| HS Code | 152704 |
| Chemical Formula | (C2H4O)n |
| Cas Number | 9002-89-5 |
| Water Solubility | Soluble in hot water above 80°C, limited in cold water |
| Degree Of Hydrolysis | 87-89% or 98-99% typical grades |
| Viscosity | 4-70 mPa·s for 4% aqueous solution at 20°C |
| Melting Point | 180-230°C (decomposes before true melting) |
| Decomposition Temperature | 200-250°C |
| Limiting Oxygen Index | 19-23% (needs flame retardant modification) |
| Char Formation | Forms intumescent char upon thermal degradation with flame retardants |
| Flame Retardant Synergy | Enhances char yield and reduces heat release rate when combined with phosphorus/nitrogen additives |
As an accredited Polyvinyl Alcohol (PVA) for Flame Retardant Materials factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in 25 kg moisture-proof laminated bags, sealed for safe storage and handling of PVA flame retardant materials. |
| Container Loading (20′ FCL) | 20′ FCL loading of PVA for flame retardants: 25kg bags on pallets, ventilated, dry, secured for safe transit. |
| Shipping | Ship as non-hazardous dry powder in sealed polyethylene-lined bags or fiber drums. Protect from moisture, humidity, and direct sunlight. Avoid creating dust clouds; PVA is combustible. Use standard ground freight with proper labeling. Keep away from ignition sources and store in a cool, dry area during transit. |
| Storage | Store Polyvinyl Alcohol (PVA) in a cool, dry, well-ventilated area away from heat, open flames, and ignition sources. Keep containers tightly sealed to prevent moisture absorption and dust generation. Avoid contact with strong oxidizers and incompatible chemicals. Ensure proper labeling and spill controls; use grounded equipment and appropriate PPE during handling. |
| Shelf Life | Shelf life is typically 2–3 years when stored in a cool, dry place and kept sealed to avoid moisture absorption. |
In single-component waterborne intumescent coatings for structural steel, polyvinyl alcohol (partially hydrolyzed, degree of polymerization 1700–2400) functions simultaneously as the primary film-forming binder and as a carbonific char source that interacts with the ammonium polyphosphate/pentaerythritol/melamine (APP/PER/MEL) intumescent triad. The dry-film composition typically incorporates PVA at 6–12 wt% alongside 22–30 wt% APP (phase II, n > 1000), 8–12 wt% pentaerythritol, and 10–15 wt% melamine, with the balance comprising titanium dioxide and rheology modifiers. Compliance with EN 13381-8:2013 and GB 14907–2018 demands that the swollen char layer withstand a hydrocarbon fire curve without substrate adhesion failure or char cracking beyond the critical elongation threshold of 0.8 mm at 500°C. In production-scale batching, a high-speed disperser equipped with a 350 mm diameter Cowles blade operating at a tip speed of 18–25 m/s reduces the Hegman grind to 25–30 µm; airless spray application follows at a wet-film thickness of 800–1200 µm in a single pass, with flash-off intervals controlled to 10–15 minutes between coats to prevent solvent pops. A documented limitation emerges from PVA’s equilibrium moisture sorption: at relative humidity above 60% and 23°C, the dried film reabsorbs atmospheric water and swells, lowering the intumescent expansion ratio by 15–22% in cone calorimeter evaluation conducted per ISO 5660-1:2015. To address this drift, partial acetalization of the PVA backbone with butyraldehyde is performed during dedicated binder synthesis, shifting the glass transition temperature from approximately 45°C to 68°C and reducing equilibrium moisture uptake to 3–5% at 50% RH. The finished products are certified fire-protective layers for I-section beams and hollow steel columns in commercial high-rise construction, where the dry film thickness is routinely inspected with an electromagnetic gauge to ensure uniform 1.2–2.5 mm DFT across flanges and webs.
Phosphonium-salt precondensates (THPC-urea, typically applied at 25–35% solids on mass of fabric) impart adequate initial flame resistance to cotton twill used in protective clothing, yet the finishes exhibit a marked drop in afterflame time after 15–20 industrial launderings under ISO 15797. Incorporation of polyvinyl alcohol (degree of hydrolysis 87–89 mol%, 4–6 wt% in the pad bath) as a reactive co-binder, followed by a pad–dry–cure sequence (nip pressure 2.5–3.0 bar, drying at 100–120°C, curing at 150–170°C for 2–4 minutes), creates a crosslinked network that mechanically entraps the flame-retardant species within the fiber interstices. The formulation must comply with NFPA 701:2023 Method 2 and BS 5852:2006 ignition source 5, where char length shall not exceed 200 mm. At the stenter frame, fabric width control within ±2% of the greige dimension is mandatory because PVA stiffens the hand, and over-drying induces selvage curling that disrupts downstream cutting. Operational data from a 10-chamber hot flue stenter running at 25–35 m/min indicate that pad-liquor viscosity, measured by a Brookfield LVT spindle 3 at 60 rpm, must be maintained between 800 and 1200 mPa·s to prevent an uneven add-on profile; excursions beyond this range cause trough-level starvation and localized afterflame failures in the warp direction. The final textile article, a flame-resistant uniform fabric with a finished weight of 330–380 g/m², undergoes random draw vertical flame testing where afterglow suppression is directly correlated with the degree of PVA crosslinking, as assessed by methylene blue staining and a hot-water extraction weight loss below 4%.
Low-ignition-loss cable-sheathing compounds formulated with ethylene vinyl acetate copolymer (28% VA content, melt flow index 3–6 g/10 min at 190°C/2.16 kg) and magnesium hydroxide (60–65 phr, median particle size 1.8–2.5 µm) benefit from the addition of 2.0–3.5 phr polyvinyl alcohol powder as a solid-phase char promoter that densifies the residue during combustion. The PVA (<0.15% residual moisture after 4 h at 105°C in a desiccant-bed dryer) is metered into a co-rotating twin-screw extruder (L/D 44:1, screw diameter 40 mm) through a side feeder positioned downstream of the first kneading block to restrict its overall thermal exposure to less than 45 seconds above 170°C. Zone temperatures are profiled from 145°C near the feed throat to 190°C at the die head, with a maximum permissible melt temperature of 200°C; exceeding this threshold initiates chain-stripping degradation that liberates acetic acid vapor, accelerating corrosion of the induction-hardened barrel lining and generating black speck contamination at a density above 0.3 specks/m² of jacket surface. This process elevates the limiting oxygen index from 33% to 38–40% and reduces the cone calorimeter peak heat release rate (incident flux 50 kW/m²) by 15–25%, enabling consistent compliance with IEC 60332-1-2:2015 vertical flame spread and UL 1581 VW-1. On a production-scale single-screw cable extruder (75 mm, Maillefer BM-type screw, compression ratio 2.8:1), the introduction of PVA increases die-head pressure fluctuation amplitude by 8–12%, necessitating a gear pump with a pressure feedback loop set to 0.2 MPa tolerance to stabilize wall thickness at 1.0–1.4 mm for a 3-core building wire. The final product is a halogen-free, low-smoke sheathed cable rated 450/750V for fixed installations in public-access buildings, where emission compliance per EN 60754-2:2020 must demonstrate acidity levels below 2.0 µS/mm.
| PVA Loading (phr) | LOI (%) ASTM D2863 | UL 94 Rating (3.2 mm) | Peak HRR Reduction vs 0 phr (%) ISO 5660 | Char Residue at 700°C (%) TGA N₂ |
| 0 | 31–33 | V-2 | baseline | 38–41 |
| 1.5 | 34–36 | V-1 | 8–12 | 43–47 |
| 2.5 | 37–39 | V-0 | 16–22 | 48–53 |
| 3.5 | 39–41 | V-0 (no afterglow) | 22–28 | 52–57 |
Lamination of tropical hardwood veneers (okoumé, meranti) for fire-rated plywood increasingly substitutes 15–25% of the urea–formaldehyde prepolymer solids with an aqueous polyvinyl alcohol solution (viscosity grade 25–30 mPa·s at 4% concentration, 20°C), maintaining total resin solids at 52–55% and adding ammonium polyphosphate (8–12 wt% on dry resin) as the phosphorous donor. After blending in a planetary mixer at 60–80 rpm for 20–30 minutes, the adhesive is applied via a four-roller spreader delivering 140–180 g/m² single-side glue line, followed by assembly pressing at 1.0–1.5 MPa and 110–125°C for a press time of 45–60 seconds per mm of panel thickness. Compliance is verified against EN 314-2:1993 Class 3 bond durability and ASTM E84-23a surface flame spread (Class A requires Flame Spread Index ≤ 25). A practical incompatibility arises when the ammonium polyphosphate grade exhibits a water solubility exceeding 0.5 g/100 mL at 25°C: in service, moisture migration through the veneer interfaces leaches phosphate species to the surface, forming a crystalline efflorescence that reduces the bond’s shear strength by 12–18% after 28 days of 85% RH conditioning. To counter this, co-addition of 2–3 wt% melamine cyanurate increases the interlayer viscosity during the hot-press cycle and reduces the leachable fraction. The finished panel is a 18–25 mm thick flame-retardant plywood intended for interior wall linings in institutional buildings, where the surface is routinely overlaid with high-pressure laminate before installation.
Honeycomb paperboard cores for fire-rated internal door leaves are frequently impregnated in an aqueous bath containing 7–9 wt% PVA (partially hydrolyzed, 87–89 mol%), 15–20 wt% ammonium polyphosphate (crystal form II, average chain length 800–1000), and 4–6 wt% dicyandiamide as a blowing promoter. A single-pass reverse-roll coater operating at 12–18 m/min deposits a dry add-on of 35–45 g/m², which raises the core’s orthogonal-to-face compressive strength to 0.8–1.2 MPa while conferring intumescent behavior validated by thermogravimetric analysis (ASTM E1131-08) showing a char yield increase of 8–12% at 600°C under nitrogen. The cellular structure is assessed against UL 94 VTM-0 for thin-wall materials, yet the honeycomb assembly is additionally evaluated per ASTM E84-23a for the entire door core; a Flame Spread Index below 25 and Smoke Developed Index below 450 are typical targets for 20-minute fire-rated door assemblies. A humidity-dependent defect occurs when the coated core is stored at relative humidity >75% prior to facing: PVA’s swelling moderates the gap between the paper cell walls, causing an irregular binder migration that results in anisotropic char expansion that can reach 4–6x the substrate thickness rather than the uniform 2–3x assumed in thermal barrier calculations, creating points of premature heat transmission through the door leaf during the EN 1634-1 integrity test.
When a compostable packaging article must pass a vertical flame spread classification equivalent to Euroclass B while remaining disintegrable under industrial composting conditions, polyvinyl alcohol (degree of hydrolysis 88 mol%, 4% aqueous viscosity 20–30 mPa·s) constitutes 75–88 wt% of the formulation and acts simultaneously as the thermoplastic matrix and as the primary carbon source during combustion. The flame retardant package consists of aluminum trihydroxide (8–12 wt%, median particle diameter 1.0–1.5 µm) and an oligomeric phosphonate ester plasticizer (4–7 wt%) that also lowers the melt processing temperature to 165–185°C, critical for cast-film extrusion through a flat die with a 0.5–0.8 mm lip gap. The cast film, with a gauge of 30–50 µm, undergoes biaxial orientation at a draw ratio of 2.5:1 in the machine direction and 1.8:1 in the transverse direction before passing through a conditioning chamber set to 25°C, 50% RH for 48 hours to stabilize equilibrium moisture at 4–6%. Compliance with EN 13501-1:2018 Class B-s1,d0 requires that the total heat release (THR600s) remains below 7.5 MJ and the smoke growth rate index (SMOGRA) below 30 m²/s², as measured in the single burning item test. Simultaneously, the material must demonstrate 90% mineralization within 90 days under ISO 14855-1:2012 respirometric conditions, a threshold that is compromised if the phosphonate plasticizer content exceeds 7 wt% because the phosphorous species partially inhibit microbial colonization. A documented operational boundary in blown-film trials (screw diameter 45 mm, blow-up ratio 2.2:1) is that PVA’s inherent oxygen barrier property rapidly drops when the film is plasticized above 12% total plasticizer content, lowering the oxygen transmission rate to below 10 cm³/m²·day·atm at 0% RH but sacrificing tear resistance — leading to splitting at the nip rollers when the film is wound at tensions above 8 N per 100 mm width. The final article is a transparent, anti-static, flame-retarded compostable bag for electronic component shipment, marked with the DIN CERTCO seedling logo and the CE marking under the Construction Products Regulation when used as a protective inner liner in fire-sensitive assemblies.
| Application Segment | Primary Compliance Standard(s) | Critical Test Method | Key Performance Criterion |
| Intumescent steel coating | EN 13381-8:2013, GB 14907–2018 | ISO 5660-1:2015 cone calorimeter | Char expansion ratio, adhesion after fire curve |
| Textile back-coating | NFPA 701:2023, BS 5852:2006 | ISO 15797 industrial washing | Char length ≤ 200 mm after 20 launderings |
| LSZH cable sheathing | IEC 60332-1-2:2015, UL 1581 VW-1 | IEC 60754-2:2020 | Acidity ≤ 2.0 µS/mm, char density |
| Fire-rated plywood adhesive | EN 314-2:1993, ASTM E84-23a | EN 314-1:2004 shear test | Flame Spread Index ≤ 25, bond integrity after 85% RH |
| Paper honeycomb core impregnation | UL 94 VTM-0, ASTM E84-23a | ASTM E1131-08 TGA | Char yield increase 8–12% at 600°C |
| Compostable FR film | EN 13501-1:2018, EN 13432:2000 | ISO 14855-1:2012 | THR600s ≤ 7.5 MJ, mineralization 90% in 90 days |
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Polyvinyl alcohol (PVA) serves as a polymeric carbonific agent in intumescent flame retardant systems, contributing char formation, film binding, and adhesion in aqueous and melt-compounded formulations. Commercial PVA variants are classified by degree of hydrolysis and viscosity of a 4 wt% aqueous solution measured at 20°C (DIN 53015 or equivalent). Fully hydrolyzed grades (alcoholysis 98.0–99.8 mol%, e.g., designation 1799, 1797) exhibit higher crystallinity, lower cold-water solubility, and reduced equilibrium moisture uptake relative to partially hydrolyzed types (86.0–89.0 mol%, e.g., 1788, 0588). Unlike low-molecular-weight char sources such as pentaerythritol (PER) or dipentaerythritol (DPE), PVA simultaneously functions as a film-former, permitting continuous intumescent coatings without supplementary latex binders. Thermal decomposition initiates above 200°C with elimination of water and acetic acid, generating conjugated polyene sequences that aromatize into a carbonaceous char under fire exposure. In isolation, PVA is not flame-retardant; its limiting oxygen index (LOI) per ASTM D2863 is approximately 19–22%. Flame retardancy is achieved only in combination with an acid donor (e.g., ammonium polyphosphate, APP) and a blowing agent (e.g., melamine). The product’s differentiation from starch, PER, and other carbonifics lies in its ability to generate mechanically coherent char layers that resist cracking and delamination during intumescent expansion.
| Commercial Designation | Alcoholysis Degree (mol%) | Viscosity (mPa·s, 4%, 20°C) | Ash (wt%, max) | Char Residue (N2, 600°C, PVA alone) | Char Residue (N2, 600°C, + 30 wt% APP) |
|---|---|---|---|---|---|
| 1799 | 99.0–99.8 | 22–28 | 0.5 | <5 wt% | 30–35 wt% |
| 1797 | 97.0–98.5 | 25–31 | 0.5 | <5 wt% | 28–33 wt% |
| 1788 | 87.0–89.0 | 20–26 | 0.5 | 3–5 wt% | 27–32 wt% |
| 0588 | 86.0–88.0 | 5.0–6.5 | 0.5 | 2–4 wt% | 25–30 wt% |
Char residue values were determined by thermogravimetric analysis (TGA) at a heating rate of 10°C/min under nitrogen, conforming to ISO 11358-1. The 30 wt% APP loading is representative of a 1:2 PVA-to-APP mass ratio typical in intumescent coating topcoats. Differences from pentaerythritol-based systems are pronounced: PER/APP mixtures yield comparable char mass but exhibit a powdery, non-cohesive residue, whereas PVA-derived char retains structural integrity with expansion ratios of 15:1 to 25:1 when the acid source and blowing agent are optimized.
Aqueous PVA intumescent coating production requires controlled dissolution, dispersion, and drying to avoid premature water loss, skin-over, or micro-cracking. The polymer is dissolved in deionized water at 85–95°C under low-shear mixing (anchor stirrer, 60–120 rpm) to achieve a 10–15 wt% stock solution. Flame retardant fillers—APP (40–50 parts per hundred resin, phr), melamine (10–20 phr), and optional co-carbonific—are incorporated via high-shear dispersion (dissolver disc, tip speed 15–25 m/s) into the cooled solution at 30–40°C to inhibit thermal degradation of APP. The target application viscosity is 3000–5000 mPa·s at 25°C (Brookfield RV, spindle #6, 20 rpm). Below 2000 mPa·s, sedimentation of APP particulates occurs within 4 h; above 6000 mPa·s, air entrapment during knife-over-roll coating becomes irreversible.
Coating is performed on a laboratory-scale continuous line (e.g., Mathis LTE-T with knife coater) at line speeds of 0.5–1.5 m/min onto substrates pre-dried to <0.5% residual moisture. Drying proceeds in two thermal zones: infrared pre-gelling at 80–100°C for 30–60 s to form a surface skin, followed by convective drying at 120–140°C with impingement air velocity of 2–4 m/s to reduce residual moisture below 2 wt%. A critical failure mode is blistering when the skin-over rate outpaces bulk moisture transport; the maximum tolerable Drying Rate Index (DRI) within the first 15 s is 0.8 g/m²·s. Pre-drying of the liquid formulation is mandatory at ambient relative humidity exceeding 60%, as moisture uptake by PVA plasticizes the film, reducing glass transition temperature (Tg) from 85°C to below 40°C and causing tackiness that traps particulate contamination. Addition of glyoxal crosslinker at 5 wt% on PVA raises the moisture resistance but depresses the intumescent expansion ratio from 18:1 to approximately 9:1 at 500°C as measured by furnace expansion test per EN 1363-1, a trade-off that must be balanced based on end-use humidity exposure.
Integration of fully hydrolyzed PVA (1799) into this process necessitates a pressurized dissolution vessel operating at 110–120°C and 0.1–0.2 MPa gauge to achieve complete solubilization, whereas partially hydrolyzed 1788 dissolves at atmospheric pressure. For this reason, partially hydrolyzed grades dominate coating applications, accepting a modest penalty in moisture resistance in exchange for simpler processing. Water absorption after 24 h immersion per ASTM D570 is 18–25 wt% for 1788-based coatings without crosslinker, compared to 8–12 wt% for crosslinked 1799-based analogues.
Incorporation of polyvinyl alcohol into thermoplastics via twin-screw extrusion for flame retardant masterbatch production demands rigorous control of residence time, shear heating, and volatile removal. A co-rotating, intermeshing twin-screw extruder with barrel length-to-diameter ratio L/D 40:1 (e.g., Coperion ZSK 26 Mv Plus) is configured with a temperature profile of 150/160/170/180/185/190/195/195/190/185°C from feed throat to strand die. PVA powder (partially hydrolyzed, 1788, particle size D50 < 150 µm) is pre-blended with a plasticizer (glycerol or sorbitol at 15 phr) to depress the melting point into the 160–180°C processing window. The plasticizer is absorbed into the PVA granules in a heated ribbon blender for 30 min at 80°C prior to extrusion; incomplete absorption causes phase separation and surging at the feed throat. The flame retardant package—typically APP (60 phr) and melamine (20 phr)—is fed downstream via a side-stuffer at barrel section L/D 22 to minimize thermal exposure. Screw speed is maintained at 200–300 rpm, yielding specific mechanical energy input of 0.15–0.22 kWh/kg and a melt residence time of 45–90 s.
Melt temperature measured by an immersion thermocouple at the die must not exceed 210°C. Acetic acid evolution from residual acetate groups accelerates autocatalytically above this threshold, causing molecular weight degradation and, paradoxically, crosslinking via intermolecular etherification. The onset of gel formation is detected as a progressive rise in die pressure: normal operating range is 50–80 bar; sustained readings above 100 bar demand immediate screw speed reduction or a shutdown to prevent die blockage. Pelletized strand output is hygroscopic and must be immediately dried in a desiccant dryer (dew point -40°C, 80°C, 4 h) and sealed in aluminum-laminated barrier bags. The let-down ratio of masterbatch into polypropylene (PP homopolymer, MFI 3 g/10 min per ISO 1133-1) is typically 25 wt% to achieve a UL 94 V-0 classification at 1.6 mm thickness, with an LOI of 28% (ASTM D2863). In contrast to PER-based masterbatches, PVA-based systems do not produce sublimate plate-out on mold vents or die lips, because PVA degradation does not generate volatile small molecules below 200°C.
| Property (Test Method) | PVA/APP (1:2) | Starch/APP (1:2) | PER/APP (1:2) |
|---|---|---|---|
| LOI, cotton fabric (ASTM D2863), 15% add-on | 29% | 24% | 27% |
| LOI after 5 wash cycles (ISO 6330, 40°C, with crosslinker) | 28% | 21% | 22% |
| Peak heat release rate reduction, cone calorimeter (ISO 5660-1, 35 kW/m²) | 55% | 40% | 50% |
| Film flexibility (Mandrel bend, 2 mm rod, 23°C) | No cracking | Cracks propagate | Not film-forming |
| Water absorption, 24 h (ASTM D570) | 22% (uncrosslinked) | >35% | 12% (but requires binder) |
Flexible textile back-coatings for cotton and cotton-polyester blends benefit from PVA’s film-forming capacity. Starch-based formulations yield brittle coatings that spall during folding, compromising fire barrier continuity; PER is not a film former and depends on latex binders that increase smoke density. PVA-based systems, deposited at 15% dry add-on via knife coater and crosslinked with 4 wt% dimethyloldihydroxyethyleneurea (DMDHEU), exhibit no visible cracking after 500 mandrel flex cycles at 2 mm radius. Cone calorimeter data (ISO 5660-1, incident heat flux 35 kW/m²) confirm a peak heat release rate reduction of 55% relative to uncoated control, with corresponding smoke production rate (ISO 5660-1 Annex A) reduced by 30% compared to a styrene-butadiene latex/PER equivalent at identical add-on. This difference in smoke performance is attributed to the absence of aromatic smoke precursors in the PVA backbone, in contrast to styrenic latex binders. Laundering durability per ISO 6330 (5 cycles, 40°C, reference detergent) is superior to starch systems, but PVA requires a crosslinker to prevent progressive leaching of the water-soluble polymer; without crosslinking, LOI drops from 29% to 23% after 5 cycles.
Polyvinyl alcohol is manufactured to meet regulatory frameworks pertinent to flame retardant materials. Grades intended for indirect food contact applications comply with U.S. FDA 21 CFR 175.300 (resinous and polymeric coatings) and EU 10/2011/EU (plastic materials in food contact) when the residual vinyl acetate monomer content is below 5 mg/kg. The polymer is not classified as a substance of very high concern (SVHC) under REACH and satisfies RoHS Directive 2011/65/EU restrictions on heavy metals. Operational boundaries must be respected: PVA is incompatible with strong acids that catalyze acetal formation and with polyamide matrices where amine end-groups accelerate thermal degradation. Storage requires sealed containers at temperatures below 30°C and relative humidity below 55%; opened bags exposed to 60% RH for more than 8 h exhibit measurable moisture uptake that interferes with gravimetric feeding accuracy in extrusion. Shelf life from date of manufacture is 12 months when stored under the defined conditions. In high-humidity outdoor service, unprotected PVA-based intumescent coatings must be topcoated with a moisture barrier (e.g., a polyurethane or epoxy clear coat) to prevent plasticization-induced loss of fire performance.
