| HS Code | 241116 |
| Chemical Name | Polyvinyl Butyral |
| Cas Number | 63148-65-2 |
| Physical Form | White to pale yellow powder or granules |
| Molecular Weight | 40,000–250,000 g/mol (grade-dependent) |
| Glass Transition Temperature | 60–80 °C |
| Hydroxyl Content | 18–23 wt% |
| Butyral Content | 70–80 wt% |
| Acetate Content | 0.5–3 wt% |
| Viscosity | 5–100 mPa·s (in 10 wt% ethanol solution, 20 °C) |
| Density | 1.08–1.12 g/cm³ |
| Softening Point | 150–180 °C |
| Tensile Strength | 30–50 MPa |
| Elongation At Break | 50–150% |
| Water Absorption | 1–3 wt% (24 h at 23 °C, 50% RH) |
| Solubility | Soluble in ethanol, methanol, isopropanol, and glycol ethers; insoluble in water |
| Refractive Index | 1.49–1.50 |
| Acid Value | ≤1 mg KOH/g |
| Compatibility | Compatible with phenolic resins, epoxy resins, and plasticizers |
As an accredited PVB for Pressure-Sensitive Adhesives & Hot-Melt Adhesives factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Supplied in 25 kg moisture-proof bags, ensuring safe handling and stability for pressure-sensitive and hot-melt adhesive formulations. |
| Container Loading (20′ FCL) | PVB for adhesives is loaded into a 20′ FCL, palletized, secured, and protected from moisture. |
| Shipping | PVB for adhesives ships as a solid resin in sealed, moisture-proof bags or drums. Store in a cool, dry area away from heat sources. Avoid exposure to humidity and dust formation. Non-hazardous cargo, but secure proper ventilation during transport. Handle with care to prevent bag damage and contamination. |
| Storage | Store PVB in a cool, dry, well-ventilated area, away from direct sunlight, heat sources, and open flames. Keep containers tightly sealed to prevent moisture absorption and contamination. Ideal temperature range is below 30°C. Under proper conditions, shelf life typically extends up to 24 months. Avoid stacking excessively to preserve packaging integrity. |
| Shelf Life | Shelf life is typically 24 months when stored in a cool, dry place away from moisture and sunlight. |
In roll-to-roll coating of solvent-cast glass protection films, PVB serves as the elastomeric backbone on comma-bar or slot-die lines running at 18–25 m/min. The resin grade is selected with vinyl alcohol content of 18–20 mol%, dissolved in a 70:30 methyl ethyl ketone/ethanol blend at 18–22 wt% solids, with triethylene glycol bis(2-ethylhexanoate) as plasticizer at 20–30 phr and a hydrogenated rosin ester tackifier at 5–12 phr. A hindered phenol antioxidant is added at 0.3 phr to suppress solution degradation during drying. Dry coat weight is controlled at 20–35 g/m² on a silicone-treated polyester liner through three drying zones at 60 °C, 80 °C, and 115 °C, with final residual solvent held below 50 ppm by gas chromatographic headspace analysis.
The primary process conflict is plasticizer migration. Above 35 phr plasticizer, initial loop tack measured by ASTM D6195-03(2019) increases beyond 12 N/25 mm, but after 7 days at 70 °C in contact with float glass, 180° peel adhesion per ASTM D3330/D3330M-04(2018) Test Method A declines by 30–40% as a low-cohesion boundary layer forms at the glass interface. Moisture is a second threshold: at relative humidity above 60%, evaporative cooling during coating produces surface blushing and micro-void formation. PVB resin must therefore be pre-dried at 60 °C for 2 h, and the casting room maintained below 55% RH. Extended UV exposure causes edge ghosting because residual tackifier domains migrate and increase haze after removal, measured by ASTM D1003-21. Amine-containing glass cleaners or silane coupling agents should be avoided in storage because residual alkalinity accelerates acetal hydrolysis and butyraldehyde release.
PVB is compounded into edge banding hot-melt adhesives on a co-rotating twin-screw extruder with L/D 32:1, barrel zones set from 120 °C in the feed throat to 160 °C at the die, and applied through a slot nozzle at 185–200 °C onto rigid PVC or ABS tapes. A representative formulation contains 25–45 wt% PVB, 20–35 wt% EVA with 28% vinyl acetate, 30–40 wt% aromatic hydrocarbon tackifier, 5–10 wt% Fischer-Tropsch wax, and 0.5 phr antioxidant. Apparent viscosity measured by ASTM D3236-15 with Thermosel spindle SC 27 at 10 rpm increases from 18,000–25,000 mPa·s at 25 wt% PVB to 45,000–60,000 mPa·s at 40 wt% PVB. The material is pseudoplastic, and the apparent viscosity plateau above 190 °C is a false process window because melt pump pressure remains stable while wall shear stress drops, masking reduced melt strength at the slot-die lip.
Shear adhesion failure temperature on 0.4 mm rigid PVC edge banding rises by 12–18 °C when PVB content is raised from 25 to 40 wt%, measured by ASTM D4498-07(2015). Peel strength on melamine-faced MDF under ASTM D1876-08(2015) at 23 °C remains 10–15 N/25 mm. Above 40 wt% PVB, slot-die melt fracture appears unless the die temperature is increased to 210 °C. Residence time above 200 °C must not exceed 8 min because PVB degradation releases butyraldehyde and acetic acid. A nitrogen blanket over the pre-melt reservoir is required for runs longer than 4 h.
| PVB loading (wt%) | EVA 28% VA (wt%) | Hydrocarbon tackifier (wt%) | Viscosity at 190 °C (mPa·s) | SAFT (°C) | 180° peel on melamine-faced MDF (N/25 mm) |
|---|---|---|---|---|---|
| 25 | 35 | 30 | 18,000–25,000 | 62–66 | 11–13 |
| 35 | 25 | 30 | 30,000–38,000 | 70–74 | 12–14 |
| 45 | 15 | 30 | 45,000–60,000 | 78–84 | 10–12 |
Profile wrapping lines operating above 80% relative humidity require PVB granules to be pre-dried in a desiccant-bed dryer with -40 °C dew point to 0.02% moisture by Karl Fischer titration before compounding. Residual moisture above 0.05% generates micro-foam in the slot-die melt film and lowers peel adhesion to PVC profile wrap by 20–30% under ASTM D1876-08(2015).
For pleated filter element assembly, a PVB-based hot melt is compounded at 170–185 °C with a semicrystalline polyamide and a modified polyolefin elastomer. The melt is applied by roll coater to steel or polyamide end caps before the pleated cellulose/synthetic media package is inserted. Lap shear strength on electrogalvanized steel per ISO 4587:2003 is typically 4.5–6.0 MPa at 23 °C for a bondline thickness of 0.1–0.2 mm. After immersion in SAE 15W-40 oil at 120 °C for 168 h, shear strength retention is 70–80% only when the PVB is not extended with monomeric adipate plasticizer. Monomeric esters migrate into the filter media and reduce media burst strength by more than 25%; polymeric plasticizers or plasticizer-free grades are used where oil contact is continuous. The process limitation is residence time: in a double-arm kneader with nitrogen blanket, the compounded melt should be discharged within 15 min to limit oxidative yellowing. Published multi-run data for this specific filter media configuration is limited; the cited ranges reflect coil-laminated adhesive qualification reports rather than universal design values.
When PVB is used as a high-temperature shear modifier in acrylic pressure-sensitive tape for engine-compartment wire harnesses, the solvent-based adhesive is slot-die coated at 35–50 g/m² onto a 25 μm PET film and dried in a three-zone oven at 80 °C, 100 °C, and 120 °C. The addition of 10–15 wt% PVB raises shear adhesion failure temperature by 15–20 °C under ASTM D4498-07(2015), but reduces 180° peel on stainless steel by 1.5–3.0 N/25 mm under ASTM D3330/D3330M-04(2018). After heat aging at 125 °C for 500 h, the PVB-modified acrylic tape retains more than 90% of its initial static shear performance, while an unmodified acrylic control loses 25–30%. The low-temperature tack limit is the main constraint: at -10 °C, loop tack per ASTM D6195-03(2019) falls below 2 N/25 mm unless PVB content is held below 12 wt% and the acrylic base polymer has a glass transition temperature below -20 °C.
PVB can replace EVA in slot-die or sprayable hot-melt formulations for laminating polyester textile to open-cell polyurethane foam in automotive seating. The hot melt is applied at 160–175 °C at 12–20 g/m², with nip pressure set at 0.4 MPa and open time held between 15 s and 25 s. Peel strength after lamination measured by ISO 11339:2022 is 8–12 N/25 mm at 23 °C. Monomeric phthalate plasticizers must be excluded because they migrate into open-cell polyurethane foam within 48 h at 70 °C and produce yellow staining visible under ISO 105-A02 grey scale. Cyclohexanedicarboxylate or polymeric citrate esters with molecular weight above 400 g/mol reduce plasticizer loss to less than 0.5% by ASTM D1203-16. After 500 h at 85 °C/85% RH, peel retention above 80% is achievable only with vinyl alcohol content below 20 mol% because higher hydroxyl grades absorb moisture and reduce hot-tack. The formulation is incompatible with amine-based catalysts used in polyurethane foam; residual amine accelerates acetal hydrolysis at lamination temperatures.
For laminating heat-strengthened glass to aluminum or stainless steel in interior partitions, PVB is solvent-cast or hot-pressed as an interlayer adhesive. The grade selected carries 18–20 mol% vinyl alcohol, compounded with 15–25 phr plasticizer and 0.5–1.0 wt% glycidoxypropyltrimethoxysilane. Lap shear strength on aluminum per ISO 4587:2003 is 5.0–7.5 MPa when the hydroxyl-to-plasticizer ratio is maintained between 2.5 and 3.5. Below 2.0, plasticizer surface accumulation lowers shear strength; above 4.0, the interlayer becomes inflexible and low-temperature impact peel fails. After 7 days in damp heat at 85 °C/85% RH, adhesion retention above 75% requires glass surface contamination below 5 µg/cm² and application of a silane primer. The adhesive must not be combined with amine-containing edge sealants because residual amine catalyzes acetal hydrolysis and butyraldehyde release.
| Application | Standard / Method | Property | Target range or requirement |
|---|---|---|---|
| Solvent-cast glass PSA | ASTM D3330/D3330M-04(2018) Test A | 180° peel on float glass after 15 min dwell | 6–10 N/25 mm |
| Solvent-cast glass PSA | ASTM D6195-03(2019) | Loop tack | 8–12 N/25 mm |
| Edge banding HMA | ASTM D3236-15 | Apparent viscosity at 190 °C | 25,000–60,000 mPa·s |
| Edge banding HMA | ASTM D4498-07(2015) | Shear adhesion failure temperature | ≥75 °C |
| Filter HMA | ISO 4587:2003 | Lap shear on steel | ≥4.5 MPa |
| Textile lamination HMA | ISO 11339:2022 | T-peel at 23 °C | 8–12 N/25 mm |
| Glass-to-metal adhesive | ISO 4587:2003 | Lap shear on aluminum | ≥5.0 MPa |
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PVB resin for pressure-sensitive adhesives and hot-melt adhesives is an acetalization product of polyvinyl alcohol and butyraldehyde, retaining a controlled hydroxyl fraction along the polymer backbone. Commercial grades used in adhesive compounding include Mowital B 30 H, Mowital B 60 H, Butvar B-72, Butvar B-74, and equivalent S-Lec grades. No single model designation covers the product class; grade selection is governed by solution viscosity, residual polyvinyl alcohol content, acetate content, glass transition temperature, and particle morphology. Typical residual hydroxyl content is 11–25 wt%, residual acetate is ≤3 wt%, and butyral content is 75–88 wt%. The resin is soluble in alcohols, ketones, glycol ethers, and aromatic/alcohol blends, but insoluble in water and aliphatic hydrocarbons. In hot-melt systems, it contributes polar adhesion to glass, metal oxides, and primed polyester; in pressure-sensitive adhesive blends it functions as a high-glass-transition cohesive modifier rather than as a base elastomer.
Residual hydroxyl content controls hydrogen bonding, moisture uptake, plasticizer compatibility, and melt viscosity. Low-hydroxyl grades in the 11–13 wt% range show lower equilibrium moisture gain and lower melt viscosity at comparable molecular weight, but reduced specific adhesion to glass. Intermediate grades with 17.5–21 wt% polyvinyl alcohol content provide the highest lap shear on glass and aluminium in laminating hot melts. High-hydroxyl grades above 21 wt% require pre-drying and produce higher melt viscosity, which complicates slot-die coating and gravure application. Glass transition temperature measured by ISO 11357-2 typically falls between 62°C and 78°C for adhesive-grade resins. Softening point measured by ASTM E28 is grade-dependent and generally above 110°C. Acetate content, normally below 3 wt%, influences solubility and plasticizer uptake; elevated acetate lowers hydroxyl-associated viscosity but also lowers tensile strength and high-energy-surface adhesion.
Solution viscosity is the most widely used incoming quality-control parameter because melt flow rate alone does not capture the shear-thinning and plasticizer response of PVB. The data in Table 1 are compiled from published technical datasheet values for representative adhesive grades, with Brookfield viscosity measured at 10 % solids and 20°C. Butvar grades are measured in a 60:40 toluene/ethanol blend; Mowital grades use ethanol.
| Grade | 10% solution viscosity (mPa·s, 20°C) | Tg (°C, ISO 11357-2) | Residual PVOH (wt%) | Typical adhesive use |
|---|---|---|---|---|
| Mowital B 30 H | 2.5–4.0 | 68 | 18–21 | Low-viscosity solvent PSA modifier and plasticized HMA |
| Mowital B 60 H | 8.0–12.0 | 70 | 20–25 | HMA cohesive-strength additive for glass and metal |
| Butvar B-72 | 12–18 | 72–78 | 17.5–20.0 | Laminating HMA and cast film adhesive |
| Butvar B-74 | 20–35 | 72–78 | 17.5–20.0 | High-cohesion laminating and film adhesive |
| Butvar B-76 | 8–12 | 62–68 | 11–13 | Lower-moisture HMA and plasticizer-resistant PSA |
| Butvar B-79 | 7–10 | 70 | 10.5–13 | Low-viscosity melt adhesive with reduced hydroxyl |
Table 1 is a screening compilation, not a specification; individual lots must be verified against the supplier certificate of analysis. The limited published melt-flow data for PVB means that solution viscosity, residual hydroxyl content, and glass transition temperature are the practical specification controls for incoming adhesive raw material.
Substitution of EVA by PVB in hot-melt laminating adhesives is not a drop-in replacement. PVB increases melt viscosity and narrows the melt-temperature window. On corotating twin-screw extruders with L/D 32:1–44:1 and vacuum venting, PVB/HMA compounds are typically processed at melt temperatures of 150–180°C. Barrel temperatures above 200°C accelerate liberation of butyraldehyde and discoloration; production lines therefore use temperature-controlled melt reservoirs and heated hoses held at 160–180°C. Hot-melt viscosity measured by ASTM D3236 with a Brookfield Thermosel at 160°C commonly exceeds 10,000 mPa·s for unplasticized medium-molecular-weight grades. Formulators reduce viscosity to 5,000–15,000 mPa·s by adding benzoate or citrate plasticizers at 5–20 phr. Higher plasticizer loading reduces lap shear but improves wet-out on corona-treated polyester film. Slot-die pressure fluctuation and edge-bead instability are observed when melt viscosity exceeds approximately 20,000 mPa·s at 160°C. The processing advantage over EVA is higher glass adhesion and tensile strength; the limitation is the narrower operating window and the need for moisture control.
Plasticizer selection is a critical compounding variable. Polar esters such as acetyl tributyl citrate, triethylene glycol bis(2-ethylhexanoate), and selected benzoates solvate PVB without phase separation at up to 20 phr; paraffinic mineral oil and low-polarity polyisobutylene are generally incompatible and produce haze or surface exudation. Migration kinetics in PVB matrices are slower than in EVA because hydroxyl-group hydrogen bonding restricts plasticizer diffusion. This improves aged adhesion retention but increases the time required to reach equilibrium mixing in batch sigma-blade mixers. Production-scale experience indicates that adding plasticizer to the mixer bowl before PVB powder reduces torque compared with reverse addition, although published torque data for this exact configuration is limited. Free-flowing PVB powder with bulk density between 0.3 g/cm³ and 0.5 g/cm³ is used for gravimetric feeding; densified or pelletised grades with bulk density above 0.6 g/cm³ reduce dust and segregation in downstream coating rooms.
In solvent-borne pressure-sensitive adhesive compounding, PVB is typically incorporated at 5–15 wt% of total solids into acrylic or styrenic block copolymer formulations. The resin raises the glass transition of the dried film, shifts the plateau modulus upward, and increases shear holding power measured by PSTC-107 or ASTM D3654. It is not a tackifier and typically reduces loop tack and 180° peel on low-energy substrates if total loading exceeds 15 wt%. Published data for this specific configuration is limited, but production coating trials show that 10 wt% PVB addition can reduce cold flow in transfer films and improve die-cut edge cleanout. The resin is dissolved at 15–25 % solids in ethanol/toluene or ethyl acetate/ethanol blends. Filtration through 10 µm absolute-rated filter cartridges is required to remove gel particles and reduce coating streak defects. Compared with rosin ester tackifiers, PVB contributes less ambient-temperature pressure-sensitive tack but better temperature resistance and optical clarity. It is generally not used as the primary PSA elastomer because the unplasticized film is too rigid and its glass transition is too close to room temperature for cold-tack performance.
PVB is hygroscopic because of its residual hydroxyl content. Equilibrium moisture in pellets stored at 23°C and 50 % relative humidity is typically below 1.5 wt%, but material exposed to RH > 60 % can exceed 2.5 wt%. Moisture measurement by ISO 15512 is recommended before melt compounding. Best practice is to pre-dry resin in desiccant or vacuum dryers at 60–70°C for 4 h to below 0.5 wt%; higher drying temperatures can cause particle fusion in static tray dryers. Wet resin produces bubbles and pinholes in slot-die coating, hydrolytic molecular-weight loss during melt processing, and increased odour from butyraldehyde release. Strongly acidic tackifier resins should be avoided because acid-catalysed acetal hydrolysis can liberate butyraldehyde and reduce molecular weight. Long-term storage requires sealed, moisture-barrier packaging; opened bags should be consumed within 24 h when ambient packaging-area humidity exceeds 55 %.
Specification limits for hot-melt and PSA grades should include residual volatile matter. Moisture and residual solvent below 0.5 wt% are required for melt processing. Solution viscosity tolerance is commonly ±10 % of the supplier nominal value. Ash residue after 800°C ignition is often specified below 0.1 wt%. Silica or talc antiblocking agents may be added to powder grades at 0.5–2 wt% to improve feeding; these residues must be considered in optical film applications where haze is controlled by ASTM D1003.
Against conventional hot-melt adhesive polymers, PVB is differentiated by high glass transition temperature, high tensile strength, and specific adhesion to high-energy surfaces. Table 2 provides a comparative screening matrix based on published typical properties and standard test methods.
| Property | PVB adhesive grade | EVA 18–28 wt% VA | APAO | Dimer acid polyamide |
|---|---|---|---|---|
| Glass transition, ISO 11357-2 | 62–78°C | -30 to 0°C | -30°C | 30–50°C |
| Softening point, ASTM E28 | 110–160°C | 80–120°C | 90–140°C | 100–160°C |
| Melt viscosity at 160°C | High, often >10,000 mPa·s | Low, typically <5,000 mPa·s | Low, typically <5,000 mPa·s | Medium, 5,000–15,000 mPa·s |
| Adhesion to glass | High | Moderate | Low | Moderate |
| Adhesion to untreated PE/PP | Poor | Moderate | High | Moderate |
| Moisture sensitivity | High | Low | Low | Moderate |
| Food-contact options | FDA 21 CFR 175.105 where formulated | FDA 21 CFR 175.105 | FDA 21 CFR 175.105 | FDA 21 CFR 175.105 |
The most consequential difference is the polarity of the PVB backbone. EVA and APAO rely on ethylene or propylene chain segments and show better adhesion to nonpolar olefins; PVB bonds preferentially to glass, ceramic frit, aluminium, and polyester. The operational boundary is therefore substrate-dependent: PVB is not recommended for untreated polyethylene or polypropylene without a tie layer or surface treatment. Alkaline fillers should be screened because they can neutralise acidic stabilisers and shift the resin pH. In comparison with dimer acid polyamide, PVB offers lower melt processing temperature but lower thermal resistance above 120°C; polyamide remains preferable for sustained service above 120°C. PVB also exhibits excellent optical clarity and resistance to aliphatic hydrocarbons, but ketones and alcohols redissolve the adhesive.
Published data for PVB in pressure-sensitive adhesives under ISO 11339 T-peel or PSTC-5 loop tack is more limited than for EVA hot-melt systems. Process validation on the target coating line is required before grade substitution. The primary operational boundaries are melt temperature below 200°C, pre-dried moisture below 0.5 wt%, and exclusion of strongly acidic tackifier components to prevent acetal hydrolysis.
