| HS Code | 637968 |
| Product Name | PVB WW-A-50 |
| Chemical Name | Polyvinyl Butyral |
| Cas Number | 63148-65-2 |
| Appearance | White free-flowing powder |
| Density | 1.08 - 1.12 g/cm³ |
| Refractive Index | 1.49 |
| Glass Transition Temperature | 70°C (approx.) |
| Softening Point | 120 - 135°C |
| Viscosity 10 Ethanol Solution Tu 4 Cup 20 C | 50 ± 5 seconds |
| Average Molecular Weight | 50,000 g/mol (approx.) |
| Hydroxyl Content | 20 - 25% |
| Acetate Content | ≤ 3% |
| Butyral Content | ~75% |
| Solubility | Soluble in alcohols, ketones, esters, chlorinated hydrocarbons; insoluble in water |
As an accredited PVB WW-A-50 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | PVB WW-A-50 is supplied as free-flowing powder in 25 kg multilayer paper bags with an inner polyethylene liner. |
| Container Loading (20′ FCL) | 20′ FCL container loading for PVB WW-A-50: standard 20-foot full container, palletized bags, secured and stowed safely for efficient transport. |
| Shipping | PVB WW-A-50 (polyvinyl butyral resin) is a non-hazardous, non-flammable solid. Ship in sealed, moisture-proof packaging to prevent clumping and degradation. Keep dry, away from direct heat or ignition sources. No UN dangerous goods classification required; standard dry freight or truck transport is suitable. |
| Storage | Store PVB WW-A-50 in a cool, dry, well-ventilated area away from heat, open flames, and ignition sources. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid contact with strong oxidizers. Maintain stable temperatures, ideally below 25°C, and follow local fire safety regulations for polymeric materials. |
| Shelf Life | Store in a cool, dry place. Shelf life is typically two years from date of manufacture when unopened. |
In laminated safety glass manufacture, PVB WW-A-50 is dry-blended with triethylene glycol bis(2-ethylhexanoate) plasticizer at 20–35 phr and extruded into continuous interlayer film through a co-rotating twin-screw extruder with an L/D ratio between 30:1 and 48:1. The melt is filtered through a 200 µm mesh pack and delivered by gear pump to a slot die with lip gaps set for 0.38 mm to 1.52 mm final film thickness. The cast film is equilibrated in a humidity-controlled clean room to 0.35–0.55 wt% residual moisture because this band directly controls glass-to-PVB pummel adhesion. Glass lamination lines use a prepress nip at 100–130 °C followed by autoclave exposure at 1.1–1.5 MPa and 135–140 °C for 60–120 min, depending on glass thickness, to eliminate trapped air and complete the adhesion reaction. Compliance for this sector is governed by ISO 12543-2:2021 for architectural laminated safety glass, ASTM C1172-19 for flat glass interlayer durability, and UNECE R43 (revision 4) or ANSI Z26.1 for automotive glazing; Chinese OEM deliveries typically require GB 9656-2021 certification. Terminal products include automotive windscreens, side-laminated privacy glazing, architectural balustrades, hurricane bolted glazing units, and acoustic trilayer interlayers in which a soft acoustic core is coextruded between two PVB WW-A-50 skin layers. Operational boundaries include storage in sealed moisture-barrier bags below 10 °C and re-drying if moisture exceeds 0.6 wt%, because moisture above this level generates autoclave bubbles and increases edge clouding after bag opening.
| Standard designation | Test or control parameter | Relevance to PVB WW-A-50 lamination |
|---|---|---|
| ISO 12543-2:2021 | Laminated safety glass classification | Autoclave pressure/temperature record and impact test selection |
| ASTM C1172-19 | Flat glass interlayer durability | Pummel adhesion after lamination |
| UNECE R43 | Automotive safety glazing test | Optical distortion and ball-drop fragmentation control |
| ASTM D1003-21 | Haze measurement | ≤1.5% for 0.76 mm film |
PVB WW-A-50 is incorporated at 8–12 wt% of total ink solids in alcohol/ester flexographic and gravure ink vehicles to alter solvent-release kinetics and improve adhesion to corona-treated BOPP, PET, and aluminium foil. The resin is first dissolved at 15–20 wt% solids in a mixture of n-propanol, propyl acetate, and ethyl acetate, then pigmented using a high-speed disperser at 12–15 m/s tip speed for 40–60 min; the premix is milled through a horizontal bead mill with 0.8–1.0 mm zirconia beads at 1200–1500 rpm until Hegman 7 dispersion is achieved. The letdown is adjusted to 18–22 s Zahn 3 at 25 °C and printed through an anilox roll of 360–440 LPI and 4.5–7.8 BCM; dryer tunnel settings of 70–90 °C remove sufficient solvent while retaining enough residual solvent to prevent microvoiding in the ink film. For food-contact converters, the formulation must satisfy 21 CFR 175.300 for resinous and polymeric coatings or 21 CFR 175.105 for coatings used with a functional barrier, and the finished print must comply with EU Regulation (EU) No 10/2011 overall migration limit of 10 mg/dm²; ink producers follow the EuPIA Good Manufacturing Practice for food-contact printing inks. Terminal printed materials include snack food wrappers, confectionery films, pharmaceutical sachet overwrap lamination, and surface-print tags where alcohol resistance and low odour after 48 h aging are required. The solubility window narrows above 5 wt% water in the solvent blend, where PVB begins to precipitate as a white particulate; formulators should also avoid nitrocellulose/alkyd co-binders with high free acidity because acid-catalyzed acetal exchange raises solution viscosity during storage.
On steel and aluminium pretreatment lines, PVB WW-A-50 is compounded into a two-part wash primer at 5–9 wt% solids in the base component and activated with 2–4 wt% phosphoric acid immediately before spray application. The base component is dispersed under high shear with 10–18 wt% zinc phosphate or chromium-free anticorrosive pigment in a mixture of isopropanol, 2-butoxyethanol, and acetone, then passed through a 10 µm filter bag to reject agglomerates. Application by conventional pressure pot or air-assisted airless spray deposits 8–12 µm dry film thickness over grit-blasted steel prepared to ISO 8501-1 Sa 2½ or chromated aluminium. Drying occurs at 15–30 °C for 20–30 min; topcoating is mandated within 4–8 h to avoid intercoat adhesion failure caused by moisture ingress and acid salt ageing. System qualification under ISO 12944-5:2019 for corrosivity classes C3 through C5 requires scribe-creep testing per ASTM D1654-08 after neutral salt spray exposure per ISO 9227:2022; Cr(VI)-free formulations must comply with REACH Regulation (EC) No 1907/2006 Annex XVII restrictions on chromate compounds and with RoHS Directive 2011/65/EU for restricted substances in coated equipment. Terminal products include structural steel bridge modules, offshore containerized equipment, aluminium architectural extrusions for curtain wall framing, and export machinery parts where long transit corrosion protection is required. Pot life after acid activation is limited to 8–12 h at 25 °C; viscosity increases sharply as the acid reacts with PVB hydroxyl groups, and gelation occurs beyond 24 h. Application below 5 °C or above 85% relative humidity produces blush and poor adhesion.
Tape casting of barium titanate dielectric and LTCC glass-ceramic layers uses PVB WW-A-50 as the primary thermoplastic binder at 8–12 parts by weight per 100 parts ceramic powder, with 4–6 parts plasticizer and 0.5–1.5 parts phosphate ester dispersant in a MEK–ethanol solvent system. The slurry is attritor-milled with 3 mm yttria-stabilized zirconia beads for 18–24 h, filtered through a 50 µm screen, and deaired under 200–500 mbar vacuum until viscosity stabilizes between 3000–5000 mPa·s at 10 s⁻¹. The tape is cast at a wet thickness of 0.5–2.0 mm and dried at 60–80 °C until residual solvent is below 2 wt%. The debindering step in box or conveyor furnaces proceeds in two stages: a first segment from 150 °C to 280 °C at 0.5–1.0 °C/min to remove plasticizer and side-chain fragments without skinning, and a second segment from 350 °C to 450 °C with a 2–4 h hold in flowing air to oxidize residual carbon. Furnace oxygen levels are held above 10 vol%; carbon residue after burnout is controlled below 0.05 wt% to avoid shifts in dielectric loss tangent. Binder selection for MLCC and LTCC must satisfy RoHS Directive 2011/65/EU Annex II limits of 1000 ppm Pb, 100 ppm Cd, and 1000 ppm Cr(VI), with additional supplier verification under REACH Regulation (EC) No 1907/2006 for SVHC content; automotive MLCC production is embedded in IATF 16949:2016 process control systems. Terminal products include nickel-electrode multilayer ceramic capacitors, LTCC substrates for RF modules, piezoelectric actuator stacks, and solid oxide fuel cell electrolyte tapes. Ramp rates above 1.5 °C/min between 150 °C and 280 °C create blister defects in tapes thicker than 0.8 mm; the binder must not be combined with high-acid-number dispersants that accelerate acetal hydrolysis and destabilize slurry viscosity over 72 h.
PVB WW-A-50 is formulated into gravure-applied heat-seal coatings at 10–20 wt% solids in MEK/ethyl acetate and coated onto aluminium foil at 2–4 g/m² dry coat weight to produce peelable pharmaceutical lidding closures. Gravure cylinders use 70–90 lines/cm electrode-engraved cells and 1–2 µm surface roughness to meter the coating; drying tunnels at 70–100 °C reduce residual solvent to below 100 ppm in the finished lidding stock. The coated foil seals to PVC/PVDC blister films at 140–180 °C jaw temperature, 0.5–1.2 s dwell time, and 3–5 bar sealing pressure; the resulting seal can be tailored from peelable to burst-peel by blending PVB grades with different hydroxyl content. Compliance is anchored to 21 CFR 175.300 for resinous and polymeric coatings on food-contact foil and to EU Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm²; pharmaceutical lidding may require current pharmacopoeia migration and trace-metal testing. Terminal products include unit-dose pharmaceutical blister packs, solvent-free child-resistant lidding, and diagnostic reagent foil pouches. Moisture uptake above 2 wt% in the PVB coating before heat sealing causes blushing and weak seals on PVC; the coating must be kept in sealed foil bags. The solution is incompatible with waterborne in-line primers that carry residual anionic acidity, as pH shift can precipitate PVB at the lap seam.
Magnetic stripe card manufacture uses PVB WW-A-50 as a high-wetting binder at 12–18 wt% of the magnetic coating solids to disperse acicular gamma-Fe2O3 or barium ferrite platelets without pigment aggregation during bead milling. The coating is prepared by dissolving the PVB in a ketone/aromatic solvent mixture, adding the magnetic pigment at 70–80 wt% solids, and milling through a horizontal bead mill with 0.6–0.8 mm ceramic beads until a Hegman grind of 7.5–8 is reached. The resulting dispersion is applied by slot die or engraved roller onto biaxially oriented PET carrier at 8–12 µm wet film thickness, passed through a magnetic orientation field of 1500–2500 G to align the particles, and dried at 50–80 °C before calendering. Encoded stripe conformance for access control and identity cards is tested under ISO/IEC 7811-2:2018 for low-coercivity magnetic stripes and ISO/IEC 7811-6:2018 for high-coercivity stripes; card substrate dimensional and thermal requirements are handled under ISO/IEC 7810:2019 for ID-1 cards. Terminal products include hotel key cards, transit tickets, access control badges, and membership cards with one to three tracks of encoded data. Published data for PVB WW-A-50 in this specific magnetic media configuration is limited; the processing window above is derived from general PVB magnetic coating literature and converter batch records. The coating loses dimensional stability above 60 °C, so lamination onto PVC card cores must not exceed 90 °C for more than 5 min.
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PVB WW-A-50 is a medium-viscosity polyvinyl butyral resin produced by acid-catalyzed acetalization of polyvinyl alcohol with butyraldehyde. The resin is supplied as a free-flowing powder and is built from a random copolymer containing vinyl butyral, vinyl alcohol, and residual vinyl acetate repeating units. In this product class, butyral content is commonly controlled between 70 and 78 wt%, hydroxyl content between 18 and 21 wt%, and residual vinyl acetate below 3 wt%. These ranges are class-level release windows; the certificate of analysis for PVB WW-A-50 should be reviewed for lot-specific values. Loose bulk density is typically 0.25–0.35 g/cm³, and tapped bulk density is near 0.45 g/cm³. Differential scanning calorimetry according to ISO 11357-2 normally places the resin glass transition temperature between 65 and 75 °C before plasticization. The residual moisture of unfilled resin should be maintained below 0.5 wt% because higher moisture accelerates hydrolysis during melt processing and alters solution rheology.
The product is used where a balance of adhesion, tensile strength, and plasticizer uptake is required. Target applications include laminated safety glass interlayer film, solvent-borne primer and ink binders, ceramic green-tape binders, and heat-sealable coatings. In interlayer film, PVB WW-A-50 is usually plasticized with triethylene glycol bis(2-ethylhexanoate) or dibutyl sebacate at loadings from 25 to 35 phr. The selection of the “A-50” viscosity designator influences the plasticizer absorption rate and final melt viscosity; therefore extrusion conditions must be adjusted relative to lower molecular weight grades.
| Parameter | Typical window | Test method |
|---|---|---|
| Butyral content | 70–78 wt% | Internal titration / supplier COA |
| Hydroxyl content | 18–21 wt% | Internal titration / supplier COA |
| Vinyl acetate content | < 3 wt% | Internal titration / supplier COA |
| Solution viscosity, 10 wt% in ethanol/toluene | 40–60 mPa·s | ISO 2555 or Brookfield RV |
| Volatile content | ≤ 0.5 wt% | ISO 3251 |
| Ash content | ≤ 0.1 wt% | ISO 3451-1 |
| Density | 1.08–1.12 g/cm³ | ISO 1183-1 |
| Glass transition temperature | 65–75 °C | ISO 11357-2 |
The numerical 50 in the designation is interpreted as a nominal medium-viscosity signal, not as a universal solvent specification. When PVB WW-A-50 is dissolved at 10 wt% in a solvent blend of ethanol and toluene at 25 °C, typical solution viscosity falls between 40 and 60 mPa·s. Solvent choice changes the viscosity. Alcohol-rich systems interact strongly with the hydroxyl groups and produce lower viscosity than ketone-rich systems. Solutions prepared for gravure coating commonly use 10–15 wt% resin solids in isopropanol/acetone or ethanol/toluene blends. Reverse-roll applicators with a gap setting between 50 and 120 µm can deposit dry films from 5 to 25 µm at line speeds of 15–40 m/min. Production-scale coating operations using PVB WW-A-50 should install 25 µm absolute filtration upstream of the coating head to remove gel bodies and reduce die streaking. High solids above 20 wt% are generally avoided because the solution can exhibit thixotropic recovery and spitting at the gravure nip.
Water addition to the solvent blend is a critical process limit. Because PVB WW-A-50 carries a higher hydroxyl fraction than lower-hydroxyl butyral resins, it tolerates some alcohol-water mixtures, but phase separation occurs when water content exceeds roughly 4–6 wt% of the solvent blend at 20 °C. This limit should be verified by turbidimetric titration for each solvent batch, since residual acetate and butyral contents shift the cloud point. Coaters that pre-mix resin in alcohol and then dilute with water at high shear may generate microgel particles that appear as fisheyes in the cured coating.
In ceramic green-tape processing, PVB WW-A-50 is dissolved in toluene/ethanol mixtures and combined with barium titanate or alumina powders. Slurry viscosity is adjusted to 1,000–5,000 mPa·s for doctor-blade casting, and the PVB acts as the primary thermoplastic binder. Residual ash below 0.1 wt% is critical because high ash creates dielectric defects in multilayer ceramic capacitors. The product is chosen over lower-viscosity binders when green tape requires higher tensile strength for punching and registration. Binder burnout occurs in air at 350–450 °C; thermogravimetric analysis according to ISO 11358-1 is used to confirm complete removal. Published data for PVB WW-A-50 in specific ceramic tape formulations is limited, so slurry rheology and burnout profiles should be generated for each powder system.
Melt processing of PVB WW-A-50 into interlayer film requires careful moisture management. Resin received with residual moisture above 0.3 wt% should be pre-dried in a dehumidified hopper at 55–65 °C for 4–6 h before compounding. The resin is dry-blended with plasticizer at 25–35 phr and fed into a counter-rotating twin-screw extruder with an L/D ratio of at least 30:1. Barrel temperatures are typically set from 170 to 220 °C, and melt temperature should remain below 230 °C. Higher melt temperature accelerates deacetalization and produces acetaldehyde and conjugated unsaturation, causing yellowing and adhesion drift.
Plasticized PVB WW-A-50 exhibits shear-thinning melt rheology with a power-law index commonly between 0.25 and 0.45 at 180 °C. The die pressure in a flat-film line is therefore strongly dependent on throughput, and melt fracture can appear at the die lip if shear rate exceeds the critical shear rate for the plasticizer content. Equipment fitted with a flexible-lip die and automatic thickness scanning is used to maintain film thickness across widths of 1.8–3.2 m. Nominal interlayer thicknesses of 0.38 mm, 0.76 mm, and 1.52 mm are standard for laminated glass, with film gauge variation controlled to ± 0.05 mm in converter specifications.
After extrusion, film is conditioned at 23 °C and 50 % RH to a moisture content below 0.5 wt% before packaging. PVB interlayer film is hygroscopic; exposure at 85 % RH can raise moisture content above 1.0 wt%, which reduces autoclave flow and changes the glass-polymer interfacial adhesion. Packaging in sealed aluminum foil laminate is required. Cold storage at 5–10 °C is used for prolonged shelf life, but film must be conditioned to room temperature before layup to avoid condensation.
Lamination cycles for PVB WW-A-50-based interlayers use vacuum de-airing at 120–130 °C for 30–60 min, followed by autoclave at 1.0–1.5 MPa and 130–140 °C. The heating rate should not exceed 5 °C/min during the autoclave ramp because trapped air and plasticizer migration at the glass edge can produce bubbles.
Adhesion of PVB WW-A-50 to soda-lime float glass is governed by the residual hydroxyl content and the concentration of adhesion-control salts such as potassium acetate or magnesium acetate. In laminated glass manufacturing, salt loadings from 0.02 to 0.10 phr shift pummel adhesion from high delamination toward higher glass retention. Pummel adhesion values are determined after laminate preparation following ISO 12543-4; automotive interlayers commonly target a mean pummel value between 3 and 6. A lower pummel value corresponds to high glass adhesion and may be appropriate for structural glazing, while architectural laminates may require lower adhesion to meet impact retention tests.
Impact performance is evaluated on glass/PVB/glass laminates according to ISO 12543-2 and ANSI Z26.1 or ECE R43, depending on end use. In these tests, thickness selection and plasticizer content are primary variables. PVB WW-A-50 at 0.76 mm thickness is often used in automotive side and windshield constructions, but published data for this specific grade under every regulatory configuration is limited. Manufacturers should generate application-specific data for ballistic, hurricane, or sound-damping laminates.
The hydroxyl content of PVB WW-A-50 influences both water absorption and the dynamic mechanical response of plasticized interlayers. In dynamic mechanical thermal analysis of plasticized film at 1 Hz and 2 °C/min heating, the main tan δ peak of PVB interlayers generally appears between 15 and 35 °C after plasticization, although the exact peak depends on plasticizer type and loading. Hydroxyl groups increase hydrogen-bond density in the amorphous phase, widening the glass transition and raising the storage modulus above the glass transition. This broadening is relevant to sound-damping glazing because the loss factor in the 10–50 °C service window determines acoustic performance. Measurements on beam-shaped laminated glass specimens under ISO 16940 show that the coincidence dip in sound transmission loss is shifted by the interlayer loss factor; however, published data for PVB WW-A-50 in acoustic laminate assemblies is limited, and prototype testing on the target glass configuration is required.
Moisture uptake must be interpreted alongside this viscoelastic behavior. At 23 °C and 50 % RH, plasticized PVB interlayers made from PVB WW-A-50 may reach equilibrium moisture near 0.4–0.6 wt%, depending on plasticizer selection and film thickness. At 85 % RH, values above 1.0 wt% are common. Absorbed water acts as a plasticizer and lowers the glass transition temperature, which can increase damping at low temperature but reduce high-temperature stiffness. Laminators should therefore condition interlayers under controlled humidity before layup and avoid processing on high-humidity days unless the cleanroom is maintained below 25 % RH.
Substitution is not direct because lower-hydroxyl PVB grades such as Butvar B-72 dissolve more readily in non-polar solvents and absorb less atmospheric moisture. PVB WW-A-50, with a higher hydroxyl fraction, improves wetting on metal surfaces and provides more reactive sites for zinc tetroxychromate or phosphate adhesion promoters. In wash primer systems, the resin is first dissolved in isopropanol at 10–20 wt% solids and then acidified with phosphoric acid before combination with pigment. The higher hydroxyl content can shorten induction time, but it also raises moisture sensitivity after cure. Salt-spray testing according to ASTM B117 on cold-rolled steel panels has shown that dry film thickness below 15 µm may develop blistering before 500 h when the coating is not topcoated. For this reason, PVB WW-A-50-based wash primers are usually specified as thin adhesion layers beneath epoxy or polyurethane topcoats, not as standalone barrier coatings.
Another difference is thermal stability. PVB WW-A-50 can tolerate short excursions to 180 °C during cure, but extended exposure above 200 °C causes crosslinking and discoloration. In coil coating, peak metal temperatures are therefore limited below 200 °C unless the formulation contains stabilizers. Lower-hydroxyl PVB types may exhibit less adhesion to bare steel but better humidity resistance, so the selection is dictated by the end-use corrosion specification.
| Parameter | PVB WW-A-50 | Lower-hydroxyl PVB | High-molecular-weight PVB |
|---|---|---|---|
| Hydroxyl content | 18–21 wt% | 11–14 wt% | 18–20 wt% |
| Solution viscosity, 10 wt% | 40–60 mPa·s | 10–20 mPa·s | > 100 mPa·s |
| Typical melt processing range | 170–220 °C | 160–200 °C | 180–230 °C |
| Moisture uptake at 50 % RH | ~0.4 wt% | ~0.2 wt% | ~0.5 wt% |
| Main use | Interlayer film, primers, ceramic binder | Low-viscosity inks and solvent-borne coatings | High-strength film and structural interlayers |
Regulatory documentation for PVB WW-A-50 should be requested from the resin supplier for the specific production site. For adhesives and coatings used in food-contact applications, compliance must be established under FDA 21 CFR 175.105 or 177.1420 where applicable, and the product should be evaluated for residual butyraldehyde and formaldehyde under EU 10/2011 when plastic food contact is relevant. REACH registration for polyvinyl butyral is based on the polymer exemption, but imported compound blends may require substance-volume tracking. For electrical or electronic applications, RoHS requirements apply only to the final article and not to the resin alone. Storage in unopened original bags below 35 °C and below 60 % RH is recommended; under these conditions, the usable shelf life is commonly 24 months from the date of manufacture. Bulk handling systems should be grounded to dissipate static charge because PVB dust can form ignitable dust clouds. Published data for ignition sensitivity of PVB WW-A-50 specifically is limited; therefore dust hazard analysis should be conducted on the actual resin lot and particle-size distribution.
