| HS Code | 575954 |
| Chemical Name | Vinyl Acetate Monomer |
| Cas Number | 108-05-4 |
| Molecular Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Purity | ≥99.9% |
| Appearance | Clear colorless liquid |
| Water Content | ≤0.05% |
| Acidity As Acetic Acid | ≤0.005% |
| Inhibitor Hydroquinone Content | 3-5 ppm |
| Boiling Point | 72.7°C |
| Flash Point | -8°C (closed cup) |
| Density At 20c | 0.932 g/cm3 |
| Refractive Index At 20c | 1.394 |
| Color Apha | ≤10 |
As an accredited Electronic Grade Reagent VAM (Electronic Adhesive Intermediate) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Each package contains 1 L of Electronic Grade Reagent VAM, sealed in a clean HDPE bottle under inert nitrogen. |
| Container Loading (20′ FCL) | 20′ FCL: Electronic Grade Reagent VAM loaded in sealed, dry containers with proper dunnage, ensuring contamination-free transport. |
| Shipping | Ship as UN 1301, Vinyl acetate monomer, in dedicated ISO tanks or stainless steel drums under nitrogen blanket. Keep away from heat, sparks, and oxidizers. Use grounded equipment, secure upright loads, and ensure proper hazard labeling. Transport via authorized carriers in well-ventilated containers to prevent polymerization and vapor accumulation. |
| Storage | Store in tightly sealed, original containers in a cool, dry, well-ventilated area away from heat, ignition sources, and direct sunlight. Maintain stable temperatures (5–35°C) to prevent polymerization or degradation. Avoid moisture, oxidizers, acids, and peroxides. Use explosion-proof equipment and proper grounding. Inspect regularly for leaks or container damage. Keep storage area clearly labeled and accessible for emergency response. |
| Shelf Life | Shelf life is typically 6–12 months when stored sealed, cool, and away from light and moisture. |
Vinyl acetate monomer of electronic-grade specification enters photovoltaic encapsulant resin as the polar comonomer in ethylene–vinyl acetate copolymerization, where the vinyl acetate incorporation window of 28–33 wt% is selected to depress crystallinity below the lamination temperature while retaining sufficient mechanical modulus after peroxide crosslinking. The copolymer is produced in a high-pressure free-radical process at 1,800–2,500 bar and 150–300 °C; in tubular reactors the reaction heat is removed across jacketed walls, and the polymer is separated from unreacted monomer in high-pressure separators. Electronic-grade VAM controls chain-transfer behavior because water and acetic acid act as polar impurities that shift melt flow rate and broaden molecular weight distribution. Melt flow rate of the resulting EVA is measured at 190 °C under 2.16 kg load according to ISO 1133-1:2022; photovoltaic encapsulant grades commonly fall between 15 g/10 min and 40 g/10 min. Tensile modulus and elongation at break are evaluated after lamination, with tensile testing performed according to ISO 527-3 or ASTM D638 depending on film versus sheet geometry. In production film lines, residual water in VAM above 300 mg/kg has been observed as bubble defects at the extruder die and as gel specks after peroxide cure; residual acetic acid above 50 mg/kg accelerates cell metallization corrosion during damp-heat exposure. The encapsulant film is compounded on a corotating twin-screw extruder with L/D 40:1 to disperse a peroxide initiator at 0.6–1.5 wt% and a silane adhesion promoter at 0.3–0.8 wt%. Lamination at 145–160 °C for 10–20 min produces a crosslinked network with gel content 70–90% by xylene extraction. Qualification of the module follows IEC 61215-1:2021 for design approval and IEC 61730-1:2016 for safety, with encapsulant volume resistivity required to remain above 1×1014 Ω·cm after damp-heat aging.
| Specification point | Acceptance range | Test method |
|---|---|---|
| Purity by GC-FID | ≥99.9% | Internal GC-FID method |
| Water | ≤300 mg/kg | ASTM E203 |
| Acidity as acetic acid | ≤50 mg/kg | ASTM D1613 |
| Total metals | ≤1 mg/kg | ISO 17294-2:2016 ICP-MS |
| Chloride | ≤2 mg/kg | Combustion ion chromatography |
| MEHQ inhibitor | 5–20 mg/kg | HPLC |
| APHA color | ≤5 | ASTM D1209 |
During multilayer ceramic capacitor green-tape production, ash content in the PVAc binder is the controlling variable because sodium, potassium, and iron introduced at the monomer stage survive solution polymerization and solvent recovery and appear in the sintered BaTiO₃ dielectric after binder burnout. Electronic-grade VAM polymerized into PVAc for tape casting is normally specified with total metals below 1 mg/kg, chloride below 2 mg/kg, and water below 300 mg/kg. PVAc for this application is prepared by solution polymerization in ethyl acetate or methyl ethyl ketone at 60–80 °C with an azo initiator; weight-average molecular weights between 40,000 g/mol and 100,000 g/mol are preferred to balance green strength and solvent solubility. Tape-casting slurry formulation based on 100 phr BaTiO₃ typically contains 8–20 phr PVAc, 2–8 phr phthalate plasticizer, and 50–120 phr solvent. The green tape is cast on a PET carrier at thickness 5–30 µm, and the dried tape is laminated and cut before binder burnout. Binder burnout is evaluated by thermogravimetry per ISO 11358-1:2022 in air at 10 °C/min; PVAc decomposition onset occurs at 250–300 °C, with maximum mass loss at 350–420 °C and residual ash below 0.02 wt% per ISO 3451-1:2019. Production-scale failure modes include brown specks and pinholes when chloride above 2 mg/kg in the monomer corrodes the doctor blade and deposits metal particles in the cast film. Sintered dielectric sheets are subsequently inspected for insulation resistance and dielectric breakdown per IEC 60384-22; electronic-grade VAM contributes to clean burnout without residual conductive ash that would lower reliability under bias humidity.
In wave-solder assembly lines, EVA hot-melt tack compounds used for temporary component fixturing are based on ethylene–vinyl acetate copolymers with vinyl acetate content 18–28 wt%. The vinyl acetate monomer supplied as electronic-grade reagent must not introduce free acetic acid, which accelerates viscosity drift in the heated reservoir and leaves conductive residue on printed circuit board surfaces after solder exposure. Compounding is performed in a jacketed sigma-blade mixer or extruder at 160–190 °C; a typical formulation includes EVA resin 30–70 wt%, hydrogenated tackifier resin 20–40 wt%, microcrystalline wax 5–15 wt%, and antioxidant 0.5–1.5 wt%. Application temperature at the dispense tip is controlled to 160–200 °C; open time ranges from 10 s to 60 s, and set time from 5 s to 15 s. Viscosity at 180 °C is commonly 500–5,000 mPa·s by Brookfield Thermosel. After wave soldering, residues are tested by solvent extract resistivity per IPC TM-650 2.3.25, and assembly specifications may reject boards with ionic contamination above 1.56 µg/cm² NaCl equivalent. Hot-melt fixturing is not suitable for sustained service temperatures above 80 °C because creep of EVA-based compounds reduces positional accuracy. The use of electronic-grade VAM reduces batch-to-batch variation in acid number, which is measured on the compounded hot-melt after 24 h at 180 °C to detect degradation-induced conductivity drift.
Low-outgassing lamination adhesives for polyimide flexible circuit stiffeners are frequently formulated from vinyl acetate–ethylene copolymer dispersions with ethylene content 10–25 wt% and glass transition temperature -10 °C to 10 °C. The emulsion polymerization is stabilized by a polyvinyl alcohol protective colloid derived from the same vinyl acetate monomer supply; electronic-grade VAM reduces the initial carboxylic acid and metal load that would otherwise persist in the dispersion and contribute to ion migration under bias. Post-polymerization stripping reduces residual VAM below 100 mg/kg; this step is less effective if the monomer feed already contains high levels of acetic acid because acid-catalyzed hydrolysis generates additional acetate species. Dispersion viscosity is measured at 23 °C with a Brookfield RVT viscometer, spindle 4 at 20 rpm, and is normally 1,000–4,000 mPa·s; pH is 4.0–5.5, and minimum film formation temperature is 0–10 °C. Slot-die coating at 25–100 µm wet film thickness and drying at 80–120 °C produce a laminating bond on polyimide with peel strength after lamination measured per IPC TM-650 2.4.9. Published data for this specific slot-die configuration is limited; the quoted coating and drying ranges represent standard flexible circuit lamination practice rather than a single machine qualification. The critical electronic-grade VAM parameter for this application is low chloride content, because chloride remaining in the dried adhesive can combine with moisture to form electrolytic cells at exposed copper traces under flexural stress.
For aqueous acrylic PSA emulsion polymerization, polyvinyl alcohol protective colloid is produced by saponification of PVAc manufactured from electronic-grade VAM; partial hydrolysis to 87–89 mol% and a 4% solution viscosity of 20–40 mPa·s at 20 °C are typical for acrylic pressure-sensitive adhesive latexes. The protective colloid is charged at 0.5–5 wt% based on total monomer and influences latex particle size in the 150–350 nm range, shear stability, and final PSA peel and loop tack. Residual sodium acetate from the saponification step is the main ionic contaminant; when electronic-grade VAM with total metals below 1 mg/kg is used, sodium acetate in the dried PSA film is reduced below 10 mg/kg and surface resistivity measured by IEC 62631-3-2 remains above 1×1013 Ω. High-shear dispersion on a rotor-stator mixer at 3,000 rpm is used to prepare the aqueous phase; excessive sodium ion content shifts particle size distribution and increases coagulum in 200 L pilot batches. The acrylic PSA is coated onto release liner at 50–150 g/m² dry coat weight and transferred to cleanroom protective film for display glass handling. Residual ash and chloride are evaluated on the dried adhesive film by ion chromatography after combustion, with reject limits of <10 mg/kg chloride and <1 mg/kg sodium. The use of electronic-grade VAM is therefore a direct control point for adhesive cleanliness before the PSA is applied to polarizer or cover-glass surfaces.
Before wafer mounting, soluble polyvinyl alcohol temporary bonding layers for wafer backgrinding and laser dicing are prepared from fully or partially hydrolyzed PVOH synthesized from electronic-grade VAM through PVAc alcoholysis. The monomer must be low in water and acetic acid to avoid generating sodium acetate during the saponification step; sodium acetate raises the ionic contamination of the temporary bond interface and can cause localized corrosion of aluminum bond pads. A 98 mol% hydrolyzed PVOH with a 4% solution viscosity of 20–60 mPa·s at 20 °C is dissolved in deionized water at 80–95 °C to form a 10–15 wt% solution, cast on a siliconized PET liner, and dried at 90–120 °C to residual moisture 5–10%. Wafer mounting is conducted at 100–130 °C and 0.2–0.5 MPa; debonding is by immersion in deionized water at 25 °C for partially hydrolyzed grades or 80 °C for fully hydrolyzed grades. Ionic cleanliness of the PVOH is verified by acid digestion and ICP-MS per ISO 17294-2:2016, with sodium and potassium each below 10 mg/kg and chloride below 5 mg/kg in the electronic adhesive intermediate supply chain. Published data for this specific wafer-temporary-bonding configuration is limited beyond PVOH film supplier specifications; the quoted mounting and debonding ranges represent standard water-soluble temporary adhesive practice rather than a single wafer-fab qualification. The main incompatibility is with cationic wafer-cleaning residue, which precipitates the PVOH and reduces debonding uniformity.
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Electronic Grade Reagent VAM (Electronic Adhesive Intermediate) is a purified vinyl acetate monomer stabilized with 4-methoxyphenol and intended for use as a reactive comonomer or intermediate in electronic adhesive, encapsulant, and conformal coating resin systems. The substance is identified by CAS 108-05-4, molecular formula C4H6O2, and molar mass 86.09 g/mol. Commercial model designations are purity-based rather than device-specific; typical designations include EG-VAM-4N for 99.99 wt% minimum assay and EG-VAM-5N for 99.999 wt% minimum assay where offered. Such codes are supplier-specific and do not replace lot inspection against a certificate of analysis. The material is ordered primarily by impurity envelope, packaging type, water content, and inhibitor range rather than by model number alone.
The monomer must remain sufficiently inhibited for safe transfer and storage, while the impurity envelope must not introduce mobile ionic species into cured adhesive films. The latter requirement drives electronic-grade limits below general industrial vinyl acetate monomer specifications such as ASTM D2190.
Industrial VAM meeting ASTM D2190 may be supplied at 99.5 wt% assay with water content up to 0.1 wt% and acidity up to 0.02 wt% as acetic acid. Those limits are often too broad for adhesive resins that contact copper leadframes, silver-filled conductive adhesives, or wire-bonded semiconductor devices. Electronic-grade VAM is controlled for sodium, potassium, iron, copper, zinc, aluminum, calcium, and magnesium at or below 0.1 ppm individually in high-tier material, with a total target of 0.5 ppm for the screened metals. Analysis is performed by inductively coupled plasma mass spectrometry after closed-vessel microwave digestion. Chloride and sulfate are held at or below 0.1 ppm each. Packaging is fluoropolymer-lined steel or stainless steel, and the product is filtered through 0.1 µm membrane cartridges before filling. The lower water content—commonly ≤0.05 wt% and ≤0.03 wt% for 5N tier—limits hydrolysis to acetaldehyde and acetic acid during storage and cure.
No separate public ASTM specification exists for electronic-grade VAM. Supplier-specific limits must therefore be mapped to the ionic cleanliness requirements of the intended assembly process. In practice, qualification uses extracted-ion measurements and biased humidity exposure rather than monomer assay alone.
Because the material is a reactive ester, specification values are reported on an as-is basis after inhibitor addition. Table 1 presents a representative specification envelope assembled from publicly available product data sheets and electronic-grade supplier literature; commercial lots may differ.
| Parameter | Representative range | Test method or instrumentation |
|---|---|---|
| Vinyl acetate assay | ≥99.9 wt%; 5N tier ≥99.999 wt% | Capillary GC-FID area normalization; ASTM D2190 |
| Water | ≤0.05 wt%; 5N tier ≤0.03 wt% | Karl Fischer coulometric titration; ASTM E203 |
| Acidity as acetic acid | ≤0.005 wt% | Alcoholic KOH titration; ASTM D1613 |
| Color | ≤5 APHA | Platinum-cobalt visual/spectrophotometric; ASTM D1209 |
| 4-Methoxyphenol inhibitor | 3–5 ppm | Reversed-phase HPLC with UV detection at 280 nm |
| Chloride | ≤0.1 ppm | Ion chromatography after aqueous extraction or combustion; in-house validated |
| Sulfate | ≤0.1 ppm | Ion chromatography; in-house validated |
| Trace metal screen: Na, K, Ca, Mg, Fe, Cu, Zn, Al | each ≤0.1 ppm; total ≤0.5 ppm for specified elements in high-tier lots | ICP-MS after closed-vessel microwave acid digestion |
| Non-volatile residue | ≤0.001 wt% | Gravimetric after controlled evaporation at 105 °C |
| Particulate matter | 0.1 µm filtered; published particle-count specifications for electronic-grade VAM are limited | Membrane filtration before filling |
For wire-bonded and flip-chip resin systems, residues are often assessed after cure by aqueous extraction of cured resin coupons in deionized water at 85 °C for 24 h, followed by ion chromatography and ICP-MS. Pass/fail limits are device-specific, but typical failure thresholds are 0.5 ppm extracted chloride and 0.5 ppm total alkali metals relative to cured resin mass. These measurements are part of qualification under JEDEC JESD22-A101 steady-state temperature-humidity-bias life testing; insulation resistance must remain above 10^8 Ω after 1000 h at 85 °C and 85% RH with 10 V DC bias.
Electronic-grade VAM is not obtained simply by one additional distillation pass. The purification train includes a fractional distillation column with 30–50 theoretical stages, a reboiler operated below 90 °C to limit acetaldehyde formation, and a condenser system with controlled water content. Reflux ratio is held between 1.2:1 and 3.0:1 for high-purity cuts. Low boilers—acetaldehyde, methyl acetate, and dissolved water—are removed as light ends; high boilers including acetic acid and dimer-like esters remain in the bottoms. Reboiler surfaces must be passivated 316L stainless steel or fluoropolymer-lined to avoid iron contamination. Batch-to-batch variance is controlled by gas chromatography of each distillation cut and by blending only cuts that meet the electronic-grade ionic envelope. Published data for exact column designs used by electronic-grade VAM producers is limited; the above description is representative of industrial vinyl acetate purification practice.
The 4-methoxyphenol inhibitor in VAM is oxygen-dependent. The stabilizer forms phenoxy radicals that trap carbon-centered radicals, but it requires dissolved oxygen in the monomer to maintain the redox cycle. Bulk storage is therefore maintained under air or a gas mixture containing 5–8 vol% oxygen; pure nitrogen blanketing can deactivate the inhibitor and shorten the induction period. The standard stabilizer range is 3–5 ppm. At concentrations below 3 ppm, the monomer remains pumpable but shows a measurable decrease in thermal onset in differential scanning calorimetry. When onset temperature drops by more than 10 °C from the lot-specific baseline at a heating rate of 5 °C/min, the material is considered destabilized and is either replenished with 4-methoxyphenol or consumed immediately in a controlled polymerization feed.
In UV-curable electronic adhesives, residual stabilizer carries a second constraint: 4-methoxyphenol absorbs in the UV range and retards free-radical photopolymerization. Raising the photoinitiator dosage from 1.0 wt% to 2.0 wt% can compensate when inhibitor is at the upper limit of 5 ppm, but higher photoinitiator loading raises extractable residues after cure. Formulators therefore prefer inhibitor levels at the lower end of the range when curing with 365 nm LED lamps. The practical processing window is narrow: maintain enough inhibitor for safe storage without exceeding the dose that increases cure time beyond the target line speed. Published data for this specific electronic-grade VAM configuration is limited; the thermal and UV cure values above are representative of stabilizer behavior in vinyl ester monomers and are not an ASTM specification.
In high-shear compounding of ethylene-vinyl acetate encapsulant resins for photovoltaic module assembly, VAM is incorporated through the copolymer feed rather than as a post-additive. A co-rotating twin-screw extruder with 40:1 L/D ratio and segmented screw elements is used for compounding EVA with peroxide initiator, silane adhesion promoter, and antioxidants. Barrel temperature zones are profiled from 90 °C to 180 °C; vent port vacuum is maintained at 80 kPa absolute or below to strip residual monomer and volatile byproducts. The compounded encapsulant is extruded into film and cured during module lamination at 150 °C for 15 min. Gel content after cure is determined by Soxhlet extraction according to ASTM D2765; values of 70–85% are typical for photovoltaic EVA films. Melt flow rate is measured at 190 °C with a 2.16 kg weight according to ISO 1133-1:2022, and EVA encapsulants outside 15–40 g/10 min often show lamination voids. Residual VAM in the cured film must be below 0.1 wt%; otherwise bubble formation and backsheet adhesion loss occur during damp heat conditioning at 85 °C and 85% RH as specified in IEC 61215. Pre-drying of EVA granules at 60 °C for 4 h is required if moisture uptake exceeds 0.05 wt% before extrusion.
Metal ion residues in VAM-derived adhesive resins are stable at room temperature but become mobile under humidified electrical bias. Sodium and potassium are the lowest-mobility failures if present above 0.1 ppm in the cured layer because they migrate along glass fiber interfaces or filler surfaces and produce dendrites. Transition metals copper and iron catalyze oxidative degradation of ester linkages and contribute to discoloration during reflow. A defined trace metal budget is therefore applied to the liquid monomer and confirmed on the cured resin. Ion chromatographic analysis of water extracts from 24 h extraction at 85 °C detects anions that promote copper corrosion; chloride is typically controlled more tightly than the monomer specification when the resin contacts bare copper substrates.
In semiconductor packaging, adhesive resins are evaluated under JEDEC JESD22-A101. The test board pattern is a comb structure; bias is 10 V DC during 1000 h at 85 °C/85% RH. A pass condition is insulation resistance greater than 10^8 Ω at the end of exposure with no dendrite formation. These tests are not monomer-level specifications but are the system-level acceptance criteria that drive the trace metal limits shown in Table 1.
For adhesive resin design, electronic-grade VAM is compared with methacrylate and styrene monomers on the basis of homopolymer glass transition temperature, water solubility, and polarity. Table 2 lists approximate values used in polymer selection; reactivity ratios with styrene and methyl methacrylate are available in polymer handbook literature and are omitted because they are feedstock-specific and temperature-dependent.
| Property | Electronic-grade VAM | Methyl methacrylate | Butyl acrylate | Styrene |
|---|---|---|---|---|
| CAS | 108-05-4 | 80-62-6 | 141-32-2 | 100-42-5 |
| Homopolymer Tg | approx 30 °C | approx 105 °C | approx -54 °C | approx 100 °C |
| Water solubility at 25 °C | approx 2.0 g/100 mL | approx 1.5 g/100 mL | approx 0.1 g/100 mL | approx 0.03 g/100 mL |
| Polymerization class | Vinyl ester radical | Methacrylate radical | Acrylate radical | Vinyl aromatic radical |
| Electronic adhesive role | Flexible encapsulant, tackifier | Rigid optical adhesive | Pressure-sensitive adhesive comonomer | Refractive index modifier |
Differences in homopolymer glass transition temperature explain why VAM is selected for flexible encapsulant and tackifier resins rather than for high-hardness optical adhesives. Polyvinyl acetate has a Tg near 30 °C and shows lower cure shrinkage than methacrylate homopolymers; poly(methyl methacrylate) has a Tg near 105 °C and is used where rigidity and clarity dominate. Butyl acrylate copolymers reduce tack but increase hydrophobicity; styrene raises refractive index and aromatic content but increases rigidity. The ester group in VAM is susceptible to hydrolysis under strong alkaline or acidic conditions. In copper-bearing electronic assemblies, this is the reason for the low acidity and low water specification and for avoiding amine-based additives that can generate local alkaline microenvironments.
Storage conditions for the monomer are determined by flammability and by the oxygen dependence of the inhibitor. The liquid has a closed-cup flash point of -8 °C and a boiling point of approximately 72.7 °C at 101.3 kPa. The vapor is denser than air and may travel to ignition sources; storage areas require explosion-proof electrical classification, grounding, and local exhaust. Containers are stored upright at 15–25 °C and protected from ultraviolet radiation. The inhibitor requires oxygen; therefore, containers should not be blanketed with pure nitrogen unless the stabilizer is specifically supplemented and the process risk assessment accepts the change. Avoid copper, brass, and iron in transfer systems because dissolved metals accelerate free-radical polymer formation and introduce ionic contamination. Keep the monomer separate from peroxides, azo initiators, strong oxidizers, and amines, and avoid moisture during transfer because water promotes hydrolysis to acetaldehyde and acetic acid.
According to Regulation EC 1907/2006 Annex II, safety data sheets report hazard communication for the substance; users must verify whether the finished adhesive formulation requires specific restrictions under Directive 2011/65/EU Annex II or REACH Annex XVII. The monomer itself is not sufficient to establish finished-product compliance.
When VAM is used as a reactive diluent in UV-curable electronic adhesives, line speed and surface cure must be balanced against oxygen inhibition at the adhesive-air interface. VAM-containing formulations usually require inerting or a paraffin wax additive to achieve tack-free surfaces under 365 nm LED exposure; otherwise the surface remains uncured because oxygen consumes initiating radicals. Typical photoinitiator systems include α-hydroxyketone compounds at 1.0–2.0 wt% and, where necessary, a tertiary amine synergist. However, amine addition must be limited because residual amine can extract into interfacial moisture and raise pH at the copper-adhesive interface. The operational boundary is that amine synergists are not recommended above 0.1 wt% in formulations destined for wire-bonded devices unless extracted-ion testing demonstrates compliance. This final processing constraint defines the upper limit for the inhibitor-compensating photoinitiator strategy described earlier.
