Sinopec PVA 088-35 (PVA 2088)

Sinopec PVA 088-35, also referred to by the internally coded designation PVA 2088, is a partially hydrolysed polyvinyl alcohol manufactured via continuous methanolysis of polyvinyl acetate at Sinopec Sichuan Vinylon Works. The numeric designation 2088 conveys a nominal degree of polymerisation of 2000 and a degree of hydrolysis of 88 mol%. As a free-flowing white powder with an apparent bulk density typically between 0.40 and 0.55 g/cm³, the grade is supplied in 20 kg multiwall paper sacks or bulk bags. The polymer dissolves readily in water at temperatures above 80 °C to yield clear solutions with pseudoplastic flow behaviour; the 4 % aqueous solution viscosity is tightly controlled at 35.0 ± 3.0 mPa·s measured at 20 °C in accordance with GB/T 12010.2-2010 (Brookfield LVDV, spindle No. 2, 60 rpm). Its primary functions span protective colloid for emulsion polymerisation, base resin for polyvinyl butyral manufacture, textile warp size, paper and carton adhesives, and water-soluble film intermediate. Because the balance of hydroxyl and residual acetate groups dictates crystallinity, solubility, and interfacial adhesion, this grade occupies a narrow processing window that distinguishes it from both fully hydrolysed grades such as 1799 and from higher or lower viscosity partially hydrolysed members of the Sinopec PVA portfolio.

Physicochemical Profile and Batch-to-Batch Consistency

The manufacturer reports lot release data verified against the Chinese national standard series GB/T 12010. Routine monitoring covers the parameters listed in Table 1, with limits intended to cap volatile fraction and ash-derived insolubles that would otherwise impair film clarity or adhesive joint durability. Ash levels, determined by combustion at 800 °C per GB/T 12010.7-2010 and cross-checked against inductively coupled plasma optical emission spectroscopy for sodium and iron, are held below 1.0 % to minimise haze in cast films and to avoid catalyst residues that accelerate discolouration during hot melt compounding. Volatile matter, predominantly water and residual methanol, is controlled to ≤ 5.0 % as received and to ≤ 0.5 % after pre-drying at 105 °C for 2 h in a forced-air oven; this pre-drying step becomes mandatory when the powder is fed to a twin-screw extruder with a 36:1 L/D ratio where evolved steam generates unacceptable back-pressure at the vent port.

How Does the 88 % Hydrolysis Plateau Influence Adhesion to Porous Cellulosic Substrates?

In water-based adhesives for paper tube winding, carton side-seam bonding, and wood veneer layup, the 88 mol% hydrolysis of 088-35 creates an optimal density of free hydroxyl groups sufficient to hydrogen-bond with cellulose fibres while the residual acetate blocks limit excessive crystallinity that would otherwise embrittle the dried film. Peel strength on kraft linerboard, measured by ASTM D1876 after conditioning at 23 °C and 50 % RH, shows that an adhesive formulated with 12 wt% PVA 088-35 and 1.5 wt% glycerin plasticiser yields values between 1.8 and 2.5 N/cm, compared with 1.2 – 1.6 N/cm for a fully hydrolysed grade (1799) that requires higher water temperature for complete dissolution and exhibits less cold flow into fibre interstices. The 35 mPa·s viscosity provides a balance between machine runnability and substrate penetration: when resin solids are held at 15 % and a nip roller pressure of 0.3 MPa is applied on a spiral tube winder operating at 60 m/min, the wet adhesive film remains contiguous without excessive strike-through that would cause tube collapse. Substituting 2488 (viscosity 50 mPa·s) at the same solids forces operators to reduce line speed by 15 – 20 % to maintain coat weight, while 088-20 (viscosity 20 mPa·s) leads to starved glue lines and flicking at the applicator roll. The difference in open time, quantified by the green tack decay curve recorded with a texture analyser, is also significant: 088-35 retains a tack force above 0.5 N for 12 – 15 s on uncoated paperboard, whereas 2488 drops below the same threshold in 8 s due to faster skin formation as water migrates into the board.

In polyvinyl butyral (PVB) resin manufacture, 088-35 is the preferred polyvinyl alcohol feedstock for acid-catalysed acetalisation with butyraldehyde in an aqueous–solvent biphasic system. The polymerisation degree of 2000 yields a PVB polymer with a weight-average molecular weight typically in the range of 2.5 × 10⁵ to 3.8 × 10⁵ g mol⁻¹ (gel permeation chromatography, polystyrene-equivalent calibration), which provides the required melt strength for sheeting processes while keeping the torque profile on a co-rotating twin-screw extruder (diameter 25 mm, 36:1 L/D, ten barrel zones) below 80 Nm when the plasticiser triethylene glycol di-2-ethylhexanoate (3G8) is metered at 35 phr. If a higher-DP grade such as 2488 (DP 2400) is substituted, the acetalised flake develops a higher intrinsic viscosity, and the extruder exhibits melt-pressure spikes exceeding 12 MPa at the screen pack unless the screw profile is redesigned with additional kneading blocks. Conversely, the lower-DP 088-20 (DP 1700) produces a PVB interlayer with insufficient tear resistance—yielding Elmendorf tear strengths below 30 N/mm per ASTM D1922—that fails the mandatory interlayer qualification for laminated safety glass according to ANSI Z97.1 drop-weight impact requirements. Published data for this specific configuration is limited, but industrial practice confirms that 088-35 sits on the lower bound of viable DP for architectural PVB while avoiding the downstream conversion difficulties of the 24-series.

When 088-35 Replaces 2488 in Warp Sizing — A Shift in Desizing Efficiency

On high-speed single-end sizing machines processing Ne 40 ring-spun cotton yarn, the lower solution viscosity of 088-35 translates into a reduced wet pickup at equivalent solids content, ranging from 8 – 10 % size add-on compared with 12 – 14 % for 2488 at 7 % dry solids in the size box, as measured by the difference in conditioned warp beam weight per ISO 7211-2. Although the size film tensile strength of 088-35, determined on cast films conditioned at 65 % RH (ASTM D882), is lower at 38 – 42 MPa versus 48 – 52 MPa for 2488, weaving efficiency on air-jet looms remains comparable because the partially hydrolysed grade exhibits a lower glass transition temperature and retains sufficient elongation at break (> 150 %) to accommodate loom shedding dynamics without brittle fracture at the drop wire. The decisive operational difference appears at the desizing stage: 088-35 desizes completely in hot water at 70 °C within 15 min in a continuous open-width washer (four-box configuration), whereas 2488 requires a scray dwell time extended by 40 % or a temperature increase to 85 °C to reach ≤ 0.5 % residual size on fabric, measured by the ceric ammonium nitrate oxidimetric method (ISO 1833-11). Table 2 summarises key differentiating features across four commonly referenced Sinopec PVA grades used in sizing recipes.

Sizing formulations that blend 088-35 with oxidised corn starch at a 70:30 PVA-to-starch ratio show no phase separation during size box circulation at 85 °C, provided the starch is pre-gelatinised separately and dosed through a static mixer. Under these conditions, the desized effluent exhibits a chemical oxygen demand of 3200 – 3800 mg/L, which is systematically lower than the COD generated by the equivalent 2488-starch blend, reducing the load on the on-site anaerobic treatment reactor.

Film Barrier Properties and Oxygen Transmission Limits

Blown film produced from 088-35 on a single-screw extruder (diameter 45 mm, 30:1 L/D, screw compression ratio 3.5:1) with a melt temperature of 190 °C and a blow-up ratio of 2.5:1 reaches an oxygen transmission rate of 1.2 – 1.8 cm³·mm/m²·day·atm at 23 °C and 50 % RH when tested per ASTM F1927, provided the resin is pre-dried to <0.3 % moisture. This OTR positions the film as a moderate barrier, inferior to polyvinylidene chloride but useful for polar aprotic compounds in water-soluble unit-dose sachets. The critical dissolution temperature in still water, determined by the weight loss of a 50 µm film specimen after 60 s immersion, is 68 – 72 °C; this contrasts with 1799 film that retains integrity up to 92 °C and with 1792 film that softens at 78 – 82 °C. The processing window for blown film is narrow (± 5 °C at the die lip) because the partially hydrolysed polymer undergoes additional thermal dehydration above 210 °C, leading to acid-catalysed chain scission and a drop in melt strength visible as bubble instability. Handling precautions include storing the powder in sealed, moisture-proof containers at ≤ 30 °C and ≤ 60 % RH, and avoiding open exposure adjacent to alkaline cleaning agents or amine-based additives, which can catalyse saponification or promote insolubilisation via complex formation with borate and titanate ions. The product is registered under REACH (EC number 618-340-3) and conforms to RoHS Directive 2011/65/EU recast, but food-contact suitability must be assessed case by case against FDA 21 CFR § 177.1670 or the corresponding national regulation, as certain applications may require an additional migration test panel.