Sinopec PVA 100-27

Sinopec PVA 100-27 is a fully hydrolyzed polyvinyl alcohol resin manufactured via alcoholysis of polyvinyl acetate under controlled suspension conditions. Its specification sheet identifies a 4 wt% aqueous solution viscosity at 20 °C in the range 25.0–30.0 mPa·s, measured according to GB/T 12010.2 (rotational viscometer method), and a degree of hydrolysis of 98.0–99.0 mol% (GB/T 12010.4). Ash content is held below 0.5 wt%, volatile matter below 5.0 wt%, and pH in a 4% solution between 5.0 and 7.0. These numbers establish the grade as a mid-viscosity, fully hydrolyzed PVA positioned between the lower-viscosity 100-14 and the higher-viscosity 100-37 within Sinopec’s fully hydrolyzed series. Unlike partially hydrolyzed grades such as 088-20, the high degree of hydrolysis of 100-27 results in a 1,3-diol structure content exceeding 1.7 mol%, elevating the crystalline melting point to approximately 228–232 °C and reducing cold-water solubility markedly.

What Constitutes the Molecular Architecture of Sinopec PVA 100-27?

The backbone consists of head-to-tail vinyl alcohol units with residual acetate groups distributed randomly, typically below 2.0 mol%. Gel permeation chromatography against poly(ethylene oxide) standards gives a weight-average molecular weight near 110,000–120,000 g/mol, corresponding to a degree of polymerization of roughly 2400–2600. The tacticity, governed by the radical polymerization of the vinyl acetate precursor, is predominantly atactic. The polymer’s high syndiotactic diad fraction—common in suspension-polymerized PVA—promotes interchain hydrogen bonding, which directly influences the film’s tensile modulus and its resistance to dissolution below 60 °C. Moisture regain at 65% RH and 20 °C stabilizes around 4.5–5.0 wt%, a factor that must be accounted for when weighing air-dried powder for solvent-based formulations.

When Dissolution Kinetics Dictate Process Design

Without a header, this section begins as a dense technical paragraph. The cook temperature for complete dissolution in water lies between 90 °C and 95 °C under moderate shear; below 85 °C, undissolved gel particles persist, leading to fisheye defects in cast films. Plant trials conducted on a 200 L jacketed stainless-steel vessel equipped with a twin-shaft dissolver (anchor + high-speed disperser, 15 kW) show that a 10 wt% solids slurry pre-soaked at 25 °C for 30 min and then ramped to 93 °C over 45 min yields a Brookfield viscosity stability of ±2% after 2 h holding. Foaming becomes problematic when the agitator tip speed exceeds 3.5 m/s; defoamer dosing with a silicone-free, food-grade polyether at 0.02–0.05 wt% is operational standard.

Incompatibility arises with borate ions and certain divalent metal salts: addition of borax at pH> 8 triggers instantaneous crosslinking, raising viscosity beyond pumpable limits within seconds. Therefore, 100-27 solutions should not be buffered with borate-based preservatives unless a competing polyol complexing agent is added first. Published data for long-term storage of 15 wt% solutions at 40 °C show a gradual increase in solution viscosity of 0.5–1.0 mPa·s per week due to progressive intermolecular hydrogen bonding rearrangement, a drift that can be mitigated by cooling to 10 °C or adding 2 wt% of a lower alcohol such as isopropanol as a temporary rheology stabilizer.

Film Formation and Solubility Characteristics

Solution-cast films dried on a chrome-plated belt at 120 °C with a residence time of 8 min develop a density of 1.27–1.31 g/cm³. Tensile testing under ASTM D882-18 on 50 μm conditioned films ( 23 °C, 50% RH) reveals a tensile strength of 60–70 MPa and an elongation at break of 150–200%. The high crystalline fraction, determined by differential scanning calorimetry at a heating rate of 10 °C/min, of approximately 38–42% provides excellent gas barrier properties: oxygen permeability at 0% RH is measured below 0.5 cm³·20 μm/m²·day·atm per ASTM D3985-17. However, above 80% RH, the permeability increases fourfold as water plasticizes the amorphous regions, a limitation critical in high-humidity packaging applications where a top-coat of nitrocellulose lacquer is often applied.

Adhesive and Sizing Applications in Paper Converting

In the paper and corrugated board industry, 100-27 is compounded into starch-based adhesives at 2–5 parts per hundred dry starch to boost wet tack and water resistance without fully replacing the low-cost carrier starch. The addition raises the adhesive’s viscosity from approximately 600 mPa·s to 1200–1800 mPa·s (Brookfield, spindle 3, 20 rpm), measured immediately after cooking at 90 °C, and the green bond strength on a single-facer line running 150 m/min increases by 30–40% when using 3 wt% PVA addition. The insolubilization step uses either ammonium zirconium carbonate at 0.5 wt% on starch solids or a glyoxal-based crosslinker at pH 5.5–6.0. Over-crosslinking with glyoxal beyond 1.0% leads to brittle bonds that fail the TAPPI T 821 pin adhesion test. Machine trials recorded a reduction in warp during single-face lamination of 0.3–0.5 mm per 300 mm board width relative to all-starch controls.

Textile warp sizing represents another high-volume use. The size formulation of 8.5% solids containing 100-27 as the primary film former, supplemented with 1% of an acrylic acid ester size and 0.3% of a wax lubricant, shows a size add-on of 12 ± 1% on Ne 40 cotton yarns. Weaving efficiency on air-jet looms at 600 rpm improves by 4–5% compared to a partly hydrolyzed PVA (088-20) sized under identical conditions, attributed to the fully hydrolyzed grade’s lower moisture sensitivity in the weaving shed at 70% RH. Desizing with hot water at 90 °C for 20 min removes 99% of the film, verified by iodine stain test. A limitation: heavily twisted filament viscose yarns sized with 100-27 may exhibit excessive hairiness reduction, causing reed marks if the size film is not plasticized with at least 5% of a polyglycol plasticizer.

Emulsion Polymerization: The Role as Protective Colloid

In vinyl acetate-based emulsion polymerization, 100-27 acts as a non-ionic protective colloid. Its high molecular weight and hydrolysis degree yield a strong steric barrier during nucleation, allowing stable latices of 50–55% solids with a particle size of 1.2–2.5 μm. Grafted PVA content on the latex particle surface reaches 15–20% of total colloid fed, as determined by extraction with boiling water followed by gravimetric analysis. The resulting polyvinyl acetate homopolymer emulsions formulated with 4% 100-27 display a minimum film formation temperature (MFFT) of 2–4 °C lower than those protected with a lower-DP PVA, due to internal plasticization by the grafted layer. Adhesive manufacturers report improved wet set speed in wood bonding compared to emulsions prepared with 100-14; this is consistent with the higher cohesive strength of the higher-molecular-weight interphase. However, viscosity of the finished latex is higher (roughly 8000–12,000 mPa·s at 25 °C, Brookfield 20 rpm), which may limit spray application without dilution to 45% solids.

Processing and Handling Constraints

Moisture content of virgin powder as supplied is 3–5%. Exposure to ambient air at relative humidity above 60% leads to rapid pickup, causing clumping in pneumatic conveying lines. Pre-drying in a fluidized bed dryer at 80 °C to a residual moisture of ≤0.5% is mandatory when the powder is to be melt-processed into cast extruded film via a single-screw extruder with a barrier screw of L/D 30:1 and a melt temperature profile from 180 °C to 220 °C. Even with drying, the narrow processing window—onset of decomposition occurs at 220–230 °C—forces strict residence-time control. Throughput on a 45 mm extruder should not exceed 15 kg/h without a screw cooling core to prevent overheating at the compression section. A polyethylene glycol plasticizer at 5–10 phr is typically required to bring the melt flow index to a processable 2–5 g/10 min (230 °C, 2.16 kg, ISO 1133-1:2022). Without plasticizer, the MFI is below 0.5 g/10 min, making thin-gauge sheet extrusion impractical. Published data for this specific configuration—extrusion-grade formulations using 100-27 without additional tackifiers—is limited, as most extrusion applications favor lower-molecular-weight partially hydrolyzed PVA grades.

In water-based slurry operations, the foam tendency mentioned earlier requires defoamer addition, but defoamer choice is constrained: silicone-based defoamers cause cratering in dried films intended for optical applications. Therefore, a polyglycerol ester defoamer at 0.03% is typically used and its effect on contact angle measured before full-scale adoption. Contact angle on stainless steel with a 8% solution increases by 5–7 degrees when defoamer is present, which may reduce wetting in paper sizing but can be compensated by increasing the size press roll pressure by 2–3 kN/m.

Differentiation from Other Partially and Fully Hydrolyzed Grades

The primary differentiation of 100-27 from the widely used partially hydrolyzed grade 088-20 (hydrolysis degree 86.0–90.0 mol%) lies in its much lower cold-water solubility. An 088-20 powder dissolves to a clear solution at 20–25 °C within minutes; 100-27 requires heating to above 85 °C. This makes 100-27 unsuitable for use as a cold-water packaging film component but advantageous in hot-melt adhesive formulations where room-temperature blocking resistance is critical. Compared to the higher-viscosity 100-37 (35.0–42.0 mPa·s), 100-27 offers a lower solution viscosity for equivalent solids content, easing pumping and filtration through 200-mesh screens without backpressure exceeding 0.5 MPa. In warp sizing, 100-27 yields lower shed deposition on reed and drop wires than 100-37, reducing loom stop frequency by approximately 2–3 stops per 100,000 picks. Against Kuraray Poval 117, a similar fully hydrolyzed grade with a viscosity around 27 mPa·s, 100-27 shows a slightly broader molecular weight distribution (polydispersity index ~2.6 vs. ~2.3 for Poval 117, by GPC), which manifests as a 5–10% lower elastic modulus in gel at equivalent concentration but better film impact resistance at low plasticizer levels, per some converter reports. Sinopec’s suspension polymerization route also yields a particle size distribution of 100–300 μm with a fine content (<75 μm) limited to <2%, reducing dusting during mechanical handling compared to some alternative suppliers’ grades. The absence of a surface-sizing step during manufacture, however, means that 100-27 granules may dissolve somewhat slower than externally coated Poval grades unless the powder is pre-slurried with a wetting agent such as 0.1% sodium lauryl sulfate.