| HS Code | 249440 |
| Product Name | Butvar B-72 |
| Chemical Name | Poly(vinyl butyral) |
| Appearance | White granular powder |
| Glass Transition Temperature C | 67 |
| Molecular Weight Mw | 170,000-250,000 |
| Hydroxyl Content By Weight | 17.5-20 |
| Acetate Content By Weight | 0-2.5 |
| Butyral Content By Weight | 80-82 |
| Viscosity 10 W V In Methanol At 25 C Cp | 28-34 |
| Solubility | Soluble in methanol, ethanol, isopropanol, and butanol; insoluble in water |
| Acid Number Mg Koh G | <1 |
As an accredited Butvar B-72 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Butvar B-72 is supplied as white granules in a sealed container, commonly packaged in a 1-pound jar. |
| Container Loading (20′ FCL) | Butvar B-72 resin loaded in 20′ FCL, palletized, shrink-wrapped, secured, and protected from moisture for safe transport. |
| Shipping | Butvar B-72 is a polyvinyl butyral resin supplied as a free-flowing powder. It is generally non-hazardous and not regulated as dangerous goods for transport. Ship in sealed containers to prevent moisture absorption and dust generation. Store away from ignition sources, keep dry, and avoid extreme temperatures. |
| Storage | Store Butvar B-72 in a cool, dry, well-ventilated area away from heat, open flames, and strong oxidizers. Keep the container tightly sealed to prevent moisture absorption and contamination. Avoid exposure to direct sunlight. Under proper conditions, shelf life is typically several years. Always follow manufacturer’s safety data sheet for specific requirements. |
| Shelf Life | Butvar B-72 has a long shelf life—many years—if stored cool, dry, and away from light. |
In multilayer ceramic capacitor (MLCC) tape casting, Butvar B-72 is introduced as the high-molecular-weight poly(vinyl butyral) binder in a ternary solvent blend of 60:40 toluene:ethanol or azeotropic methyl ethyl ketone:ethanol. The hydroxyl content of the grade, expressed as poly(vinyl alcohol), falls between 17.5 wt% and 20.0 wt%, and the supplier technical bulletin lists a glass transition temperature near 72 °C. Slurry preparation on production lines uses a high-shear disperser followed by a bead mill charged with 0.4–0.6 mm yttria-stabilized zirconia media; the ceramic solid is typically BaTiO3 with a mean particle size below 0.5 μm, although doped barium titanate and nickel electrode pastes are processed with the same binder system. The sequence of addition is controlled: the dispersant is adsorbed onto the ceramic surface before Butvar B-72 solution is added, preventing competitive displacement that would raise slurry viscosity. Typical slurry solids loading ranges from 45 wt% to 60 wt%, with Butvar B-72 addition between 4 wt% and 8 wt% of ceramic powder. Viscosity is maintained between 800 mPa·s and 3,500 mPa·s at 25 °C using a Brookfield RV spindle at 20 rpm; higher solids are preferred for thin dielectric layers below 5 μm, but shear-thinning behavior must be confirmed by sweep measurements under ASTM D2196.
Casting is performed on a continuous doctor-blade caster with gap settings between 0.3 mm and 0.6 mm, depending on target green tape thickness, which for MLCC production may be 2–15 μm after drying. Drying zone temperatures are staged from 50 °C to 90 °C; residual solvent above 2 wt% in the green tape creates blocking on the roll and must be avoided. Because Butvar B-72 is hygroscopic, ceramic powders are pre-dried at 120 °C for 24 h when ambient relative humidity exceeds 60%. Plasticizer is required to reduce the glass transition temperature of the green tape; common plasticizers include dioctyl phthalate or benzyl butyl phthalate added at 25–40 phr relative to binder. Without plasticizer, the 72 °C glass transition of the resin produces a green tape that cracks during punching and blanking. However, excess plasticizer above 45 phr migrates to the tape surface, increasing tack and causing layer-to-layer adhesion in stacked MLCC builds.
The primary process conflict is binder burnout against retained green strength and carbon residue. Thermo-oxidative decomposition of Butvar B-72 proceeds through side-chain scission and subsequent main-chain oxidation; thermogravimetric analysis under ASTM E1131 in air is used to map the weight-loss profile. Industrial burnout profiles for tapes thicker than 10 μm typically limit ramp rates to 1 °C/min between 200 °C and 450 °C, with a 2–4 h hold at 450 °C before the sintering ramp. Ramp rates above 2 °C/min are associated with blister defects and delamination because decomposition gases cannot escape through the compacted ceramic matrix. The same hydroxyl groups that give Butvar B-72 its high green strength can retain moisture in humid environments, and water evolves during early burnout, so the 200–250 °C window is often held for 1 h. Residual carbon in barium titanate after burnout is kept below 0.1 wt% before densification at 1,100–1,300 °C; carbon levels above this threshold shift dielectric loss. Slurry pH is maintained between 4 and 8 because acid-catalyzed acetal hydrolysis reduces binder molecular weight and lowers green tape tensile strength.
Butvar B-72 functions as the film-forming resin in two-component poly(vinyl butyral) wash primers for steel and aluminium substrates. The base component contains Butvar B-72 at 7–9 wt% in a solvent blend of isopropanol, n-butanol, and toluene; the acid component is phosphoric acid at 2–4 wt% of total primer. When mixed, the acid reacts with the metal surface to produce a phosphate conversion layer while the PVB binder encapsulates zinc phosphate or zinc chromate corrosion inhibitors. The acid-to-resin ratio is maintained near 0.4; higher ratios accelerate acetal hydrolysis and destroy film integrity before the primer can cure. Spray application with suction or pressure-pot equipment at 0.2–0.3 MPa air pressure deposits a dry film thickness of 8–15 μm. The wet film must be allowed to convert the surface for 15–30 min before topcoating; overcoating too early can trap phosphoric acid at the interface and cause intercoat adhesion failure.
Pot life after mixing is limited by heat and acid-catalyzed chain scission of the PVB acetal. At 25 °C, viscosity drift becomes measurable after 6–8 h; above 30 °C, the same drift occurs in half the time. Production batches are therefore split. Storage of the unmixed base component at 5–30 °C is standard; exposure to moisture accelerates the acid component’s absorption of water and should be limited. Adhesion is verified by ISO 2409 cross-cut testing on degreased steel after 24 h ambient cure, and salt spray resistance is assessed per ASTM B117 with scribed panels. Amine-based topcoats should not be applied directly over unaged primer because amine migration can neutralize the acid phosphate layer. The table below lists the test matrix used in metal pretreatment trials.
| Test method | Property evaluated |
|---|---|
| ISO 2409 | Cross-cut adhesion on degreased cold-rolled steel after 24 h |
| ASTM B117 | Neutral salt spray resistance of scribed primed panels |
| ISO 1519 | Cylindrical mandrel bend flexibility and cracking resistance |
| ASTM D3359 | Tape adhesion of topcoat over aged wash primer |
Deposition of flexographic printing inks on corona-treated low-density polyethylene and biaxially oriented polypropylene uses Butvar B-72 as a co-binder in solvent-based ink systems. In this application, the resin contributes adhesion to the modified polyolefin surface and disperses high-surface-area organic pigments. A typical base ink contains 10–15 wt% Butvar B-72, 8–12 wt% nitrocellulose, and 15–20 wt% pigment in an ethanol/ethyl acetate/propyl acetate solvent blend. The ink is adjusted to a #2 Zahn cup flow time of 18–25 s at 25 °C; higher flow times produce film-weight variation on press. Drying is carried out in forced-air dryers at 60–70 °C, because the high-molecular-weight PVB releases solvent more slowly than low-viscosity grades and can retain ethyl acetate after the dryer tunnels. Rub resistance is measured with a Sutherland rub tester per ASTM D5264; blocking resistance is evaluated on face-to-face printed film under 0.1 MPa pressure at 50 °C for 24 h. The hydroxyl-rich structure also increases ink resolubility in ethanol, which is both an advantage for press cleaning and a limitation if the printed surface is exposed to high-humidity or alcohol-containing condensates before lamination. In high-speed gravure above 150 m/min, residual solvent levels are monitored by gas chromatography with a specification below 5 mg/m² on the printed web to avoid lamination odour and delamination.
In magnetic tape coating, Butvar B-72 is introduced into a mixed binder system to wet and stabilise acicular magnetic pigments such as γ-Fe2O3, Co-modified γ-Fe2O3, or barium ferrite. The hydroxyl groups on the PVB chain adsorb onto surface oxide sites of the pigment and reduce reagglomeration during high-shear milling. A production dispersion is processed in a horizontal bead mill with 0.6–0.8 mm zirconia beads at a tip speed of 8–12 m/s; pigment loading is 70–80 wt% of total solids, while Butvar B-72 represents 15–25 wt% of the binder solids. The solvent system is typically cyclohexanone, toluene, and methyl ethyl ketone, with the PVB first dissolved to 10 wt% solids before pigment addition. Crosslinking of the binder with a blocked isocyanate or melamine-formaldehyde resin is required to reduce thermoplastic flow and improve hardness; without crosslinking, the tape loses dimensional stability above 70 °C, close to the resin’s glass transition. Orientation of the acicular particles in a magnetic field is performed after coating; squareness ratio and coercivity are measured by vibrating sample magnetometry. Published data for Butvar B-72 in next-generation metal particle tapes is limited, but the resin remains relevant for archival and specialty audio formulations where long-term magnetic stability and low tape shedding are required. Moisture ingress into the millbase above 60% relative humidity raises viscosity by hydrogen bonding with the hydroxyl sites, so solvent and pigment moisture specifications are enforced before milling.
Modification of nitrile-phenolic structural adhesives with Butvar B-72 introduces controlled thermoplastic flow and improves peel strength on etched aluminium. In a typical two-part or film adhesive formulation, the PVB content is 5–15 wt% of total solids and is blended with a nitrile rubber and a resole phenolic resin on a two-roll mill or in methyl ethyl ketone solution. Cure is performed between 160 °C and 180 °C under 0.3–0.7 MPa pressure for 30–60 min. Lap shear strength on chromic-acid-etched 2024-T3 aluminium is measured per ASTM D1002; toughness improvement is assessed by T-peel per ASTM D1876. Excess Butvar B-72 above 20 wt% of the adhesive solids reduces elevated-temperature shear strength above 80 °C because the thermoplastic domains soften and the adhesive exhibits creep. The hydroxyl groups of Butvar B-72 can react with methylol groups in the phenolic resin, which improves hot strength at the low end of the addition range. In adhesive film production, the viscosity of the solvent-based coating mix is maintained between 2,000 mPa·s and 6,000 mPa·s at 25 °C for knife-over-roll coating. When the adhesive is formulated for food packaging laminating, the relevant US FDA clearance is 21 CFR 175.105, and the formulator must verify that all other components meet the same section.
For temporary protection of polished glass, stainless steel, and optical surfaces during fabrication and shipment, a 10–15 wt% solution of Butvar B-72 in ethanol or a 90:10 ethanol:acetone blend is flow-coated or sprayed to a dry film thickness of 20–30 μm. The dried film is removed by manual peeling after service; reheating above 50 °C is not required for removal. This application is limited to smooth non-porous substrates and does not replace cured masking for abrasive blasting or chemical immersion.
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Butvar B-72 is a thermoplastic polyvinyl butyral resin manufactured by Eastman Chemical Company and supplied as a free-flowing white powder under CAS registry number 63148-65-2. The polymer backbone contains vinyl butyral, vinyl alcohol, and vinyl acetate repeat units. Typical compositional ranges are 18.0–20.0% polyvinyl alcohol and 0–2.5% polyvinyl acetate by weight. The resin has a specific gravity of 1.10, a glass transition temperature of 72–78 °C as measured under ASTM D3418-15, and a weight-average molecular weight reported in manufacturer technical bulletins as 170,000–250,000 g/mol. At 25 °C, a 10% solution in 60:40 toluene:ethanol has a Brookfield viscosity of 170–250 mPa·s. This viscosity specification is the primary constraint in high-solids formulation and separates B-72 from lower-viscosity grades in the same product line. The resin is not supplied pre-plasticized; final film flexibility is controlled by external plasticizers such as dibutyl sebacate or di-2-ethylhexyl phthalate, typically at 20–40 phr. At 20 phr plasticizer, solvent-cast film tested under ASTM D638-14 typically exhibits tensile strength of 35–45 MPa and elongation at break of 50–100%, with exact values dependent on residual solvent content and film drying protocol. Because the powder is hygroscopic, drying at 60–70 °C for 2–4 h is required when ambient relative humidity exceeds 60% or when melt processing is planned. Butvar B-72 should not be confused with Paraloid B-72, an ethyl methacrylate copolymer used in conservation; the shared B-72 designation is not a chemical equivalence.
The primary difference is molecular weight and resulting solution rheology. Butvar B-74, B-76, B-79, and B-98 are progressively lower-molecular-weight alternatives with lower viscosity at equal solids. B-72 is selected when a film or adhesive must resist cohesive failure after solvent removal, while B-79 or B-98 is preferred for high-solids gravure, flexographic, or spray applications where viscosity must remain below 250–500 mPa·s at the coating head. The table below lists typical values from manufacturer technical bulletins; these values are not sales specifications.
| Property | Butvar B-72 | Butvar B-74 | Butvar B-76 | Butvar B-79 |
|---|---|---|---|---|
| Weight-average molecular weight (g/mol) | 170,000–250,000 | 120,000–150,000 | 90,000–120,000 | 50,000–80,000 |
| Viscosity of 10% solution in 60:40 toluene:ethanol at 25 °C (mPa·s) | 170–250 | 100–150 | 45–65 | 12–18 |
| Polyvinyl alcohol content (wt%) | 18.0–20.0 | 17.5–20.0 | 17.5–20.0 | 17.5–20.0 |
| Glass transition temperature (°C) | 72–78 | 72–78 | 72–78 | 72–78 |
Compared with the ethyl methacrylate copolymer commonly designated Paraloid B-72, Butvar B-72 requires polar solvent blends such as 60:40 toluene:ethanol or methyl ethyl ketone–isopropanol for complete dissolution. Paraloid B-72 dissolves in acetone, toluene, or xylene. The polyvinyl butyral backbone provides hydroxyl-mediated adhesion to glass, aluminum, and steel, while the acrylic grade does not contain the same hydroxyl functionality. This difference is critical when the abbreviation B-72 appears in a conservation or coating specification without a polymer class. Other polyvinyl butyral suppliers may offer grades with similar Mw and hydroxyl content, but differences in residual sodium acetate, acetal distribution, and molecular weight distribution can alter solubility, color, and adhesion. A direct substitution into a qualified formulation is not recommended without re-running the viscosity curve and adhesion panels.
In high-shear coating lines operating with direct gravure or reverse roll, the useful solution concentration of Butvar B-72 is limited to 10–15% solids in 60:40 toluene:ethanol. At 15% solids, viscosity can exceed 1000 mPa·s at 25 °C; heated transfer lines at 35–40 °C reduce viscosity enough to maintain uniform wet film. Production-scale coating of PVB solutions typically requires inline filtration through a 100 µm filter to remove undissolved gel specks. Insufficient solvent blending or fast solvent addition can create gel particles at the coating edge; the vessel should be agitated with a high-torque disperser at 300–500 rpm until the solution clears, then held for 4–6 h for complete hydration. Arrhenius-type viscosity reduction between 25 and 40 °C is approximately 2–3% per °C for dilute solutions, although solvent evaporation losses at the higher temperature require closed transfer lines. For spray application, dilution to 5–8% solids and a nozzle pressure of 2–3 bar are typical starting points; atomization should be verified with a particle-size analyzer because B-72 solutions exhibit pseudoplasticity at high shear.
Because the acetal functionality is stable in dilute phosphoric acid, Butvar B-72 is formulated as a wash-primer binder in alcohol–toluene diluent at 0.5–1.0% acid concentration and retains adhesion to degreased steel after crosslinking with a phenolic or epoxy resin. Crosshatch adhesion to cold-rolled steel after 24 h cure is typically 4B–5B under ASTM D3359-17 when the primer is applied at 8–10 µm dry film thickness. Salt spray exposure under ASTM B117-19 for 500 h does not guarantee corrosion protection unless an inhibitive pigment is incorporated; the PVB binder functions as a film former, not as an active corrosion inhibitor. Formulation with strongly alkaline pigments is not recommended because the acetal groups are sensitive to hydrolysis above pH 8.5.
Butvar B-72 dissolves in lower alcohols, glycol ethers, esters, ketones, and chlorinated solvents, but not in aliphatic hydrocarbons or water. The most common solvent blend is 60:40 toluene:ethanol; substitution of ethanol with isopropanol increases viscosity, while addition of methyl ethyl ketone lowers viscosity and accelerates drying. The solvent should not contain more than 2% water because water acts as a nonsolvent and promotes phase separation. Solution viscosity is routinely measured under ASTM D2196-20 at 25 °C; for quality control, viscosity drift over 28 days should remain within ±10% of initial value.
Viscosity at a given solids content depends on molecular weight and solvent composition. For B-72, a 10% solids solution in 60:40 toluene:ethanol falls between 170 and 250 mPa·s. Raising solids to 15% can increase viscosity to 1000–1500 mPa·s depending on solvent grade. This nonlinearity means that solvent dilution curves must be generated empirically for each batch; published data for this specific configuration is limited. The addition of plasticizer reduces solution viscosity, but plasticizer should be added after the resin is fully dissolved to avoid swelling and slow dissolution.
Butvar B-72 is not directly equivalent to the plasticized PVB sheet used in laminated glass. Laminated-glass interlayer uses PVB with a plasticizer content of 30–50 phr and a lower residual hydroxyl content in some grades to control adhesion. B-72 can be plasticized to similar flexibility, but the resulting sheet must be tested for optical haze under ASTM D1003-21 and pummel adhesion under ECE R43 if used in safety glazing. Adhesion to untreated low-density polyethylene is negligible; corona treatment to 38–42 mN/m surface energy is needed. On glass, the resin bonds through hydroxyl groups, but high humidity during cure can reduce interfacial strength. Peel adhesion to aluminum foil under ASTM D903-98 depends on plasticizer and cure temperature; published data for this specific configuration is limited.
Butvar B-72 can be extruded or calendered only after plasticizer addition and rigorous moisture control. The processing window at the die is 170–195 °C; residence time should be kept below 3–5 min to prevent yellowing from acetal degradation. Twin-screw compounding is performed with an L/D ratio of at least 40:1 and moderate-shear screw elements, because high shear raises melt temperature above the degradation threshold. Pre-drying at 60–70 °C to a moisture content below 0.2% is required; residual moisture generates bubbles and surface roughness in extruded sheet. A vented barrel is recommended, but vacuum should be limited to avoid drawing low-molecular-weight plasticizer.
In injection molding of plasticized B-72, the barrel profile is typically set at 150/170/185/190 °C from feed to nozzle, with a mold temperature of 20–40 °C. Hot runners are not recommended because residence time in the manifold causes gel formation. These boundaries are based on the thermal degradation behavior of polyvinyl butyral and are not grade-specific guarantees; published data for this specific configuration is limited.
In ceramic green-tape casting, Butvar B-72 is selected over ethyl cellulose when low residual carbon after burnout is required. Thermogravimetric analysis under nitrogen shows a degradation onset near 350 °C; ethyl cellulose leaves higher residual carbon. For tape casting, the resin is dissolved at 8–12% solids in 60:40 toluene:ethanol, then mixed with dispersant and plasticizer before ball milling. The mill slurry should be sealed to limit solvent loss to below 2% per 24 h because evaporation increases viscosity and changes tape thickness.
Butvar B-72 is also used in heat-activated adhesives for paper, fabric, and metal foils. When compounded with a blocked isocyanate or phenolic resole, the hydroxyl content of 18.0–20.0% provides crosslink sites. The recommended cure window for a B-72/resole system is 150–170 °C for 10–20 min; temperatures above 200 °C cause yellowing and loss of toughness due to acetal degradation. The material should not be combined with amine-based epoxy catalysts in solvent mixtures because alkaline conditions promote deacetalization and increase viscosity drift during storage.
The powder should be stored below 35 °C and protected from moisture. Opened bags should be re-closed under nitrogen if ambient relative humidity exceeds 60%, because moisture absorption changes flow properties and can cause agglomeration in volumetric feeders. In solvent plants, dust-free transfer systems should be grounded; the minimum ignition energy of the powder is low enough to require inerting when handling large quantities, but published data for this specific configuration is limited.
Compliance statements for food-contact use must be verified against FDA 21 CFR 175.105 for adhesives and 21 CFR 175.300 for resinous and polymeric coatings; not every Butvar B-72 shipment is assigned the same food-contact clearances. Under European Union REACH, polyvinyl butyral is registered as a polymer, and the manufacturer should be consulted for substance volume tracking. Solvent-based preparations containing Butvar B-72 require flammability classification according to GHS and local VOC limits. The resin itself is not a hazardous mixture under CLP, but dust from the powder should be controlled to avoid combustible dust concentrations.
