Sinopec PVA 100-35

Sinopec PVA 100-35 is a fully hydrolyzed polyvinyl alcohol resin with a nominal 4 % aqueous solution viscosity of 35.0 ± 4.0 mPa·s at 20 °C (Brookfield LV, spindle 1, 60 rpm) and a degree of hydrolysis of 98.0–99.0 mol%. The bulk powder exhibits a volatile content ≤ 5.0 % (ASTM D1348, 3 h at 105 °C), ash residue ≤ 0.5 % (ISO 3451-1), and a pH of a 4 % solution in the range 5.0–7.0 (GB/T 12010.4). This grade belongs to the 100-series, in which the numeric suffix denotes the target viscosity, and the prefix indicates a degree of polymerization near 1000. The immediate family includes Sinopec PVA 100-27 (viscosity 27.0 ± 3.0 mPa·s) and PVA 100-50 (viscosity 50.0 ± 5.0 mPa·s). Where 100-27 provides lower add‑on weight and faster size-box circulation in saturator‑type slashers, 100-35 delivers a balance of film toughness, moisture resistance, and processable solution viscosity. 100-50 generates stronger films but demands higher cooking temperatures and longer dissolution times; its use in fully automated size kitchens can introduce a productivity penalty when cycle times fall below 45 min.

¹ Films cast from 10 % aqueous solution, dried at 50 °C and conditioned at 23 °C/50 % RH for 48 h.

Paper Surface Sizing and Film Formation at the Metering Size Press

On fine paper machines operating above 1200 m/min, the metering size press applies a 6–10 % solids PVA solution to the sheet surface via rod or blade metering. Sinopec PVA 100-35 yields a size-press pickup of 1.8–2.4 g/m² per side when run at 60–65 °C to delay skinning on the metering element. Under these conditions, the film-forming grade retards Bristow wheel absorption time by 40–55 % versus unsized base (Cobb₆₀ reduced from ≥200 g/m² to 22–28 g/m², TAPPI T441). Surface strength, measured by IGT pick velocity (ISO 3783), rises from 1.2–1.5 m/s on unsized substrate to 3.0–3.6 m/s. Lower-viscosity PVA 100-27 can be applied at 12 % solids without rod bounce, yet the thinner film-forming layer gives inferior dusting resistance on uncoated woodfree grades. PVA 100-50 requires dilution to 6 % or below to maintain blade-stable viscosity, which limits the dry pick‑up achievable in a single pass. An operational boundary worth noting: size-press starch co‑blends exceeding 30 % oxidized starch by dry weight can phase-separate during recirculation when the PVA 100-35 solution temperature drops below 50 °C, manifesting as surface grain on the reel.

Where operators encounter rod marks at widths above 3.6 m, experience points to shear-thinning behavior at the metering nip. Substitution of 100-35 with 100-27 often resolves the defect but sacrifices blocking resistance in subsequent sheeting operations; a blend of 70:30 100-35:100-27 has been documented to eliminate rod marks while retaining Cobb values below 30 g/m². Published data for this specific configuration is limited, but mill trials on a Voith SpeedSizer AT at 1400 m/min recorded defect-free runs exceeding 8 h.

When Warp Yarns Demand Abrasion Resistance Without Excessive Stiffness

Passing ring-spun cotton warp yarns through a slasher size box charged with PVA 100-35 at 8.5 % solids confers a size add‑on of 8–10 % owf. The cohesive film deposited on the yarn surface withstands repeated cyclic abrasion against drop wires and heddle eyes during high-speed air-jet weaving (loom speed 850–1050 rpm). Laboratory comparison using a Zweigle G551 abrasion tester reveals that 100-35-sized yarns tolerate 15–20 % more rub cycles to thread break than yarns sized with 100-27 at the same add‑on, owing to the superior film toughness of the mid-viscosity grade. Yet the bending rigidity of the sized yarn, measured on a KES-FB2 pure bending tester, remains 12–18 % lower than that achieved with PVA 100-50, a critical margin when processing low-twist yarns destined for soft-hand fabrics. On Tsudakoma ZAX9100 looms equipped with pre-wet accumulators, stop counts attributable to sizing fall below 0.4 stops/10⁵ picks when 100-35 is combined with a low‑viscosity acrylic binder at 5 % on PVA weight. Pre-drying of the resin is recommended if storage RH exceeds 60 %; moisture uptake above 5 % in the as-received bag can extend dissolution time by 20–30 min and introduce lump formation in the cooker.

Protective Colloid Behavior in Vinyl Acetate Emulsion Polymerization

In a semi-batch VAc homopolymer emulsion process with 200 rpm anchor agitation and a jacket temperature of 70 °C, fully hydrolyzed PVA 100-35 is charged as a 10 % aqueous premix at a ratio of 4–6 phr relative to monomer. The high degree of hydrolysis — 98 mol% minimum — shifts particle nucleation from micellar toward graft‑co‑polymerization, leading to a bimodal particle size distribution typically centered around 0.8 µm and 2.5 µm (laser diffraction, Malvern Mastersizer). The resultant latex exhibits shear stability measured by a Denier cup (ISO 4576) exceeding 30 min without coagulum formation. Comparable recipes using partial-hydrolysis PVA 88-50 (88 mol% hydrolysis) produce smaller primary particles — 0.3–0.5 µm — and require post‑addition of a nonionic surfactant to prevent shear‑induced gellation during high‑speed pigment grinding. The grafting efficiency of VAc onto 100-35, estimated to be 20–25 % by solvent extraction, provides a covalent anchoring layer that suppresses desorption of the protective colloid during subsequent re‑dispersion of the dry powder. Limitations appear when anionic co‑monomers such as sodium vinyl sulfonate exceed 0.5 wt% on total monomer; competitive adsorption between the grafted PVA and the free sulfonate leads to a sharp increase in coagulum (from <0.1 % to>1.5 %) within the first hour of reaction, necessitating a switch to a higher molecular weight grade or a protective colloid with lower surface activity.

What Limits Dissolution Rate in Cold‑Water Adhesive Formulations?

Granular PVA 100-35 placed in water at 20 °C swells but does not fully dissolve for 4–8 h without agitation. This stems from the high crystalline fraction (ca. 0.50 by FTIR crystallinity index) typical of fully hydrolyzed grades. Industrial practice for cold‑water adhesives therefore specifies pre‑slaking the powder with 30 % of the total batch water at 25 °C for exactly 15 min to avoid gel‑skin formation, followed by hot‑water injection to raise the mixture to 85–90 °C under a high‑shear rotor‑stator mixer (Silverson or equivalent, tip speed 15–20 m/s). Cooling to 20 °C produces a lump‑free solution within 60 min. When hot‑water jacketing is unavailable, a co‑solvent such as ethanol (5 wt% of total solvent) can accelerate cold dissolution by partially disrupting inter‑chain hydrogen bonding; published data for this specific configuration is limited, but laboratory tests show a viscosity plateau reached in 2 h at 20 °C with magnetic stirring. In wood‑bonding applications (DIN EN 204, durability class D2), 100-35-based adhesives developed bond strengths of 3.2–3.8 N/mm² on beech, comparable to 100-50 formulations but with 25 % lower gelling risk during open assembly times exceeding 15 min at 23 °C and 60 % RH.

Construction dry‑mix compounds — specifically cementitious tile adhesives conforming to EN 12004 C1 — incorporate PVA 100-35 at 0.5–1.2 wt% on total dry weight. The resin functions as a secondary water-retention agent and anti‑sag additive. Dual-component mortars containing 0.8 wt% 100-35 and 0.3 wt% methylcellulose ether (400 mPa·s, 2 % solution) maintained open time beyond 30 min on highly absorptive aerated concrete substrates (initial water absorption 1.5 kg/m²·min^0.5), while the rheology allowed trowel ridges to retain shape without slump on vertical walls. PVA 100-27 at the same dosage gave 12 % lower water retention (measured by vacuum suction test per EN 1348) due to a less cohesive film formed during the initial hydration phase. Grade 100-50, conversely, increased the mortar’s dynamic yield stress beyond 450 Pa (measured on a Brookfield RST-SST rheometer with vane spindle), which field crews report as “sticky” and difficult to open with a notched trowel. The incompatibility of fully hydrolyzed PVA with high‑alumina cement must be highlighted; the alkoxide moieties generated during PVA dissolution can complex with aluminum ions, causing a flash set that is undetectable by Vicat needle (EN 196-3) until the mix loses workability within 90 s of water addition.