SELVOL Polyvinyl Alcohol 165SF

SELVOL Polyvinyl Alcohol 165SF is a fully hydrolyzed, medium-high molecular weight polyvinyl alcohol supplied as a fine-particle powder. The grade is defined by a 4 % aqueous solution viscosity of 62–72 mPa·s at 20 °C, degree of hydrolysis ≥99.5 mol%, pH 5.0–7.0, volatiles ≤5.0 wt%, and ash as Na₂O ≤0.5 wt%. Published supplier data place the weight-average molecular weight in the 146,000–186,000 g/mol range. CAS Registry Number 9002-89-5. The suffix SF designates a fine grind rather than a change in hydrolysis or molecular weight class. Relative to standard SELVOL 165, the shared hydrolysis and viscosity specifications mean that final solution rheology and dried-film properties are closely matched, while dry-powder wetting, dusting behavior, and make-down handling differ. These characteristics position 165SF for use in surface sizing, textile warp sizing, adhesive compounding, and remoistenable coating operations that require a high-molecular-weight fully hydrolyzed PVOH with improved dry-powder dispersion.

What Process Limits Govern High-Solids Make-Down of 165SF?

Make-down in plant-scale equipment is controlled by wetting, shear history, and final cook temperature. Because 165SF is a fine-grind grade, dry powder can be inducted through a venturi eductor or rotor-stator disperser into an ambient-water pre-slurry with less lump formation than standard-grind SELVOL 165. The pre-slurry is not a solution. Complete dissolution requires heating to 90–95 °C and holding under low-shear agitation for 30–40 min; residual undissolved particles produce turbid solutions, uneven film formation, and reduced mechanical properties. At 4 % solids and 20 °C, solution viscosity is 62–72 mPa·s, and at 8–12 wt% solids the solution becomes viscous enough to require positive-displacement pumps and low-RPM agitators to avoid vortexing and shear-induced viscosity loss. The pH range of 5.0–7.0 should be measured after cooling to ambient temperature. Borate-containing additives such as sodium tetraborate can produce gelatinous viscosity build or gelation in concentrated PVOH solutions and must be evaluated separately; this sensitivity is common to fully hydrolyzed PVOH grades and is not unique to 165SF. For high-shear dispersing stages, mechanical chain scission is a known risk if rotor tip speed is maintained above the level required for wetting.

Compared with 87–89 mol% hydrolyzed grades of comparable viscosity class, SELVOL 165SF retains less residual acetate functionality and therefore forms more crystalline dried films. Residual acetate content of ≤0.5 mol% raises the temperature required for complete dissolution relative to partially hydrolyzed grades. The fine particle morphology accelerates wetting and dispersion but does not convert the product into a cold-water-soluble PVOH. If room-temperature solubility is required, a partially hydrolyzed grade is necessary. Film water resistance is differentiated by ASTM D570-22 and ASTM D882-18; fully hydrolyzed PVOH films typically exhibit lower equilibrium moisture uptake than partially hydrolyzed films at equivalent relative humidity. Surface tension measurements by ASTM D1331-20 differentiate the grades as well; the fully hydrolyzed backbone of 165SF exhibits lower interfacial activity than partially hydrolyzed grades, which limits its use as the sole protective colloid in emulsion polymerization systems requiring rapid particle nucleation. This limitation is an operational boundary, not a defect, and supports the selection of 165SF in applications where water resistance after film formation is more important than emulsification performance.

Fine Particle Morphology Alters Dispersion Kinetics Without Shifting the Viscosity Class

Particle size reduction is the principal modification in SELVOL 165SF relative to standard SELVOL 165. Both grades share the same degree of hydrolysis, solution viscosity class, pH, volatiles, and ash specifications. The difference appears during dry handling and pre-wetting: the fine-grind product has higher specific surface area, wets more rapidly in ambient water, and is less prone to lumping during direct addition through an eductor or high-shear mixing loop. The trade-off is increased dusting potential. Dust containment through local exhaust ventilation or enclosed bag-break stations is required in bulk handling areas; organic powder dust should be managed under applicable dust explosion protection standards such as NFPA 654 or site-equivalent ATEX requirements.

Table 1 summarizes the typical lot-to-lot comparison.

The practical consequence is that 165SF can be metered through high-shear eductor systems that would plug or leave undispersed agglomerates with standard-grind 165, while the final solution rheology remains unchanged. The fine grind does not alter the final solution viscosity specification, but it can improve first-pass dispersion in continuous make-down equipment and reduce the time required for visual clarity to develop in a batch cook tank.

When Hot-Water Make-Down Capacity Is Unavailable

In plants without jacketed cook tanks or steam sparging, the fine particle size of 165SF can be exploited by pre-wetting powder in ambient water at 5–7 wt% solids before injecting live steam or transferring to a heated vessel. The cold pre-slurry remains an unstable suspension; if held without agitation, settled powder can consolidate and require high shear to redisperse. Complete dissolution still requires a final temperature of 90–95 °C and a hold time sufficient to clear suspended microgel particles, typically 30–40 min in 500–2,000 L batches. Attempting to dissolve 165SF entirely at ambient temperature produces grainy, high-turbidity dispersions and reduced film strength due to undissolved polymer domains. Under the same ambient pre-wet conditions, standard-grind SELVOL 165 can form larger agglomerates and bridge in volumetric screw feeders; 165SF reduces that failure mode but does not eliminate the need for heated dissolution.

In paper and textile surface sizing, the high molecular weight and fully hydrolyzed backbone of 165SF are used to increase surface strength and water resistance. In surface sizing of paperboard, size press formulations at 5–8 wt% solids may be evaluated; Cobb water absorption is measured by ISO 535:2023, and surface strength may be assessed by ISO 3783:2014. Published data for 165SF at specific coat weights is limited; formulation adjustments must be confirmed by mill trials. In textile warp sizing, slasher formulations at 8–10 wt% solids are typical for spun cotton and polyester/cotton yarns, but add-on and weave-room performance depend on yarn construction, slasher drying capacity, and loom conditions. Because the grade is fully hydrolyzed, the sized yarn film is less water-sensitive after drying than partially hydrolyzed grades, but desizing requires hot water or enzymatic chemistry rather than ambient-water rinses alone.

Adhesive and Remoistenable Coating Performance Boundaries

Adhesive compounding with 165SF is typically driven by water resistance, solution viscosity, and film formation. In remoistenable paper coatings, the grade can be formulated at 6–9 wt% solids for roll-coater application; after drying, the fully hydrolyzed film has lower cold-water sensitivity than partially hydrolyzed films but still requires moisture or water for re-wetting. Wet tack and bond strength must be validated on the target substrate because published data for 165SF in specific adhesive formulations is limited. Borate or boric acid crosslinking can increase viscosity and produce gels; if a crosslinked system is desired, borate addition should be controlled by pH and buffer concentration, and viscosity monitored under ISO 2555 conditions. The fine particle morphology can reduce lumping during batch addition to high-viscosity adhesive mixers, but dust containment remains necessary. For paper and paperboard adhesive applications, FDA 21 CFR 175.105 is the principal relevant citation, subject to the limitations in that section.

For food-contact uses, SELVOL 165SF follows the same regulatory routes as other fully hydrolyzed PVOH grades. Table 2 lists the principal United States food-contact citations and their applicability.