| HS Code | 691480 |
| Chemical Formula | C4H6O2 |
| Molecular Weight | 86.09 g/mol |
| Appearance | clear colorless liquid |
| Purity | ≥ 99.8 wt% |
| Dpa Content | low (typically ≤ 0.05 wt% diacetate) |
| Water Content | ≤ 0.05 wt% |
| Acidity | ≤ 0.01 wt% as acetic acid |
| Inhibitor | 15–20 ppm hydroquinone |
| Boiling Point | 72.7 °C at 760 mmHg |
| Melting Point | -93 °C |
| Flash Point | -8 °C closed cup |
| Autoignition Temperature | 427 °C |
| Density | 0.932 g/cm³ at 20 °C |
| Vapor Pressure | 115 mmHg at 20 °C |
| Vapor Density | 3.0 (air = 1) |
| Viscosity | 0.4 mPa·s at 20 °C |
| Refractive Index | 1.395 at 20 °C |
| Solubility In Water | 2.3 g/100 mL at 20 °C |
As an accredited Low DPA Polymer Grade VAM factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Available in 200 L drums or 1,000 kg IBC totes, nitrogen-blanketed to maintain Low DPA VAM purity. |
| Container Loading (20′ FCL) | 20′ FCL container loaded with secured drums of Low DPA Polymer Grade VAM, properly ventilated and braced for safe transport. |
| Shipping | Low DPA Polymer Grade VAM ships as a flammable, inhibited liquid in ISO tanks or stainless steel drums under nitrogen blanketing. It must be kept away from heat, sparks, and oxidizing agents. Maintain inhibitor concentration to prevent polymerization. Use proper Class 3 hazard labels, shipping documentation, and emergency response protocols. |
| Storage | Store Low DPA Polymer Grade VAM in a cool, dry, well-ventilated area away from heat, sparks, open flames, and direct sunlight. Keep containers tightly sealed and upright, preferably under inert gas, to prevent polymerization and contamination. Avoid contact with peroxides, oxidizers, and metals like copper. Maintain proper temperature and use within recommended shelf life. |
| Shelf Life | Shelf life is typically 12 months when stored under nitrogen, kept cool, dry, and protected from light and oxygen. |
Low-DPA polymer-grade vinyl acetate monomer is specified in radical polymerization lines where residual diphenylamine acts as a chain-transfer inhibitor and color-forming species. The material is sparged with nitrogen until dissolved oxygen is below 0.2 ppm, then metered through 10 µm cartridge filtration before entering a jacketed stainless steel reactor equipped with dual impellers. In a typical polyvinyl acetate homopolymer dispersion for wood bonding, a protective colloid based on polyvinyl alcohol with 87–89 mol% hydrolysis and 13–20 mPa·s viscosity in 4% solution is dissolved in deionized water at 60–70 °C prior to monomer addition. The monomer is fed over 180–240 min under reflux at 66–70 °C, with ammonium persulfate at 0.08–0.15 wt% and sodium bicarbonate buffer at 0.05–0.10 wt% to hold pH between 3.0 and 5.0. The resulting dispersion reaches 55–60 wt% solids, residual free monomer below 0.3 wt%, and Brookfield viscosity between 2,000 and 6,000 mPa·s at 25 °C using spindle 4 at 20 rpm. Low diphenylamine residue shortens the induction period to 15–30 min and reduces yellowing in dry films stored for 90 days under natural light. Beech lap shear specimens prepared according to EN 205 and classified under EN 204 D3 typically record 8–12 MPa shear strength with wood failure above 60%. The same polymer backbone, when formulated with 2–5 wt% dibutyl phthalate or acetyl tributyl citrate, enters packaging adhesives, paper lamination, and bookbinding lines; residual diphenylamine above 5 ppm would shift Pt-Co color measured by ASTM D1209-05 above 30 APHA and create visible haze in cast films.
In C2TE-class cementitious tile adhesives, a vinyl acetate-ethylene dispersion with 70–80 wt% vinyl acetate and 20–30 wt% ethylene is produced in a pressure reactor at 15–45 bar and 40–80 °C. Ethylene is dissolved into the aqueous phase under controlled pressure while VAM is metered through a high-shear loop; low-DPA monomer reduces radical scavenging from inhibitor residues and narrows particle size distribution to 0.5–2.0 µm when measured by laser diffraction according to ISO 13320. The dispersion is colloid-stabilized or emulsifier-stabilized to 55–60 wt% solids with a glass transition temperature between −15 °C and 0 °C for the high-ethylene grade, or 0–10 °C for the lower-ethylene grade. After spray drying, the redispersible polymer powder is dry-blended at 2.0–3.5 wt% into a C2 formulation containing 35–45 wt% Portland cement, 50–60 wt% graded quartz sand, 0.3–0.6 wt% cellulose ether, and 0.1–0.3 wt% calcium formate. Tensile adhesion after water immersion, heat ageing, and freeze-thaw cycling is tested according to EN 1348 within the classification framework of EN 12004-1:2017; C2TE products require at least 1.0 MPa under each exposure, while open-time adhesion after 20 min must remain above 0.5 MPa. The ethylene content reduces film modulus and permits wetting of dusty concrete substrates, while the VAM fraction provides polar adhesion to cement hydrates. Batch-to-batch viscosity drift in the latex is controlled by maintaining residual monomer below 0.1 wt% and by sodium acetate buffer concentration below 0.2 wt%. If the monomer contains excessive diphenylamine, persulfate demand increases during polymerization and latex particle nucleation becomes erratic, producing coagulum above 0.05 wt% on 100 µm filters and lowering tensile adhesion on porcelain tiles by 0.2–0.4 MPa.
| VA content | Ethylene content | Tg | MFFT | Polymer powder dosage in C2 adhesive | EN 12004-1:2017 performance target |
|---|---|---|---|---|---|
| 85–90 wt% | 10–15 wt% | 0–10 °C | 1–5 °C | 2.5–3.5 wt% | C1: ≥0.5 MPa dry and water immersion |
| 70–80 wt% | 20–30 wt% | −15–0 °C | 0 °C | 2.0–3.0 wt% | C2TE: ≥1.0 MPa water, heat, freeze-thaw; ≥0.5 MPa after 20 min open time |
Photovoltaic module encapsulant film based on ethylene-vinyl acetate copolymer containing 28–33 wt% vinyl acetate is compounded on a twin-screw extruder with 40:1 L/D ratio and zone temperatures from 80 °C at the feed throat to 140 °C at the die. The low-DPA polymer-grade monomer used in the copolymerization prevents chromophore accumulation during compounding and lamination; cured films show total luminous transmittance above 91% by ASTM D1003-21 and yellowness index below 2.0 by ASTM E313-20. Formulation additives include tert-butyl peroxy-2-ethylhexyl carbonate at 0.6–1.2 phr, vinyltrimethoxysilane coupling agent at 0.3–0.6 phr, and a hindered phenolic antioxidant at 0.1–0.2 phr. Melt index is controlled between 12 and 40 g/10 min at 190 °C and 2.16 kg per ISO 1133-1:2022 to permit lamination at 145–155 °C for 12–18 min without excessive flash flow. Crosslinking is verified by xylene extraction according to ASTM D2765-16; gel content must exceed 75% to resist creep at 85 °C and 85% relative humidity. Volume resistivity measured by ASTM D257-14 remains above 1×1014 Ω·cm after damp-heat ageing, and peel adhesion to tempered glass exceeds 40 N/cm when stripped at 180° and 100 mm/min according to ASTM D903-98(2017). Low residual diphenylamine in the VAM feedstock is critical because amine-derived oxidation products migrate to the glass interface during lamination and reduce peel strength below 30 N/cm after 1,000 h of damp-heat exposure.
| Property | Test method | Cured EVA encapsulant requirement |
|---|---|---|
| Total luminous transmittance | ASTM D1003-21 | > 91% |
| Yellowness index | ASTM E313-20 | < 2.0 |
| Volume resistivity | ASTM D257-14 | > 1×1014 Ω·cm |
| Gel content after cure | ASTM D2765-16 | 75–90% |
| Peel adhesion to glass | ASTM D903-98(2017) | > 40 N/cm |
Saponification of polyvinyl acetate resins derived from low-DPA polymer-grade VAM is conducted in methanol at 25–40 wt% polymer solids using sodium hydroxide or sodium methoxide catalyst at 0.2–0.5 mol% based on acetyl units. The reaction proceeds at 40–60 °C in a kneader reactor or continuous belt saponifier, where the methyl acetate by-product is stripped under reduced pressure and recovered in a distillation column. Degree of hydrolysis is controlled between 87 mol% and 99 mol%; partially hydrolyzed grades used for suspension polymerization aids retain 10–13 mol% residual acetyl groups, while fully hydrolyzed fiber-sizing grades contain less than 1 mol%. Viscosity of a 4% aqueous solution at 20 °C measured by capillary viscometry according to ISO 3105 ranges from 3–70 mPa·s, corresponding to weight-average molecular weights between approximately 20,000 and 200,000 g/mol. Low diphenylamine content in the original VAM is essential for optical clarity and thermal stability of the resulting PVOH; sodium acetate ash is held below 0.5 wt%, methanol below 2 wt%, and 4% solution transmittance above 95% at 550 nm. Fiber-grade PVOH is dissolved at 8–12 wt% in hot water and applied as warp sizing on high-speed looms, while film-grade PVOH is cast into water-soluble packaging and unit-dose detergent films with dissolution times below 60 s at 10 °C.
Solvent-borne coil coating and printing ink resins based on vinyl chloride-vinyl acetate copolymers containing 85–90 wt% vinyl chloride and 10–15 wt% vinyl acetate are produced by suspension polymerization at 50–70 °C. The aqueous phase contains 0.05–0.10 wt% polyvinyl alcohol suspending agent, and lauroyl peroxide initiator is dosed at 0.1–0.5 wt%. Acid-modified terpolymers incorporate 0.5–2 wt% maleic acid or acrylic acid to improve adhesion to metallic substrates. The resin is dissolved in a ketone-ester blend such as methyl isobutyl ketone and ethyl acetate at 20–30 wt% solids; low-DPA monomer prevents yellowing of the solution and maintains Pt-Co color below 50 APHA by ASTM D1209-05. Solution viscosity is managed between 150 and 600 mPa·s at 25 °C depending on molecular weight and solvent composition. End uses include aluminum foil lacquers requiring 120–150 s pendulum damping hardness by ISO 1522, heat-sealable lid coatings for pharmaceutical blister packs, vinyl floor wear layers, and gravure inks for PVC films. The vinyl acetate component reduces crystallinity, improves pigment wetting, and permits dissolution in lower-cost solvents compared with pure vinyl chloride homopolymer.
Architectural wall paints formulated below 50 g/L VOC under EU Directive 2004/42/EC require a terpolymer binder produced by seeded semi-continuous emulsion polymerization from low-DPA polymer-grade VAM, butyl acrylate or 2-ethylhexyl acrylate, and VeoVa 9 or VeoVa 10. A typical pre-emulsion contains 40–60 wt% VAM, 25–40 wt% acrylate, and 10–25 wt% vinyl ester of versatic acid. The polymerization is initiated with ammonium persulfate at 0.3–0.6 wt% on total monomer and conducted at 75–85 °C over 4–6 h. The finished dispersion has 50–55 wt% solids, pH 8.0–9.0 after ammonia neutralization, minimum film formation temperature between 0 °C and 5 °C by ISO 2115, and glass transition temperature from −10 °C to +15 °C. In an eggshell architectural formulation at 35–45% pigment volume concentration, the binder reduces coalescent demand below 3 wt% of binder solids while maintaining wet scrub resistance measured by ISO 11998 with film loss under 5 µm after 200 cycles. Low diphenylamine content in the VAM fraction prevents post-polymerization pH drift and lowers volatile amine off-gassing; headspace testing by ASTM D6886 is used to confirm VOC compliance. Film formation on cold substrates is assessed by applying a 200 µm wet film at 5 °C and 80% relative humidity, with cracking assessed under 10× magnification after 24 h. End products include interior and exterior low-VOC wall paints, plasters, and tinted topcoats where blocking resistance after 24 h at 50 °C must exceed 4 on the 1–5 scale of ASTM D4946-89(2017).
Spray-dried redispersible polymer powders derived from polyvinyl acetate and vinyl acetate-ethylene dispersions are produced by atomizing a 45–55 wt% solids latex into a co-current hot-air dryer with inlet temperature 150–170 °C and outlet temperature 70–85 °C. Polyvinyl alcohol protective colloid at 8–15 wt% of polymer solids prevents irreversible coagulation, while 3–8 wt% kaolin or calcium carbonate reduces caking. The powder must pass through 125 µm sieve with less than 1% residue after 30 s redispersion in deionized water; bulk density is controlled between 400 and 600 g/L by ISO 60, and ash content is 8–15% by ASTM D5630. Low-DPA polymer-grade VAM limits thermal discoloration during spray drying and prevents odor carryover into dry-mix mortars. In external thermal insulation composite systems tested under ETAG 004 or EAD 040083-00-0404, the powder is dosed at 1.5–5.0 wt% of the dry formulation to improve adhesion to expanded polystyrene, water resistance, and flexibility. Base coat mortars containing 2.5–3.5 wt% powder and 5–10 wt% dispersion fiberglass mesh achieve tensile adhesion above 0.08 MPa on polystyrene and above 0.5 MPa on concrete after water immersion. Self-leveling compounds and tile adhesives use the vinyl acetate-ethylene types at 2.0–3.0 wt% to meet EN 12004-1:2017 C2TE requirements.
Waterborne barrier coatings for paperboard employ vinyl acetate-acrylate or vinyl acetate-VeoVa emulsions applied by rod, air-knife, or curtain coating at 2–6 g/m² dry coat weight. The latex is formulated at 45–55 wt% solids with glass transition temperature between −10 °C and +30 °C, pH 7.5–8.5, and Brookfield viscosity 50–500 mPa·s at 25 °C. Grease resistance is measured by the Kit test according to TAPPI T 559, with values typically between 8 and 12 after 24 h conditioning at 23 °C and 50% relative humidity. Water absorption is evaluated by ISO 535, with Cobb values below 20 g/m² for coated folding carton board. The low-DPA monomer is critical for indirect food-contact compliance because residual diphenylamine can migrate into fatty simulants; finished coatings are extracted under 21 CFR 176.170 and 21 CFR 176.180 protocols with specific migration limits for aromatic amines. Odor and off-taste panels identify amine-type defects at sub-ppm levels, so the low-DPA specification is maintained at receiving inspection by HPLC with a quantification limit of 0.5 ppm. End products include paper cups, sandwich wraps, pastry boxes, and repulpable folding cartons where the coating is compatible with standard alkaline repulping and does not reduce fiber yield below 95% in mill trials.
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Low DPA Polymer Grade VAM is a vinyl acetate monomer grade, CAS 108-05-4, empirical formula CH₃COOCH=CH₂, molecular weight 86.09 g/mol. It is supplied as a clear, colorless liquid stabilized with hydroquinone at 3–7 ppm. The low-DPA designation refers to reduced diphenylamine content, where DPA denotes diphenylamine, a nitrogen-containing stabilizer residue controlled below the general polymer-grade monomer level for polymerization processes sensitive to amine-derived color and initiator consumption. The grade designation does not change the fundamental boiling range or liquid density of vinyl acetate; it is an additional producer-defined restriction on the certificate of analysis. Published data for the exact numeric DPA cutoff is limited across producers, and receiving sites should confirm the current lot-specific value rather than applying a universal specification.
Physical properties are consistent with polymer-grade vinyl acetate monomer: boiling point 72.7 °C at 101.3 kPa, freezing point -93.2 °C, density 0.934 g/cm³ at 20 °C, vapor pressure 12.3 kPa at 20 °C, and refractive index 1.3958 at 20 °C. These values define the handling envelope but are independent of the DPA level.
Diphenylamine can act as a radical scavenger or retarder in free-radical polymerization. In redox-initiated vinyl acetate emulsion polymerization, this residue consumes a portion of the oxidant before the propagation phase, producing an extended induction period and a requirement for higher initiator addition to reach target conversion. The low-DPA monomer therefore reduces the uncontrolled nitrogen-containing load entering the reactor. This is particularly relevant when the product is polymerized in methanol for polyvinyl alcohol, where residual DPA can generate yellow chromophores during alkaline alcoholysis. The effect is not limited to color: variable DPA in incoming monomer can shift molecular weight distribution at fixed persulfate/metabisulfite loading, leading to batch-to-batch variability in Brookfield viscosity and wet coagulum.
In vinyl acetate-ethylene emulsion lines using 10–50 m³ stirred reactors, the practical qualification of low-DPA monomer is normally based on induction time and oxidant demand. A representative redox recipe operates at 70–80 °C with potassium persulfate at 0.2–0.5 phr and sodium metabisulfite at 0.1–0.3 phr. Monomer with elevated diphenylamine content delays the initial exotherm and can require trim additions of persulfate during the first 30 min of reaction. Low-DPA monomer narrows the induction time distribution because one radical-consuming variable is reduced. The exact improvement is reactor-geometry dependent; published data for a specific production line is limited, and plant qualification should be by controlled substitution with retained baseline samples.
In batch emulsion polymerization of vinyl acetate homopolymer, the low-DPA grade is used with a protective colloid such as partially hydrolyzed polyvinyl alcohol at 2–6 wt% on monomer. The organic phase is dispersed in water at 45–55 wt% solids, and the reaction is initiated with a redox couple. Typical operating parameters are jacket temperature 72–78 °C, mixer speed 60–120 rpm for a 20 m³ anchor/turbine reactor, and monomer addition over 3–4 h. Low-DPA monomer shortens the induction period and permits lower initiator top-up. The finished emulsion is filtered through 150–250 µm bag filters; wet coagulum is measured gravimetrically after 1,000 g of latex is passed through the screen. A shift from general polymer-grade VAM to low-DPA VAM under identical redox conditions can reduce wet coagulum by 0.2–0.5 g/kg in qualification trials; published data for this specific configuration is limited.
For wood adhesive applications, the emulsion is compounded with plasticizers, fillers, and polyvinyl alcohol. The low-DPA monomer does not change adhesive set speed but reduces the raw material contribution to color in tint-free films. Viscosity is adjusted with carboxymethylcellulose or fumed silica, and free monomer is steam-stripped to below 0.1 wt%. Residual vinyl acetate is measured by headspace gas chromatography; the target is set by the finished product specification rather than by the monomer DPA level.
The following acceptance matrix is representative of polymer-grade vinyl acetate monomer. Low-DPA status is additive and does not relax the general polymer-grade limits.
| Parameter | Unit | Test method | General polymer-grade limit | Low-DPA polymer-grade limit |
|---|---|---|---|---|
| Vinyl acetate purity | wt% | Gas chromatography | ≥ 99.9 | ≥ 99.9 |
| Color | APHA/Pt-Co | ASTM D1209 | ≤ 10 | ≤ 10 |
| Water | wt% | ASTM D1364 Karl Fischer | ≤ 0.05 | ≤ 0.05 |
| Acidity as acetic acid | wt% | ASTM D2086 | ≤ 0.005 | ≤ 0.005 |
| Aldehydes as acetaldehyde | wt% | Producer GC | ≤ 0.005 | ≤ 0.005 |
| Hydroquinone inhibitor | ppm | Producer HPLC/UV | 3–7 | 3–7 |
| Distillation range | °C at 101.3 kPa | ASTM D1078 | 72–73 | 72–73 |
| Diphenylamine (DPA) | mg/kg | Producer HPLC/GC-MS | Not routinely reported | Producer-defined low ceiling; CoA required |
ASTM D2190 is the primary vinyl acetate specification used by producers and users. Acidity and water are controlled because both hydrolyze or interact with alcoholysis catalysts in downstream polymer production. Hydroquinone is intentionally present; the low-DPA grade is not uninhibited. When DPA is reduced, the hydroquinone stabilizer level remains within the same 3–7 ppm window unless the receiving site specifies a different inhibitor package. The DPA limit is tested by producer-specific chromatographic methods and is reported on the certificate of analysis.
Relative to technical-grade vinyl acetate monomer, the low-DPA polymer-grade product applies stricter water, acidity, and color controls. Technical-grade material may be delivered with water up to 0.1 wt%, acidity as acetic acid up to 0.01 wt%, and APHA color up to 15, depending on producer specification. General polymer-grade VAM imposes the same water, acidity, and color limits as low-DPA polymer grade but does not report DPA. Urethane-grade or chemical-intermediate-grade VAM may be supplied with different inhibitor packages and is not qualified for optical-grade PVOH or EVOH unless the certificate of analysis demonstrates equivalence. The low-DPA designation therefore represents a subgroup of polymer-grade VAM, not a different solvent or a different chemical structure.
DPA in vinyl acetate monomer is quantified by reversed-phase HPLC with UV detection at 254 nm after solvent exchange or by gas chromatography-mass spectrometry with selected ion monitoring. Method detection limits below 0.5 mg/kg are typical in producer laboratories. Because no ASTM International method specific to DPA in vinyl acetate monomer exists, cross-producer data should be compared only when the same sample preparation and detector response calibration are used. A receiving site that uses a different detector may report values that differ by 10–20% from the producer CoA. The practical low-DPA acceptance limit is therefore producer-specific and should include a retest protocol for borderline lots.
PVOH producers use vinyl acetate in methanol solution polymerization followed by alkali-catalyzed saponification. The low-DPA grade is selected when optical clarity and low yellowness index are required for polarizing film, packaging interlayer, or optical-grade sizing applications. Alkaline alcoholysis converts PVAc to PVOH and can release amine-derived chromophores if the monomer feed contains DPA. Resin color after drying is measured on 4 wt% aqueous solutions as APHA, and cast film is measured for yellowness index per ASTM E313 and total transmittance per ASTM D1003. Low-DPA monomer removes one color-forming variable but does not eliminate the need for methanol recovery control, sodium acetate reduction, and metal-ion exclusion.
EVOH lines polymerize ethylene with vinyl acetate and then saponify the EVA copolymer. Feed impurities at the 1 mg/kg level can affect line gel counts, especially at high ethylene content. Low-DPA monomer is specified for barrier resin production where black specks and gels are controlled by optical film inspection. The processing condition in high-pressure ethylene-VAM copolymerization is typically 150–250 °C and 1,000–2,500 bar; the monomer's low-DPA status is only one part of feed purity management. Oxygen, acetaldehyde, and acid gases are monitored separately.
In adhesive and nonwoven binder applications, low-DPA VAM is used when emulsion color and residual monomer odor are critical. The monomer is copolymerized with ethylene, acrylates, or versatic acid esters in batch or continuous stirred-tank reactors. Viscosity of the finished emulsion is typically measured by ISO 2555 or ASTM D2196 at 25 °C; low-DPA monomer reduces viscosity drift driven by variable radical scavenging. The product is also used in vinyl acetate-ethylene dispersions for redispersible polymer powders, where spray-drying thermal history can intensify amine-derived color. In those lines, the monomer is fed from storage tanks maintained below 30 °C and blanketed with dry nitrogen; inhibitor concentration is verified after every transfer to avoid localized hydroquinone depletion.
In EVOH processes, the saponified EVA is extruded through flat dies and cast film lines equipped with screen changers and melt gear pumps. Melt temperature is typically 210–230 °C. Feed-derived DPA can contribute to die-lip build-up and gel formation; the low-DPA monomer is one part of an incoming feed specification that includes copper, iron, sodium, and chloride trace-metal limits. The film is inspected by optical gel counters and rated for black speck density per internal quality limits. Published data for the exact correlation between DPA concentration and gel count is limited, but producers specify the grade to narrow the impurity population entering the line.
Vinyl acetate monomer is a flammable liquid with flash point -8 °C and autoignition temperature 402 °C. Low-DPA polymer-grade VAM must be stored in carbon steel or stainless steel tanks with inert gas padding, at or below 30 °C, and away from peroxides, azo compounds, strong acids, and strong bases. Hydroquinone inhibitor is consumed by oxygen; the inhibitor concentration must be checked before the monomer is transferred to a reactor. If hydroquinone falls below 3 ppm, the monomer should not be distilled or heated because exothermic polymerization can occur. Water contact must be limited to prevent hydrolysis to acetaldehyde and acetic acid, which would increase acidity and shift the certificate-of-analysis values beyond accepted limits.
Transport classification is UN 1301, Class 3, Packing Group II. The low-DPA grade is inhibited for transport and storage; low DPA does not mean inhibitor-free. Compatible wetted materials in transfer lines include stainless steel and carbon steel; static mixing elements and copper-based alloys should be avoided unless the specific supplier technical bulletin confirms compatibility. Bulk storage tanks are normally equipped with pressure/vacuum relief valves and nitrogen blanketing at 5–15 kPa. Before a new lot is accepted, the receiving site should compare the supplier CoA against the internal specification for DPA, water, acidity, color, and hydroquinone, and should retain a sealed reference sample for odor, color, and GC purity evaluation.
