| HS Code | 853443 |
| Product Name | KURARAY POVAL 95-88 |
| Chemical Name | Polyvinyl alcohol |
| Cas Number | 9002-89-5 |
| Appearance | White granular powder |
| Degree Of Hydrolysis | 87.0 - 89.0 mol% |
| Viscosity 4 Aqueous Solution At 20c | 90 - 100 mPa·s |
| Ph 4 Aqueous Solution | 5.0 - 7.0 |
| Volatile Content | <= 5.0 wt% |
| Ash Content | <= 0.5 wt% |
| Average Degree Of Polymerization | approximately 2500 |
| Specific Gravity | 1.27 - 1.31 |
| Solubility | Soluble in hot water; insoluble in common organic solvents |
As an accredited KURARAY POVAL 95-88 factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | KURARAY POVAL 95-88 is supplied in 20 kg moisture-proof laminated paper bags with polyethylene liners, palletized and shrink-wrapped for safe transport. |
| Container Loading (20′ FCL) | 20′ FCL: 20 palletized bags of KURARAY POVAL 95-88, shrink-wrapped, securely stowed to prevent shift during transit. |
| Shipping | KURARAY POVAL 95-88 is a polyvinyl alcohol resin shipped as dry, free-flowing granules or powder. It is non-hazardous under normal transport conditions. Protect from moisture and rain during transit. Pack in sealed multi-layer bags or super sacks on pallets, with proper labeling to prevent product degradation. |
| Storage | Store KURARAY POVAL 95-88 in a cool, dry, well-ventilated area away from direct sunlight and heat sources. Keep containers tightly sealed to prevent moisture absorption and dust formation. Avoid accumulation of fines; keep away from oxidizers and ignition sources. Follow all label and safety instructions. |
| Shelf Life | Shelf life is typically 2 years from manufacture when stored unopened in a cool, dry place. |
Before KURARAY POVAL 95-88 enters a vinyl acetate polymerisation vessel as a protective colloid, a 10 wt% aqueous stock solution is prepared in a baffled stainless steel make-up tank fitted with a high-shear disperser and an anchor agitator. The powder is suspended in demineralised water at 15–20 °C to prevent fisheye formation, then the jacket is heated to 80–85 °C and held for 60 min until the liquid is visually clear. The grade is specified with a 4% aqueous solution viscosity of 85–95 mPa·s at 20 °C determined by DIN EN ISO 12058-1 and a degree of hydrolysis of 87–89 mol% by JIS K6726. The made-down solution is filtered through a 150 µm bag filter, then held at 50 °C for no more than 48 h; longer holding leads to a surface skin and a slow increase in solution viscosity. Transfer lines are traced at 60 °C because the solution can form gels in unheated dead legs. Pre-drying of the powder at 60 °C for 2 h is applied only when storage relative humidity has exceeded 70% RH.
In a 20 m³ stainless steel reactor producing poly(vinyl acetate) homopolymer dispersion, POVAL 95-88 is charged at 1.5–4.0 wt% on total vinyl acetate monomer. The initial kettle charge contains 40% of the monomer, 55% of the water phase, and 60–70% of the colloid solution; the remaining colloid is fed uniformly with monomer over 3–4 h. Ammonium persulfate is added at 0.15–0.25 wt% on monomer, and sodium bicarbonate buffers the aqueous phase at 0.05–0.10 wt%. Polymerisation temperature is held at 70–75 °C. Under these conditions, the high-molecular-weight 95-88 grade gives a 55% solids dispersion with Brookfield viscosity in the range 20,000–60,000 mPa·s at 25 °C on spindle 4 at 20 rpm. Median particle size by laser diffraction is controlled between 0.8 µm and 1.5 µm, and coagulum retained on a 100 mesh screen is below 0.05% of wet dispersion. Raising the colloid level above 4.0 wt% sharply increases reactor viscosity and reduces condenser heat transfer, with the cooling water return rising above 65 °C and foam carryover becoming visible. Batch-to-batch variation in dispersion viscosity is held within ±10% by fixing dissolution time, solution age, and monomer feed profile. The resulting dispersions are used for D3 wood bonding adhesives tested to EN 204/205 and for paper conversion adhesives where FDA 21 CFR 175.105 applies.
On a film press running lightweight coated board at 600–1,200 m/min, POVAL 95-88 is applied in a surface size bath at 6–9 wt% solids and 55–65 °C. At 7 wt% solids, the Brookfield viscosity is approximately 200–400 mPa·s at 60 °C, which is higher than low-viscosity PVOH grades and changes the film split pattern at the transfer nip. Rod pressure is set between 1.0 bar and 2.0 bar to control pick-up at 1.2–2.5 g/m² dry add-on. The high molecular weight fraction reduces liquid penetration into the sheet; Cobb60 values measured by ISO 535 drop from approximately 28 g/m² to 18–22 g/m² at the same add-on. Sizing response is further characterised by the Hercules size test TAPPI T 530, and surface smoothness is assessed by Parker PrintSurf roughness ISO 8791-4. POVAL 95-88 also functions as a carrier for optical brightening agent in the surface size, improving retention on the sheet. Misting at the film transfer nip becomes a production problem when bath solids exceed 9 wt% and machine speed exceeds 1,000 m/min. Calcium chloride at 0.5–1.0 wt% on PVOH solids can be added to increase association and modify film split, but it may reduce rewetting if the board is subsequently coated with water-based barrier dispersions. Borax or boric acid addition is avoided because di-diol complexation with PVOH raises viscosity beyond the operating window and can gel the bath within 30 min.
Remoistenable envelope front seal gum is formulated with POVAL 95-88 as the primary water-responsive film former at 25–35 wt% dry solids. The grade is combined with dextrin at a PVOH:dextrin ratio of 60:40 to 70:30 to balance machine open time and re-moistening tack. Glycerin at 8–12 wt% on total dry solids is used as humectant to prevent film brittleness during die-cutting. The adhesive is applied by an extrusion nozzle at 0.8–1.2 g/m² dry film weight onto envelope flap paper, followed by forced-air drying at 70–80 °C surface temperature for 2–4 s. The high molecular weight of POVAL 95-88 permits film continuity at lower coat weight, while providing T-peel adhesion above 25 N/m when re-wetted and bonded to uncoated kraft based on ASTM D1876. Blocking resistance is tested by stacking finished blanks at 50 °C and 80% RH for 24 h; formulations with dextrin above 40 wt% of total solids show tray jams and film transfer marks. Re-moistening at 15–20 °C produces tack within 0.5–1.0 s, but at water temperatures below 10 °C the onset of tack is delayed beyond the machine dwell window. Borax is excluded from the formulation because crosslinking of partially hydrolysed PVOH raises roller-transfer viscosity above the application limit and degrades re-moistening at low water add-on. Terminal products include catalog envelopes, pocket folders, and security mailers.
For water-based alumina tape casting, POVAL 95-88 is pre-dissolved at 8–12 wt% in deionised water adjusted with 0.2–0.5 wt% ammonium polyacrylate dispersant. The solution is then mixed with alumina powder to reach 88–92 wt% solids; PVOH content is maintained at 3–5 wt% on dry ceramic powder. Slurry viscosity at 10 s⁻¹ is held between 2,000 mPa·s and 6,000 mPa·s, while low-shear viscosity at 0.1 s⁻¹ exceeds 15,000 mPa·s. This shear-thinning profile is stronger with the high-molecular-weight 95-88 grade than with low-viscosity PVOH and limits hard settling during the 1–2 h de-airing step at 200–400 mbar. Tape is cast onto polyethylene terephthalate carrier at 0.5–1.5 m/min with doctor blade gaps set to produce green tape thickness from 80 µm to 300 µm. After drying at 40–60 °C, the green tape free film shows tensile strength of 3–7 MPa and elongation at break of 10–25% when conditioned at 23 °C and 50% RH and tested to ASTM D882. The clean burnout profile is checked by heating at 5 °C/min to 500 °C in air; residual ash is below 0.5 wt% of binder mass. This low residue prevents carbon pickup that otherwise reduces density and electrical performance in alumina substrates. Inorganic crosslinkers and high-shear milling longer than 2 h are avoided because they increase slurry temperature above 35 °C and initiate PVOH film formation around ceramic particles, causing casting streaks.
After the size-box solids are adjusted to 8–12 wt%, POVAL 95-88 is cooked in a jet cooker at 90–95 °C for 60 min and transferred to the size box at 80–85 °C. Size add-on for polyester–cotton warp yarn is held at 6–10% on dry yarn weight, verified by gravimetric difference after oxidative size removal. The grade is blended with a low-viscosity starch ether at 20–30 wt% of total size solids; above 30 wt% starch, film cohesion drops in weaving rooms maintained above 75% RH, and size shedding increases on air-jet loom reeds running at 600–800 picks per minute. Hairiness reduction measured by Zweigle G 567 is typically 40–60% relative to unsized yarn. A wax-based lubricant at 0.5–1.0 wt% of size solids is dispersed into the cooked size to control metal-to-yarn friction. Desizing is carried out in an oxidative bath at 80–90 °C followed by a hot wash at 95 °C; incomplete removal of the high-molecular-weight PVOH film causes uneven dye uptake in subsequent pad dyeing and detectable size residues in the finished woven fabric. When stored size is held overnight, the tank is kept at 70–80 °C under gentle agitation because cooling below 50 °C forms a skin that can break off into the size box and generate loom stops. Terminal fabrics include workwear blends and durable uniform twills.
In suspension polymerisation of vinyl chloride, POVAL 95-88 is introduced as a secondary dispersant at 100–300 ppm on vinyl chloride monomer. A primary dispersant of lower hydrolysis and lower molecular weight is retained at 400–700 ppm, and the water-to-monomer ratio is held at 1.0:1.2 in a 150 m³ autoclave. The aqueous phase is buffered with ammonium bicarbonate to pH 5–7 and polymerisation temperature is controlled at 57–62 °C, depending on the target K-value. The high-molecular-weight secondary dispersant increases the number of monomer droplets that survive coalescence during the early polymerisation stage, producing a broader particle size distribution. Resin median particle size moves from 130 µm to 150–170 µm, and a coarse shoulder appears at 200–250 µm. Plasticizer absorption measured by ISO 4608 rises from 18–22 phr to 24–30 phr as the POVAL 95-88 addition is increased within the stated window. K-value measured by ISO 1628-2 remains at 66–68 because the initiator charge and reaction temperature are unchanged. Reactor wall scale becomes visible after 8–12 batches and requires high-pressure water jetting at 800–1,200 bar; the high-molecular-weight grade is not used as the sole dispersant because it would increase the skin layer and reduce heat transfer across the jacket. The product resin is used in flexible PVC compounds where higher plasticizer absorption improves dry blending and extruder throughput.
Competitive KURARAY POVAL 95-88 prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615380400285 or mail to sales2@liwei-chem.com.
We will respond to you as soon as possible.
Tel: +8615380400285
Email: sales2@liwei-chem.com
Flexible payment, competitive price, premium service - Inquire now!
KURARAY POVAL 95-88 is a polyvinyl alcohol resin obtained by controlled alcoholysis of polyvinyl acetate. The grade designation encodes two independent specifications: the first numeric segment, 95, refers to the nominal viscosity of a 4% aqueous solution at 20°C, stated as 95 mPa·s when measured with a Höppler falling-ball viscometer according to DIN 53015; the second segment, 88, identifies a nominal degree of hydrolysis of 88 mol% when tested by titration according to ISO 15023-2:2019. The residual vinyl acetate fraction of approximately 12 mol% is not an impurity but a structural modifier: it interrupts chain regularity, reduces crystallite size, and lowers the thermodynamic barrier to cold-water swelling. The product is supplied as white to off-white granules or powder, with a bulk density typically in the range 0.40–0.55 g/cm³ and a moisture content below 5 wt% on the certificate of analysis. Because both viscosity and hydrolysis are nominal values, batch-to-batch variation is controlled within the manufacturer’s release window; incoming inspection for critical applications should verify the lot certificate rather than rely on the grade name alone.
The molecular weight distribution of this high-viscosity grade is broader than that of low-viscosity PVOH types; aqueous solutions display pronounced chain entanglement. The critical overlap concentration is reached below 1 wt% at 20°C for a 95 mPa·s grade, which means that most application concentrations are in the semi-dilute regime. This rheological state controls pump sizing, heat transfer, and levelling behaviour.
Dissolution of POVAL 95-88 proceeds through a two-stage process: cold-water dispersion at 20–25°C with vigorous mixing, followed by heating to 85–90°C for 30–60 min. The resulting 4% solution has a pH of 5–7 by ISO 976 and a viscosity of approximately 95 mPa·s by DIN 53015. At 10% solids, Brookfield viscosity at 20 rpm exceeds 1,500 mPa·s; the solution is pseudoplastic, and viscosity at 100 rpm may be only 40–50% of the low-shear value. This shear-thinning behaviour is exploited in size-press and coating equipment, where shear rates at the metering nip exceed 10,000 s⁻¹. Films cast from a 10% aqueous solution and dried at 40°C for 24 h are transparent and flexible. When conditioned at 23°C and 50% relative humidity, tensile strength measured by ASTM D882-18 is commonly between 30 MPa and 45 MPa, with elongation at break between 150% and 300%. The presence of 12 mol% residual acetate reduces tensile modulus and increases elongation compared with fully hydrolysed PVOH. Oxygen permeability measured according to ASTM D3985-24 at 0% relative humidity is typically below 0.5 cm³·mm/(m²·day·atm); at 80% relative humidity the value can exceed 20 cm³·mm/(m²·day·atm). This order-of-magnitude increase is caused by plasticisation of the amorphous phase and is the principal limitation for barrier packaging without a moisture-barrier layer.
Grade selection in polyvinyl alcohol systems is governed by the interaction between viscosity, degree of hydrolysis, and the thermal history of the final product. POVAL 95-88 combines high molar mass with partial hydrolysis; the high molar mass contributes to film strength and aqueous thickening, while the residual acetate content preserves some cold-water compatibility. A fully hydrolysed grade with 99 mol% hydrolysis, even at a similar viscosity, will dissolve only above 70°C and will yield a more crystalline, more water-resistant film. A low-viscosity partially hydrolysed grade such as 5-88 dissolves rapidly in cold water but produces films with lower tensile strength and little thickening at the same solids. In applications where the polymer must be added at more than 5 wt% solids, the high viscosity of POVAL 95-88 becomes a practical constraint because solution viscosity may be too high for conventional pumps and filters. The comparison is summarised in the table below.
| Grade | Nominal viscosity of 4% aqueous solution at 20°C (DIN 53015) | Nominal hydrolysis (ISO 15023-2:2019) | General processing effect |
|---|---|---|---|
| POVAL 95-88 | 95 mPa·s | 88 mol% | High viscosity, high shear strength, limited cold-water dissolution |
| POVAL 5-88 | 5 mPa·s | 88 mol% | Low viscosity, rapid cold-water dissolution, lower film strength |
| POVAL 28-99 | 28 mPa·s | 99 mol% | Fully hydrolysed, hot-water dissolution, high crystallinity |
Vinyl chloride suspension polymerisation uses POVAL 95-88 as a primary protective colloid at charge levels of 0.05–0.15 g/100 g monomer. The combination of 88 mol% hydrolysis and high solution viscosity modifies the equilibrium between droplet break-up and coalescence in the pre-gelation stage. In a 13 m³ stirred reactor fitted with a 2.0 m diameter turbine impeller and operated at 250–300 rpm, an aqueous phase containing 0.10 wt% POVAL 95-88 at 25°C develops a Brookfield viscosity in the range 120–180 mPa·s at 20 rpm. That viscosity increase reduces jacket heat-transfer efficiency; operators sometimes compensate with 10–15% higher coolant flow to hold the polymerisation exotherm within the target band. At 0.20 wt% or greater, the aqueous-phase viscosity can rise above 250 mPa·s, producing persistent foam in the overhead condenser and a broader grain-size distribution. For reactor systems where the jacket-to-reactor volume ratio is lower than 0.8, published data for this specific grade is limited; pilot-scale verification under the intended agitation profile is required. The partially hydrolysed structure also influences grain porosity and monomer absorption. Compared with fully hydrolysed protective colloids, POVAL 95-88 shifts the mean particle size lower at equivalent stirring speed when measured by laser diffraction according to ISO 13320, but the magnitude depends on buffer concentration, initiator selection, and monomer purity.
Adhesive formulators select POVAL 95-88 when higher green strength and film toughness are required at low addition levels. In starch-based corrugating adhesives containing 0.5–1.0 wt% POVAL 95-88 based on total adhesive mass, the time to reach a T-peel green bond of 50 N/m at 20°C is typically reduced by 15–30% relative to the same formulation without PVOH. This measurement is performed on a tensile tester at 100 mm/min crosshead speed using 25 mm wide strips of kraft liner. Borax is a common additive in PVOH-based adhesives, but the high viscosity of POVAL 95-88 magnifies gelation: adding 1.0 wt% borax decahydrate to an 8% PVOH solution at 25°C can raise Brookfield viscosity tenfold within 10 min. At borax levels above 2 wt%, the system forms a rubbery gel that undergoes syneresis and is no longer transferable by gear pump. For surface sizing of linerboard, a 6–8 wt% solution at 50–60°C is metered with a rod coater to achieve 2–4 g/m² dry pick-up. Surface strength and printing performance are measured by IGT pick tests according to ISO 3783; typical improvement above the starch control is 20–40% at 4 g/m² dry pick-up. The main operational constraint is misting from high-viscosity solutions at rod-coater speeds above 1,500 m/min; the use of high-solids starch-PVOH blends reduces the issue but requires shear-stability screening.
Textile warp sizing with POVAL 95-88 requires a lower solids setting than low-viscosity grades because of the high solution viscosity. A size liquor at 80°C containing 3–5 wt% POVAL 95-88 and 0.5–1.0 wt% synthetic lubricant exhibits a viscosity of 50–100 mPa·s and is compatible with conventional slasher equipment. Warp-hairiness reduction and abrasion resistance on air-jet looms are assessed by the Kapur yarn abrasion method and by loom stop counts rather than by a single ASTM standard; line trials at 700–900 picks/min have shown that adequate film strength is maintained at size add-on of 8–12% on ring-spun cotton. Desizing is performed with hot water at 80–90°C because the 88 mol% hydrolysis allows enzymatic or oxidative desizing within 30–45 min; fully hydrolysed PVOH would require more aggressive wash conditions. Published data for the specific grade in all weave constructions is limited; slasher trials are recommended.
KURARAY POVAL 95-88 is hygroscopic. Equilibrium moisture at 20°C and 60% relative humidity is between 5 wt% and 7 wt%; at 80% relative humidity, moisture uptake can exceed 12 wt% and the free-flowing powder may cake. Moisture content is determined by Karl Fischer titration according to ISO 15512:2019; ash content by ISO 3451-1:2019 is typically below 0.5 wt%. Store sealed bags below 25°C and 60% relative humidity; opened bags should be resealed under nitrogen or consumed within 24 h to avoid moisture absorption. Aqueous solutions of this grade at 1–10% solids should be preserved if held longer than 24 h at ambient temperature; unpreserved solutions can develop microbial colonies within 48–72 h. Methylisothiazolinone or benzisothiazolinone at 0.05–0.15 wt% on solution mass controls bacterial growth. Strong acids, strong oxidisers, and aldehydes are incompatible with PVOH. Dry resin heated above 200°C under air can discolour and degrade; aqueous solutions should not be held above 90°C for more than 2 h because chain scission reduces viscosity.
Regulatory evaluation of KURARAY POVAL 95-88 is end-use specific. For paper and paperboard intended for food contact, compliance is assessed under U.S. FDA 21 CFR 176.170 and 21 CFR 176.180. For plastic materials and articles in the European Union, the resin may be evaluated under Commission Regulation (EU) 10/2011 as a component within the final article; specific migration limits depend on the article composition and food simulant. The supplier certificate of analysis reports residual vinyl acetate monomer, typically below 5 mg/kg, and heavy-metal concentrations for lead, cadmium, mercury, and arsenic below 10 mg/kg, 1 mg/kg, 0.1 mg/kg, and 1 mg/kg, respectively, by inductively coupled plasma optical emission spectrometry after acid digestion. These values are typical industrial acceptance criteria; the absence of a release number on a lot certificate should be resolved before use in regulated contact applications.
