| HS Code | 647074 |
| Product Name | S-LEC BL-S |
| Manufacturer | Sekisui Chemical Co., Ltd. |
| Material | Polyvinyl butyral (PVB) |
| Form | Interlayer film roll |
| Color | Clear/transparent |
| Standard Thickness | 0.76 mm |
| Thickness Range | 0.38 mm to 1.52 mm |
| Width | Up to 3000 mm |
| Density | 1.07 g/cm³ |
| Refractive Index | 1.48 |
| Tensile Strength | ≥25 MPa |
| Elongation At Break | ≥250% |
| Tear Strength | ≥40 N/mm |
| Light Transmittance | ≥90% |
| Haze | ≤1% |
| Uv Cutoff Wavelength | 380 nm |
| Glass Transition Temperature | 20°C |
| Adhesion To Glass | 8 to 15 N/25mm |
| Moisture Content | ≤0.5% |
As an accredited S-LEC BL-S factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | S-LEC BL-S is supplied as a white powder in multi-wall paper bags with a polyethylene liner, 20 kg net per bag. |
| Container Loading (20′ FCL) | 20′ FCL container loading of S-LEC BL-S: secure packages properly, protect from moisture/heat, ensure ventilation, and follow hazardous handling rules. |
| Shipping | S-LEC BL-S is a polyvinyl butyral resin supplied as a dry, free-flowing powder or granule. Ship in sealed, moisture-proof packaging to prevent clumping. Transport at ambient temperature in clean, dry containers, avoiding excessive heat and humidity. No special hazardous-goods classification is required under normal shipping conditions. |
| Storage | Store S-LEC BL-S in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and open flames. Keep containers tightly sealed to prevent moisture absorption, as the resin is hygroscopic. Avoid exposure to rain or condensation. Maintain stable temperatures and use within recommended shelf life for optimal performance. |
| Shelf Life | Store in a cool, dry place away from moisture and heat; shelf life is typically two years from manufacture date when unopened. |
For multilayer ceramic capacitor green tape manufacturing, S-LEC BL-S is incorporated as the primary thermoplastic binder in non-aqueous tape casting systems because its oxygenated-solvent solubility and clean oxidative decomposition are compatible with BaTiO3 and nickel electrode layers. A production-scale slurry is typically formulated with 100 parts by mass calcined BaTiO3 powder, 4–10 parts S-LEC BL-S, 0.5–1.5 parts phosphate ester dispersant, 2–4 parts benzyl butyl phthalate or dioctyl phthalate, and a methyl ethyl ketone/ethanol blend adjusted to 35–45 wt% total solids. Milling is conducted in a polyamide-lined jar mill at 40–60 rpm for 16–32 h using 5 mm zirconia media; the resulting slurry is de-aired under 50 mbar absolute pressure and cast through a doctor blade with a gap of 80–300 µm onto silicon-coated polyester film. Three-zone drying at 50 °C, 70 °C, and 85 °C yields a green tape thickness of 10–50 µm with a surface roughness Ra below 0.5 µm. The target slurry viscosity is 1,200–2,500 mPa·s at 25 °C on a Brookfield RVT viscometer using spindle 4 at 20 rpm, and this window is verified against lot-to-lot resin molecular weight distribution before each production batch release.
Binder burnout is the critical process constraint. Thermogravimetric analysis of the organic fraction under air in accordance with ISO 11358-1 typically shows initial mass loss near 180 °C, with the main polyvinyl butyral decomposition interval between 250 °C and 380 °C; production tunnel kilns apply a ramp of 0.5–1.0 °C/min from 300 °C to 450 °C and hold for 2 h to reduce carbon residue below 0.03 wt% prior to sintering at 1,150–1,300 °C. Inadequate oxygen exchange in the burnout zone can leave pyrolytic carbon at the nickel electrode interface, causing delamination or capacitance loss under 85 °C/85% RH bias testing. RoHS recast 2011/65/EU and REACH registration obligations apply to the final capacitor body only if the resin leaves restricted substances above threshold concentrations, and normal burnout profiles leave no detectable organic residue above 0.01 wt%; published data for this specific grade under full production furnace atmospheres is limited and is verified on each firing curve rather than assumed from laboratory TGA. The end products are high-capacitance MLCC components in EIA 0402 to 1206 packages, where green tape thickness uniformity below ±3% is required for layer registration.
High-speed gravure lamination inks for PET, BOPP, and aluminium foil constructions use S-LEC BL-S as a co-binder for pigment dispersion and metal adhesion, but its solvency limits determine whether the ink can run at high press speed. A commercial base ink may contain 8–12 wt% S-LEC BL-S, 12–18 wt% white or coloured pigment, 2–4 wt% polyurethane adhesion promoter, 0.5–1.0 wt% silica matting agent, and a solvent blend of ethanol, n-propyl acetate, and ethyl acetate. The resin hydrosolubility of PVB with residual hydroxyl groups is controlled so that dilution with 70–80 wt% alcohol-rich solvent does not cause gelling or stringing. Dispersion is performed on a horizontal bead mill loaded with 0.6–0.8 mm yttria-stabilized zirconia beads at 8–12 m/s tip speed for 4–6 passes until grind gauge dispersion is below 10 µm per ISO 1524; the ink is then adjusted to 18–25 s flow time in a 4 mm cup per ISO 2431 at 25 °C. At press side, gravure cylinder engravings of 50–70 µm cell depth transfer an applied film weight of 3–6 g/m² dry, and lamination to metallized PET after solvent removal must achieve a bond strength above 2.5 N/15 mm when evaluated by ASTM F904.
Regulatory compliance for food-contact printed laminates centres on migration limits, and S-LEC BL-S is evaluated as a component of the finished non-food-contact layer under EU Regulation 10/2011 and FDA 21 CFR 175.105 where the printed layer is separated from food by a barrier. Residual solvent content must remain below 5 mg/m² per gas chromatographic headspace analysis before slitting, and press speed is usually limited by the solvent retention equilibrium of the PVB-containing ink rather than by mechanical drying capacity. Retort pouch constructions require that the ink layer survives 121 °C steam processing for 30 min without tunnelling or delamination; this is evaluated through visual inspection and tape adhesion per an internal specification unless a customer specifies ASTM D3359. In end use, the dried PVB-containing ink is part of the laminate that becomes food packaging, lidding films, or pharmaceutical sachets.
On galvanized steel and zinc-coated substrates, wash primers based on polyvinyl butyral resin and phosphoric acid are applied to generate an intermediate conversion layer that supports epoxy or polyurethane topcoats. A two-component formulation uses a base component containing 8–12 wt% S-LEC BL-S, 5–10 wt% zinc phosphate or zinc aluminium phosphate, 3–6 wt% talc extender, and an isopropanol/butanol solvent blend; the acid component is 85% phosphoric acid diluted in isopropanol and water. Mixing at a volume ratio of 4:1 is performed immediately before HVLP spray application at 1.5–2.0 bar air pressure and a wet film thickness corresponding to 8–15 µm dry film. The phosphoric acid attacks the zinc surface and PVB serves as a film former and adhesion promoter without embrittlement at 10–15 µm because the branched acetal structure provides flexibility.
Performance acceptance under ISO 12944-5 for corrosivity category C3 or C4 steel structures requires a pull-off adhesion value above 5.0 MPa when tested by ISO 4624 after full topcoat cure; failure within the primer layer is considered a cohesive-strength limitation of the PVB film, while failure at the zinc interface indicates inadequate acid etching. Salt spray testing per ASTM B117 for 500 h with a Type II scribe should produce less than 2 mm underfilm creep when the specified topcoat thickness is maintained. The primer must not be used as a direct exterior finish because PVB absorbs water and loses barrier properties under constant moisture without a topcoat; this is an operational boundary noted in heavy-duty coating specifications rather than a laboratory-only result. End products include structural steel sections, trailer bodies, rail car interior panels, and aluminium aerospace ground support equipment where chromate-free pretreatment is mandated by REACH and RoHS recast 2011/65/EU.
When aluminium honeycomb panels require a flexible semi-structural bond line, S-LEC BL-S is formulated with a plasticizer and an organosilane adhesion promoter to produce a dry bonding film on release paper for later press lamination. A cast film adhesive is prepared from a solvent solution containing 100 parts S-LEC BL-S, 25–40 parts dibutyl sebacate or triethylene glycol bis(2-ethylhexanoate), 1–3 parts 3-glycidoxypropyltrimethoxysilane, and 0.5–1.5 parts hindered phenolic antioxidant, knife-coated onto release paper and dried at 70–90 °C to a dry adhesive mass of 30–80 g/m². The resulting film is inserted between aluminium alloy skins and honeycomb core, then pressed at 130–150 °C and 0.2–0.5 MPa for 15–30 min; heating melts the PVB carrier, flows the adhesive into fillets at the honeycomb cell edges, and then cools to a semi-rigid tie layer. Lap shear on aluminium alloy 2024-T3 substrates tested by ASTM D1002 after 7 days at 23 °C/50% RH is used for release testing, and production batches must show a cohesive fracture mode rather than interfacial release. This adhesive class is chosen when the bond line must retain some damping and flexibility under thermal cycling from -40 °C to 80 °C rather than for maximum static shear strength; published data for S-LEC BL-S in specific honeycomb sandwich panels is limited, so pre-production bond qualification is performed on recipient substrate grades and surface preparations.
Magnetic stripe coatings and archival magnetic tape use PVB resins as part of the binder matrix for acicular iron oxide or barium ferrite pigments because the resin disperses high-loading pigments and tolerates calendering temperatures without blocking. A coating dispersion for magnetic stripe film contains 70–80 wt% magnetic pigment, 8–12 wt% S-LEC BL-S, 3–5 wt% carbon black, 1–2 wt% stearic acid lubricant, and a methyl ethyl ketone/toluene/cyclohexanone solvent blend; the mixture is processed on a horizontal sand mill at 35–45 °C to avoid heat-induced chain scission of the PVB acetal rings. Wet coating at 10–15 µm thickness on polyethylene terephthalate is dried in a multi-zone air flotation dryer at 80–110 °C, then calendered at 85–95 °C and 200–300 kN/m nip pressure. The final magnetic stripe must meet coercivity and signal amplitude requirements defined by ISO/IEC 7811-2 for high-coercivity magnetic stripes.
A limitation observed in production is that PVB-bearing magnetic coatings can absorb atmospheric moisture and undergo gradual hydrolysis at the acetal linkage if stored above 60% RH without a protective topcoat; for this reason, magnetic stripe cards are laminated with a polyester overlaminate or varnish. This moisture sensitivity is countered by adding 1–2 wt% blocked isocyanate crosslinker and storing coated intermediates in sealed barrier packaging. The end products are magnetic stripe cards, hotel key cards, transit tickets, and specialized archival magnetic tape where controlled binder flexibility during slitting and punching reduces edge cracking.
In screen-printed carbon resistive heating elements, S-LEC BL-S functions as a binder for conductive carbon black and graphite blends deposited on polyester film or phenolic-glass composite substrates. A printable paste is formulated with 18–24 wt% carbon black, 10–15 wt% synthetic graphite, 8–12 wt% S-LEC BL-S, 1–2 wt% wetting agent, and a butyl carbitol acetate/terpineol solvent system adjusted to 25–35 Pa·s apparent viscosity at 10 s⁻¹ on a cone-and-plate rheometer at 25 °C. Screen printing through a polyester mesh of 120–180 threads/cm onto a 125 µm PET substrate produces a wet layer that is dried at 120 °C for 10–15 min, yielding a dry film of 10–15 µm thickness. The target sheet resistivity for 10 W panel heaters is typically 5–20 Ω/sq at that dry film thickness, measured by four-point probe per ASTM D257. Because PVB has a glass transition near 65–75 °C, printed elements are limited to continuous service below 70 °C unless the binder is crosslinked; resistive paste formulations that require 120 °C long-term operation replace part of the PVB with a thermosetting epoxy phenolic system, and the S-LEC BL-S portion then functions mainly as a dispersing and print-definition aid. RoHS recast 2011/65/EU applies to the finished printed heater assembly. End products include low-voltage wall panels, automotive seat heaters, and battery compartment heaters for cold-climate original equipment.
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S-LEC BL-S is a high-modulus polyvinyl butyral (PVB) interlayer film manufactured by Sekisui Chemical for laminated glass assemblies in which post-glass-breakage retention, penetration resistance, and static load-bearing stiffness must exceed the performance of general-purpose PVB interlayers. The product is supplied as a calendered, plasticized film in nominal thicknesses from 0.38 mm to 1.52 mm, with multiple plies used to create thicker interlayer stacks for security glazing and structural balustrades. The suffix BL-S identifies a stiffer PVB formulation within the S-LEC interlayer family; it is specified for point-supported glass elements, overhead panels, glass stairs, and protective enclosures where standard PVB grades may allow measurable shear deformation under sustained load. Published datasheets for this grade should be consulted for current roll widths, density, and optical control values because these are batch-dependent and supplied from the manufacturer’s architectural technical service.
PVB interlayers in this class are hygroscopic and must remain in sealed polyethylene packaging until immediately before lamination. Typical incoming moisture content is controlled below 0.50 wt%, and storage areas are maintained at 10 °C to 20 °C with relative humidity below 40 %. Rolls are stored horizontally on full-length core supports to prevent flattening and plasticizer migration. Conditioning in the clean lay-up room for at least 24 h reduces condensation and edge-wrinkling defects on wide architectural formats.
Standard PVB films such as S-LEC Clear Film are formulated primarily for impact containment and are processed with comparatively low melt viscosity. Under static load, these standard interlayers flow viscously, and the laminated glass may show time-dependent deflection. BL-S is modified to increase tensile modulus and reduce long-term creep sensitivity while retaining sufficient adhesion to glass with silane-based adhesion promoters. The practical specification difference appears in deflection-limited designs calculated under ASTM E1300 or EN 16612: BL-S may allow a thinner overall glass build for a given edge-stress limit when the interlayer shear-transfer capacity is accounted for. However, the material remains a thermoplastic PVB and does not attain the shear modulus of ionoplast interlayers. Direct replacement of an ionoplast interlayer with BL-S without re-running a finite-element deflection model or full-scale proof testing is not accepted under structural glass practice.
Thickness selection for BL-S is based on shear-modulus data, tensile properties, and post-lamination optical quality. Tensile characterization follows ISO 527-3 at 23 °C and 50 % relative humidity, with the recognized caveat that PVB modulus is strain-rate dependent. Data collected at a crosshead speed of 50 mm/min or 100 mm/min may not represent low-frequency wind or occupant loads. Laminated glass containing the film is evaluated for optical quality under ISO 14782 for haze and ISO 9050 for luminous transmittance. In security glazing, acceptance criteria often require a maximum haze value after lamination and no visible bubbles or delamination within the vision area under ISO 12543-6. Because the modulus of PVB is both temperature- and moisture-sensitive, values obtained on film that has absorbed ambient moisture above 0.5 wt% are not representative for design and should be discarded.
| Standard designation | Scope | Typical evaluation for BL-S-containing laminates |
|---|---|---|
| ISO 12543-2 | Laminated safety glass | Impact resistance and mechanical stability |
| ANSI Z97.1 | Safety glazing materials in buildings | Impact classification for human-safety glazing |
| EN 14449 | Laminated glass in buildings | Factory production control and conformity |
| EN 356 | Security glazing under manual attack | Penetration resistance classification |
| ASTM E1886 | Windborne debris performance | Missile impact and pressure cycling |
| ASTM E1996 | Windborne debris specification | Wind zone and missile level selection |
| UL 972 | Burglary resisting glazing material | Physical attack resistance |
On architectural laminating lines, BL-S typically requires a longer vacuum de-airing cycle than standard PVB because its higher melt stiffness prevents rapid flow into glass surface texture during initial edge sealing. A cold de-airing step between 5 °C and 20 °C is followed by infrared preheating to 80 °C to 100 °C before the laminate enters the autoclave. Autoclave settings used in industrial practice for PVB interlayers are commonly in the range of 12 bar to 14 bar and 135 °C to 145 °C; BL-S stacks are held at peak temperature long enough for the core to reach the required bond temperature. Failure to maintain vacuum during the initial bag stage can produce edge bubbles that persist after autoclave. This failure mode is observed more often with thick multi-ply BL-S constructions than with single-ply standard PVB on roller-hearth lines.
Multi-ply laminates containing two or more BL-S plies are used in forced-entry and protective glazing. Since the interlayer has a lower thermal conductivity than glass, the centre of the stack reaches peak temperature later than the surface; total interlayer thickness in such builds often exceeds 2.28 mm. If autoclave pressure falls below 12 bar during the temperature plateau, residual air remains compressed at the glass–interlayer interface and may become visible as low-density edge haze after cooling. The defect is irreversible once the glass-to-PVB edge bond has sealed. Production equipment with pressure-holding capability of ±0.2 bar and internal air circulation sufficient to limit the glass-stack temperature differential to ±5 °C avoids this failure. Cooling after the plateau is controlled at less than 3 °C/min to avoid interlayer shrinkage that can cause delamination at cut edges.
Vacuum-bag lamination of S-LEC BL-S differs from high-volume roller-press processing because the film is not pre-tacked by heated nip rollers. The bag is evacuated to a gauge pressure below −0.08 MPa before the first heating stage, and the edge seal is inspected as a transparent band around the perimeter. A continuous band of at least 10 mm width is typically required before autoclave; if the band is interrupted, autoclaving cannot recover the edge because the film’s melt viscosity limits air diffusion in the short pressure cycle. This requirement becomes critical when polished low-iron glass substrates have surface roughness below 1.0 µm Ra, where mechanical interlocking is reduced and de-airing depends on film collapse under vacuum. Lines producing polished structural laminates often add a second vacuum cycle and maintain the clean-room lay-up temperature below 20 °C to prevent premature film softening.
Within the S-LEC PVB family, Clear Film is specified for general safety glazing where rapid de-airing and economical autoclave cycles are primary. Sound Film is specified where acoustic damping under ISO 16940 is required for facade or automotive glazing. BL-S is selected when the laminate must retain glass fragments and resist penetration under sustained load rather than optimize acoustic loss factor. The processing behaviour is not interchangeable: Clear and Sound films tolerate shorter vacuum cycles because their lower melt viscosity allows faster edge sealing, whereas BL-S requires additional dwell time and may require a higher autoclave setpoint within the standard PVB range. For a structural application with simultaneous acoustic requirements, a hybrid stack of BL-S and a sound-damping PVB or an acoustically designed interlayer is used, and the complete laminate is validated by ISO 16940 damping measurements and full-scale impact testing to the relevant security standard.
In hurricane-impact glazing, BL-S-containing laminates are evaluated to ASTM E1886 and ASTM E1996 for windborne debris impact and pressure cycling. In forced-entry and burglar-resistant glazing, EN 356 and UL 972 are among the referenced test methods. The interlayer contributes to glass retention after impact, but system performance depends on framing, glazing bite, and edge engagement. A minimum structural glazing bite of 12 mm is commonly used for high-impact laminates, and the edge sealant must be selected for compatibility with PVB plasticizer. Published data for specific bullet-resistant configurations using BL-S as the sole interlayer are limited; each security glazing stack is validated against the relevant threat-level classification before production release.
Compatibility with edge sealants is established by test coupons under ISO 11431 for joint sealant adhesion and ISO 8339 for building construction joint products. Plasticizer migration from the interlayer into certain polyurethane or polysulfide sealants can reduce interfacial bond over time. Neutral-cure silicone sealants are preferred for glazing edge work because acetoxy systems liberate acetic acid during cure, which can etch glass edges and locally alter PVB adhesion. Solvent-based primers and aromatic cleaning agents should not be applied to exposed interlayer edges.
Master rolls are slit to the required architectural width, commonly up to 3,200 mm, and are shipped on moisture-resistant cores. During slitting, web tension is maintained below the film’s yield point to prevent neckdown; variations in edge straightness greater than ±1 mm per meter can prevent correct registration on automated glass assembly tables. The slit roll is re-wrapped in sealed polyethylene after every withdrawal to limit moisture absorption in humid production halls.
Adhesion of the interlayer to glass is controlled by the glass surface condition, washing water purity, and storage humidity. Production lines use deionized water with a final-rinse conductivity below 20 µS/cm on the glass washer. Glass substrates are dried with forced air at 30 °C to 40 °C before lay-up. Insufficient drying leaves a moisture film that reduces initial PVB adhesion and increases the risk of edge bubbles after autoclave.
