Wanwei PVA 17-99 (H) (PVA 100-27)

Wanwei PVA 17-99(H), additionally trade-designated PVA 100-27, is a fully hydrolysed polyvinyl alcohol homopolymer resin produced by Anhui Wanwei Updated High-tech Material Co., Ltd. (Wanwei). The numerical suffix identifies a nominal degree of hydrolysis of 99.0–100 mol% and a 4 % aqueous solution viscosity at 20 °C of approximately 25–31 mPa·s, corresponding to an estimated weight-average degree of polymerisation in the range of 1700–1800. The alphanumeric appendage “(H)” denotes a high-viscosity sub-grade within the fully hydrolysed product family. Industrially, this grade functions as a water-soluble film former, warp size, paper surface size, emulsion polymerisation protective colloid, and adhesive binder. The following sections detail its performance envelope, processing constraints, and quantitative differentiation from partially hydrolysed homologues.

What Distinguishes the 17-99(H) from Other Partially and Fully Hydrolysed PVAs?

Fully hydrolysed polyvinyl alcohol grades such as 17-99(H) differ fundamentally from partially hydrolysed variants (e.g., Wanwei 17-88, 17-92) in residual acetate group content, crystallinity, and cold-water interaction. With ≤1.0 mol% residual acetyl groups, the 17-99(H) backbone permits extensive inter- and intra-chain hydrogen bonding, yielding a semi-crystalline morphology that is insoluble in water below 60 °C and requires dissolution temperatures of 90–98 °C under continuous agitation. In contrast, a partially hydrolysed grade such as 17-88, possessing 12.0 ± 1.0 mol% residual acetate, dissolves readily at 20–25 °C because acetyl pendant groups interrupt crystallite formation. This distinction creates a practical processing boundary: 17-99(H) must be pre-slurried in cold water and heated, while 17-88 can be incorporated directly into cold liquid size cookers. Within the fully hydrolysed range, 17-99(H) exhibits a medium-to-high molecular weight relative to grades such as 24-99 (viscosity 44–52 mPa·s) and 10-99 (viscosity 10–15 mPa·s), positioning it where film tensile strength, abrasion resistance, and solution viscosity are balanced against manageable handling viscosity in size boxes and coating stations. The higher molecular weight of 17-99(H) relative to 10-99 provides an increase in tensile strength at break of approximately 40–50 % when measured on cast film per ISO 527-3, though at the expense of higher solution viscosity and greater filtration demand in closed circulation loops.

On a metering size press operating at 800 m/min with a rod diameter of 12 mm and a wet-film pickup target of 4.5–5.5 g/m², the 17-99(H) grade is run as a 7.5–9.0 wt% aqueous solution maintained at 60–65 °C in the holding tank to prevent skinning. The higher degree of hydrolysis confers a surface energy above 50 mN/m, which, combined with a narrow molecular weight distribution (Đ ~2.1–2.4 as determined by GPC with polyethylene oxide calibration), promotes rapid coverage of cellulose fibres and immediate film formation upon drying. Cobb₆₀ values, tested according to ISO 535, are typically reduced by 25–30 g/m² compared with an unsized sheet when 0.8 wt% dry pickup of PVA is applied. Excessive bath temperatures above 70 °C accelerate microbial growth and gelation for fully hydrolysed grades stored with borax-containing adjuvants; therefore a closed-loop temperature control with ±2 °C deadband is recommended. Roll doctoring and cleaning cycles must account for the higher adhesive tack of high-hydrolysis films: on ceramic-coated metering rods, a hot-water (80 °C) purge at intervals not exceeding 4 h prevents irreversible deposit formation.

Dissolution Protocol and Viscosity Build-Up in Alkaline Size Mixes

Preparation of a 10 wt% mother solution of 17-99(H) for textile warp sizing follows a controlled heating sequence to avoid partial hydration and gel formation. The powder is first dispersed into 20–25 °C process water at a ratio of 1:4 (PVA:water) under low-shear agitation in a jacketed vessel equipped with an anchor stirrer operating at 30–40 rpm. Once a uniform slurry is formed, the temperature is ramped at 1.5 °C/min to 96–98 °C and held for 45–60 min until a clear, particle-free solution is obtained. At this concentration, a Brookfield viscometer (spindle #3, 20 rpm, 20 °C) records a viscosity of 25–31 mPa·s as per GB/T 12010.2-2010. In alkaline size recipes where 1.5–2.5 wt% borax (on PVA weight) is added to promote complexation and moisture regain of the size film, viscosity rises non-linearly: a borax addition of 2.0 wt% at pH 8.5–9.0 elevates the measured viscosity to 45–60 mPa·s at 85 °C, and upon cooling to 60 °C the system displays a steep upturn, crossing 100 mPa·s. This pronounced thermal sensitivity mandates that size boxes on multi-cylinder slashers, such as a Sucker Müller SMR type with 8 drying cylinders, maintain a minimum operating temperature of 70 °C to sustain flowability through positive-displacement pumps and avoid premature build-up on immersion rollers. Published data comparing borax-free and borax-containing 17-99(H) solutions confirm that the tan δ value from oscillatory rheometry drops below 1 at 65 °C for the borax-modified system, indicating a transition from viscous to elastic-dominated behaviour that can cause uneven film deposition on yarn.

In wood adhesive compounding, 17-99(H) is blended with polyvinyl acetate homopolymer emulsions to elevate the water resistance and heat resistance of the bond line. A typical formulation contains 15–25 parts of PVA per 100 parts of emulsion solids, pre-dissolved as a 12 wt% solution at 95 °C. The fully hydrolysed PVA, when crosslinked with glyoxal at a mol ratio of 1:0.15 (PVA:glyoxal) under acidic catalysis (pH 3.5–4.0 with 0.5 wt% citric acid), achieves a wet tensile shear strength on beech adherends of ≥4.5 MPa after 24 h immersion at 23 °C, as tested per EN 204 D3 classification. Partially hydrolysed grades, when subjected to the same crosslinker loading, fail to exceed 2.8 MPa due to their higher equilibrium moisture content and lower density of hydrogen-bond donor sites. However, pot life is constrained to 2–3 h at ambient temperature because the high hydroxyl equivalent weight of 17-99(H) accelerates crosslinking with aldehydes; blending with partially hydrolysed PVA at a mass ratio of 70:30 (17-99(H):17-88) extends working time to 5 h with a sacrifice of 15 % in wet strength. Use of calcium carbonate fillers above 20 phr in such adhesives can induce ionic crosslinking of the PVA through chelation with Ca²⁺, leading to a sharp increase in Brookfield viscosity beyond 30 000 mPa·s and eventual gelation; therefore filler content must be matched to the PVA hydrolysis degree and calcium tolerance limit.

When Replacement of 17-88 with 17-99(H) Alters Cold-Water Solubility

For water-soluble packaging films that require room-temperature disintegration, 17-99(H) is not a direct drop-in replacement for cold-water-soluble grades. Cast films produced from a 15 wt% solution of 17-99(H) on a stainless steel belt at a drying temperature of 105 °C and residence time of 8 min exhibit complete solubility only above 70 °C, in accordance with ISO 15023-2 (method for determination of total dissolution time in water). At 25 °C, dissolution is negligible beyond surface swelling, reaching ≤3 wt% dissolution after 60 min. In contrast, a film derived from 17-88 (88 mol% hydrolysis) dissolves fully within 180 s under the same test protocol. Therefore, substituting 17-99(H) into a laundry bag or agrochemical pod formulation intended for ambient-temperature use will result in an insoluble residue exceeding permitted limits under OECD 301B ready biodegradability screening. Nevertheless, in hot-water-soluble hospital laundry bags designed for thermal disinfection cycles at 85 °C, the 17-99(H) film provides a burst strength of ≥0.8 MPa (measured per ISO 2758) compared with 0.35 MPa for 17-88 film of equivalent caliper, while still disintegrating within 90 s at the operational wash temperature. Processing such film on a cast line with a chill roll set to 12 °C requires a pre-drying step for the resin: at ambient relative humidity above 60 %, the powder absorbs moisture within 30 min, causing bridging in the feed throat of a single-screw extruder with L/D 30:1 and loss of melt homogeneity. Desiccant drying at 80 °C for 3–4 h to ≤0.3 wt% residual moisture is mandatory before processing 17-99(H) through a melt-casting or blown-film line, whereas 17-88 can often be processed with a pre-dry time of 1.5 h under the same conditions.

Film casting from 15 wt% aqueous solution at 90–95 °C onto a chromium-plated belt dryer operating at 120 °C yields a film with thickness tolerance ±2 µm at a nominal thickness of 40 µm. The fully hydrolysed film demonstrates an oxygen transmission rate (OTR) of 0.8–1.2 cm³/(m²·d·bar) at 23 °C, 0 % RH (measured with a Mocon OX-TRAN 2/21 per ASTM D3985), which is approximately 50 % lower than that of an equivalent 17-88 film, owing to the more densely packed crystalline domains. However, at 85 % RH, the OTR of the 17-99(H) film increases to 12–15 cm³/(m²·d·bar) as the amorphous regions plasticise, erasing much of the advantage over partially hydrolysed grades under high-humidity conditions. This performance envelope confines the barrier application of neat 17-99(H) films to dry environments or to intermediate-ply layers in composite structures where a hydrophobic coating supresses moisture uptake. Thermal stability during extrusion is adequate up to 210 °C melt temperature; beyond 220 °C, detectable acetic acid evolution and colour formation (yellowing index per DIN 6167 rises above 15) necessitate heat stabilisation with 0.3–0.5 wt% of a phosphite antioxidant. Gel particle counts, determined by a 10 µm laser backscatter probe on a melt stream, remain below 300 particles/g when extrusion temperature is capped at 215 °C, an important threshold for defect-free thin-gauge film used in embroidery backing sheets.

As a protective colloid in emulsion polymerisation of vinyl acetate, 17-99(H) generates latexes with a narrow particle size distribution (PDI <0.15) at addition levels of 4–6 wt% based on monomer. The higher degree of hydrolysis yields a grafting efficiency above 85 %, measured by solvent extraction of ungrafted PVA, which is significantly higher than the 60–70 % typically observed with 17-88. This results in superior storage stability and mechanical stability under high-shear pumping. However, the protective action is optimised only when the reaction temperature does not exceed 70 °C; above this threshold, aqueous phase viscosity rises sharply and can initiate inverse-phase gelation if the PVA-methanol complex is not fully displaced. Consequently, jacketed reactors with cooling capacity of 1.5 kW/°C per tonne of emulsion are required to maintain the set point during the exothermic polymerisation peak, a demand that limits the use of 17-99(H) in older, non-automated production vessels originally dimensioned for partially hydrolysed colloids.