| HS Code | 711388 |
| Product Name | High Purity Low Inhibitor VAM (Laboratory Polymerization Research) |
| Chemical Name | Vinyl Acetate Monomer |
| Cas Number | 108-05-4 |
| Molecular Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Purity | ≥99.9% (GC) |
| Inhibitor Content | ≤5 ppm hydroquinone |
| Appearance | Clear colorless liquid |
| Boiling Point | 72.7 °C at 1013 hPa |
| Melting Point | -93 °C |
| Density | 0.934 g/cm³ at 20 °C |
| Refractive Index | 1.3953 at 20 °C |
| Flash Point | -8 °C (closed cup) |
| Vapor Pressure | 116 hPa at 20 °C |
| Solubility | Slightly soluble in water (2 g/100 mL at 20 °C); miscible with organic solvents |
| Storage Condition | Store at 2-8 °C under inert atmosphere |
| Polymerization Reactivity | High; readily undergoes radical polymerization once inhibitor is removed |
As an accredited High Purity Low Inhibitor VAM (Laboratory Polymerization Research) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | High Purity Low Inhibitor VAM, 1 L, packaged in a glass bottle with PTFE-lined cap for laboratory polymerization research. |
| Container Loading (20′ FCL) | One 20-foot container holds drums of high-purity, low-inhibitor VAM for laboratory polymerization research, securely stowed and labeled. |
| Shipping | Ship as UN 1301 Vinyl Acetate Monomer, Class 3 flammable liquid. Use sealed, corrosion-resistant containers under inert gas to prevent polymerization. Maintain cool temperatures, avoid heat, sparks, and UV. Label as low-inhibitor, research-grade; ensure proper ventilation and secondary containment during transit. |
| Storage | Store in tightly sealed, amber glass containers under inert gas (nitrogen or argon) in an explosion-proof refrigerator at 2–8°C. Protect from light, heat, oxygen, and ignition sources. Because inhibitor levels are low, monitor regularly for polymer formation or viscosity increase. Keep away from oxidizers, peroxides, acids, and polymerization initiators. Label with opening date and use appropriate PPE. |
| Shelf Life | Store under inert gas, refrigerated, and away from light; stable for 6 months if unopened and properly sealed. |
High-solids polyvinyl acetate solution polymerization for wood assembly adhesives and lacquer binders uses high purity low inhibitor VAM because residual hydroquinone monomethyl ether in the monomer is carried into the final polymer and can react during solvent stripping at 68–78 °C to form quinoid color bodies. The compatibility of the resulting adhesive with food-packaging laminates is governed by FDA 21 CFR 175.105 for indirect-contact adhesives, while moisture resistance of the cured joint is classified under EN 204 D2/D3. A representative free-radical formulation is VAM at 55–70 wt% of the reactor charge, ethyl acetate or methanol at 30–45 wt%, and azobisisobutyronitrile at 0.05–0.2 wt% relative to monomer. Polymerization is executed in a 1–2 L jacketed borosilicate reactor with a pitched-blade turbine at 180–300 rpm, nitrogen sparge at 0.2–0.5 L min⁻¹ per liter of reactor volume, and a condenser held at −5 °C to return volatilized monomer. Low-MEHQ monomer with a specification commonly ≤ 5 mg/kg reduces induction-period variance between batches, but oxygen ingress through the stirrer gland is the more severe process issue and must be controlled to a pressurized headspace oxygen concentration below 0.5 vol% before initiator addition. The nonvolatile content is tracked with ISO 3251:2019, and Brookfield viscosity is measured according to ISO 2555:2018. Terminal product classes covered by this research path are wood laminating adhesives, lacquer binders for cellulose nitrate coatings, and paper-sizing binders where high clarity and low residual aldehyde are required.
In low-VOC decorative paint binder development, high purity low inhibitor VAM is polymerized with vinyl versatate esters to produce a high-solids latex that resists hydrolysis under alkaline pigment slurries. The regulatory boundary for the formulated end product is set by EU Directive 2004/42/EC, which restricts water-borne interior matt wall coatings to 30 g/L VOC; further ecolabel qualification refers to ISO 16000-6:2021 for chamber emissions. A typical monomer ratio is VAM at 60–80 wt% of total monomer, vinyl neodecanoate or vinyl neononanoate at 10–30 wt%, and acrylic acid at 0.5–2 wt%; the water phase contains polyvinyl alcohol protective colloid at 2–5 wt% on total monomer, sodium lauryl sulfate anionic surfactant at 0.8–2 wt%, fatty alcohol ethoxylate nonionic surfactant at 0.5–1.5 wt%, and sodium persulfate at 0.2–0.5 wt% on total monomer. The process sequence begins with a seed latex at 2–5 wt% of the final polymer, followed by a pre-emulsion feed over 3–4 h at 70–80 °C and a post-reaction hold of 60 min. In a 2 L stirred reactor with an anchor impeller at 150–250 rpm, monomer containing residual phenolic inhibitor produces a measurable delay before the exotherm appears; the exact induction period depends on seed particle size and initiator concentration. The latex is then stripped under partial vacuum at 60 °C to reduce residual VAM below 1000 mg/kg and adjusted with sodium bicarbonate to pH 7.0–8.5. Terminal product types include interior wall paints from matte to semi-gloss, crack-bridging primers, and low-odor decorative topcoats.
In ethylene–vinyl acetate copolymer research at laboratory autoclave scale, the low-inhibitor VAM specification determines how reproducibly a peroxide initiator can be metered into a continuous stirred autoclave at 140–220 MPa and 160–280 °C. VAc content in commercial EVA spans 18–40 wt% for hot-melt applications and commonly 28–33 wt% for photovoltaic encapsulant films; the vinyl acetate unit interrupts polyethylene crystallinity and reduces the melting peak measured by ASTM D3418-21 from approximately 105–110 °C to below 70 °C at high VAc incorporation. Melt flow rate is controlled through chain-transfer agent feed and is checked at 190 °C under 2.16 kg load using ISO 1133-1:2022 or ASTM D1238-20 Procedure A. The laboratory reactor is a 0.5–2 L stirred autoclave with gas booster feeds for ethylene and VAM, and the monomer ratio is maintained by mass-flow controllers rather than batch charging; this is necessary because VAM conversion is not directly proportional to ethylene flow in the dense-phase region. Published data for specific peroxide initiator loadings at the laboratory autoclave scale is limited, but typical industrial ranges are below 0.1 wt% on total monomer. End products include PV module encapsulant films, hot-melt adhesives, cable compounds, and footwear foam. For food-contact adhesive and packaging uses, FDA 21 CFR 177.1350 supplies the EVA copolymer definition and composition limits.
| Standard / Test Method | Measured Property / Clause | Use During Lab-Scale Development |
|---|---|---|
| ISO 1133-1:2022 | MFR at 190 °C / 2.16 kg | Chain-transfer agent dose adjustment |
| ASTM D1238-20 Procedure A | MFR reproducibility | Rheology benchmark for hot-melt grades |
| FDA 21 CFR 177.1350 | EVA copolymer composition limits for food contact | Selection of VAc content for packaging-grade screening |
| ASTM D3418-21 | DSC melting peak and crystallinity | VAc content effect on encapsulant thermal transition |
| IEC 61215-1:2021 | Module design qualification | Downstream qualification of encapsulant film |
When the research objective shifts to controlled architecture of polyvinyl acetate, high purity low inhibitor VAM is required because xanthate-mediated radical polymerization is highly sensitive to the redox side reactions of hydroquinone or MEHQ; inhibitor residues consume primary radicals from azobisisobutyronitrile and shift the apparent initiator efficiency. The safety and handling framework is CLP Regulation (EC) No 1272/2008 and relevant REACH Annex entries, since VAM is a flammable liquid and a skin sensitizer. A typical laboratory ratio is [VAc]:[xanthate]:[AIBN] = 200:1:0.1 to 1000:1:0.05, with solvent at 50–70 wt% and polymerization at 60–70 °C for 8–24 h. The batch is prepared in a Schlenk flask and degassed by freeze–pump–thaw cycles to ≤ 0.1 mbar before argon backfill; positive argon pressure during sampling prevents oxygen termination. GPC with polymethyl methacrylate calibration and refractive index detection gives apparent number-average molecular weights that are typically below 50 kg mol⁻¹ before chain-transfer broadening becomes significant. The method produces PVAc macro-CTA, PVAc-block-poly(N-vinylpyrrolidone), PVAc-block-poly(N-isopropylacrylamide), and, after selective hydrolysis, polyvinyl alcohol block copolymers. Published data for specific low-inhibitor VAM grades in this configuration is limited, because the rate depends on head-to-head defects and chain transfer to monomer, which are not eliminated by low inhibitor content alone.
Suspension polymerization for high-molecular-weight polyvinyl alcohol precursors uses low inhibitor VAM because phenolic inhibitors accumulate at the monomer–water interface and interfere with the surface-active polyvinyl alcohol suspending agent. A non-controlled drop formulation uses VAc at 100 parts by weight, deionized water at 150–200 parts, partially hydrolyzed PVOH suspending agent at 0.1–0.5 wt% on water, and oil-soluble AIBN at 0.02–0.1 wt% on monomer. The reactor is a baffled borosilicate vessel with a six-blade Rushton turbine at 200–350 rpm, producing bead diameters between 100 and 500 µm depending on PVOH degree of hydrolysis and impeller tip speed. The temperature profile is held at 60 °C for 2 h, then raised to 70 °C for 4 h; conversion is intentionally stopped at 80–90% because high-conversion droplets become sticky and agglomerate. Residual VAM is removed by vacuum stripping at 40–50 kPa and 60 °C, then the beads are washed and dried to ≤ 0.2 wt% moisture. Alcoholysis with sodium hydroxide in methanol at 30–40 °C converts the PVAc to PVOH with degree of hydrolysis from 87.0 mol% to 99.9 mol% and aqueous viscosity from 3 mPa·s to 70 mPa·s at 4 wt% and 20 °C. The product class covers PVOH film, textile warp sizing, water-soluble packaging, and controlled-release films; for pharmaceutical application, the USP-NF Polyvinyl Alcohol monograph and Ph. Eur. 0683 govern purity and viscosity limits, while FDA 21 CFR 177.1670 applies to PVOH film in contact with food.
Development of vinyl acetate–ethylene (VAE) copolymer latex for construction adhesives and carpet backings starts from the same low-inhibitor monomer because redox initiation with potassium persulfate and sodium metabisulfite is especially sensitive to dissolved phenolic inhibitor. The monomer ratio is typically VAc at 70–85 wt% and ethylene at 15–30 wt%, with PVOH protective colloid at 2–5 wt% on total monomer and nonionic ethoxylate at 0.5–2 wt%; the initiator pair is metered at 0.05–0.3 wt% on total monomer. Ethylene is fed to maintain a constant total pressure of 30–60 bar in a 2 L stainless-steel reactor at 50–80 °C, using an anchor impeller at 150–250 rpm; ethylene mass transfer, not monomer feed rate, is the primary rate-limiting step. The latex is cooled, adjusted to pH 4.0–5.0 with sodium acetate buffer, and filtered through a 100–200 µm bag to quantify coagulum; pH excursions below 4.0 are a known destabilization threshold for PVOH-protected VAE latex. At ethylene contents above 15 wt%, the minimum film-forming temperature is depressed below 0 °C when measured by ISO 2115:1996, which is necessary for carpet backing adhesion in unheated storage. The compliance basis includes FDA 21 CFR 175.105 for indirect food packaging adhesives and EN 204 D3 for interior wood bonds with frequent short-term water exposure. Terminal product types are carpet backing compounds, tile adhesives, construction adhesives for porous substrates, and paper coating binders for high-speed pigment coating.
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High Purity Low Inhibitor VAM (Laboratory Polymerization Research) is released as lot-certified vinyl acetate monomer under the designation LP-VAM-LI-99.9-200. The product has a certified purity of ≥99.9% by gas chromatography and a hydroquinone monomethyl ether inhibitor concentration of 3–5 ppm. It is controlled under ASTM D2190 with supplementary lot-specific limits for water, acidity, color, and nonvolatile residue. Packaging consists of 100 mL, 500 mL, and 1 L amber borosilicate glass bottles with nitrogen headspace. The monomer is intended for laboratory radical polymerization, kinetic parameter estimation, copolymerization reactivity ratio measurements, and small-scale synthesis of polyvinyl acetate and vinyl acetate copolymers. It is not supplied as a bulk production-grade monomer or for long-term atmospheric storage.
Because the inhibitor concentration is below the common technical-grade range of 12–20 ppm, storage and handling boundaries are different. Sealed bottles may be held at ≤25 °C for up to 6 months from the packaging date. At 5 °C, the unopened product remains within a peroxide limit of ≤10 mg/kg for up to 12 months. After the nitrogen headspace is first breached, published data for open-container retention of this specific package configuration are limited, and the monomer should be consumed within 28 days or redistilled under argon before kinetic use. Every withdrawal must be performed under a slight positive nitrogen or argon pressure, and the bottle must be resealed immediately.
Typical laboratory processes include solution polymerization in ethyl acetate or methanol, semi-batch emulsion polymerization, suspension polymerization with partially hydrolyzed polyvinyl alcohol, and high-pressure ethylene-vinyl acetate copolymerization in stirred autoclaves. In these operations, the low inhibitor level reduces the phenolic radical scavenger inventory that must be consumed before steady propagation, while the residual 3–5 ppm MEHQ still provides enough stabilization during nitrogen-blanketed transfers. For techniques that require a completely inhibitor-free feed, such as xanthate-mediated RAFT or cationic polymerization, further purification under argon is required; the supplier does not claim zero-inhibitor status for this grade.
In a batch free-radical polymerization, the induction period is governed by the concentration of phenolic inhibitor and the rate at which initiator-derived radicals are produced. At 60 °C with 1.0 × 10⁻² mol/L azobisisobutyronitrile in ethyl acetate, a low-inhibitor VAM containing 5 ppm MEHQ yields a shorter and more reproducible exotherm onset than the same monomer containing 15 ppm MEHQ. The effect is easiest to detect by isothermal calorimetry or in-situ Raman monitoring, where the onset shift can be larger than the normal reactor noise floor. The lower inhibitor level does not eliminate the induction period; it reduces the molar scavenger inventory and narrows the lot-to-lot uncertainty. For absolute rate studies, the monomer may still require an inhibitor-removal column under argon, but the required bed volume is smaller than for technical-grade VAM.
The stoichiometry of MEHQ inhibition is typically treated as 2 radicals per inhibitor molecule, but this should be verified by induction-time measurements because solvent viscosity and temperature affect phenolic trapping efficiency. Above 80 °C, the effective scavenger capacity of MEHQ declines due to thermal oxidation; low-inhibitor VAM should therefore not be stored or preheated for extended periods above that temperature. The product is released with both lower and upper MEHQ bounds, allowing the researcher to subtract the inhibitor contribution from initiator consumption without assuming a single-batch value.
The release certificate is lot-specific and contains the following limits:
| Property | Method | Certified Limit |
|---|---|---|
| Vinyl acetate purity | ASTM D2190 | ≥99.9% by GC area |
| MEHQ inhibitor | ASTM D2190 / HPLC-UV | 3–5 ppm |
| Water | ASTM E203 | ≤200 mg/kg |
| Acidity as acetic acid | ASTM D1613 | ≤50 mg/kg |
| Color, Pt-Co | ASTM D1209 | ≤5 |
| Nonvolatile residue | ASTM D1353 | ≤0.005 wt% |
Gas chromatographic purity is measured using a polyethylene glycol capillary column with flame ionization detection. The method is calibrated against a certified reference standard and is capable of resolving acetaldehyde, methyl acetate, ethyl acetate, and crotonaldehyde. The limit of quantitation for acetaldehyde is 1 ppm, and for crotonaldehyde is 0.5 ppm. The MEHQ concentration is determined by reversed-phase high-performance liquid chromatography with UV detection at 280 nm; the method is calibrated with a traceable MEHQ standard. The water content is determined by coulometric Karl Fischer titration according to ASTM E203, using a titrator with a detection limit of 10 µg of water.
The acetaldehyde impurity is controlled below 10 ppm because it acts as a chain-transfer agent and broadens molecular weight distribution in polyvinyl acetate. Methyl acetate and ethyl acetate are controlled below 50 ppm each. Crotonaldehyde is controlled below 5 ppm. The water and acidity limits are enforced to prevent monomer hydrolysis and to avoid acid interference in emulsion formulations. The tightened nonvolatile residue limit reduces fouling of microfluidic reactors and laboratory distillation columns.
In comparison to stabilized technical VAM with a broad MEHQ range of 12–20 ppm, the low-inhibitor grade is supplied with a narrower inhibitor band and a higher purity floor. It does not require the pre-washing or pre-distillation step that technical monomer often needs before precise kinetic work. In contrast, in-house distilled VAM below 1 ppm MEHQ may give lower inhibition, but it lacks a standardized certificate under ASTM D2190 and is more prone to rapid peroxide formation after exposure to air. The LP-VAM-LI-99.9-200 grade therefore occupies a mid-range between stabilized bulk monomer and uninhibited distillate.
| Material | MEHQ | Purity | Water | Acidity | Typical Use |
|---|---|---|---|---|---|
| LP-VAM-LI-99.9-200 | 3–5 ppm | ≥99.9% | ≤200 mg/kg | ≤50 mg/kg | Laboratory kinetic studies; polymerization research |
| Technical stabilized VAM | 12–20 ppm | ≥99.5% | ≤400 mg/kg | ≤100 mg/kg | Bulk monomer storage and production |
| Uninhibited distilled VAM | <1 ppm | variable, often ≥99.5% | not certified | variable | Specialty low-inhibitor experiments |
In a seeded semi-batch emulsion polymerization of vinyl acetate, butyl acrylate, and acrylic acid, the monomer feed can be charged directly from a nitrogen-blanketed reservoir when the MEHQ content is 3–5 ppm. A standard laboratory formulation at 60 °C uses potassium persulfate at 0.3 wt% on total monomer and sodium dodecyl sulfate at 15 mM. With technical-grade VAM at 15 ppm MEHQ, the nucleation interval is prolonged and the final particle size distribution can broaden unless the monomer is prewashed. Low-inhibitor VAM reduces this source of variability. The final latex particle size, measured by dynamic light scattering, typically shows a polydispersity index below 0.10 after 4 h, although this result depends on the feed profile and agitation geometry. The final Brookfield viscosity at 20 rpm and 25 °C is generally between 300 mPa·s and 800 mPa·s for a 40 wt% solids polyvinyl acetate latex, depending on the protective colloid level. Residual monomer reduction still requires a sodium metabisulfite/t-butyl hydroperoxide chase, with headspace GC analysis conducted according to ISO 13741.
In high-pressure ethylene-vinyl acetate copolymerization with a 300 mL stirred autoclave, the monomer is charged at 10–25 wt% of the reactor contents with ethylene pressure at 15–30 bar and reaction temperature of 80–120 °C. The low-inhibitor product reduces the inhibitor load in the high-pressure liquid phase, which is important when the reactor is operated with short residence times and the induction period must be short. The monomer is supplied without high-boiling inhibitor-removal solvents, so no solvent residue is introduced into the copolymer. Published data for this specific package configuration in high-pressure miniplants is limited; the reactor must be fitted with a pressure relief device rated for the maximum expected pressure and the exotherm must be monitored continuously.
Laboratory polymerization rigs for this monomer typically use a 250 mL or 1 L four-neck glass reactor with a PTFE paddle stirrer, a chilled condenser, and a thermocouple placed below the liquid surface. The monomer feed is delivered through PTFE tubing by a syringe pump or positive-displacement pump at 0.5–5.0 mL/min. The reactor is sparged with nitrogen for 30 min before charging and kept under a slight positive nitrogen pressure during the run. Temperature control should be held within ±0.5 °C, because vinyl acetate propagation is sensitive to temperature and the initiator half-life changes sharply with temperature. The low-inhibitor monomer should be fed only from amber or nitrogen-blanketed reservoirs; clear PVC tubing and transparent feed lines should be shielded from ambient light to reduce photopolymerization risk.
In solution polymerization, the typical solvent system is ethyl acetate or methanol at 30–50 wt% monomer. A 1 L jacketed reactor with a 50 mm diameter PTFE anchor stirrer and a digital thermocouple is operated at 60–70 °C. The low-inhibitor VAM is fed over 2–4 h at 0.5–5.0 mL/min, while the initiator solution is fed separately. Agitation is maintained at 200–400 rpm. At higher speeds, vortexing can entrain oxygen and reduce the induction-period benefit. The polymer solution is sampled through a septum port; gravimetric conversion is measured by removing volatiles at 120 °C under vacuum. The final polyvinyl acetate molecular weight is determined by size-exclusion chromatography against polystyrene standards in tetrahydrofuran using ISO 13885 for the liquid chromatographic system.
When zero-inhibitor baselines are required, the low-inhibitor VAM can be passed through a short activated alumina column under argon. The column should be 10 cm long with an internal diameter of 1 cm, packed with neutral activated alumina that has been dried at 250 °C for 12 h. The effluent should be used immediately and not stored, because the column removes the protective MEHQ. This procedure is common for kinetic studies with low-temperature azo initiators at 30–40 °C, where a long induction period may be difficult to distinguish from slow initiator decomposition. Published data for this specific low-inhibitor grade with column treatment is limited; columns should be tested with a blank monomer run before critical kinetic measurements.
The monomer has a closed-cup flash point of -8 °C and an autoignition temperature of 427 °C. Vapors are heavier than air and can accumulate at bench level. The low inhibitor concentration reduces the oxygen scavenging reserve, so storage and transfer must be oxygen-free. Peroxide formation is the main degradation route; a sealed bottle under air, rather than nitrogen, can form measurable peroxides within a shorter period than technical-grade VAM. Reaction vessels should include a pressure-relief device and a quench tank charged with a hydroquinone solution. Copper, brass, and copper-containing alloys are not permitted in transfer lines or distillation columns because copper ions can initiate radical polymerization. Transfer equipment should use 316L stainless steel, PTFE, or high-density polyethylene. The monomer is incompatible with strong oxidizing agents, strong bases, and concentrated sulfuric acid. Contact with amines is not recommended as a stabilization strategy because amine addition can lead to base-catalyzed side reactions.
Because the monomer contains only 3–5 ppm MEHQ, the residual phenolic stabilizer level in the final polymer is typically below the detection limit of standard extraction methods. This is relevant for polyvinyl acetate used in adhesives, paper coatings, and ink binders, where residual phenolic antioxidants can migrate and cause interfacial discoloration. The low-inhibitor grade does not contain added high-boiling solvents or copper-based stabilizers, which simplifies post-polymerization workup. When residual monomer is stripped from the final latex or solution, the low MEHQ level also reduces the formation of colored quinone-derived byproducts during high-temperature devolatilization.
Some high-purity VAM grades use p-methoxyphenol or hydroquinone at different concentrations; those stabilizers have different UV absorbance and different partitioning into aqueous emulsions. The LP-VAM-LI-99.9-200 grade uses MEHQ because its behavior in kinetic studies is well documented and its concentration can be quantified by HPLC without interference from acetic acid. The product should not be assumed to behave identically to low-inhibitor vinyl acetate sourced from different producers, even if the nominal purity is the same.
Operational boundaries include the following: the low-inhibitor grade should not be held in bulk storage tanks with air-blanketed headspace, should not be exposed to copper-containing transfer components, and should not be mixed with amines or strong oxidizers. The product is supplied under an inert headspace and is intended solely for laboratory polymerization research, not for production-scale bulk polymerization or long-term atmospheric storage. For reactor experiments, the monomer should be charged within 24 h of opening the bottle when ambient humidity exceeds 60%, because water uptake can exceed the certified water limit and alter hydrolysis rates.
