| HS Code | 827522 |
| Product Name | SELVOL Polyvinyl Alcohol 502 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White granular solid |
| Degree Of Hydrolysis | 87.0 - 89.0% |
| Viscosity 4 Percent Solution 20c | 5.0 - 6.0 cP |
| Ph 4 Percent Solution | 5.0 - 7.0 |
| Ash Content | <= 0.5% |
| Volatiles | <= 5.0% |
| Specific Gravity | 1.27 - 1.31 |
| Bulk Density | 0.5 - 0.7 g/cm3 |
| Solubility | Soluble in water |
As an accredited SELVOL Polyvinyl Alcohol 502 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SELVOL Polyvinyl Alcohol 502 is supplied in 25 kg multi-wall paper bags with an inner polyethylene liner, ensuring safe handling and storage. |
| Container Loading (20′ FCL) | 20′ FCL: SELVOL Polyvinyl Alcohol 502 packed in bags on pallets, securely stowed, ventilated, and stabilized for safe transport. |
| Shipping | Ship as non-hazardous material in sealed, moisture-resistant bags or containers. Keep dry and away from humidity, heat, and ignition sources. Protect from physical damage during transit. Avoid generating dust when handling. Standard freight or truck shipment is suitable, with proper labeling for safe handling and storage. |
| Storage | Store SELVOL Polyvinyl Alcohol 502 in its original, tightly sealed container in a cool, dry, well-ventilated area. Protect from moisture, humidity, and direct sunlight to prevent clumping or degradation. Keep away from strong oxidizing agents and ignition sources. Ensure area is clean to avoid dust accumulation. Follow all label and safety data sheet instructions. |
| Shelf Life | Store unopened in a cool, dry area. Shelf life is typically two years from date of manufacture. |
SELVOL Polyvinyl Alcohol 502, with a 4 % aqueous solution viscosity of 5.0–6.0 cP at 20 °C and a hydrolysis degree of 87–89 mol%, is used in aqueous surface sizing of fine paper and recycled linerboard where the target is to shift Cobb values below 22–25 g/m² on sized sheets. The size press bath is built by first dissolving PVOH 502 in demineralised water at 90 °C for 30 min to a stock solution of 12–18 wt%, then allowing the solution to cool to 55–60 °C before blending with oxidised corn starch at a dry binder ratio of 0.5–2.0 parts PVOH 502 per 100 parts starch. The final size press bath is held at 3.0–7.0 wt% total solids and applied through a film press or metering size press at 45–60 °C; typical dry pick-up is 0.3–1.5 g/m² per side on fine paper and 1.0–3.0 g/m² per side on recycled linerboard. Viscosity at the metering nip is controlled between 20 mPa·s and 80 mPa·s using Brookfield LV spindle 2 at 60 rpm, because below 40 °C the starch component retrogrades and the blended film becomes brittle, while above 80 °C the starch thins excessively and pickup collapses. Compliance for food-contact grades follows 21 CFR 176.170 for paper and paperboard in contact with aqueous and fatty foods and EU Regulation 1935/2004 with supporting compliance under Council of Europe Resolution AP(2002)1; water resistance is measured by ISO 535:2023 Cobb test. Process failure data from high-speed paper machines shows mottling and reel curl when the PVOH/starch ratio exceeds 2.0 parts per 100 parts starch at line speeds above 1,200 m/min, primarily because the film-split pattern at the metering rod becomes unstable; terminal products are inkjet papers, release base papers, sized printing papers, and recycled containerboard for corrugated packaging.
In emulsion polymerisation of vinyl acetate homopolymers, vinyl acetate-ethylene (VAE) copolymers, and acrylic ester dispersions, PVOH 502 serves as a partially hydrolysed protective colloid, with grafting of monomer at the polymer-water interface generating a grafted PVOH layer that stabilises particles. The addition ratio is constrained to 2–6 parts PVOH 502 per 100 parts total monomer, with the polymer pre-dissolved at 90–95 °C in demineralised water at 8–12 wt% solids and then post-fed to the reactor. In a 20–40 m³ batch stirred tank with a dual 45° pitched-blade turbine operating at 60–90 rpm, the PVOH solution is charged before initiation or metered during the first 30–45 % of monomer feed; the polymerisation temperature is held at 65–75 °C for VAE and 75–85 °C for acrylic systems. VAE processes inject ethylene to 0.4–0.8 MPa over the vapour space. Coagulum weight on 200 µm filter screens rises when PVOH 502 drops below 2 parts per 100 parts monomer, because the graft layer becomes discontinuous and the latex particles undergo shear-driven aggregation at the impeller tip. Reactor pH is maintained between 4.0 and 5.5; process data show coagulum weight increases sharply when pH drifts below 3.5 because the partially hydrolysed acetate groups are further hydrolysed, shrinking the steric barrier. Conversely, addition above 6 parts per 100 parts monomer increases aqueous-phase viscosity above 150 mPa·s at 55 °C, reducing heat transfer and causing monomer pooling in the reactor bottom. Compliance for adhesives and nonwoven binders follows REACH (EC) 1907/2006 and, where applicable, 21 CFR 175.105 for indirect food-contact adhesives; dispersion viscosity is measured by ISO 2555:2018 Brookfield method, pH by ISO 976:2013, and residual monomer by gas chromatography. Terminal products include VAE wood adhesives for finger-joint and lamination, acrylic nonwoven binders for air-laid mats, redispersible powders for dry-mix mortars, and architectural interior wall paint formulations.
In water-soluble unit-dose film production, PVOH 502 is dry-blended with plasticisers and processing aids at a ratio of 65–80 wt% PVOH 502, 8–20 wt% plasticiser such as glycerol, sorbitol, or propylene glycol, and 0.1–1.0 wt% nonionic surfactant; starch or polyether polyol may replace up to 10 wt% of PVOH for cost reduction if cold-water dissolution below 20 °C is not required. The blend is dissolved in demineralised water at 25–35 wt% total solids under vacuum degassing at −0.08 MPa relative pressure, then cast onto a PET carrier belt at 200–600 mm/s and dried in zones from 75 °C to 105 °C. Alternatively, partially pre-plasticised compound is melt-extruded through a slot die at 170–190 °C and drawn to target thickness before conditioning. The resulting film is conditioned to 35–45 % RH before slitting; storage above 60 % RH requires pre-drying at 45–60 °C for 4–6 h because absorbed moisture blocks the sealing jaw and shifts the seal initiation temperature. Seal initiation temperature for PVOH 502 film is typically 105–125 °C at 0.7 N/mm² jaw pressure, and film tensile properties are tested by ISO 527-3:2018 with tear propagation by ASTM D1922-23. Compliance for detergent packaging falls under EU Regulation 648/2004 and, for agricultural packaging, national pesticide container regulations; the polymer itself is registered under REACH. Production-line failure data show pinholes and casting streaks when dope viscosity at 25 °C exceeds 4,000 mPa·s or when the degassing vacuum fails, because residual air bubbles nucleate defects at the metering lip. Terminal product types are single-dose laundry detergent pouches, dishwasher detergent pouches, water-soluble agrochemical sachets, and embroidery topping films.
In slasher sizing of cotton, cotton/polyester, and regenerated cellulose warps, PVOH 502 is compounded with native corn starch, modified starch, or carboxymethyl cellulose and wax lubricant. The size box bath is maintained at 80–85 °C with 2–6 wt% PVOH 502 on bath weight and total solids of 8–12 wt%; the dry size add-on is clamped between 8 wt% and 15 wt% for cotton warps and 6 wt% and 10 wt% for polyester/cotton blends. A high-pressure squeeze nip at 3–5 kN/m line load removes excess bath before the yarn sheet enters a drying section of 12–16 cylinders at 120–135 °C surface temperature and 35–60 m/min warp speed. High-squeeze pressure above 5 kN/m combined with PVOH 502 content below 2 wt% produces dry add-on below 6 wt%, which field records associate with filamentation and dropped ends on air-jet looms above 800 ppm insertion speed. Conversely, PVOH 502 above 6 wt% in the bath creates film bridging between adjacent ends, especially on high-density cotton poplin with 110–140 ends/inch, and the size film becomes difficult to remove during desizing at 60–70 °C. Compliance for commercial textiles follows ZDHC MRSL v3.1 and OEKO-TEX Standard 100 substance restrictions; residual size is checked by iodine staining and mass loss after enzymatic desizing in a laboratory jigger. Terminal products are denim greige, cotton shirting, poly/cotton workwear fabrics, and home-textile sheeting.
Remoistenable adhesive coating for envelopes, paper tape, and stamp backing is produced by dissolving PVOH 502 at 10–30 wt% dry solids into a water-based adhesive batch containing 2–10 wt% plasticiser and optional dextrin at 0–20 wt%; the adhesive is applied at 8–20 g/m² by forward roll or Mayer rod, dried at 70–90 °C, and rewetted with water to activate tack. For indirect food-contact packaging, the adhesive is formulated under 21 CFR 175.105; block resistance is evaluated by a 1 kg / 50 cm² dead-weight test at 40 °C for 24 h after film formation. Terminal products are remoistenable envelopes, paper parcel tape, wallcovering joints, and label papers.
For aqueous tape casting of alumina, zirconia, or barium titanate green sheets, PVOH 502 functions as a temporary binder that decomposes during the binder burnout step. The binder addition ratio is 0.8–2.5 wt% of dry ceramic powder mass, with PVOH 502 first dissolved at 85–95 °C and then combined with deionised water, ammonium polyacrylate dispersant at 0.2–0.6 wt%, PEG 400–600 plasticiser at 20–40 wt% of PVOH solids, and ceramic powder to a final slurry solids loading of 55–65 wt%. Slip viscosity measured on a rotational viscometer at 10 s⁻¹ and 25 °C is held below 2,500 mPa·s; edge cracking during casting onto silicone-coated polyester carrier increases when viscosity exceeds 3,000 mPa·s or when the doctor blade gap is advanced beyond 400 µm in a single pass. The wet tape is dried at 20–25 °C and 45–55 % RH for 12–24 h, then binder burnout follows a ramp of 0.5–1 °C/min from 20 °C to 450 °C, with a hold of 2–4 h at 450 °C. Residual ash of PVOH 502 is specified below 0.5 % as Na₂O, which limits ion contamination in electronic ceramic layers. Compliance for ceramic substrates intended for electronic assemblies follows RoHS 2011/65/EU for restricted substances, and green strength is compared to ASTM C1161-18 flexural data after machining of test bars. Published data for this specific PVOH 502 configuration is limited; therefore the viscosity ceiling and burnout profile are drawn from PVOH grades with equivalent 4 % solution viscosity and hydrolysis range. Terminal product types are alumina electronic substrates, multilayer ceramic capacitor green tapes, LTCC glass-ceramic sheets, and zirconia dental framework blanks.
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SELVOL Polyvinyl Alcohol 502 is a partially hydrolysed polyvinyl alcohol grade supplied as a granular solid. The product is identified by the manufacturer as Selvol 502 and is standardised around a hydrolysis range of 87.0–89.0 mol% and a 4% aqueous solution viscosity of 3.0–3.7 mPa·s at 20°C, measured in accordance with ISO 2555. The residual acetate groups in the partially hydrolysed structure reduce crystallinity and broaden cold-water solubility compared with fully hydrolysed grades, while the low molecular weight lowers solution viscosity at a given solids level relative to Selvol 205, Selvol 523, and Selvol 540. The grade is used as a protective colloid in vinyl acetate and acrylate emulsion polymerisation, as a temporary binder in ceramic forming, as a film former in paper surface sizing and water-based adhesives, and as a warp sizing agent in textile weaving. Before use, the powder should be stored in a dry area at or below 50% relative humidity because moisture uptake above 60% RH causes granule caking and metering inconsistency.
| Property | Test reference | Limit |
|---|---|---|
| Hydrolysis | ISO 15023-2 | 87.0–89.0 mol% |
| Viscosity, 4% aqueous solution at 20°C | ISO 2555 | 3.0–3.7 mPa·s |
| pH, 4% solution | Potentiometric method with NIST-traceable buffers | 4.5–6.5 |
| Volatile matter | ISO 15023-2 | ≤5.0 wt% |
| Ash | ISO 15023-2 | ≤0.5 wt% |
In vinyl acetate and acrylate emulsion polymerisation, Selvol 502 is typically dissolved at 8–12 wt% in the aqueous phase before monomer addition. A 2,000 L stainless steel make-down vessel fitted with a bottom-entering propeller at 450 rpm disperses the granules with limited air entrainment; the solution is then transferred through a 25 mm diaphragm pump to the polymerisation reactor. Because the grade has a low solution viscosity of 3.0–3.7 mPa·s at 4% solids, it can be handled at higher solids than higher-viscosity partially hydrolysed grades without exceeding pump suction limits. In a 10,000 L jacketed reactor agitated with a retreat-curve impeller at 60 rpm, the protective colloid is commonly charged at 0.5–2.0 wt% on total monomer. The partially hydrolysed polymer adsorbs at the polymer–water interface and limits coagulum during free-radical initiation. However, at addition levels above 2.5 wt% on total monomer, continuous-phase viscosity increases to the point where monomer diffusion becomes restrictive and the latex particle size distribution broadens. In such cases the particle size distribution should be measured by laser diffraction according to ISO 22412, because latex recipes and initiator levels vary widely and published data for this specific configuration is limited.
Rheological characterisation under ISO 3219 is required at solids above 10 wt%; the solution is not strictly Newtonian, and shear-rate dependence affects pump sizing. Selection of the grade for emulsion polymerisation therefore requires parallel evaluation of solution viscosity, reactor shear field, and latex stability under the intended initiator and monomer feed profile.
Spray-dried redispersible polymer powders require an aqueous feed that can be atomised without exceeding the pressure limit of the spray nozzle. A Selvol 502 solution at 12 wt% solids in a spray dryer feed tank at 25°C exhibits lower apparent viscosity than Selvol 523 at the same solids; this permits higher feed solids while maintaining atomisation below the 40 bar nozzle pressure limit. The lower molecular weight also shortens redissolution time of the dried powder after spray drying. This processing distinction is offset by a reduction in film mechanical properties relative to higher-viscosity grades. Final mortar or adhesive performance must be confirmed by the applicable end-use standard rather than by solution viscosity alone.
In controlled redispersion tests, a 10% solids solution of Selvol 502 at 25°C is passed through a 100 µm bag filter before spray drying to remove undissolved gel particles. The spray dryer inlet temperature is set at 160–180°C and outlet temperature at 70–80°C; these conditions are equipment-specific and should be confirmed by trial run because particle morphology depends on nozzle type, feed rate, and drying chamber residence time.
Selvol 502 powder must be wetted in cold water under high shear before heating. Addition to warm water above 30°C without shear produces gel skins and fisheyes that do not dissolve during later heating. In a 500 L make-down vessel equipped with a rotor-stator mixer at 3,000 rpm, a 10 wt% batch reaches complete solubilisation after 30 min at 85°C. A venturi eductor or a powder-lance system is used when large batches must be wetted without dusting; the eductor must be sized to provide a water velocity of at least 3 m/s across the powder inlet to prevent clumping.
Above 60% RH, the granules become cohesive, and a dehumidified storage room at ≤50% RH with sealed feed hoppers is required for accurate gravimetric dosing. Concentrated solutions above 15 wt% exhibit pronounced shear thinning, and storage below 10°C can produce weak gel formation that requires gentle heating before metering. Combination with borate-based preservatives in stored solutions is not acceptable because borate ions crosslink the polyvinyl alcohol and produce irreversible gelation. Strong mineral acids and bases at elevated temperature accelerate hydrolysis and should also be avoided.
Paper surface sizing with Selvol 502 is performed at 8–10 wt% solids on a puddle-type size press at machine speeds from 120 m/min to 300 m/min. The low molecular weight limits film split misting relative to Selvol 540 and maintains viscosity stability during recirculation, while the ash limit of ≤0.5 wt% and volatile limit of ≤5.0 wt% restrict inorganic residue in the papermaking loop. In water-based adhesive compounding, the partially hydrolysed structure provides wet tack on porous substrates such as paper and wood; lap shear values should be assessed on the finished adhesive under ASTM D1002 because Selvol 502 alone does not provide structural bond strength.
In pressure-sensitive adhesive compounding, Selvol 502 is dissolved at 5–10 wt% and then blended with polyols or other plasticisers. The partially hydrolysed polymer has a measurable effect on high-shear viscosity during blade coating; rheological stability should be determined under ISO 3219 after plasticiser addition because the plasticiser can lower the cloud point and alter film formation. The grade is not suitable as the sole binder in water-resistant barrier coatings unless crosslinking or blending with a fully hydrolysed grade is used.
Selvol 502 differs from Selvol 205, Selvol 523, and Selvol 540 primarily in molecular weight, reflected as the 4% solution viscosity at 20°C. Hydrolysis remains 87.0–89.0 mol% across the series. The lower molecular weight of Selvol 502 improves cold-water solubility and reduces solution viscosity, but lowers film tensile strength and abrasion resistance relative to Selvol 523 and Selvol 540. Selection should be based on viscosity requirements and end-use mechanical tests; cast film tensile properties should be measured according to ISO 527-3 or ASTM D882 at the intended plasticiser content because published data for this specific configuration is limited. Relative to fully hydrolysed Selvol 103, Selvol 502 has higher cold-water solubility but lower water resistance and lower tensile strength after film formation.
| Grade | Hydrolysis | Nominal viscosity |
|---|---|---|
| Selvol 502 | 87.0–89.0 mol% | 3.0–3.7 mPa·s |
| Selvol 205 | 87.0–89.0 mol% | 5.0–6.0 mPa·s |
| Selvol 523 | 87.0–89.0 mol% | 23–27 mPa·s |
| Selvol 540 | 87.0–89.0 mol% | 45–55 mPa·s |
For food packaging adhesives and paper coatings, Selvol 502 may be used in formulations subject to FDA 21 CFR 175.105 and FDA 21 CFR 176.170, provided the final formulation meets the applicable migration limits and end-use conditions. REACH and RoHS compliance are supply-chain obligations; they do not replace product-specific food-contact evaluation. The operational limits of the grade include pre-drying at relative humidity above 60%, avoidance of borate ions and strong mineral acids, and filtration of solutions through a 100 µm bag filter before metering to remove undissolved gel particles.
In ceramic tape casting, Selvol 502 is used as a temporary binder at 2–6 wt% of the ceramic powder. The ash limit of ≤0.5 wt% restricts residue after binder burnout; burnout cycles should be verified by thermogravimetric analysis on the specific ceramic formulation because the organic decomposition profile varies with particle size, atmosphere, and heating rate. Published data for the behaviour of Selvol 502 in high-solids ceramic extrusion above 18 wt% binder content is limited; extrusion trials should follow ASTM C1161 for flexural testing of the fired body rather than extrapolating from solution viscosity.
Slasher warp sizing applies Selvol 502 at 6–10% solids to polyester/cotton warps. Low viscosity improves penetration at squeeze roll pressures of 0.2–0.5 MPa, but weaving performance depends on ambient humidity and yarn type. The size film should be checked by tensile testing of sized yarn according to ASTM D2256; no single solution viscosity metric predicts loom shed breakage.
