C. The initial dissolution phase is viscosity-limited; adding all rubber at once produces a non-flowable gel before full dissolution. Dissolver tip speed is kept at 10–15 m/s until polymer lumps disappear, then reduced to 5–8 m/s during resin addition. Final adhesive viscosity is typically adjusted to 2000–5000 mPa·s at 23°C. When applied to two substrates, the solvent is flashed for 10–15 min at 23°C/50% RH, producing an open time of 20–40 min. The dried films are contact-bonded under 0.5–1.0 MPa pressure; bond strength development is immediate, but moisture absorbed by the film increases the risk of foaming under humidity above 70% RH. Terminal products include decorative laminate bonding, upholstery foam, automotive headliner edges, and shoe upper-to-sole adhesives where heat reactivation is not used. F675-based contact adhesives are not recommended for continuous immersion in aromatic fuels or plasticiser-rich PVC substrates because the butadiene midblock is susceptible to swelling and plasticiser migration.

Injection-molded microcellular sole stocks utilise F675 as the continuous elastomeric phase at 55–75 phr of total polymer, extended with 20–40 phr of naphthenic oil and 15–35 phr of general-purpose polystyrene. The addition ratio is expressed as the base rubber phase, not a minor additive, because the compound requires high elastic recovery, low density, and sufficient melt fluidity for injection molding. The polystyrene phase reduces melt viscosity and increases hardness; at polystyrene loadings above 35 phr the compound becomes brittle at low temperature. Azodicarbonamide exothermic blowing agent is added at 1–4 phr together with 3–5 phr zinc oxide and 1 phr stearic acid. Expansion ratio and skin-core morphology are sensitive to melt temperature; a processing window of 165–190°C at the nozzle is maintained, with mold temperature between 25°C and 40°C. If melt temperature exceeds 195°C, premature gas evolution occurs inside the screw, producing surface pinholes and density variation; below 160°C the high viscosity of F675 causes short shots and poor knit-line strength. Production equipment includes an internal mixer at 120–150°C for the first compounding stage, followed by a pelletizing extruder and a reciprocating-screw injection molding machine with clamp force matched to a mold cavity projection of 0.8–1.2 tonnes/cm².

Compliance for footwear compounds is assessed through REACH 1907/2006 Annex XVII restrictions on PAH content and dimethyl fumarate, ISO 20871:2018 for outsole abrasion resistance, ASTM D1630-16 for NBS abrasion, and ISO 17707:2018 for flex resistance of soling materials. Density is measured by ISO 845; hardness by ISO 868 using Shore A or Shore Type C scales. Terminal products include injection-molded midsoles for athletic shoes, single-density outsoles for sandals and slippers, and lightweight soling sheets that are die-cut and adhesively attached. F675 is selected over lower-styrene linear SBS when the sole requires higher tensile strength and dimensional stability after repeated flexing. The limitation of this grade in footwear is the relatively high melt viscosity at low shear; thin-walled sole designs below 3 mm wall thickness may require a blend with oil-extended SBS or an SBS/polystyrene masterbatch to fill the cavity completely.

Impact modification of general-purpose polystyrene demands a dispersed SBS phase no larger than 2 µm

F675 is compounded with general-purpose polystyrene at 5–15 wt% to produce translucent to opaque impact-modified sheet and injection-molding compound. The addition ratio is set below 20 wt% because the elastomer reduces tensile yield strength and heat deflection temperature when it becomes co-continuous. In a twin-screw extruder with L/D 40:1, melt temperature is maintained at 190–210°C; screw speed is 300–500 rpm. The dispersed SBS phase is sized by shear rate and interfacial tension; processing under low shear leaves domains above 2 µm that produce only marginal impact improvement, while very high shear reduces domain size below 0.3 µm and may lower impact efficiency by reducing craze stabilization. The target morphology is a dispersed particle size of 0.5–2.0 µm with good matrix adhesion. The extruder is typically configured with downstream injection of oil at 1–5 wt% to adjust melt flow and prevent excessive screw torque during the SBS dispersion step.

Impact strength is tested by notched Izod ISO 180 or ASTM D256; tensile properties are measured by ISO 527-1:2019 and ASTM D638-14; melt flow rate is reported under ISO 1133-1:2022 at 200°C/5 kg. Compliance is assessed under RoHS 2011/65/EU, REACH 1907/2006, and IEC 62321 when electronic enclosures are targeted. Downstream terminal products include appliance housings, office equipment covers, consumer electronics enclosures, and impact-resistant sheets for thermoformed packaging. The process limitation is thermal stability of the butadiene segment: repeated extrusion of regrind above 240°C causes crosslinking and yellowing, so regrind content is typically limited to 30 wt% unless an additional process stabilizer package is used. Published data for this specific F675/GPPS configuration is limited; the stated morphological window is derived from commercial practice with linear SBS grades of comparable styrene content and molecular weight.

Compliance matrix for the F675 downstream scenarios: