| HS Code | 402063 |
| Chemical Name | Poly(vinyl acetate) resin |
| Cas Number | 9003-20-7 |
| Chemical Formula | (C4H6O2)n |
| Physical Form | Solid flakes |
| Appearance | White to off-white flakes |
| Odor | Mild, characteristic faint odor |
| Specific Gravity | 1.18 at 20°C |
| Bulk Density | Approximately 600 kg/m³ |
| Refractive Index | 1.466 |
| Molecular Weight | Grade dependent; typical Mw 50,000-200,000 |
| Glass Transition Temperature | Approximately 30°C |
| Softening Point | 35-50°C depending on grade |
| Solubility | Soluble in methanol, ethanol, ethyl acetate, acetone, methyl ethyl ketone, and aromatic hydrocarbons; insoluble in water, gasoline, and aliphatic hydrocarbons |
| Viscosity | Grade dependent; solution viscosity increases with molecular weight |
| Tensile Strength | Approximately 15-30 MPa depending on grade and testing conditions |
| Elongation At Break | Typically 100-300% depending on formulation |
| Water Absorption | Low; less than 2% after 24-hour immersion |
| Dielectric Constant | Approximately 3.5-3.8 at 1 kHz |
| Storage Stability | Stable under normal dry, cool storage; avoid prolonged exposure to heat and moisture |
As an accredited PVAc Resin Flakes factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | PVAc Resin Flakes packaged in 25 kg multi-wall paper bags with polyethylene liner, palletized and shrink-wrapped. |
| Container Loading (20′ FCL) | 20′ FCL container loading of PVAc resin flakes: bagged, palletized, securely stowed, ventilated, protected from moisture for safe transport. |
| Shipping | PVAc Resin Flakes ship as non-hazardous, stable polymer material. Pack in polypropylene woven bags with polyethylene liners, palletized and stretch-wrapped for moisture protection. Keep dry, ventilated, and away from heat sources. Suitable for standard truck or sea freight containers, avoiding direct sunlight and humidity during transit. |
| Storage | Store PVAc resin flakes in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid contact with oxidizing agents. Maintain stable temperatures and proper labeling. Under these conditions, shelf life is typically preserved for an extended period. |
| Shelf Life | Shelf life: 24 months when stored sealed in a cool, dry place, protected from moisture and direct sunlight. |
Polyvinyl acetate resin flakes are dissolved at 20–40 wt% solids in an ethyl acetate:MEK:toluene blend for solvent-borne laminating adhesives used in flexible packaging. The resin is charged after the ester and ketone are combined; toluene is introduced later to regulate evaporation rate. Batch viscosity is measured at 25°C with a Brookfield RV spindle 4 at 20 rpm, and the target is typically 500–2,500 mPa·s for gravure or reverse-roll application. Higher-molecular-weight flakes produce greater stringiness and require additional solvent to maintain the same wet coat weight. On a production coater operating at 120–250 m/min, a wet film of 3–6 µm is applied to polyester or oriented polypropylene and dried in a three-zone oven with zone temperatures of 60°C, 80°C, and 100°C. Flake moisture above 0.3 wt% often generates solution haze; pre-drying in a forced-air hopper at 45°C for 2–4 h is required when storage RH exceeds 60%. The terminal structures are multilayer snack and confectionery pouches. Where the finished laminate enters food contact, the adhesive is formulated to comply with FDA 21 CFR 175.105 or Regulation (EC) No 1935/2004 in the European converting zone. A process boundary is external plasticizer tolerance; when a citrate ester is added above 15 wt% to lower heat-seal temperature, roll blocking can occur at 35°C storage.
In paper core and tube winding, the limiting variables are open time and wet tack rather than final tensile adhesion. Flake-grade PVAc is typically dissolved at 25–35 wt% solids in ethyl acetate or acetone. A high-viscosity solution of 1,200–2,000 mPa·s at 25°C is applied at 80–120 g/m² to spiral-wound paper plies. The adhesive must retain tack for 8–15 s after transfer to the paper surface because the winding mandrel pulls the plies at 40–80 m/min. If the resin flakes contain more than 0.3 wt% low-molecular-weight oligomer or free monomer, open time collapses and file-edge lift becomes visible on the finished core. Terminal products include paper cores for textile rolls, tape cores, and tubular packaging. In the European converting sector, adhesive systems intended for indirect food contact are assessed under Regulation (EC) No 1935/2004 and may need to comply with the overall migration limits in Commission Regulation (EU) No 10/2011 when the finished article is a food-contact core. A production-scale failure observed on spiral winders is gellation in the return doctor blade reservoir because acetone-rich solvent evaporates preferentially; solvent blends containing 10–20 vol% n-propyl acetate reduce this effect but increase dry time.
The selection of PVAc flake grade for chewing gum base is governed by molecular weight, residual vinyl acetate monomer, and softening point. The material is permitted as a masticatory substance in FDA 21 CFR 172.615. Batches are normally specified with an ASTM E28 softening point between 65°C and 100°C; the lower end gives softer chew and faster flavour release, while the upper end provides longer chew and higher cold-flow resistance. The gum base is compounded in a sigma-blade mixer at 55–65°C with food-grade elastomers, waxes, plasticizers, and fillers. PVAc content in the finished gum base can range from 10 wt% to 40 wt% depending on the desired texture profile. Terminal products include compressed gum, pellet gum, and sugar-free coating centres. Migration kinetics in the gum matrix determine whether the low-molecular-weight fraction blooms to the surface; grades with broad molecular weight distribution show earlier texture hardening under 40°C shelf-life testing. Residue control is part of the trust boundary; food-grade specifications require compliance with JECFA provisions where applicable. Published data for specific molecular weight distributions in proprietary gum bases is limited; manufacturing practice relies on sensory panel texture mapping in addition to numerical rheological data.
| Application segment | Reference standard or regulation | Controlling parameter |
|---|---|---|
| Solvent laminating adhesive | FDA 21 CFR 175.105, ASTM D1876 | Residual solvent, T-peel strength |
| Paper tube winding | EU No 1935/2004, EU No 10/2011 | Overall migration, open time |
| Chewing gum base | FDA 21 CFR 172.615, JECFA | Softening point ASTM E28, molecular weight |
| Heat-seal lacquer | FDA 21 CFR 175.300 | Heat-seal strength ASTM F88 |
| Wood assembly adhesive | EN 204, D2/D3 | Conditioned bond strength |
In heat-seal lacquer formulations for paper-to-paper and film-to-board structures, PVAc flakes are compounded into solvent-borne coatings applied at 3–5 g/m² dry weight by direct gravure, then dried below 80°C to prevent coalescence on the web. The activation window on a tray sealer is typically 100–150°C at 2–4 bar for 0.5–2.0 s. When the activation temperature is forced below 110°C with external plasticizers, migration of the plasticizer to the seal interface and into the paper substrate becomes the dominant failure route. A high-plasticizer formulation may pass initial fibre-tear testing but lose seal strength after 60 days at 40°C. Seal strength is measured by ASTM F88 for flexible packages or by spring-loaded tensile gripping for rigid board. Terminal products include pharmaceutical insert wallets, blister lidding, and carton closure lacquers. Where the finished seal contacts food, the coating must meet FDA 21 CFR 175.300 for resinous and polymeric coatings or the applicable national legislation. Amine-based additives or ammonia must be excluded from the solvent system because they accelerate partial deacetylation of PVAc during storage, producing hydroxyl groups that increase low-shear viscosity and create gel bodies.
Resin flakes are also formulated into solvent-borne assembly adhesives for wood veneer and edge-glued panel work. The polymer is dissolved to 45–55 wt% solids in a mixture of methyl ethyl ketone and acetone; a liquid plasticizer, typically a benzoate ester, is added at 5–10 parts per hundred resin. The adhesive is roller-coated at 120–180 g/m² onto both surfaces. Open assembly time is 5–12 min at 20°C and 60% RH; closed assembly time is 15–30 min under cold-press pressure of 0.3–0.7 MPa. Bond strength after 7 days is evaluated according to EN 204 classification. Solvent-borne PVAc flake adhesives often meet D2 but require a crosslinker for D3 water-resistance durability. Where an isocyanate crosslinker is introduced, pot life drops to 4–8 h. Terminal products are laminated furniture components and non-structural edge-glued panels. Field data from cold-press lines show that incomplete flake dissolution produces undissolved particles under veneer; filtration through a 100 µm bag filter before the coater is standard practice.
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PVAc Resin Flakes are solid polyvinyl acetate homopolymer particles produced by free-radical polymerization of vinyl acetate, followed by steam stripping, precipitation, and mechanical flaking. They are supplied as non-tacky flakes rather than powders to reduce dust explosion risk and improve handling in solution cut operations. Specification sheets for solvent-borne grades generally report a non-volatile content of ≥ 98 wt%, moisture ≤ 1.0 wt%, ash ≤ 0.3 wt%, free vinyl acetate monomer ≤ 0.5 wt%, and Brookfield solution viscosity at 10 g/100 mL in ethyl acetate at 25 °C from 8 mPa·s to 120 mPa·s depending on molar mass class. The glass transition temperature is normally 28–32 °C by differential scanning calorimetry per ISO 11357-2, and the degree of hydrolysis for homopolymer grades remains below 3 mol%. These values distinguish PVAc flakes from their water-soluble hydrolysis product, poly(vinyl alcohol), and from ethylene-vinyl acetate copolymers, which are selected when hot-melt processing at 170–190 °C is required.
Solution preparation is the first critical step and is frequently performed in jacketed stainless-steel dissolvers with variable-speed agitation. Low-viscosity grades dissolve in methyl ethyl ketone or ethyl acetate at 25–40 °C within 30–60 min; high-viscosity grades require 60–120 min and may need staged solvent addition to avoid a viscous skin on the solids charge. At solids content below 25 wt%, the solution is Newtonian or weakly shear-thinning; above 30 wt%, pseudoplastic flow becomes measurable on a Brookfield LV viscometer according to ISO 2555. The agitator should operate at 100–300 rpm with a pitched-blade turbine because localized shear heating at faster tip speeds can trigger deacetylation at hot spots. Field experience with a 500 kg dissolver indicated that a medium-viscosity flake charged without pre-sieving formed gel agglomerates at the solvent surface when agitation was below 80 rpm; the resulting production batch required filtration through a 100 µm bag filter to remove fish-eye defects before coating. Moisture is a second thermal controller: water in the solvent or flake accelerates ester cleavage and increases final film haze. At ambient relative humidity above 60 %, flakes should be predried at 35–45 °C for 2–4 h in a dehumidified tray dryer, because residual moisture above 0.5 wt% reduces adhesive clarity on polyester film and can lower peel adhesion by 15–30 % under ASTM D903-98 testing.
On porous paper and wood substrates, the adhesive mechanism relies on solvent-borne penetration, mechanical interlocking, and coalescence. For lithographic laminating adhesives, a 40–55 wt% solids solution in ethyl acetate/toluene blends is applied by reverse-gravure or slot-die coating at 6–12 g/m² dry coat weight. The wet laminate is nipped at 2–5 bar and dried in tunnel ovens with staged air temperatures from 50 °C to 85 °C. Since PVAc is incompatible with aliphatic hydrocarbons, adhesion on clay-coated board is often assessed by fibre-tear percentage rather than peel force alone; industrial operators adjust dry coat weight until fibre failure exceeds 90 %. Published peel values for this exact configuration are limited because fibre failure generally occurs before adhesive failure.
Unmodified PVAc is a thermoplastic with limited resistance to cold flow. In woodworking adhesives, creep resistance is improved by adding 2–5 phr of an emulsifiable isocyanate or zirconium salt crosslinker after dissolution; the resulting joints can satisfy EN 204/205 D2 or D3 water-resistance classes when tested according to the standard schedule. D4 boil-resistance is not attainable with unmodified PVAc flakes alone and requires phenolic or amino resin modification. The selection between PVAc and EVA often occurs at the thermal stability boundary. Thermal gravimetric analysis under nitrogen shows the onset of deacetylation at 120–130 °C, and the liberated acetic acid accelerates further ester cleavage. Therefore, dry PVAc homopolymer is not recommended for single-screw extrusion above 120 °C unless the machine includes devolatilization and the feed is pre-stabilized. EVA copolymers tolerate 170–190 °C compounding because the ethylene units dilute labile acetate sequences, and this difference is decisive for hot-melt bookbinding lines where melt temperature must remain stable during 8–12 h of continuous running.
| Parameter | Test method | Typical range |
|---|---|---|
| Non-volatile content | ISO 3251 | ≥ 98 wt% |
| Moisture content | Karl Fischer titration | ≤ 1.0 wt% |
| Ash content | ISO 3451-1 | ≤ 0.3 wt% |
| Free vinyl acetate monomer | Headspace gas chromatography | ≤ 0.5 wt% |
| Solution viscosity, 10 % in ethyl acetate at 25 °C | ISO 2555 | 8–120 mPa·s by grade |
| Bulk density | ISO 60 | 0.45–0.65 g/cm³ |
| Glass transition temperature | ISO 11357-2 | 28–32 °C |
| Degree of hydrolysis | Titration or FTIR | ≤ 3 mol% |
| Appearance | Visual | White to pale yellow flakes, free of foreign matter |
For model selection, suppliers tend to designate flake grades by nominal solution viscosity rather than by a harmonized numeric code. A grade marked PVAc-25 may indicate a nominal Brookfield viscosity of 25 mPa·s at 10 % solids in ethyl acetate at 25 °C, but the solvent basis and temperature are not standardized across all producers. Low-viscosity flakes below 15 mPa·s are used as resin extenders, remoistening primers, and saponification feedstock; medium-viscosity flakes from 20 mPa·s to 45 mPa·s are used in laminating and wood adhesives; high-viscosity grades above 60 mPa·s improve cohesive strength but require lower coating solids and longer drying capacity. Incoming inspection should not rely on the trade designation alone; the solution viscosity should be verified by ISO 2555 and the residual monomer by headspace gas chromatography.
Remoistenable adhesive coatings are a specific PVAc flake application in which the dry film must be non-blocking during storage but water-activatable during high-speed envelope sealing. A typical formulation combines medium-viscosity flakes, triethyl citrate or dibutyl phthalate at 10–20 phr, and dextrin or gum arabic at 5–15 phr; the solids are usually 35–45 wt% in ethanol/water blends. After drying, the coating remains non-blocking below 35 °C and rewets at 10–25 °C within 2–5 s under a water wheel or lick roller. The critical threshold is plasticizer content: above 20 phr, blocking in stacked envelopes increases; below 10 phr, water re-activation becomes too slow for automated envelope machinery. Manufacturers monitor both blocking resistance and rewet tack because these parameters move in opposite directions with plasticizer addition. Published data for specific commercial formulations is limited, but the plasticizer window is well established in adhesive laboratory practice.
Solvent-cast PVAc films exhibit a refractive index near 1.46–1.47 and are optically clear when residual catalyst and particulates are controlled. Unplasticized films are relatively hard, with elongation at break typically below 20 %; plasticized films can exceed 200 % elongation depending on plasticizer type and film thickness. Residual solvent in laminated structures is measured by gas chromatography according to ISO 11890-2, and residual ethyl acetate above 50 mg/m² is objectionable in food packaging because of odour and potential migration. Final solvent retention is controlled by the last oven zone temperature, air velocity, and web speed; a high-viscosity flake will require either reduced line speed or increased oven residence time because the diffusion coefficient of ethyl acetate in a glassy PVAc film decreases sharply below the glass transition temperature.
For indirect food-contact adhesives, polyvinyl acetate is subject to FDA 21 CFR 175.105, which defines the conditions under which adhesive components may be used in articles contacting food. The masticatory substance listing for chewing gum base in FDA 21 CFR 172.615 includes polyvinyl acetate and requires that the material meet the specified minimum molecular weight and residual vinyl acetate monomer controls; current supplier certificates should be consulted for exact limits because monograph revisions may apply. In the European market, polyvinyl acetate flake suppliers issue REACH-compliant Safety Data Sheets and may reference the harmonized classification for acetic acid generated during thermal degradation, but the polymer itself is normally exempt from registration as a polymer under the REACH monomer-or-other-substance approach.
| Regulatory area | Reference | Required control |
|---|---|---|
| Indirect food-contact adhesives | FDA 21 CFR 175.105 | Adhesive component; residual monomer and migration limits managed by formulator |
| Chewing gum base | FDA 21 CFR 172.615 | Polyvinyl acetate permitted; molecular weight and residual monomer limits apply |
| EU chemicals management | REACH | Registration of monomer and SDS exposure scenarios for downstream use |
| Hazardous substances restriction | RoHS Directive 2011/65/EU | No intentional addition of lead, cadmium, mercury, hexavalent chromium, PBB, or PBDE |
| Wood adhesive durability | EN 204/205 | Unmodified PVAc is D1; D2/D3 requires crosslinker formulation |
Compared with poly(vinyl alcohol), PVAc flakes are solvent-borne, water-insoluble, and lower in hydroxyl functionality; the two products are complementary rather than directly interchangeable. Compared with ethylene-vinyl acetate copolymers, PVAc homopolymer has a sharper thermal degradation onset and cannot be used as a neat hot-melt resin at high extrusion temperatures, but it offers stronger cellulose adhesion and higher remoistenability in paper and packaging applications. Compared with solvent-borne acrylic resins, PVAc flakes generally have lower UV resistance and lower acid number, typically below 1 mg KOH/g, which reduces interaction with alkali-sensitive paper coatings but also limits pigment wetting. Storage stability is best below 35 °C and below 60 % RH; repeated cycling through the glass transition can cause cold flow and form block-like agglomerates. PVAc flakes are incompatible with strong aqueous alkali and primary amines, which catalyze saponification and release acetic acid; therefore, such materials should not be stored in the same solvent cut or added to the dissolver without formulation controls.
