| HS Code | 313042 |
| Product Name | SELVOL Polyvinyl Alcohol 325 |
| Chemical Name | Poly(vinyl alcohol) |
| Cas Number | 9002-89-5 |
| Appearance | White to cream granular solid |
| Hydrolysis | 98.0-98.8 mol% |
| Viscosity 4 Aqueous Solution At 20 C | 28-32 mPa·s |
| Ph 4 Aqueous Solution | 5.5-7.0 |
| Ash Content | ≤1.2% |
| Volatile Matter | ≤5.0% |
| Solubility | Soluble in hot water; insoluble in cold water and common organic solvents |
As an accredited SELVOL Polyvinyl Alcohol 325 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SELVOL Polyvinyl Alcohol 325 is supplied as a white powder in 25 kg multi-layer paper bags with inner liner for dry storage. |
| Container Loading (20′ FCL) | SELVOL PVA 325 loaded in 20′ FCL as 25kg bags on pallets, securely blocked and braced, approximately 20 metric tons. |
| Shipping | SELVOL Polyvinyl Alcohol 325 ships as a free-flowing white granular powder in multi-wall paper bags with polyethylene liners, palletized and stretch-wrapped. It is non-hazardous per DOT; no hazmat endorsement required. Protect from moisture, keep bags sealed, and use standard dry freight transport with proper labeling. |
| Storage | Store SELVOL Polyvinyl Alcohol 325 in its original, tightly sealed container in a cool, dry, well-ventilated area. Protect from moisture, excessive heat, and direct sunlight. Keep away from ignition sources and incompatible materials. Avoid generating dust; keep container clean and closed when not in use to maintain product quality. |
| Shelf Life | SELVOL Polyvinyl Alcohol 325 has a shelf life of two years when stored in a cool, dry area. |
SELVOL Polyvinyl Alcohol 325 is a fully hydrolyzed, high-viscosity PVOH grade with a 4% aqueous solution viscosity of 28.0–32.0 cP at 20 °C, hydrolysis of 98.0–98.8 mol%, and residual ash content below 0.5% as Na₂O. The solution preparation requires mechanical heating above 85 °C with high-shear equipment such as a Cowles saw-tooth disperser or an in-line rotor-stator homogenizer; cold-water swelling without temperature rise produces gel particles that cannot be fully dispersed in downstream mixing. The high molecular weight and near-complete hydrolysis of the grade yield films with elevated tensile strength, organic-solvent resistance, and low cold-water solubility, which define the application boundaries described below.
For high-density woven cotton and polyester/cotton warp yarns, SELVOL Polyvinyl Alcohol 325 is formulated into a warp size concentrate at 8–12 wt% solids, cooked at 90–95 °C for 30–45 minutes under low-shear circulation before transfer to the size box. The high-viscosity grade produces a size film with tensile strength typically in the range of 50–70 MPa when measured on cast films according to ISO 527-3:2018, and this contributes to lower warp breakage rates on air-jet looms running at 600–800 picks/min. For polyester-rich blends, adhesion to hydrophobic fiber surfaces is improved by adding a non-ionic wetting agent at 0.2–0.5 wt% of the size bath; without the wetting agent, the dry size film sheds at heald eyelets and reed dents. The grade requires increased desizing energy compared with low-viscosity PVOH; hot-water prewashing above 70 °C followed by oxidative desizing with hydrogen peroxide at 1–2 mL/L in alkaline steam is used for cotton warps, while enzymatic desizing is slower and must be confirmed by gravimetric size removal or an iodine-boric acid spot test. In size recovery units, the grade can be ultrafiltered, but gel-layer accumulation on polysulfone membranes is observed when the feed solids exceed 7 wt%, and a crossflow velocity above 3 m/s is required to maintain permeate flux.
Size press blends of oxidized starch and SELVOL Polyvinyl Alcohol 325 exhibit non-Newtonian shear-thinning behaviour that governs film transfer at the metering nip. A typical surface-sizing formulation contains 1 part PVOH 325 solids to 3–4 parts oxidized starch solids at a total solids of 6–9%, with each component cooked separately and then blended in the circulation tank. The high solution viscosity of the grade restricts total solids above 9%; above this level the Brookfield viscosity of the blend may exceed 150–200 mPa·s at 60 °C, causing film splitting and uneven pickup on film-transfer metering equipment. Cobb values measured according to ISO 535:2014 can be reduced by 20–30% relative to starch-only sizing when the PVOH fraction is increased, but runnability on pond-type size presses is limited by misting and foaming. The addition of 0.05% of a mineral-oil-based defoamer is typically required because the high-molecular-weight grade stabilizes foam in recycled furnish. Surface strength is evaluated with an IGT printability tester according to TAPPI T499; improvements of 0.5–1.2 m/s in pick velocity are typical when PVOH solids replace 10–15% of the starch fraction. For food-contact paper and paperboard, compliance should be verified against 21 CFR 176.170 and 21 CFR 175.105 depending on the final package construction and food type.
When envelope flap and paper tape converters require a dry film that blocks cleanly in storage yet re-moistens rapidly on a water wheel, SELVOL Polyvinyl Alcohol 325 can be formulated as the primary film former at 15–25 wt% solids, with glycerol or sorbitol at 5–10 wt% of total solids and a plasticizer such as triacetin or neopentyl glycol dibenzoate at 2–5 wt%. The dry film resists blocking at 40 °C and 60% RH when tested according to ASTM D1146-15, and re-moistens on mail-sealing equipment with dwell times of 1–3 seconds. Engraved transfer rollers with 30–45 lines/cm deposit 8–15 g/m² dry coat weight; above 15 g/m², the dry film tends to curl the paper substrate during drying. The rewet tack is sensitive to humectant ratio: sorbitol levels above 10 wt% depress blocking resistance but extend open time beyond 20 seconds on high-speed flap-sealing lines. Borax can be added at 0.5–1.0 wt% to increase wet tack through reversible borate–diol crosslinking, but the formulated adhesive must be held below pH 8.5 to avoid syneresis and yield stress build-up in the coating pan.
In technical ceramic extrusion, the green-binder function of SELVOL Polyvinyl Alcohol 325 is evaluated through paste rheology, green strength, and ash residue after debinding. Alumina, zirconia, cordierite, and titania-based honeycomb monolith formulations use the binder at 1.5–4.0 wt% based on dry ceramic powder mass. The binder is pre-dissolved in water at 10–15 wt% solids and added to the batch in a planetary mixer or Z-blade kneader. The high molecular weight of the grade increases plastic viscosity to 1,000–3,000 Pa·s at shear rates below 10 s⁻¹, which supports shape retention in honeycomb die lands with wall thicknesses below 100 µm. Green flexural strength of dried alumina test bars measured in three-point bending according to ASTM C1161-18 typically increases from 1.5–3.0 MPa for binderless spray-dried compacts to 6–12 MPa at 3 wt% binder addition; this reduces edge damage in subsequent green machining. Because the ash content of the grade is specified below 0.5% as Na₂O, the residual inorganic load after burnout is low, but sodium at the upper specification limit can interact with silica-rich bodies and alter sintering behavior. Debinding uses a two-stage ramp: 180–220 °C for 1–2 hours to remove water, then 550–650 °C for 2–4 hours to decompose the PVOH backbone. Heating rates between 0.5–1.0 K/min through the 250–450 °C region are required for cross-sections above 10 mm to prevent internal pressure from volatile decomposition products.
Extrusion casting of SELVOL Polyvinyl Alcohol 325 requires careful plasticizer management because the high degree of hydrolysis suppresses low-temperature dissolution. Film formulations contain 10–20 phr of plasticizer, usually glycerol plus sorbitol, to bring elongation at break into the range of 150–250% when tested according to ISO 527-3:2018. A single-screw or twin-screw extruder with barrel zones between 160 °C and 210 °C and a polished chill roll at 20–40 °C is used; screw torque rises rapidly if feed moisture falls below 10 phr. The resulting film dissolves only above 75–85 °C in agitated water, which makes it unsuitable for cold-water release applications but useful for packaging where delayed solubility is required. The cast film can be laminated to paper or nonwoven substrates using water-based adhesives, but drying must remain below 120 °C to avoid pinhole formation. Water-vapour transmission rate measured according to ISO 15106-3:2019 is lower than that of partially hydrolyzed grades at 50% RH and 23 °C, but at 85% RH the film plasticizes and the barrier deteriorates; the grade should not be specified as a high-humidity barrier. In detergent unit-dose pouch structures, 325 is typically blended with a medium-viscosity PVOH to balance seam-sealing window and wash dissolution; 325 alone may show incomplete dissolution at 30 °C wash cycles.
In dry-mix cementitious tile adhesives classified under EN 12004-1:2017, SELVOL Polyvinyl Alcohol 325 functions as a water-retention and anti-sag powder at addition rates of 0.3–1.0 wt% of total dry blend. The grade is dry-blended with Portland cement, graded sand, redispersible polymer powder, and cellulose ether before bagging; when mixed with water, the PVOH swells and increases dynamic viscosity of the wet mortar to 600–1,200 Pa·s at 5 minutes after mixing. Water retention measured by the vacuum filter method or EN 1348:2007 improves to 90–95%, reducing skin formation on open-time panels. Adhesion to fully vitrified porcelain tiles after 28 days of water immersion, tested according to EN 1348:2007, is maintained at 0.8–1.2 MPa when the PVOH level is below 0.5%; above 1.0 wt%, excess water-phase viscosity lowers wet density and can produce pinholes at the tile interface. The powder must remain moisture-protected during storage because partial pre-dissolution in the bag forms lumps that standard paddle mixers at 400–600 rpm cannot disperse. Formulators should avoid combining 325 with high levels of borate-modified retarders; the borate–diol interaction forms a gel that raises mortar yield stress and reduces trowel slip. Initial setting time should be checked according to EN 196-3 when dosage exceeds 0.5 wt%, because PVOH can retard cement hydration by film formation on C₃S surfaces.
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SELVOL Polyvinyl Alcohol 325 is a partially hydrolyzed polyvinyl alcohol resin supplied as a white to off-white granular powder. The typical specification includes a 4% aqueous solution viscosity of 28–32 mPa·s at 20 °C, a degree of hydrolysis of 87.0–89.0 mol%, pH of 4.5–6.5 for a 4% solution, volatile matter not exceeding 5.0%, and ash not exceeding 0.5%. Residual acetate groups therefore represent approximately 11–13 mol% along the polymer backbone. The material is characterized under ISO 15023-2 or equivalent PVOH grade protocols, with aqueous solution viscosity commonly determined using a Brookfield rotational viscometer. The polymer is registered under CAS 9002-89-5 and is recognized as a water-soluble film former rather than a crosslinking resin. These properties place SELVOL 325 in the intermediate-viscosity segment of partially hydrolyzed PVOH grades, between low-viscosity protective colloids and high-viscosity film-forming resins.
| Grade | 4% Solution Viscosity at 20 °C | Degree of Hydrolysis | Processing Consequence |
|---|---|---|---|
| SELVOL 205 | 5–6 mPa·s | 87–89 mol% | Lower solution viscosity, reduced film tensile strength, easier transfer and air release in adhesive mixing |
| SELVOL 325 | 28–32 mPa·s | 87–89 mol% | Intermediate viscosity, higher film strength than SELVOL 205, lower solution viscosity than SELVOL 425 |
| SELVOL 425 | 62–72 mPa·s | 87–89 mol% | Higher viscosity, greater film toughness, increased shear thickening in emulsion systems |
On production-scale dissolution equipment, SELVOL 325 is typically slurried in 20–30 °C water at low shear before heating to 80–90 °C with continuous axial-flow agitation. Direct addition of dry powder into a hot, high-shear vortex can generate partially hydrated agglomerates, commonly called fish eyes, which require extended hold times above 80 °C to clear. Complete dissolution is confirmed by absence of visible gels and stable Brookfield viscosity after cooling to 25 °C. High-shear rotor-stator devices may be used for initial dispersion, but prolonged shear at elevated temperature can reduce apparent solution viscosity through polymer chain scission. Batch-to-batch hydrolysis variation is normally constrained by the 87.0–89.0 mol% specification, but uncontrolled moisture uptake during storage can shift solution solids and change the amount of dry polymer actually delivered when weigh feeders are not moisture-corrected. This is observed as drift in size-box solids or emulsion reactor viscosity on continuous lines.
Partially hydrolyzed grades such as SELVOL 325 retain 11–13 mol% acetate groups along the polyvinyl alcohol chain. Fully hydrolyzed PVOH resins typically retain 2 mol% or less residual acetate. The difference shifts dissolution temperature, aqueous surface activity, and adhesion to nonporous substrates. SELVOL 325 dissolves more readily in cold water and yields clear solutions at 80–90 °C, whereas fully hydrolyzed grades often require heating to 90–95 °C and may form haze upon cooling if insufficiently filtered. Film water resistance is lower for SELVOL 325 because the acetate groups disrupt interchain hydrogen bonding and increase equilibrium moisture uptake. This property is useful where re-wettability or water-redispersibility is required, and it becomes a liability in bonded structures exposed to sustained humidity. Residual acetate functionality also improves adhesion to hydrophobic polymer films and some coated papers, but peel strength under high-humidity conditions is reduced compared with fully hydrolyzed PVOH films. These differences are routinely observed in adhesive laminating lines and textile warp sizing, where hydrolysis level is selected according to end-use humidity and bond-line performance rather than solution clarity alone.
Emulsion polymerization trials using SELVOL 325 as the primary protective colloid typically operate at addition levels of 2–5% by weight of total monomer, depending on target latex particle size and final emulsion viscosity. In a jacketed glass-lined reactor with anchor agitation at 120–180 rpm, substitution of SELVOL 205 with SELVOL 325 increases reactor torque and final emulsion Brookfield viscosity at the same solids content. The higher molecular weight fraction adsorbs onto vinyl acetate or vinyl acetate-ethylene droplets, creating a thicker hydrated layer and increasing low-shear viscosity. The same molecular weight contribution improves mechanical stability during transfer and against freeze-thaw cycles, although final film clarity can decrease if the polymerization temperature drops below the cloud point of the partially hydrolyzed PVOH. Formulators evaluating SELVOL 325 for emulsion stabilization typically verify latex viscosity, grit formation, and particle size distribution via ISO 22412 or equivalent dynamic light scattering methods. Published data for this specific reactor configuration is limited, so pilot-scale agitation power and monomer feed rate remain the controlling variables for scale-up.
Addition of borax or boric acid to a SELVOL 325 solution produces reversible di-diol crosslinks between adjacent hydroxyl-acetate sequences. The resulting viscosity increase is pH-dependent and becomes pronounced above pH 8. In corrugating adhesive and remoistenable adhesive operations, this interaction is used deliberately to build short flow character and rapid green tack, but the borate-to-PVOH ratio must be controlled because gelation can occur at borate salt concentrations as low as 0.1–0.5% of solution weight, depending on temperature and degree of hydrolysis. SELVOL 325 shows higher reactivity toward borate ions than fully hydrolyzed grades because the acetate groups alter local polymer conformation and availability of adjacent hydroxyl pairs. Sodium tetraborate decahydrate is normally staged after the PVOH solution has cooled to below 45 °C to avoid localized gelation. Formulations containing borate should be protected from pH drift and high-shear pumping because crosslinked domains can be mechanically disrupted, causing irreversible loss of viscosity during a production run. Avoid combination with amine-based additives that raise pH and accelerate premature crosslinking in the holding tank.
Textile warp sizing baths using SELVOL 325 are commonly maintained at 6–10% solids and 70–80 °C on slasher sizing equipment, where the size film is pressed into yarn by nip rolls. The intermediate viscosity of SELVOL 325 permits adequate add-on without the excessive size-box viscosity that can occur with SELVOL 425 in dense yarn sets. Tensile properties of sized yarn are determined according to ASTM D2256, and abrasion resistance of the size film is evaluated with a Taber-type rotary platform under ASTM D3884. SELVOL 325 films are re-wettable and can be desized with hot water, reducing the need for oxidative desizing agents compared with some starches and fully hydrolyzed PVOH grades. Residual foam in the size box at high machine speed can be a limitation; defoamer selection must be compatibility-tested because silicone-based defoamers can deposit on yarn and interfere with downstream dye uptake. The same grade is used in paper surface sizing at 2–8% solids on film press, gate-roll size press, or rod metering coater equipment, where surface strength improvement is evaluated by an IGT pick tester according to ISO 3783 or TAPPI T 476.
Dry SELVOL 325 is hygroscopic and should be stored in unopened bags at ambient temperature and low relative humidity. The typical volatile matter specification of ≤5.0% is not a storage limit; moisture uptake above 60% relative humidity can cause powder caking and bridging in hoppers, especially in climate-uncontrolled warehouses. The product is combustible as an organic dust; dust control measures should follow NFPA 652 for combustible dust hazard assessment. Pneumatic transfer systems should be grounded to prevent static accumulation. Dissolution vessels should be closed or ventilated to manage water vapor during heating. The polymer is stable under normal storage, but prolonged exposure to strong acids, strong bases, or oxidizing agents can degrade the chain and lower solution viscosity. Operational boundaries therefore include exclusion of oxidizer storage in the same area, moisture protection for opened bags, and verification of solution viscosity after prolonged holding at elevated temperature.
Regulatory documentation for SELVOL 325 is commonly organized around food-contact adhesive and paper/paperboard applications. The following citations are cited in supplier documentation and should be confirmed against the current safety data sheet and applicable country-specific requirements.
| Citation | Application Boundary | Limitation |
|---|---|---|
| 21 CFR 175.105 | Adhesives for food packaging | Use as a component of adhesives; extractives limitations apply |
| 21 CFR 176.170 | Paper and paperboard in contact with aqueous and fatty foods | Migration limits and end-use restrictions under specified test protocols |
| 21 CFR 176.180 | Paper and paperboard in contact with dry foods | Dry food only unless specified conditions are met |
| TSCA inventory | Industrial chemical commerce | Polymer listing applies; monomer residues may be regulated separately |
Food-contact clearance is not a single-test certification. Conversion of SELVOL 325 into finished packaging components requires end-use migration testing according to the cited sections and applicable overall migration protocols. Published data for this specific configuration is limited where extraction conditions depend on paper furnish, coating weight, adhesive coat weight, and food simulant selection.
