LG-501S is evaluated in polymer-modified bitumen (PMB) for heavy-duty pavement and airport apron compounds as a linear styrene-butadiene-styrene block copolymer with a nominal bound styrene content of 31.0 wt% and a melt flow index of 5.0 g/10 min at 200 °C, 5.0 kg load per ASTM D1238. In production-scale rotor-stator high-shear mills, dried pellets are fed into 60/70 pen base bitumen preheated to 180–185 °C at loadings between 4.0 wt% and 6.0 wt%. High-shear dispersion at 3,000–4,000 rpm is maintained for 45–60 min. Plant operating records show that a rotor-stator tip speed below 18 m/s leaves unswollen gel particles that appear as surface lumps in thin-film oven aged samples, while tip speeds above 23 m/s increase bitumen temperature locally to more than 195 °C and generate irreversible oxidation, with a viscosity rise of 1.5–2.0 Pa·s at 135 °C in the finished PMB. The dispersed SBS phase raises the ASTM D36 softening point from a typical base value of 48–50 °C to a plateau of 68–72 °C at 5.0 wt% LG-501S, while ASTM D5 needle penetration at 25 °C falls to 40–45 dmm. Elastic recovery measured by ASTM D6084 at 25 °C remains above 80% only when the blend is not overheated, because the styrene end-block network is the carrier of recovery and the polybutadiene mid-block is sensitive to oxidative scission.
Storage stability per EN 13399 requires the difference in softening point between top and bottom sections after 48 h at 163 °C to be below 2.5 °C; this is met with LG-501S when the bitumen is fully swollen before the compound leaves the mill and when aromatic-rich flux oil is not added above 2.0 wt%. For multigrade paving, the multiple stress creep recovery test AASHTO T350 at 3.2 kPa is used to reject PMB batches with excessive rutting susceptibility. Batches produced with 5.0 wt% LG-501S commonly display non-recoverable creep compliance Jnr values below 0.5 kPa⁻¹ at 64 °C when the base bitumen is from a stable crude slate; verification is required for each refinery because paraffinic wax above 2.5 wt% in the base bitumen delays swelling and produces a bimodal rubber particle distribution. In field operation, the main batch-to-batch failure mode is not SBS content but residual water in the pellet feed. SBS pellets stored in unsealed silos at relative humidity above 60% absorb surface moisture that flashes in hot bitumen and creates foam, lowering effective dwell time in the high-shear mill. Drying in a dehumidified hopper at 60–70 °C for 2 h is standard for high-humidity regions. The finished PMB should not be held at 170 °C for more than 24 h without inert-gas blanketing.
What Determines Split Tear and Expansion Ratio in Foamed Soles Based on LG-501S?
Foamed sole compounds based on LG-501S are built around a starting formulation of 100 phr SBS, 25–35 phr paraffinic or naphthenic oil, 15–25 phr crystal polystyrene, 10–15 phr calcium carbonate, 1.0–1.5 phr zinc oxide, 0.5–1.0 phr stearic acid, 1.8–2.5 phr azodicarbonamide, and 0.3–0.5 phr dicumyl peroxide. The preblend is dispersed in a Banbury internal mixer at 110–120 °C for 12–15 min, then sheeted on a two-roll mill at 80–90 °C before pelletizing. Foaming is performed on vertical or horizontal injection machines with barrel temperatures of 150–170 °C, mold temperatures of 170–180 °C, injection pressure of 60–80 MPa, and clamp force of 180–220 tonnes for multi-cavity sole moulds. Under these conditions, the expanded sole density typically falls to 0.28–0.35 g/cm³ per ASTM D792, equivalent to an expansion ratio of 1.5–1.8. The compression set remains at 30–40% when measured by ASTM D395 Method B after 22 h at 23 °C, while split tear measured by ASTM D3574 Test F is sensitive to the ratio of crystal polystyrene to process oil. Increasing crystal polystyrene above 25 phr raises hardness but causes a rapid loss of split tear because the continuous styrenic phase becomes too brittle for flex-crack resistance.
Batch-to-batch variation in azodicarbonamide particle size below 8 µm is the dominant cause of non-uniform foam cell diameter. When the blowing agent decomposes too early at mold temperatures above 185 °C, the outer skin cures before gas evolution is complete and the sole collapses in the forefoot section. When mold temperature falls below 160 °C, the skin thickness increases and the density exceeds 0.50 g/cm³, which is outside the weight target for sports-type midsoles. Pinholes appear when SBS pellets are not pre-dried at 60 °C for 2 h before compounding, particularly above 60% relative humidity in tropical plants. The finished sole compound is screened for EU market compliance against REACH Annex XVII entry 50 PAH limits and AfPS GS 2019:01 PAK category 1; solvent-extractable PAH results below 1 mg/kg are typically achievable when white oil content is held below 35 phr, but the oil source must be confirmed because aromatic residue is the main contributor.
Production of sprayable solvent-based contact adhesives with LG-501S uses a high-torque planetary mixer or dissolver to dissolve 100 phr LG-501S into a toluene/hexane/ethyl acetate blend at 28–32 wt% total solids. A C9 aromatic/aliphatic tackifying resin at 80–100 phr and a rosin ester at 20–30 phr are pre-dissolved in toluene before SBS addition, with 1–2 phr of a phenolic antioxidant. Dissolution is complete after 6–8 h at 25–35 °C; the resulting adhesive viscosity at 25 °C ranges from 2,500–4,500 mPa·s. For spray application, the adhesive is thinned to 250–500 mPa·s and applied at a wet film thickness of 120–180 µm. After an open time of 20–30 min at 23 °C and 50% relative humidity, the two substrates are activated with infrared radiation at 60–70 °C for 10–15 s and pressed. Bonded assemblies of leather to rubber typically show T-peel strength above 4 N/mm per ASTM D1876 and lap shear strength above 2.0 MPa per ISO 4587. The main field limitation is plasticizer migration from flexible PVC; when attached PVC contains more than 10 wt% dioctyl phthalate, the adhesive film softens and shear strength drops within 72 h at 50 °C. Barrier primers or lower plasticizer PVC must be specified for high-load automotive trim assemblies.
| Application | LG-501S loading | Processing window | Upper control limit | Anchor test method |
|---|
| Polymer-modified bitumen | 4.0–6.0 wt% of bitumen | 180–185 °C, 3,000–4,000 rpm, 45–60 min | 195 °C local melt temperature | ASTM D6084, EN 13399 |
| Foamed footwear sole | 100 phr base resin | Banbury 110–120 °C; mould 170–180 °C | 185 °C mould skin cure | ASTM D792, ASTM D395 |
| Polystyrene impact modification | 8.0–15.0 wt% of compound | Co-rotating twin-screw L/D 36–44, 190–210 °C | 210 °C at die plate | ISO 180/1A, ISO 1133 |
| Oil-extended TPE mat | 35.0–40.0 wt% of compound | Twin-screw L/D 40, oil injection at barrel 5 | 200 °C barrel outlet | ISO 868, ISO 37 |
| Bitumen waterproofing membrane | 2.5–4.0 wt% of bitumen compound | Planetary mixer 170–180 °C; calender 15–20 m/min | 180 °C compound temperature | EN 1109, EN 1928 |
Melt Filtration Pressure as an Indicator of Polystyrene Impact Modification Efficiency
The impact modification of general-purpose polystyrene with LG-501S is accomplished by melt blending 8.0–15.0 wt% SBS into GPPS on a co-rotating twin-screw extruder with L/D 36–44, barrel temperatures of 190–210 °C, die temperature of 200 °C, and screw speed of 300–350 rpm. Published Izod data specific to LG-501S in GPPS are limited, so each plant must qualify the exact pellet blend with a test mould before tool steel is cut. Commercial GPPS grades with notched Izod values below 2.0 kJ/m² per ISO 180/1A typically require 10–15 wt% LG-501S to exceed 6.0 kJ/m² in homogeneous injection-moulded plaques. The same loading reduces melt flow index from approximately 8.0 g/10 min to 4.5–5.0 g/10 min per ISO 1133 at 200 °C, 5.0 kg. On production lines using a 100/80/100 mesh screen pack, melt filtration pressure typically rises from 4.0 MPa to 6.0–6.5 MPa at 12 wt% SBS. A pressure increase greater than 2.0 MPa within 10 min indicates poor dispersion, gel buildup from local residence time, or insufficient melting of the SBS phase. The upper temperature limit must be observed because butadiene block degradation at die temperatures above 210 °C generates gel specks and lowers impact efficiency even when the barrel setpoint appears stable.
For indirect food contact applications, the finished GPPS/SBS compound is evaluated under FDA 21 CFR 177.1810 for styrene block copolymers and under EU Regulation 10/2011 for overall migration using the time and temperature conditions matched to the final package use. Chlorinated paraffin and residual free styrene must be excluded from the compound if the converter requires low sensory taint in dairy packaging. On injection moulding lines for appliance housings, the blend processes with a clamp force requirement approximately 15% higher than neat GPPS due to increased melt viscosity; vented barrels are recommended if the regrind fraction exceeds 30% because recycled GPPS can carry surface moisture that hydrolyses residual unsaturation and produces silver streaks.
Oil Extension Does Not Eliminate Barrel Residence-Time Sensitivity
Oil-extended TPE compounds for injection-moulded automotive boot liners and industrial mats are prepared with LG-501S at 35.0–40.0 wt%, polypropylene homopolymer at 10.0–12.0 wt%, hydrotreated white oil at 45.0–50.0 wt%, and calcium carbonate at 3.0 wt%. Compounding is carried out on a co-rotating twin-screw extruder with L/D 40, barrel temperatures of 180–200 °C, and white oil injection downstream through a gear pump at barrel 5. Underwater pelletizing preserves pellet geometry and prevents the tacking that occurs with strand cooling when oil content exceeds 45 wt%. Finished pellets show Shore A hardness of 40–45 per ISO 868, tensile strength of 6–8 MPa per ISO 37, elongation at break of 500–600%, and melt flow index of 15–25 g/10 min per ISO 1133 at 190 °C, 2.16 kg. Injection moulding is performed at 180–190 °C melt temperature, mould temperature of 20–30 °C, injection pressure of 50–70 MPa, and clamp force of 120–160 tonnes for mat cavities. The melt must not be held at 190 °C for more than 6 min because the styrenic end-blocks relax and the compound loses drawdown strength, producing short shots in deep mat ribs.
Fogging is measured by ISO 6452 for automotive interior mat specifications; oil volatility dominates fogging behaviour, so hydrotreated white oil with pour point below -20 °C and flash point above 270 °C is selected. Flammability is tested per FMVSS 302; compounds with unfilled oil content above 50 wt% can fail horizontal burn rate unless a mineral filler or phosphorous-based flame retardant is added. The main field failure mode is oil bleeding after 7 days at 50 °C, observed as surface tack and dust pickup on production floor samples. This is controlled by maintaining polypropylene content above 10 wt% and calcium carbonate above 3.0 wt%, and by verifying oil absorption capacity of the filler batch. The migration of low-molecular-weight oil to the surface is not a visual defect alone; it increases torque degradation on injection screws because the screw root becomes coated and material conveyance becomes erratic.
If Calendering Speed Exceeds 20 m/min in SBS-Modified Bitumen Waterproofing Membrane Lines
In SBS-modified bitumen waterproofing membranes, LG-501S is dispersed into oxidized or non-oxidized bitumen at 2.5–4.0 wt% together with 30–40 wt% limestone filler, a mineral stabilizer, and often an atactic polypropylene modifier. The compound is mixed in a planetary mixer at 170–180 °C and transferred to a calender where it is coated onto a polyester or glass-fibre carrier. Compound viscosity at 180 °C is typically 12–18 Pa·s; this range is sufficient to prevent strike-through into the carrier while allowing even spread on the calender rolls. Low temperature flexibility per EN 1109 at -10 °C and watertightness per EN 1928 Method A are the two core release tests for the finished membrane. When calendering speed exceeds 20 m/min, the SBS-modified bitumen compound shows neck-in and thickness variation in the edge zones, and the carrier can shift out of centre because the melt strength of the modified bitumen is insufficient to hold the web under high draw. The control action is to reduce line speed below 18 m/min or increase LG-501S to 3.5–4.0 wt%; the latter raises compound viscosity and heat resistance but reduces cold flexibility if filler is not simultaneously reduced below 35 wt%.
The production line should be equipped with a 100 µm screen changer because undispersed SBS gel particles from insufficient mixing time create streaks that are detectable only after the membrane is cooled and folded. Streaks are a cause of field water ingress because they form low-thickness channels across the membrane. Heat-treated storage at 70 °C for 28 days is used as an internal accelerated ageing screen; dimensional change and exudation of oil from the calender compound must be below 2.0% for the specification to hold. LG-501S contributes to elastic recovery in the compounded bitumen, but the high filler loading in waterproofing membrane formulations limits the recovery available relative to paving PMB. This trade-off must be resolved through calender roll gap, line tension, and filler particle size distribution rather than through additional SBS alone.
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LG Chem SBS LG-501S is a linear styrene-butadiene-styrene block copolymer supplied in porous pellet form. Manufacturer documentation classifies the grade as a medium-styrene thermoplastic elastomer with a nominal bound styrene content of 30 wt% and a diblock content controlled below 18 wt%. The molecular architecture consists of polystyrene end-blocks that segregate into glassy domains with a glass transition temperature near 95 °C, while the polybutadiene midblock retains a glass transition near −85 °C; this phase separation yields elastomeric recovery without vulcanization. The linear structure differentiates LG-501S from radial SBS grades of equivalent styrene content through lower melt elasticity and narrower molecular weight distribution, which reduces die swell in profile extrusion and lowers mixing torque in high-shear bitumen dispersion. Property declarations on the manufacturer’s datasheet are cross-referenced to ISO 21561-1:2015 for bound styrene, ISO 1133-1:2022 for melt mass-flow rate, ISO 37:2017 for tensile stress-strain, and ASTM D2240-15e1 for Shore A hardness. The grade is not oil-extended; its melt mass-flow rate is generally higher than high-viscosity radial grades designed for low-temperature asphalt elastomers and lower than high-flow adhesive grades in the LG Chem SBS range. Available packaging should be confirmed with regional distributor, but the porous pellet form increases solvent uptake rate compared with dense pellets and also increases surface area for moisture adsorption.
Regulatory and standard references applicable to LG-501S property declarations and end-use compliance
| Parameter or requirement | Standard/regulation | Relevant clause/method | Application context |
|---|
| Bound styrene content | ISO 21561-1:2015 | Ozonolysis method | Specification control |
| Melt mass-flow rate | ISO 1133-1:2022 | Procedure A, 190 °C/5 kg | Processability comparison |
| Tensile stress-strain | ISO 37:2017 | Type 2 dumbbell, 500 mm/min | Elastomeric performance |
| Hardness | ASTM D2240-15e1 | Shore A, 15 s dwell | End-use property |
| Volatile matter | ASTM D5668-19 | Method A, 105 °C to constant mass | Drying control |
| Polymer-modified bitumen | EN 14023:2010 | Annex A | PMB specification |
| Storage stability | EN 13399:2017 | Clause 7 | Phase separation assessment |
| Food contact | FDA 21 CFR 177.1810 | Subparagraph (a) | Subject to end-use migration testing |
| RoHS screening | IEC 62321-3-1:2013 | XRF screening | Compliance verification |
What Are the Storage, Drying, and Stabilizer Requirements for LG-501S?
Storage and drying constitute the first process boundary. The product is specified with volatile matter below 0.5 wt%, but pellets stored at relative humidity above 60% can adsorb surface moisture. Dehumidified air drying at 55–65 °C for 2–4 h is recommended when residual moisture exceeds 0.2 wt%; moisture at the die can produce splay, gross melt destabilization, and surface delamination in profile extrusion. The unsaturated polybutadiene segment is stabilized during manufacture, but the polymer remains sensitive to ozone and ultraviolet exposure. Storage should therefore be maintained in sealed containers below 30 °C and away from UV light. Amine-based antistatic additives should not be introduced into the melt stream; secondary amines react with residual double bonds at extrusion temperatures above 190 °C and increase gel counts. Field experience on 40 mm co-rotating twin-screw extruders with L/D 32:1 shows gel content rising within 20 min of additive contamination. Volatile and moisture verification is performed by ISO 11358-1:2022 thermogravimetry and ISO 15512:2019 Karl Fischer titration, respectively.
Bitumen modification with LG-501S normally proceeds in a vertical high-shear mill or colloid mill, where 3–5 wt% SBS is dispersed into penetration-grade bitumen at 170–180 °C for 60–120 min. A Silverson or Siefer mill operating at 3,000–5,000 rpm develops shear rates sufficient to reduce the SBS domain size to 5–20 µm; the resulting polymer network raises the softening point and elastic recovery of the binder. Process control relies on EN 14023:2010; softening point is measured by EN 1427:2015, elastic recovery by EN 13398:2017, and storage stability by EN 13399:2017. The linear architecture of LG-501S provides lower mixing torque than radial SBS at equal polymer content, but phase separation at the top and bottom of vertical storage tanks must be checked by EN 13399 because the lower molecular weight fraction can segregate after 72 h at 160 °C. When the binder is subsequently emulsified, the polymer particle size and cross-linking behavior interact with cationic emulsifier chemistry; published data for LG-501S in emulsion-based PMB systems is limited, and plant trials are required to establish pH and calcium chloride breaks. Additionally, the grade can be used in asphalt recycling formulations at lower addition levels of 2–3 wt% when combined with reclaimed asphalt pavement, provided the aged binder is first characterized by EN 12591:2018 penetration and softening point methods. In such blends, the higher melt flow of LG-501S relative to high-viscosity radial grades assists wetting of reclaimed aggregate, but the final blend must be tested for elastic recovery after 48 h of stirred storage.
When Solvent-Based Adhesive Formulations Require Reduced Die Swell and Controlled Gel Content
In adhesive compounding, LG-501S is dissolved into mixtures of toluene, cyclohexane, and ethyl acetate at solids contents of 20–35 wt%. A high-torque dissolver with tip speed of 6–10 m/s is used to wet the porous pellets; subsequent addition of hydrogenated rosin ester or C5/C9 hydrocarbon resin at 40–60 phr adjusts tack and shear adhesion. The resultant solution viscosity at 25 °C typically lies between 1,000 and 5,000 mPa·s depending on solids content and resin loading; viscosity is monitored by ISO 2555:2018 using a Brookfield RVT viscometer with spindle 3 at 20 rpm. For peel adhesion, films cast on PET and tested according to ASTM D3330-04 with a dwell time of 24 h on stainless steel show loop tack values that depend strongly on resin type; published data for LG-501S in this specific configuration is limited. The linear structure of LG-501S produces lower die swell than radial SBS in slot-die coating, which is advantageous for thin adhesive films, but the lower melt elasticity also reduces cohesive strength at high temperatures. Formulations should be prepared with antioxidant and UV stabilizer packages; exposure of unstabilized solution to ambient oxygen at 40 °C leads to viscosity drift within 7 days. In hot-melt adhesive formulations, LG-501S is typically blended with end-block-compatible tackifiers at 140–160 °C in a sigma-blade mixer; compatibility is evaluated by differential scanning calorimetry according to ISO 11357-2:2020 to determine glass transition shifts. Adhesion to polypropylene is often limited without a chlorinated polyolefin coupling agent, and cohesive failure can occur above 60 °C unless the formulation includes a high-softening-point resin.
Rheological characterization of LG-501S is typically performed in a capillary rheometer at 180–200 °C using a die with L/D 16:1 and apparent shear rates from 10 to 1,000 s⁻¹. The flow curve exhibits shear-thinning behavior with a power-law index below 0.6 at high shear. Oscillatory shear according to ISO 6721-10:2021 shows a well-defined plateau modulus above the polybutadiene glass transition; the plateau boundary lies at approximately 0.1–0.5 MPa. Dynamic mechanical analysis from −120 °C to 150 °C at 1 Hz according to ISO 6721-1:2019 identifies the two glass transition peaks used to confirm domain separation. These rheological features support selection of melt pump speed and die pressure in compounding lines. Compared with high-styrene SBS, LG-501S has a lower plateau modulus and a higher loss tangent at service temperatures above 40 °C, which reduces heat buildup under cyclic deformation and can extend fatigue life in flexible applications. However, the lower plateau modulus also imposes an upper service temperature boundary of approximately 70 °C for continuous load-bearing uses; beyond this boundary, creep under ISO 899-1:2017 becomes measurable within 24 h at stresses above 0.1 MPa.
Comparative architecture and processing differences between LG-501S and reference SBS types
| Parameter | LG-501S linear SBS | Radial SBS reference | High-styrene SBS reference | Test method |
|---|
| Nominal bound styrene | 30 wt% | 30 wt% | 40 wt% | ISO 21561-1:2015 |
| Hardness range | 62–68 Shore A | 60–66 Shore A | 78–85 Shore A | ASTM D2240-15e1 |
| Melt elasticity/die swell | lower at equivalent MFR | higher | moderate | ISO 11443:2021 |
| Low-shear solution viscosity | lower | higher | similar | ISO 2555:2018 |
| Tensile strength trend | moderate | moderate-high | higher | ISO 37:2017 |
| Elongation at break trend | higher | moderate | lower | ISO 37:2017 |
Injection Molding and Twin-Screw Compounding of LG-501S with Styrenic and Olefinic Matrices
For thermoplastic compounds, LG-501S is used as a toughening modifier for polystyrene, high-impact polystyrene, and polyolefins. A co-rotating twin-screw extruder with L/D 32:1 and barrel profile 130–180 °C is typical; the feed throat is maintained below 40 °C to prevent pellet bridging and premature softening. The grade is added at 5–30 wt% depending on the balance of impact strength and flexural modulus required; impact testing follows ISO 180:2019 or ASTM D256-23, and tensile modulus follows ISO 527-2:2012. When compared to high-styrene SBS grades, LG-501S gives lower Shore A hardness and higher elongation, making it more suitable for soft-touch grips and flexible compounds. In injection molding, clamp force settings of 50–150 t for multicavity tools have been used with melt temperatures of 150–180 °C; mold cooling at 20–60 °C controls shrinkage. The linear architecture reduces die swell relative to radial SBS, but the melt strength is lower, so blow molding and thick-wall thermoforming require careful parison control. Published data for LG-501S in microcellular foam injection molding is limited.
