Sinopec PVA 092-35 is a partially hydrolyzed polyvinyl alcohol resin classified under the alphanumeric system where the first three digits indicate the nominal degree of hydrolysis and the suffix denotes the 4 % aqueous solution viscosity measured at
20 °C in accordance with
GB/T 12010.2‑2008. The grade carries a hydrolysis specification of
92.0 ± 1.0 mol % and a Brookfield LV viscosity (spindle 1,
60 rpm) of
35.0 ± 3.0 mPa·s. Volatile matter is controlled to ≤
5.0 %, ash content to ≤
0.5 %, and the pH of a 4 % solution ranges from
5.0 to
7.0. The resin maintains a minimum
99.0 % passage through a
20‑mesh screen, ensuring minimal fisheye formation during dissolution.
When Cold‑Water Solubility Dictates Process Efficiency
Unlike fully hydrolyzed grades that demand heating to
95 °C or higher for complete hydration, PVA 092‑35 undergoes near‑complete dissolution in demineralized water at
20–25 °C under moderate agitation. In a production‑scale
500 L dissolver equipped with a dual‑shaft disperser, a
10 % solids slurry prepared by pre‑wetting the granules with cold water at a
3:1 water‑to‑resin ratio reaches a Hegman grind of
0 within
30 min at
800 rpm. The low‑temperature dissolution profile removes the need for jacketed heating, eliminates steam‑side fouling, and permits direct blending with heat‑sensitive co‑binders such as dextrin or protein‑based adhesives. Viscosity‑shear behavior follows a pseudoplastic power‑law model with a flow‑behavior index n of approximately
0.55 at shear rates between
10 and
100 s⁻¹, as determined on a controlled‑stress rheometer with a
40 mm parallel‑plate geometry. At a shear rate of
10 s⁻¹ the apparent viscosity of a
4 % solution averages
35 mPa·s, falling to
20 mPa·s at
100 s⁻¹, which facilitates roll‑coater or size‑press transfer without misting. After
24‑h static storage at
5 °C the solution shows no gelation or cloud point shift, indicating adequate cold‑storage stability for multi‑shift operations.
What Differentiates PVA 092‑35 from Low‑Viscosity, High‑Hydrolysis Analogues?
The mid‑range viscosity and
92 mol % hydrolysis place this grade in a distinct performance band compared with lower‑viscosity partially hydrolyzed types such as PVA 088‑50 (
88 mol % hydrolysis, viscosity
5.0 mPa·s) and with high‑hydrolysis, ultra‑low‑viscosity grades used in specialty stabilizer applications. The higher molecular weight fraction, reflected in the
35 mPa·s viscosity, increases cohesive strength in adhesive films and reduces binder migration during drying of coated substrates. In a modified polyvinyl acetate wood‑glue formulation containing
4.5 wt % PVA 092‑35 as protective colloid, the wet tack measured on beech veneer in accordance with
DIN EN 205:2016 reaches
4.8 N/mm², compared with
2.9 N/mm² for an otherwise identical formulation using PVA 088‑50. The
92 mol % hydrolysis level imparts sufficient hydroxyl density to interact with cellulosic substrates while retaining cold‑water solubility; fully hydrolyzed PVA 1799 (
98.5 mol %) demands hot‑water cooking and yields films with lower elongation at break, limiting dynamic flexibility. A systematic comparison is provided in Table 1.
| Property | PVA 092‑35 | PVA 088‑50 | PVA 1799 | Test Method |
|---|
| Hydrolysis | 92.0 ± 1.0 mol % | 88.0 ± 2.0 mol % | 98.5 ± 1.0 mol % | GB/T 12010.2 |
| 4 % viscosity (20 °C) | 35.0 ± 3.0 mPa·s | 5.0 ± 1.0 mPa·s | 27.0 ± 2.0 mPa·s | GB/T 12010.2 |
| Minimum dissolution temperature | ≤ 25 °C | ≤ 25 °C | ≥ 85 °C | internal method |
| Film tensile strength (MPa) | 38 – 44 | 20 – 28 | 60 – 70 | ISO 527‑3 |
| Film elongation at break | 150 – 200 % | 250 – 350 % | 8 – 15 % | ISO 527‑3 |
| Wood adhesive wet tack (beech) | 4.8 N/mm² | 2.9 N/mm² | not applicable | DIN EN 205 |
| Solution cold‑storage stability (5 °C, 24 h) | no gelation | slight viscosity rise | immediate gelation | qualitative |
Film Mechanical Property Threshold: 092‑35 vs. Fully Hydrolyzed Grades
While fully hydrolyzed PVA films deliver oxygen‑barrier performance nearing
0.5 cm³·mm/m²·day·atm at
50 % RH (ASTM D3985), the partially hydrolyzed PVA 092‑35 film sacrifices a portion of that barrier advantage in exchange for elongation and cold‑water removability. A cast film dried at
60 °C and conditioned at
23 °C,
50 % RH for
48 h exhibits a tensile strength of
40 MPa (type 5A dumbbell, ISO 527‑3) and elongation of
180 %. This elongation envelope permits the film to comply with uneven substrate surfaces without fracturing when used as a temporary protective peelable coating. In contrast, PVA 1799 films rupture at
10 % elongation, limiting use to rigid substrates. Water‑vapor transmission rate of PVA 092‑35 film (
25 µm thickness) measured at
38 °C,
90 % RH according to ASTM E96/E96M is
85 g/m²·day, roughly three times that of a
1799 film under identical conditions. The trade‑off is acceptable in applications where wash‑away convenience outweighs absolute barrier requirements.
From Granule to Dissolution: Processing in Aqueous Formulations
PVA 092‑35 granules exhibit a bulk density of approximately
0.55 g/cm³ and a tendency toward dust generation when transferred pneumatically. Closed conveying under nitrogen with a dust‑collection filter rated for
0.5 µm particulates is advised. The dissolution protocol begins by charging the required amount of ambient‑temperature demineralized water into a vessel fitted with a low‑shear anchor stirrer and a high‑speed disperser. Granules are added slowly through a vibratory feeder at a rate of
5 kg/min per
100 L of water while the disperser operates at
1200 rpm. Following powder incorporation, the batch is mixed at
200 rpm for
45 min to remove micro‑gels. Any persistent foam, which can interfere with metering pumps, is suppressed by addition of a silicone‑free defoamer at ≤
0.05 % on solution weight. The finished solution must be filtered through a
40‑mesh in‑line strainer before transfer to the holding tank.
Replacing the conventional hot‑cook step with the cold‑dissolution regimen for PVA 092‑35 reduces energy consumption by an estimated
0.12 kWh/kg of dry resin on a
1 000‑L batch scale and shortens total preparation cycle from approximately
3 h to
1 h. The product is not compatible with borate‑based gelling agents or polyvalent metal ions such as Fe³⁺ and Al³⁺, which cause instantaneous crosslinking and insoluble precipitates. When incorporated into emulsion polymerization as a protective colloid, it should be dosed as a
10 % aqueous solution and added before initiation of the monomer feed to secure uniform grafting onto the vinyl acetate backbone.
In surface sizing of fine paper and board grades, PVA 092‑35 is typically applied at a dry pick‑up of
0.8 – 1.2 g/m² via a metering size press. A formulation comprising oxidized corn starch and
6 % PVA 092‑35 on starch dry weight yields a surface strength, as measured by IGT pick resistance (ISO 3783), of
3.2 m/s versus
2.1 m/s for starch alone. Cobb water absorption (ISO 535:2023,
60 s contact) remains at
28 g/m², indicating minimal impact on sizing holdout when the PVA loading is kept below
1.5 g/m². The grade’s narrow hydrolysis distribution avoids the blocking tendency sometimes observed with lower‑hydrolysis PVA grades on calender stacks.
Textile warp sizing takes advantage of the balance between adhesion to cotton/polyester yarns and ease of desizing. A
7.0 % solution applied at
85 °C on a single‑size‑box slasher at a squeeze pressure of
10 kN/m deposits
6.5 % add‑on. Weaving efficiency on a rapier loom running at
450 rpm is maintained above
96 % with warp stops below
0.5 per 10⁵ picks. Desizing proceeds within
15 min in hot water at
60 °C without enzymes, a significant advantage over fully hydrolyzed PVA films that require prolonged scouring.
Regulatory acceptance for food‑contact applications is supported by
FDA 21 CFR 176.170 (components of paper and paperboard in contact with aqueous and fatty foods) and
FDA 21 CFR 175.105 (adhesives). The material is also in compliance with EU
Regulation (EC) 1935/2004 and, when used under the specified migration limits, meets the requirements set out in Chinese standard
GB 9685‑2016 for food contact materials. A summary of relevant regulatory and testing frameworks is provided in Table 2.
| Regulation/Standard | Scope | Key Requirement |
|---|
| FDA 21 CFR 176.170 | Paper/paperboard in contact with food | Extractives limits per food type |
| FDA 21 CFR 175.105 | Adhesives | Good manufacturing practice |
| EC 1935/2004 | Framework for food contact materials | No migration endangering health |
| GB 9685‑2016 | Additive positive list (China) | Specific migration limits apply |
| GB/T 12010.2‑2008 | PVA test methods | Hydrolysis, viscosity, ash, pH |
| ISO 535:2023 | Paper Cobb water absorption | Test duration 60 s |
| ISO 3783 | Paper surface pick resistance (IGT) | Speed vs. pick threshold |
Storage stability is predicated on
RH < 65 % and a temperature window of
10–30 °C; exposure to relative humidity above
70 % can elevate the volatile matter to>
6.0 % within
72 h, affecting metering accuracy in gravimetric feeders. When resealed after partial use, the original packaging retains product integrity for up to
24 months from the date of manufacture. No performance degradation has been observed in accelerated aging at
40 °C over
12 weeks, as assessed by viscosity retention and dissolution clarity.
