Introduced into China’s petrochemical portfolio as a workhorse partially hydrolyzed polyvinyl alcohol, Sinopec PVA 100‑27S occupies the viscosity band between rapid-dissolving low‑DP grades and fully hydrolyzed high‑crystallinity analogues. Analytical certificates routinely report a
4 % aqueous solution viscosity of
25.0–31.0 mPa·s at
20 °C (ISO 12058‑1:2018, Brookfield LV, spindle No. 1,
30 rpm), a hydrolysis degree of
87.0–89.0 mol% determined by back‑titration of residual acetate groups, and an ash content held below
0.5 % through post‑saponification methanol washing. The “S” suffix denotes a granular particle morphology with a bulk density of
0.40–0.55 g·cm⁻³, engineered to minimise dusting during pneumatic conveying in continuous sizing‑cooking installations. This intermediate molecular architecture—a polymerisation degree near
1000 and a controlled residual acetyl content—delivers a cold‑water swelling profile that transitions to full dissolution above
85 °C, avoiding the gelation artefacts observed in higher‑acetate copolymers while retaining film‑forming strength superior to low‑viscosity
17‑88 types.
When the Warp Sheet Demands a 12 % Size Paste That Withstands Shedding Forces Above 280 cN·tex⁻¹
On air‑jet weaving lines operating at insertion rates exceeding
1200 picks·min⁻¹, the warp yarn encounters cyclic abrasion and tensile peaks that rapidly expose any weakness in the size film. Polyester‑cotton blends sized with a
10–12 % solids cook of PVA 100‑27S, prepared in a continuous jet cooker at
110 °C with a residence time of
15–20 min, produce a clear, clot‑free liquor with a falling‑ball viscosity of
60–80 s (DIN cup
4 mm). The deposited film, after cylinder drying at
130 °C touch‑roll temperature, exhibits a tensile strength of
42–48 MPa (ASTM D882‑18,
50 %RH conditioning) and an elongation at break of
180–220 %, a balance that bridges the brittleness of fully hydrolysed PVA and the cold‑flow tendency of low‑DP grades. In mill trials comparing 100‑27S with a standard
17‑88 paste on
Ne 40 combed cotton, warp stops per
10⁵ picks dropped from
2.7 to
1.1 when the higher molecular‑weight grade was adopted, at a size add‑on of
9.5 %. The processing window narrows, however: cook‑tank temperature must remain below
120 °C to avoid chain scission that drops size‑film toughness below
18 J·m⁻³, and the desizing bath requires
0.5 g·L⁻¹ of an α‑amylase‑compatible wetting agent to achieve>
95 % PVA removal in a two‑step enzyme‑oxidative sequence—a constraint not present with fully synthetic copolymers.
In weaving preparation, the critical conflict arises from the opposing requirements of film hardness for stiffer yarns and easy removal after scouring. PVA 100‑27S resolves this through its hydrolysis degree: the
12–14 mol% residual acetate groups disrupt inter‑chain hydrogen bonding sufficiently to permit cold‑water swelling, yet the DP
1000 backbone provides film cohesion exceeding
40 MPa. Field data gathered on a Tsudakoma ZAX9100 air‑jet loom showed that adding
2 % of a medium‑molecular‑weight polyacrylic acid to the size mix can push the shedding endurance limit to
320 cN·tex⁻¹, but only when the base PVA viscosity remains above
25 mPa·s—a threshold that filters out low‑DP grades.
Emulsion stabilisation under the shadow of coagulum formation
Emulsion polymerisation of vinyl acetate‑ethylene (VAE) copolymers utilises PVA 100‑27S as a protective colloid at dosages between
4 % and
8 % based on monomer mass. The grade’s molecular weight and hydrolysis profile generate a hydrodynamic layer thickness that postpones the onset of particle coalescence during the holding phase at
80 °C. In a
20 m³ stainless‑steel reactor fitted with an anchor impeller operating at
40 rpm, a
6 % loading of 100‑27S yields a latex of
55 % solids with a final coagulum content below
0.05 % (wet weight on
100 µm screen) and a Brookfield viscosity of
3500 mPa·s at
20 rpm. The acetate windows in the polymer backbone permit a grafting efficiency of roughly
15–20 %, creating a covalent anchor that stabilises the latex through freeze‑thaw cycles; after three
−10 °C/+25 °C cycles, the grit retention rate remains above
92 % (ISO 4576:1996).
The processing boundary appears when the colloid concentration exceeds
10 %—the resulting high‑viscosity prepaste can stall the nitrogen‑displacement mixing step and cause monomer pooling at the liquid surface, raising residual vinyl acetate monomer (VAM) above
500 ppm. To avoid this, plant operators maintain a pre‑emulsion temperature of
40 °C during colloid dissolution and restrict paddle‑tip speed to
2.5 m·s⁻¹. Published data for this specific configuration is limited with respect to continuous tubular reactor geometries.
In direct comparison with a
10 % partially hydrolysed grade of
DP 500, 100‑27S imparts a narrower particle‑size distribution (span
0.8 vs.
1.4) at equal colloid loading, but requires
20 % longer dissolution time at
90 °C, a trade‑off routinely managed by installing a secondary hold‑tank for overnight batch pre‑hydration.
Specification envelope — Sinopec PVA 100‑27S
| Property | Value | Test Method |
|---|
| Viscosity (4 % aqueous, 20 °C) | 25.0–31.0 mPa·s | ISO 12058‑1:2018 |
| Hydrolysis degree | 87.0–89.0 mol% | Internal titration; saponification number |
| Volatile matter | ≤ 5.0 % | ISO 787‑2:1981 |
| Ash (Na₂O) | ≤ 0.5 % | ISO 3451‑1:2019 |
| pH (4 % solution) | 5.0–7.0 | ISO 787‑9:2019 |
| Bulk density | 0.40–0.55 g·cm⁻³ | ASTM D1895‑17 |
| Particle size (retained on 150 µm) | ≤ 5 % | ISO 4610:2001 |
Paper surface strength and the role of pre‑gelatinised starch co‑binders
Coating‑kitchen formulations for ink‑jet paper substrates often blend
1 part PVA 100‑27S with
3–5 parts oxidised corn starch on a dry basis, targeting a pickup of
2.5–3.5 g·m⁻² per side. The PVA component raises the IGT pick resistance (ISO 3783:06, pendulum drive, medium‑viscosity oil) from
0.8 m·s⁻¹ for starch‑only coatings to
2.1 m·s⁻¹ when
25 % of the binder is replaced by 100‑27S. During application on a flooded‑nip metering size press running at
800 m·min⁻¹, the film‑split pattern remains free of orange‑peel defects provided the Brookfield viscosity of the blend is held at
200–400 mPa·s at
100 rpm; the broader molecular‑weight distribution of 100‑27S relative to narrow‑cut PVA grades contributes a slight shear‑thinning character that reduces misting at the roll exit.
Coatings formulated above
8 % PVA solids in the total binder system encounter a rheological hazard: the interaction between PVA’s free hydroxyls and the borate‑crosslinked starch network can trigger a viscosity spike of
300–500 mPa·s within
20 min of mixing, sufficient to clog the supply filters. Pre‑dispersion of the PVA in cold water followed by gradual heating to
85 °C under mild agitation (
200 rpm) delays this gelation onset by
45 min, a window that matches the residence time in a standard ring‑main circulation system. Avoid combination with amine‑based insolubiliser accelerators (e.g., polyethylenimine) at a pH above
8.0—premature crosslinking results in grit counts exceeding
50 particles per 100 m² when measured by a laser scanner.
Water‑sensitive adhesive films: what changes when the additive package includes boric acid?
Remoistenable envelope adhesives utilise a cold‑blending approach in which PVA 100‑27S powder is dispersed in a plasticiser‑water‑glycerine mixture at
15 °C before being heated to
88 °C for
30 min. Upon cooling, a
20 % solids solution yields a tack‑free film with a wet‑film tack acquisition time of
12–15 s (Proctor‑Gamble tack test,
50 %RH). Inclusion of
0.3 % boric acid raises the film’s softening point to
85 °C (differential scanning calorimetry,
10 K·min⁻¹) and prevents blocking in stacks stored at
40 °C. The equilibrium moisture content of the film at
60 %RH settles at
8–10 %, balancing flexibility with dimensional stability.
Operators substituting 100‑27S for a lower‑viscosity
17‑88 grade must recalibrate the metering slot settings because the 100‑27S formulation exhibits a
25 % higher dynamic viscosity at the application temperature of
45 °C; failure to adjust leads to stripe‑coating defects and adhesive consumption rises by
1.2 g·m⁻². The boric acid esterification depends on the availability of 1,2‑diol segments, which are partially masked in 100‑27S by residual acetate groups, so the crosslink density reaches equilibrium only after
24 h of ambient ageing.
In applications where FDA 21 CFR 175.105 compliance is invoked, the as‑received grade must be accompanied by a certificate documenting that residual vinyl acetate monomer is below
5 ppm and that methanol extractives conform to the migration limits of
0.5 mg·dm⁻². Multilayer film laminations that employ 100‑27S as a tie layer between polyethylene and aluminium foil exhibit peel strengths of
4.5 N·(25 mm)⁻¹ (ASTM D903‑98,
180° peel) after corona treatment of the PE to
42 dyn·cm⁻¹, a performance level that degrades to
2.0 N·(25 mm)⁻¹ if the hydrolysis degree of the PVA drops to
82 mol%, underscoring the importance of the
87–89 mol% specification window.
