| HS Code | 964954 |
| Chemical Name | Vinyl Acetate Monomer |
| Cas Number | 108-05-4 |
| Molecular Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Purity | >=99.99% |
| Inhibitor Content | 0 ppm (inhibitor-free) |
| Water Content | <=100 ppm |
| Acidity As Acetic Acid | <=20 ppm |
| Boiling Point | 72.7 °C |
| Freezing Point | -93 °C |
| Density At 20c | 0.932 g/cm3 |
| Refractive Index At 20c | 1.3959 |
| Viscosity At 20c | 0.43 mPa·s |
As an accredited Inhibitor-Free Ultra High Purity VAM (Precision Active Polymerization) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Supplied in factory-sealed, nitrogen-purged stainless steel drums; net weight 25 kg, ensuring inhibitor-free ultra-high purity and safe polymerization. |
| Container Loading (20′ FCL) | 20′ FCL loading of Inhibitor-Free Ultra High Purity VAM: inerted, moisture-protected drums secured for safe precision polymerization transport. |
| Shipping | Inhibitor-free, ultra-high-purity VAM requires cold-chain shipment under inert gas to prevent premature polymerization. Packaged in sealed, sterile, passivated containers with moisture barrier. Must be transported as regulated hazardous material, avoiding heat, light, and contamination. Immediate use upon receipt recommended for precision active polymerization. |
| Storage | Store under inert gas (e.g., nitrogen) in a clean, dry, sealed stainless steel or glass container. Maintain temperatures between 2–8°C to prevent thermal-initiated polymerization. Avoid light, oxygen, moisture, and all catalysts/contaminants. Do not use with inhibitors. Regularly check for viscosity increases or cloudiness. Follow strict handling protocols to maintain ultra-high purity and stability. |
| Shelf Life | Store cold, use within 6 months; protect from light, oxygen, and contamination to prevent premature polymerization. |
Inhibitor-free ultra high purity vinyl acetate monomer is handled as a kinetic-grade raw material rather than a commodity monomer because the absence of hydroquinone monomethyl ether changes the induction-time profile of free-radical polymerizations. Storage requires nitrogen blanketing and jacketed cooling below 10 °C; exposure to copper, brass, or iron surfaces above 20 °C can initiate exothermic homopolymerization. The downstream application scenarios below are restricted to mature industrial polymerization routes where the monomer addition ratio, process equipment, and finished-good compliance are governed by the codes cited in each section.
Continuous methanolysis of poly(vinyl acetate) to poly(vinyl alcohol) with residual acetyl content below 2 mol% requires a VAM feedstock whose aldehyde and water content do not participate in acetal ring formation or chain termination during the saponification stage. In the polymerization step, VAM is charged in methanol at 25–45 wt% based on solution mass, with methanol acting as both solvent and chain-transfer modifier; azo-bis-isobutyronitrile or peroxide initiators are dosed at 0.02–0.5 wt% on VAM mass in a continuous belt polymerizer or kneader reactor operating at 60–75 °C and residence time 4–10 h. Inhibitor-free status removes the inhibitor-derived component of the induction period, allowing the target degree of polymerization to be reached without raising initiator concentration and without increasing methanol-soluble oligomer content in the intermediate poly(vinyl acetate). Alcoholysis uses sodium methoxide at 0.2–2.0 mol% relative to acetyl groups in a screw-fed saponification unit; saponification degree is controlled by the methyl acetate-to-water ratio in the recycle stream, with deviations beyond ±0.5 mol% hydrolysis detected by ISO 15023-1:2017 classification bands. Residual vinyl acetate monomer in the final poly(vinyl alcohol) is limited to <5 mg/kg for direct food-contact film under 21 CFR 177.1670 and Commission Regulation (EU) No 10/2011. Terminal product types include 88 mol%, 98 mol%, and 99+ mol% poly(vinyl alcohol) resins for warp sizing, paper surface sizing, detergent unit-dose film, and polarizer base film where gel particle counts above 20 particles/100 g at 25 μm are rejected. Operational boundary: methanol recovery columns must maintain water content below 0.5 wt% in recycled solvent; otherwise the degree of hydrolysis drifts downward due to the reversible saponification equilibrium.
Ethylene-vinyl acetate copolymer for photovoltaic encapsulant and hot-melt adhesive grades is produced in high-pressure autoclave reactors where vinyl acetate monomer feed ratio is 28–33 wt% of total monomer mass to achieve a copolymer vinyl acetate content of 28–33%. The inhibitor-free specification prevents deactivation of the low-temperature peroxide initiator package, which is injected at 100–250 ppm on total feed mass and decomposes within 150–280 °C at 140–300 MPa; residual hydroquinone monomethyl ether from commodity VAM would reduce initiator efficiency and shift the molecular weight distribution toward higher polydispersity. Reactor control relies on ASTM D5594 for vinyl acetate content and ASTM D1238 for melt flow rate. The autoclave operates with unreacted VAM and ethylene recycle; compressor fouling from trace inhibitor-derived oligomer is a known plant bottleneck, and oxygen in recycled ethylene must be kept below 10 ppm by volume to prevent explosive decomposition and radical scavenging. Compliance for photovoltaic encapsulant films is verified against IEC 61215-1:2021 and IEC 61730-1:2018, with crosslinking degree after lamination tested by ASTM D2765. Terminal finished product types are single-layer EVA encapsulant film, EVA-based hot-melt adhesives for packaging, and crosslinkable cable compounds. Operational boundary: increasing vinyl acetate content above 33% lowers crystallinity below 15% and raises storage-modulus loss at 80 °C; published data for this specific configuration is limited when processing ultra high purity monomer with metallocene ethylene.
Semi-batch emulsion copolymerization of vinyl acetate with butyl acrylate for low-VOC architectural coatings is formulated with VAM at 60–85 wt% of total monomer, butyl acrylate at 15–40 wt%, acrylic acid at 1–2 wt%, and hydroxyethyl cellulose or poly(vinyl alcohol) protective colloid at 1–3 wt% on total monomer. The reaction is conducted in a jacketed stainless steel reactor with turbine agitation, redox initiation at 55–75 °C, and starved-feed monomer addition over 3–5 h; inhibitor-free VAM removes the need for extended pre-charge nitrogen purge because the radical flux at the beginning of the feed profile is not consumed by residual hydroquinone monomethyl ether. Finished latex must comply with 2004/42/EC Decopaint directive VOC limits and is tested by ASTM D3960-04(2018) or ISO 11890-2:2020; minimum film-forming temperature is adjusted between 0 °C and 15 °C by the butyl acrylate ratio and coalescent loading. Terminal product types include interior matte wall paints, primer-sealers, and low-odor semi-gloss enamels. Operational boundary: polyvalent metal salts in pigment slurries cause premature flocculation at pH above 8.5, so ammonia neutralization is limited to pH 7.5–8.5 and zinc- or aluminum-containing defoamers are avoided.
Vinyl acetate-ethylene emulsion designed for spray drying is formulated with VAM at 70–90 wt% and ethylene at 10–30 wt% in the polymer phase to yield glass transition temperatures below 15 °C, while poly(vinyl alcohol) protective colloid is added at 5–15 wt% on polymer solids to survive cement pore-water alkalinity. The emulsion polymerization is run at 40–60 °C under ethylene pressure of 15–40 bar in a reactor equipped with a mass-flow ethylene dosing skid; spray drying uses inlet air 110–150 °C and outlet air 50–70 °C, followed by addition of 0.5–1.5 wt% anti-caking silica to maintain flow. In dry mortar formulation, the redispersible polymer powder is dosed at 1.5–4.0 wt% of total dry mix for C2TE classification; tensile adhesion strength after 28 days water immersion is evaluated by EN 12004:2007+A1:2012 and EN 1348:2007. Compliance for indoor air emissions is assessed under REACH Regulation (EC) No 1907/2006 and the ISO 13007-1:2014 classification system. Terminal product types are polymer-modified tile adhesives, self-leveling underlayments, and external thermal insulation composite system base coats. Operational boundary: spray-drying outlet temperature above 70 °C causes irreversible blocking of the redispersible powder, while residual moisture above 2 wt% lowers shelf life below 6 months; both parameters are controlled online by dew-point and particle-size monitoring.
Vinyl acetate-based self-crosslinking nonwoven binders are formulated with VAM at 60–85 wt% of total monomer, ethylene or butyl acrylate at 10–25 wt%, N-methylolacrylamide crosslinker at 2–5 wt%, and a surfactant package at 0.5–2.0 wt%. The emulsion is polymerized in a semi-batch reactor at 60–80 °C, then applied by saturation bonding or foam bonding on a production-scale stenter with three-zone drying at 100–130 °C; dry add-on is controlled between 10–25 wt% on fiber web mass. Gel fraction above 15%, measured by methyl ethyl ketone extraction at 80 °C for 4 h, raises wet tensile index but reduces liquid strike-through time and increases web stiffness, so crosslinker feed is stopped before the gel fraction boundary. In hygiene nonwovens, binder wet strength is tested by ISO 9073-3:1989 and absorbency by ISO 9073-6:2000; formaldehyde release from N-methylolacrylamide-containing binder is limited under REACH Annex XVII and OEKO-TEX Standard 100 residual limits. Terminal product types are diaper topsheet binders, adult incontinence acquisition layer binders, filtration media, and wet-laid wipes. Operational boundary: amines or strongly alkaline wetting agents must not be added before the cure zone because they neutralize the acid catalyst and leave the crosslinker unreacted, raising formaldehyde release; cure line speed is set so that web surface temperature does not exceed 150 °C to avoid yellowing.
Pressure-sensitive adhesives based on vinyl acetate-2-ethylhexyl acrylate copolymers are prepared with VAM at 55–75 wt% of total monomer, 2-ethylhexyl acrylate at 25–45 wt%, acrylic acid at 1–3 wt%, and a chain transfer agent such as tert-dodecyl mercaptan at 0.01–0.2 wt% to limit gel fraction. The emulsion polymerization uses a seeded semi-batch profile at 70–85 °C, followed by redox post-initiation to drop free monomer below 500 ppm; the adhesive is coated on a rotogravure line at 15–25 g/m² dry coat weight onto release liner or facestock. The inhibitor-free VAM shortens the post-initiation period because residual hydroquinone monomethyl ether does not consume the redox couple, allowing free monomer reduction without extended hold time or additional redox booster. Compliance for tack, peel adhesion, and shear resistance is tested by ISO 29862:2018 for 180° peel, ASTM D3654/D3654M-19 for shear, and FINAT FTM-9 for loop tack. Terminal product types are removable paper labels, freezer-grade labels, carton sealing tape, and surface protection films. Operational boundary: residual tert-dodecyl mercaptan above 0.2 wt% increases odor and retards shelf-life tack, while pH below 4.0 causes rheology drift in transfer coating; ammonia or sodium hydroxide adjustment is held to pH 4.5–5.0.
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Vinyl acetate monomer, CAS 108-05-4, EINECS 203-545-4, is supplied as Inhibitor-Free Ultra High Purity VAM (Precision Active Polymerization) under product code VAM-UHP-IF. The grade is manufactured without intentional addition of hydroquinone monomethyl ether inhibitor, and the residual MEHQ concentration is controlled below 1 ppm by high-efficiency distillation and closed-loop packaging. The design intent is to remove scavenger-derived induction periods from the monomer supply so that polymerization initiation is governed by initiator chemistry, dissolved oxygen, and trace peroxide content rather than by stabilizer consumption. Physical constants include a normal boiling point of 72.0–72.5°C at 101.3 kPa, a closed-cup flash point of -8°C by ASTM D56, and a density of approximately 0.934 g/cm³ at 20°C. Precision Active Polymerization is a release-profile designation rather than a distinct chemical entity; the monomer remains vinyl acetate, but the trace impurity profile is controlled for predictable active-center generation in downstream polymerization.
Bulk handling of VAM-UHP-IF differs from storage of conventional MEHQ-stabilized vinyl acetate because the radical-absorbing capacity is intentionally absent. In an uninsulated receiving tank, polymerization can begin at localized hot spots generated by external heat tracing, direct sunlight, or contamination with peroxides formed in an oxygen-containing headspace. Receiving vessels should therefore be refrigerated, nitrogen-blanketed, and fitted with independent temperature alarms. Stainless steel 316L or passivated aluminum tanks with internal cooling coils are preferred; carbon steel is not recommended because trace iron can accelerate peroxide decomposition and reduce the dosing predictability of the monomer.
Field experience on a 2,000 L jacketed receiving tank indicates that batch temperature rise without external heat input is the earliest observable indication of unintended polymerization. An increase of more than 2°C/h above a set point of 5°C should trigger transfer to a quench tank containing inhibited VAM or a phenolic stabilizer such as phenothiazine at 10–25 ppm. If the internal monomer temperature exceeds 30°C, the transfer line should be isolated and the remaining content cooled by external refrigeration before sampling for soluble polymer content. The maximum recommended storage duration without downstream re-inhibition is 7 days at ≤10°C under a nitrogen pad containing <5 ppm oxygen. At temperatures above 25°C, transfer should be completed within 24 h; published stability data for longer storage in uninsulated totes is limited.
The absence of stabilizer also imposes a restriction on additive contact. Alkanolamine and ammonia-based neutralizing agents should not be introduced into inhibitor-free VAM because base-catalyzed ester hydrolysis can generate color bodies and shift the acidity of the monomer. Copper and copper alloys are similarly incompatible because trace copper can catalyze peroxide decomposition and produce colored copper salts. Transfer lines and seals should be constructed of stainless steel, polytetrafluoroethylene, or phenolic-cured epoxy-lined carbon steel.
The release specification for VAM-UHP-IF is compared with a conventional MEHQ-stabilized vinyl acetate monomer in Table 1. Values are reported on an as-received basis unless otherwise specified.
| Property | VAM-UHP-IF | Conventional MEHQ-stabilized VAM | Test method |
|---|---|---|---|
| Vinyl acetate purity | ≥99.9% | ≥99.8% | ASTM D2190 |
| Residual MEHQ | <1 ppm | 3–5 ppm | ASTM D2190 |
| Acidity as acetic acid | ≤0.005% | ≤0.01% | ASTM D1613 |
| Water content | ≤0.05% | ≤0.05% | ASTM D1364 |
| Acetaldehyde | ≤0.005% | ≤0.01% | ASTM D2190 |
| Color, platinum-cobalt | ≤5 | ≤10 | ASTM D1209 |
| Distillation range at 101.3 kPa | 72.0–72.5°C | 71.8–72.5°C | ASTM D1078 |
| Nonvolatile residue | ≤0.002% | ≤0.005% | ASTM D1353 |
Inhibitor-free does not mean simply reduced inhibitor. Post-distillation removal of MEHQ from a standard grade can lower the measured inhibitor concentration, but the process can also leave behind nonvolatile inhibitor transformation products and may raise the acetaldehyde level through thermal exposure. The VAM-UHP-IF specification therefore combines low residual MEHQ with low total acidity, low water, low aldehyde, and low nonvolatile residue in one release profile. This distinction is relevant when the polymerization is evaluated by chain-end fidelity, molecular weight distribution, or color-sensitive downstream processing rather than only by monomer conversion.
The practical difference appears during reactor startup. With a conventional monomer containing 3–5 ppm MEHQ, a portion of the initial radical flux is consumed by the phenolic stabilizer before the first propagating chains reach measurable concentration. That consumption creates an induction period that varies with stabilizer distribution, initiator feed, and reactor wall deposits. With VAM-UHP-IF at <1 ppm MEHQ, the startup delay is governed primarily by dissolved oxygen and trace peroxide content. Those variables can be controlled by inert-gas sparging, refrigerated storage, and exclusion of peroxide-forming atmospheres; they are not controlled by the supplier-added radical trap.
Low acidity is particularly important for controlled radical polymerization of vinyl acetate. In reversible addition-fragmentation chain transfer or macromolecular design by interchange of xanthates, the thiocarbonylthio group is sensitive to acidic hydrolysis. A monomer acidity above 0.01% as acetic acid can shift the apparent transfer constant and broaden the molecular weight distribution. The VAM-UHP-IF limit of ≤0.005% reduces that interference and permits the chain-transfer agent consumption profile to be interpreted against the intended kinetic model. In polyvinyl alcohol production, residual aldehyde participates in acetal bridging and can increase the yellow index of the hydrolyzed film. The lower aldehyde limit is therefore specified for applications where film color is measured by ASTM E313 or equivalent reflectance methods.
Analytical confirmation uses ASTM D2190 gas chromatography for purity, ASTM D1364 Karl Fischer titration for water, ASTM D1613 potentiometric titration for acidity, ASTM D1209 platinum-cobalt color, and ASTM D1078 distillation range. In a 1,000 L pilot-scale batch polymerization reactor fitted with two-stage pitched-blade agitation, the onset of exotherm was more reproducible when switching from commodity VAM to VAM-UHP-IF; the induction time variation across three consecutive campaigns was smaller than the variation produced by a 2°C jacket temperature offset. Published data for this specific configuration is limited, and plant-specific initiator feeds should be validated by reaction calorimetry before scaling to production.
In high-pressure ethylene-vinyl acetate copolymerization, the inhibitor-free monomer allows peroxide initiator demand to be tied more directly to target melt index rather than to an unknown stabilizer sink. The resulting copolymer can be characterized by melt flow rate using ISO 1133-1:2022 at 190°C with 2.16 kg, while tensile properties are measured by ISO 527-2 or ASTM D638 depending on the governing specification. In emulsion polymerization, VAM-UHP-IF is typically fed to the pre-emulsion after nitrogen sparging. The main processing constraint is not monomer purity but the faster exotherm onset at the beginning of the reaction. Production-scale reactors with limited cooling capacity may require a lower initial initiator charge until the first batch confirms the expected exotherm profile by heat-flow calorimetry.
The product is incompatible with free-radical initiators, peroxides, strong acids, strong bases, copper alloys, and oxygen-rich gas streams when long-term storage is intended. Opening a sealed vessel in an atmosphere with relative humidity above 60% can increase water content through condensation; transfer should therefore use closed-loop equipment with a dry nitrogen break. If the monomer must be held for more than 7 days, downstream re-inhibition or storage at ≤5°C with continuous headspace oxygen monitoring is required.
Verification of residual MEHQ is performed by high-performance liquid chromatography with diode-array detection at 280 nm using external MEHQ calibration. The method detection limit for the release test is <0.5 ppm. Each packaging unit is identified by lot number and shipped under a nitrogen pad. The receiving protocol should include internal temperature and headspace oxygen checks before unloading because thermal abuse in transit can activate peroxide contaminants that are not visible by routine appearance testing.
For solution polymerization of vinyl acetate, the low water and low acidity profile reduces hydrolysis during monomer preheating and permits tighter control of solution viscosity development. Viscosity progression is monitored by ASTM D1084 or by cone-and-plate viscometry depending on the reactor solids target. For continuous emissions and workplace exposure, the closed-cup flash point of -8°C by ASTM D56 imposes explosion-group electrical classification and vapor recovery requirements. These are monomer-specific conditions and are not removed by the ultra high purity designation.
