| HS Code | 923499 |
| Product Name | VAM HQ 15–20 ppm |
| Chemical Name | Vinyl acetate monomer stabilized with 15–20 ppm hydroquinone |
| Cas Number | 108-05-4 |
| Molecular Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Appearance | Clear, colorless liquid |
| Odor | Sweet, fruity, pungent |
| Inhibitor Content | 15–20 ppm hydroquinone (HQ) |
| Assay Purity | ≥ 99.9% vinyl acetate |
| Boiling Point | 72.7 °C |
| Melting Point | -93 °C |
| Flash Point | -8 °C (closed cup) |
| Density | 0.934 g/cm³ at 20 °C |
| Vapor Pressure | 115 hPa at 20 °C |
| Solubility | Slightly soluble in water; miscible with alcohols, ethers, and most organic solvents |
As an accredited VAM HQ 15–20 ppm factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | VAM HQ 15–20 ppm is packaged in 200-liter drums, nitrogen-blanketed and labeled; quantity per drum: 180 kg net. |
| Container Loading (20′ FCL) | 20′ FCL: VAM HQ 15–20 ppm loaded in secure, clean, ventilated container; drums/IBCs properly stowed and restrained. |
| Shipping | VAM HQ (15–20 ppm) is shipped as a stabilized, flammable liquid in dedicated ISO tanks, drums, or tank containers. Transport must prevent polymerization by maintaining inhibitor levels and avoiding heat/ignition sources. Proper grounding, ventilation, and hazard labeling are required. Comply with ADR/IMDG regulations for safe handling and transport. |
| Storage | Store VAM HQ (15–20 ppm) in a cool, dry, well-ventilated area away from heat, sparks, open flames, and direct sunlight. Keep containers tightly closed and upright, preferably under inert gas blanketing. Segregate from oxidizers, peroxides, and acids. Use grounded, explosion-proof equipment. Maintain temperatures below recommended limits to prevent polymerization, and inspect containers regularly for leaks or damage. |
| Shelf Life | Shelf life is typically 12 months from manufacture when stored below 25°C, away from light, in sealed original containers. |
Applications for vinyl acetate monomer (VAM) stabilised with hydroquinone (HQ) at 15–20 ppm span emulsion polymerisation, high-pressure copolymerisation, solution polymerisation, and conversion to dispersible powders or binders. The HQ content conforms to ASTM D2190-07(2021), which defines hydroquinone in VAM at 3–20 ppm. At 15–20 ppm, hydroquinone is in the upper stabilised region, so downstream handling must account for radical consumption, quinone colour formation, pH sensitivity, and altered initiation profiles. In storage, hydroquinone works with dissolved oxygen to retard spontaneous polymerisation; if the monomer is nitrogen-blanketed for extended periods, the inhibitor chemistry changes because less benzoquinone is generated. This section does not prescribe hydroquinone removal; instead, it documents the effect of residual 15–20 ppm HQ across distinct downstream chemistries.
For aqueous polyvinyl acetate homopolymer dispersions used as D3 and D4 wood adhesives, the 15–20 ppm HQ in the VAM feed is normally not removed before emulsion polymerisation. In a 10 m³ stainless-steel reactor with baffles and a two-stage 45° pitched-blade turbine, the aqueous heel is heated to 62–68 °C and contains 8–12% of the total VAM, 4–6 phr polyvinyl alcohol protective colloid with a degree of hydrolysis of 88–92 mol%, sodium bicarbonate buffer to hold pH 4.3–4.8, and the first potassium persulfate charge. Hydroquinone consumes sulfate radicals before polymer particle nucleation begins, producing an induction interval that is observed as delayed exotherm. When the HQ level is near 20 ppm, the initial persulfate demand is commonly shifted upward by 10–20% compared with a feed at 5 ppm to align the exotherm peak with the first monomer feed step; published data for this specific configuration is limited, but the adjustment direction follows radical stoichiometry. The nucleation stage shifts from dominant micellar nucleation toward a mixed homogeneous–coagulative contribution, which broadens the particle size distribution and can reduce low-shear viscosity. Final dispersion solids are set at 50–60 wt%, Brookfield viscosity is measured by ISO 2555 at 25 °C, pH by ISO 976, and D3/D4 wood bond strength by EN 205 under EN 204. Plasticiser such as triacetin or dibenzoate ester at 5–12 phr may be post-added after free monomer falls below 0.5 wt%. End products include furniture assembly adhesives, edge-gluing adhesives, paper tube winding compounds, and bookbinding emulsions. The main incompatibility is alkaline filler or substrate: if the dispersion is compounded above pH 8, residual quinoid species can create yellow discoloration in pale wood bonds.
Vinyl acetate-ethylene dispersions are produced in pressure-rated stainless-steel autoclaves at ethylene partial pressure 20–60 bar and temperature 40–55 °C, using a low-temperature redox initiation system of potassium persulfate and sodium formaldehyde sulfoxylate. The low reaction temperature magnifies the retarding effect of 15–20 ppm HQ; radical trapping by HQ and its oxidation product benzoquinone translates into delayed nucleation and a higher residual VAM level at the first monomer feed stage unless the reducing-agent feed is increased. Production lines typically divide the reducing agent into multiple shots, raising the initial sulfoxylate dose from 0.05 wt% to 0.12 wt% based on total monomer when the HQ value reaches the upper 20 ppm limit. The monomer storage tank is usually vented to atmosphere to maintain dissolved oxygen, because hydroquinone requires oxygen to generate benzoquinone as an active storage inhibitor; before charging a nitrogen-purged reactor, the VAM line is flushed to avoid oxygen carry-over. The dispersion pH is held at 4.0–5.0 with sodium acetate. Ethylene content is adjusted between 10 wt% and 30 wt% to obtain a glass transition from −15 °C to +10 °C; the minimum film-forming temperature is measured by ISO 2115. The end-use formulations are cement-based tile adhesives and ETICS base coats. Spray-dried redispersible polymer powders from such dispersions contain 8–15 wt% polyvinyl alcohol and 0.5–2.0 wt% anti-caking kaolin, with bulk density by ISO 60 and ash by ISO 3451. The powder must redisperse in alkaline cement at pH 12–13; residual HQ/quinone is less damaging in grey or mineral-pigmented compounds than in white architectural coatings, but an excessive quinone level can still disrupt protective colloid distribution and reduce wet adhesion. C2 tile adhesives under EN 12004 require tensile adhesion above 0.5 N/mm² after water immersion; ETICS base coats under ETAG 004 must retain adhesion to EPS board of at least 0.08 MPa after accelerated ageing.
| Test property | Standard method | Acceptance window for VAE construction dispersions |
|---|---|---|
| Solids content | ISO 3251 | 50–60 wt% |
| Brookfield viscosity | ISO 2555 | 2,000–20,000 mPa·s |
| pH | ISO 976 | 4.0–5.5 |
| Minimum film-forming temperature | ISO 2115 | 0–10 °C |
| Tile adhesive tensile adhesion | EN 12004 | ≥0.5 N/mm² after water immersion |
| ETICS base coat adhesion | ETAG 004 | ≥0.08 MPa on insulation board |
In high-pressure EVA copolymerisation, VAM with 15–20 ppm HQ is injected into a continuous stirred autoclave or multi-zone tubular reactor at 1,400–2,200 bar. The reaction temperatures in the autoclave zones are commonly 150–280 °C. At these conditions the hydroquinone inhibitor is consumed quickly, but the finite residence time of the feed zone means that initiation is still retarded relative to a non-inhibited feed. Film-grade EVA with 18–28 wt% vinyl acetate is specified primarily by melt index under ASTM D1238 at 190 °C with 2.16 kg; the melt index may fall below the target if initiator addition is not adjusted when HQ is at 20 ppm. The dominant molecular-weight control is chain transfer to polymer, monomer, and modifier, so HQ does not independently set the average molecular weight, but hydroquinone-derived benzoquinone can contribute to a broader molar mass distribution near the front of the reactor. In photovoltaic encapsulant grades with 28–33 wt% vinyl acetate, the EVA is compounded with peroxide, silane adhesion promoters, and antioxidants, then extruded into film. Peroxide cure at 145–155 °C is affected by any radical-scavenging residual from the monomer, so the peroxide masterbatch is adjusted based on incoming EVA gel content measured by ASTM D2765. Film transparency is measured by ASTM D1003; yellowness index by ASTM E313. End products include hot-melt adhesives with melt index 150–500 g/10 min, multi-layer barrier films, footwear foams, and solar encapsulant films. Operational limitation: if the VAM feed is not homogenised and HQ concentration fluctuates in the 15–20 ppm range, the melt index excursion in continuous lines is more pronounced than in batch lines because feedback correction of initiator has a lag of several residence times.
Continuous polyvinyl alcohol lines that use methanol as solvent and chain-transfer agent run the polymerisation at 60–70 °C with azobisisobutyronitrile or hydrogen peroxide–tartaric acid initiation. The VAM feed containing 15–20 ppm HQ shows an induction delay that is more visible in a continuous stirred-tank cascade than in a batch system because unreacted HQ passes into the next vessel if the first reactor fails to reach high conversion. Methanol chain transfer dominates the degree-of-polymerisation target, but HQ consumes primary radicals and reduces early conversion; the plant compensates by increasing initiator feed in the first reactor, not by raising temperature, because temperature shifts the saponification profile and the alcoholysis degree. After polymerisation, the PVAc solution is saponified with sodium hydroxide in methanol; residual HQ or its oxidised quinone forms coloured complexes in this alkaline stage, raising yellowness index. Textile sizing and paper sizing grades are specified by 4% aqueous solution viscosity under DIN 53015 or ISO 3105, degree of hydrolysis by ISO 15023-2, ash by ISO 3451, and yellowness index by ASTM E313. Grades with 98–99 mol% hydrolysis are used in textile warps and paper sizing; 87–89 mol% grades are used as protective colloids in emulsion polymerisation. Polyvinyl butyral resin for safety glass interlayers is particularly sensitive to hydroquinone-derived colour, because the later condensation with butyraldehyde does not remove quinoid chromophores. The main processing boundary is oxygen exposure: if methanol storage is not nitrogen-blanketed, hydroquinone forms additional benzoquinone, which can act as a chain-transfer or terminating species and shift the viscosity grade downward. Published data for the exact impact of 15–20 ppm HQ on the polydispersity of commercial PVOH is limited, but the direction of the effect is consistent with lower early radical flux and more variable chain initiation.
On architectural coating production lines, VAM with 15–20 ppm HQ is comonomer in semi-batch emulsion polymers with vinyl neodecanoate and n-butyl acrylate. The polymerisation is run at 68–78 °C, which partially mitigates the inhibition compared with low-temperature redox systems, but the pre-emulsion must be acidic because alkaline pre-emulsion can oxidise HQ to coloured benzoquinone before the monomer is polymerised. pH is maintained at 4.2–5.0 with sodium bicarbonate or ammonium hydroxide. The monomer feed is continued for 3.5–5.0 h; a delayed exotherm in the first 30–45 min is often corrected by increasing the ammonium persulfate feed from the mid-range to the upper end of 0.1–0.5 wt% on total monomer. The final latex is then post-treated with a redox chase of 0.05–0.15 wt% aqueous tertiary-butyl hydroperoxide and sodium formaldehyde sulfoxylate to reduce free monomer below 0.1 wt% and destroy residual quinoid species. Typical latex specifications include solids 50–55 wt%, Brookfield viscosity 500–5,000 mPa·s by ISO 2555, pH 7.5–8.5 after ammonia addition, minimum film-forming temperature below 5 °C by ISO 2115, and volatile organic compound content under 2004/42/EC. Scrub resistance is measured by ISO 11998, wet adhesion by ISO 2409, and artificial weathering by ISO 11341. The end products are interior and exterior matt paints, semi-gloss waterborne enamels, and tinted facade coatings. The main incompatibility is with unsaturated alkyd or oil-modified additives; they can increase quinone colour formation during open-time drying, so such additives are either omitted or tested with an accelerated yellowing protocol at 50 °C for 14 days.
Self-crosslinking vinyl acetate binders for nonwoven and glass-mat substrates are polymerised in semi-batch reactors at 65–72 °C with N-methylolacrylamide at 2–5 wt% on total monomer. The HQ in VAM is a minor radical scavenger at this temperature, but its oxidation product can interfere with the acid-catalysed cure step at 130–150 °C by consuming formaldehyde released from N-methylolacrylamide and by producing coloured residues in the bonded substrate. The polymer dispersion is applied by spray, foam, or immersion; the wet pick-up is controlled to 20–35% on fibre weight for air-laid and wet-laid nonwovens. After drying, the nonwoven is cured in a through-air oven or stenter for 1–4 min depending on basis weight. The cure window narrows when dispersion pH is below 3.0 because hydroquinone can be regenerated from quinone and may react with crosslinker; therefore citric acid or ammonium chloride catalysts are dosed at 0.3–2.0 wt% based on solids and the pH is held near 3.5–4.5. Tensile strength and elongation are tested by ISO 9073-3 or ASTM D5034, wet strength retention by ISO 9073-3 after immersion in water at 23 °C for 24 h, and formaldehyde release by EN ISO 14184-1. The final products are filtration media, battery separators, roofing glass mat, automotive headliners, and hygiene top sheet. The main operational boundary is the combination of residual HQ and high cure temperature: if the oven dwell exceeds 3 min at 150 °C, yellowing may appear on white filtration grades, so lower cure temperature and longer dwell are preferred for pale grades.
For paper coating applications, low-viscosity vinyl acetate polymers and vinyl acetate–maleate copolymers are produced from the same HQ-stabilised VAM, but the final acceptance is driven by yellowness index rather than bond strength. The coating colour typically contains 30–50 parts of calcium carbonate or kaolin per 100 parts latex, a starch or polyvinyl alcohol co-binder, and a rheology modifier. The latex is synthesised at 65–75 °C with nonionic and anionic surfactants and then post-treated with an organic peroxide–reducing agent chase until free monomer is below 0.05 wt%. Residual HQ is not usually quantified in the dried coating, but its presence becomes visible when the coating pH exceeds 8.5, especially in the presence of calcium carbonate, because benzoquinone forms brown quinoid condensation products. Therefore the filler slurry is pre-dispersed with a polyacrylate dispersant and the latex is added last to control pH. The coated board is calendered and tested for brightness by ISO 11475, yellowness index by ASTM E313, and surface strength by ISO 3783. If the coated paper is intended for fatty-food contact, the supplier must document compliance with FDA 21 CFR 176.170 and 176.180, or EU 1935/2004 through migration testing under EU 10/2011. End uses include release liners, coated board, inkjet top coats, and dry-strength modifiers for paper. The limiting condition is wet-end use of cationic starch: if the latex contains anionic stabiliser and residual HQ, the complex with cationic starch can generate microflocs that reduce runnability; this is avoided by pre-diluting the latex to 10–15% solids before mixing with cationic additives.
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Vinyl acetate monomer (VAM) inhibited with hydroquinone at 15–20 ppm is a stabilized liquid intermediate for emulsion, suspension, and solution polymerization. The hydroquinone band is narrower than the general commercial range of 3–20 ppm permitted under ASTM D2190-07. Release specifications include vinyl acetate assay ≥99.8 wt% by gas chromatography, water ≤0.050 wt% by ASTM D1364-11, acidity as acetic acid ≤0.010 wt% by ASTM D1613-05, and Pt-Co color ≤10 by ASTM D1209-05. Density is controlled at 20 °C within 0.932–0.936 g/cm³ by ASTM D4052-18. The closed-cup flash point is −8 °C by ASTM D56-22. Hydroquinone content is reported as supplied and is not an inhibitor content guarantee after repeated partial transfers, because the inhibitor is consumed by oxygen and trace radicals over time.
Storage stability in bulk tanks is oxygen-coupled. Hydroquinone does not act as a permanent radical scavenger; it requires molecular oxygen to recycle the quinone/hydroquinone redox couple. A 25 m³ stainless steel vertical tank held at 20–28 °C must maintain a vapor-space oxygen concentration of 5–8 vol% under a nitrogen/oxygen pad to prevent visible polymer formation over a 6-month hold. Tanks above 10 m³ are specified with internal floating roofs, continuous oxygen analyzers, and restricted vapor vents. Transfer equipment uses stainless steel 316L or epoxy-lined carbon steel, with centrifugal pumps operating below 2 m/s flow velocity and electrical bonding to prevent static discharge. The lower explosive limit is 2.6 vol% and the upper explosive limit is 13.4 vol%, so vapor spaces must be actively managed rather than treated as inert.
Hydroquinone concentration is measured by high-performance liquid chromatography with ultraviolet detection at 290 nm after extraction into water/acetonitrile. Samples are ambered and analyzed within 2 h to limit oxidation to benzoquinone. The method is calibrated against freshly prepared hydroquinone standards; aged standards understate inhibitor concentration because quinone formation shifts the chromatographic response. The 15–20 ppm band is used as a release criterion and as a lot-traceability parameter, not as a shelf-life guarantee. For processors with high-solids polyvinyl acetate emulsions, a batch-specific inhibitor-demand test is inserted into raw material release to reduce induction-time drift across incoming lots.
In polyvinyl acetate emulsion polymerization, hydroquinone partitions between the aqueous phase and the monomer phase. The water solubility of hydroquinone at 25 °C is approximately 70 g/L, so a portion of the inhibitor scavenges persulfate-derived radicals before they enter monomer droplets. With potassium persulfate at 70–75 °C, hydroquinone is oxidized to semiquinone and benzoquinone, both of which continue to consume radicals. The resulting inhibition period is not a fixed supplier parameter; it depends on initiator half-life, pH, dissolved oxygen, and the presence of bisulfite or ferrous redox couples. The 10 h half-life temperature of potassium persulfate is approximately 69 °C, and operations near this temperature are more sensitive to changes in inhibitor concentration. In monomer feeds that are not distilled before charging, the initiator feed cannot be reduced simply because the hydroquinone content is at the lower end of 15–20 ppm; a reactor-scale induction test is required.
High-pressure ethylene-vinyl acetate copolymer processes use the hydroquinone level to suppress autopolymerization in feed accumulators and preheater tube walls below 120 °C. Above 150 °C, hydroquinone is thermally consumed and partially volatilized, and it no longer provides meaningful inhibition. In this regime, fouling control depends on oxygen addition to the ethylene stream and on pressure letdown design rather than on inhibitor concentration. Published data for the interaction of hydroquinone with fouling at ethylene pressures above 1,500 bar is limited; therefore, process qualification requires pilot-scale heat exchanger testing with the specific VAM lot.
For continuous polyvinyl alcohol precursor trains, residual hydroquinone and its oxidation products can contribute to color after saponification. At 15–20 ppm, the effect is generally managed by methanol dissolution and sodium hydroxide saponification, but low-color polyvinyl alcohol grades may require pre-polymerization inhibitor removal. Distillation, activated alumina contact, or dilute sodium hydroxide washing can reduce hydroquinone below 1 ppm before charging when the final color specification is below 10 APHA. These operations are conducted in closed systems because of the monomer flash point of −8 °C.
| Property | Control Limit | Test Method | Operational Note |
|---|---|---|---|
| Vinyl acetate assay | ≥99.8 wt% | ASTM D2190-07 | Gas chromatography after inhibition |
| Hydroquinone content | 15–20 ppm | ASTM D2190-07 | As supplied; oxygen-dependent |
| Water | ≤0.050 wt% | ASTM D1364-11 | Karl Fischer titration |
| Acidity as acetic acid | ≤0.010 wt% | ASTM D1613-05 | Acid-base titration |
| Color | ≤10 Pt-Co | ASTM D1209-05 | Platinum-cobalt scale |
| Density at 20 °C | 0.932–0.936 g/cm³ | ASTM D4052-18 | Oscillating U-tube |
| Flash point | −8 °C | ASTM D56-22 | Tag closed cup |
The product is classified as a flammable liquid category 2 under the Globally Harmonized System for Classification and Labelling. Storage temperature is limited to 30 °C to keep inhibitor consumption within the release band; outdoor tanks in regions above 35 °C are insulated or shaded. Copper and copper alloys are incompatible because copper ions accelerate the autoxidation cycle and generate quinone-colored complexes. Stainless steel 316L or epoxy-lined carbon steel is specified. The dynamic viscosity is approximately 0.4 mPa·s at 20 °C, and the vapor pressure is approximately 11.1 kPa at 20 °C; closed-loop transfer, vapor return, and pressure/vacuum relief valves sized to API 2000 are required.
Contact with strong acids, strong bases, or amine-based additives must be controlled through dedicated lines and segregation. Above pH 7, hydrolysis of vinyl acetate to acetaldehyde and acetic acid becomes measurable, and alkaline pH also destroys hydroquinone. In emulsion polymerization, the monomer is added after the aqueous phase has been buffered to pH 4–5. This pH window limits hydrolysis while preserving persulfate initiation. The product should not be mixed with nitrile-based rubber hoses that contain amine antioxidants; polytetrafluoroethylene or stainless steel flex lines are preferred.
Batch-to-batch variation within the 15–20 ppm hydroquinone band is traceable to inhibitor injection control during production loading. The product certificate reports the inhibitor content in milligrams per kilogram; the actual consumption during storage is not captured by the certificate. Long-hold tanks should therefore be sampled at 30-day intervals and analyzed for hydroquinone and water, because water ingress through conservancy breathers can promote hydrolysis even when the inhibitor is present. Re-certification after a 6-month hold is performed by the same methods listed in the specification table.
Compared with vinyl acetate inhibited by 4-methoxyphenol (MEHQ), the hydroquinone-inhibited product shifts the inhibition locus toward the aqueous phase in emulsion systems. Hydroquinone is readily extracted into water, whereas MEHQ remains predominantly in the monomer phase. As a result, HQ at 15–20 ppm can delay initiation before droplet nucleation, while MEHQ tends to reduce propagation after nucleation. In redox-initiated systems at 50–60 °C, hydroquinone may consume reducing agents such as sodium metabisulfite or ferrous sulfate. The reducing-agent feed is adjusted only after a feed-stage inhibitor-demand test, because overcompensation leads to low-molecular-weight polymer and increased coagulum.
Product differences from low-inhibitor VAM at 3–5 ppm hydroquinone are tied to logistics rather than fundamental chemistry. The 15–20 ppm product is selected for unheated marine transport, tropical tank farms, and multi-stage transloading, where repeated vapor-space exposure can deplete inhibitor. The upper bound of 20 ppm is an operational limit rather than a regulatory threshold. In continuous emulsion trains, a shift from 15 ppm to 20 ppm hydroquinone may be visible as a longer induction time; sites using automatic initiator ratio control based on calorimetric data can compensate, but sites using fixed initiator ratios should run an incoming lot inhibitor-demand test.
Autopolymerization risk is not controlled by raising hydroquinone above 20 ppm if the vapor space is inadvertently purged with pure nitrogen. In a 40 m³ railcar, a pure nitrogen pad can strip dissolved oxygen from the monomer, suppress the quinone/hydroquinone regeneration cycle, and permit trace peroxides to accumulate. The failure mode is delayed polymerization in the vessel rather than immediate monomer loss. The correct storage atmosphere is a nitrogen/oxygen mixture with 5–8 vol% oxygen, continuous oxygen analysis, and a vapor return line during loading. Pressure/vacuum relief valves should be sized to API 2000; the electrical classification must account for a flash point of −8 °C, a lower explosive limit of 2.6 vol%, an upper explosive limit of 13.4 vol%, and an autoignition temperature of 402 °C.
At temperatures above 30 °C, thermal initiation increases and hydroquinone consumption accelerates. Storage tanks in high-ambient-temperature locations use external insulation and a reflective top coat. Vapor-space oxygen measurement is integrated into the tank level control system; if oxygen falls below 2 vol%, transfer is suspended and the pad is adjusted before further movement. This operational boundary applies equally to tank farms and railcar unloading stations.
Railcar unloading stations that serve multiple products require dedicated VAM lines or a rigorous cleaning procedure. Cross-contamination with acrylate or methacrylate monomers can introduce active inhibitors such as MEHQ or phenothiazine that alter the radical scavenging profile of the receiving tank. The resulting mixed-inhibitor system is not described by a single hydroquinone concentration; the polymerization induction time may become sensitive to oxygen partial pressure and pH in ways that are not predictable from the hydroquinone certificate. For this reason, product transfer after a grade switch is performed only after a validated cleaning procedure, and the first transfer is sampled for inhibitor profile before release to polymerization.
The monomer is registered under REACH for CAS 108-05-4, EC 203-638-1. Hydroquinone is classified as a skin sensitizer, but at 15–20 ppm the product does not carry the sensitizing concentration threshold of neat hydroquinone. Maintenance workers entering tanks must still follow confined-space procedures and atmosphere testing, particularly because hydroquinone can oxidize to colored quinones in the presence of air and iron. Use in food-contact polymers is not established by the monomer certificate alone; the final polymer must be evaluated under the applicable food-contact regulation, such as FDA 21 CFR 175.105 or FDA 21 CFR 176.170, or the equivalent EU food-contact measure for the finished article.
