Shuangxin 17-99L PVA (PVA 100-27L)

Shuangxin 17-99L PVA (also listed as PVA 100-27L in procurement documentation) is a fully hydrolysed polyvinyl alcohol resin carrying a nominal degree of polymerisation of 1700 and an alcoholysis degree of 99.0–100.0 mol%. The alternate grade designation PVA 100-27L reflects a nominal solution viscosity of 27 mPa·s in a 4% aqueous solution at 20 °C; the 100 prefix is associated with fully hydrolysed chemistry in some supplier nomenclature systems, while the L suffix is used by the vendor to denote a low-ash or low-volatile variant. Published data for this exact suffix is limited, and release values should be confirmed against the producer certificate of analysis. As supplied, the material is a granular solid with release limits for volatile matter at ≤5.0 % and ash at ≤0.7 % by mass. The fully hydrolysed backbone gives high crystallinity, low cold-water solubility, and a dissolution temperature above 88 °C. The routine release properties and corresponding Chinese national test methods are listed below.

The dual designation does not indicate a blend; both designations refer to the same fully hydrolysed product class. Where the two names appear together, 17-99L is the Chinese domestic grade designation and 100-27L is used in export documentation. Laboratories should cross-check the lot number and certificate of analysis because suffix usage can differ between production sites.

How Does Fully Hydrolysed 17-99L Differ from Partially Hydrolysed PVA Grades?

The principal structural difference between 17-99L and partially hydrolysed PVA grades such as 17-88 is the residual acetate group content. A fully hydrolysed resin with an alcoholysis degree of 99.0–100.0 mol% contains 0–1.0 mol% residual acetate groups, whereas a 17-88 grade retains approximately 12 mol% acetate groups. The acetate groups disrupt interchain hydrogen bonding and reduce crystallinity; the result is that 17-88 hydrates and dissolves in water at 20–40 °C, while 17-99L develops a clear solution only after heating to 88–95 °C. This dissolution temperature differential changes process design. Coating and sizing lines switching from 17-88 to 17-99L must raise storage-tank and jacketed-kettle temperatures and must manage higher hot-solution viscosity at equivalent solids. Fully hydrolysed films also show greater resistance to room-temperature re-wetting, which is relevant when dried film is exposed to condensation or alkaline paper converting environments. Conversely, partial hydrolysis improves wetting and adhesion to hydrophobic surfaces, so 17-88 is preferred for cold-water adhesive systems where re-solubility is an advantage.

Preparation of a 10 wt% stock solution at production scale involves dispersing the powder in cold demineralised water at 25–35 °C under agitation before heating to 90–95 °C. Direct addition of dry powder to hot water produces gel shells and fisheyes that require extended holding and can blind 100–150 µm filter cartridges. In a 5,000 L jacketed vessel equipped with a 45°-pitched blade turbine running at 80–120 rpm, complete dissolution is typically observed within 60–90 min at 90–95 °C. After cooling, a 4% solids solution should fall within 25.0–31.0 mPa·s at 20 °C when checked by Brookfield viscometer; values outside this window commonly indicate either moisture uptake during storage or thermal-mechanical chain scission. Vacuum deaeration at 20–30 kPa absolute is applied before film casting or precision coating to remove entrained air that otherwise forms craters and streak defects. Centrifugal or cartridge filtration to 50–100 µm is recommended downstream of the letdown tank to remove residual gel particles.

When 17-99L Replaces 17-88 in Paper Surface Sizing and Textile Warp Sizing

Substitution of 17-99L for partially hydrolysed 17-88 in paper surface sizing raises the working bath temperature from 30–50 °C to 80–95 °C. The fully hydrolysed film exhibits higher tensile stiffness and lower elongation at break, which improves surface pick resistance but increases brittleness; plasticisers such as glycerol or PEG 400 are therefore incorporated at 5–15 phr. In textile warp sizing, the high crystallinity of 17-99L maintains yarn abrasion resistance at low humidity but can produce size shedding if the drying section exceeds 140 °C. Production lines using 17-99L commonly set the size box temperature at 85–90 °C and doctor blade pressure between 150–400 kPa depending on machine speed. Residence time above 95 °C should not exceed 120 min because hydrolysis and oxidation reduce viscosity, and batch-to-batch variation in ash below 0.7 % can alter film clarity on coloured grades. The higher solution viscosity also reduces penetration into unbleached recycled fibre, so the internal sizing chemical demand may need adjustment to maintain ash retention.

In polyvinyl acetate emulsion polymerisation, 17-99L is used as a protective colloid at 2–8 wt% on monomer. The fully hydrolysed grade produces higher aqueous-phase viscosity per unit mass than 17-88 and yields emulsions with larger particle sizes if the colloid addition is not adjusted. Dried films from 17-99L-containing adhesives resist re-dissolution in cold water but remain alkali-sensitive. Formulators using borax or boric acid should exercise caution because syneresis or gelation can occur at concentrations above 0.1 wt% of wet adhesive. The grade is also used for hot-water-soluble film where solubility is required only above 80 °C; published data for this specific configuration is limited, and laboratory dissolution trials are required before line qualification. For caustic-strippable temporary coatings, the fully hydrolysed grade provides controlled solubility in dilute sodium hydroxide at 0.5–2.0 mol/L, but swelling rate depends on film thickness and plasticiser content.

In coating applications requiring permanent water resistance, 17-99L is crosslinked with glyoxal at 0.5–2.0 wt% based on resin solids or with ammonium zirconium carbonate at 1–3 wt%. The crosslinking reaction is pH-sensitive; glyoxal reactivity increases under acidic conditions at pH 4–5, while ammonium zirconium carbonate requires pH 8–9. Pot life decreases with temperature, so formulated baths should be held below 30 °C and used within 8 h. Crosslinked films resist re-wetting but become thermoset-like and cannot be re-dissolved; this is an important difference from uncrosslinked 17-88-based films that can be removed with cold water.

Extrusion, Film Casting, and Oxygen Barrier Performance of 17-99L

Thermoplastic conversion of 17-99L requires plasticisation because the crystalline melting region is above the onset of thermal degradation. Typical compounds contain 10–25 phr glycerol, sorbitol, or trimethylolpropane and are produced on a twin-screw extruder with L/D 30:1, barrel zones at 150–190 °C, and screw speeds of 200–300 rpm. Melt temperatures above 200 °C produce yellowing and gel particles. Cast film of 40–60 µm thickness can show oxygen transmission rates below 1.0 cm³·m⁻²·d⁻¹·bar⁻¹ at 0% relative humidity by ASTM D3985, but the barrier property deteriorates rapidly above 60% relative humidity. Plasticiser migration kinetics also alter barrier and mechanical properties over time; films should be conditioned at 50% relative humidity and 23 °C before tensile testing under ASTM D882. Typical slot-die cast-film operations run a 1,200 mm die with 0.6–0.8 mm die gap and a casting roll held at 40 °C; draw resonance is controlled by keeping the air gap below 20 mm and adjusting melt viscosity through water content.

Controlling Ash, Volatile Matter, and Sieve Residue in 17-99L

The release limit for ash at ≤0.7 % is not merely a purity marker; it reflects residual sodium acetate from saponification. At film extrusion temperatures, excess ash can accumulate on die lips as a white deposit and increase haze in cast films. Volatile matter above 5.0 % reduces feed consistency and can generate steam pressure in the extruder vent, causing surging. Converters should therefore verify as-received moisture by loss-on-drying or Karl Fischer titration and store the resin at relative humidity below 60 %. Sieve residue is monitored to control fisheye formation: over-coarse granules dissolve slowly, while excessive fines below 0.075 mm create dust and hydration agglomerates. Typical process specifications include ≤2.0 % retained on 0.25 mm and ≤10.0 % passing 0.075 mm; however, the producer’s certificate of analysis is the controlling document for the Shuangxin designation.

Within the fully hydrolysed series, higher-numbered grades such as 20-99 and 26-99 have degree-of-polymerisation values above 1700 and correspondingly higher solution viscosity at equivalent solids. They are selected where dry film toughness and water resistance must increase, but they require lower coating solids and longer dissolution times. In contrast, lower-viscosity fully hydrolysed grades such as 13-99 or 14-99 dissolve more easily and allow higher solids, but produce lower tensile strength films. The 17-99L grade occupies a mid-range position: at 4% solids its 25.0–31.0 mPa·s viscosity provides sufficient film build in sizing and adhesive applications without excessive high-shear viscosity during pumping. Selection between 17-99L and 20-99 should be based on rheological measurements at the intended solids, not on dry-film data alone.

Because the fully hydrolysed backbone is hygroscopic, resin storage requires a dry environment with ambient relative humidity below 60 %; pre-drying at 80–90 °C for 2–4 h is recommended if the volatile content exceeds 5.0 %. The product is incompatible with strong oxidising agents, concentrated halogens, and aldehydes that can crosslink and produce insoluble gels. Aqueous solutions support microbial growth, and batches held longer than 24 h at ambient temperature should be preserved or cooled to 5–10 °C. The grade should not be combined with amine-based additives in high-pH formulations if viscosity stability is a critical requirement. Because public literature for the Shuangxin 17-99L /PVA 100-27L designation is limited, final qualification should use vendor certificate-of-analysis data and plant-scale trials.