| HS Code | 376211 |
| Material | Polyvinyl alcohol (PVA) |
| Type | Type 2 chopped fiber filler |
| Physical Form | Short-cut monofilament fibers |
| Color | Off-white to pale yellow |
| Fiber Length | 6 mm to 12 mm (typical industrial cut lengths) |
| Fiber Diameter | 12 to 20 micrometers |
| Specific Gravity | 1.26 to 1.30 |
| Tensile Strength | 1200 to 1600 MPa |
| Elastic Modulus | 25 to 35 GPa |
| Elongation At Break | 7% to 12% |
| Alkali Resistance | Excellent in alkaline environments |
| Thermal Stability | Decomposes above 220 degrees Celsius |
| Dispersibility | Uniformly disperses in water and cementitious or resin systems |
As an accredited STW Type 2-PVA Fiber Filler factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | STW Type 2-PVA Fiber Filler is supplied in sealed 25 kg moisture-resistant bags with clear labeling and handling instructions. |
| Container Loading (20′ FCL) | Loaded 20′ FCL with palletized STW Type 2-PVA Fiber Filler, secured tightly, moisture-proofed, and container sealed for safe transit. |
| Shipping | STW Type 2-PVA Fiber Filler ships as a non-hazardous, dry material in sealed, moisture-resistant bags or drums. Ensure secure palletization to prevent damage. Transport is available via standard ground freight. Avoid excessive humidity during transit and storage. Proper labeling and documentation per standard chemical logistics are required. |
| Storage | Store STW Type 2-PVA Fiber Filler in a cool, dry, well-ventilated area away from direct sunlight and ignition sources. Keep container tightly sealed to prevent moisture absorption, which can affect performance. Avoid contact with oxidizing agents and foodstuffs. Maintain stable temperatures between 5–35°C and rotate stock to ensure shelf life, typically 12 months from date of manufacture. |
| Shelf Life | Shelf life: 24 months from date of manufacture when stored unopened in a cool, dry place away from moisture and direct sunlight. |
In strain-hardening cementitious composite (SHCC/ECC) manufacture, STW Type 2 PVA fiber filler is introduced at 2.0 vol%, equivalent to approximately 26 kg/m³ at a polymer density of 1.29 g/cm³, not as a shrinkage-control afterthought but as the dispersed toughening phase that enables tensile strain-hardening in a nominally brittle mortar. The formulation window is narrow: binder systems commonly operate at water-to-binder ratios between 0.24 and 0.26, with fly ash-to-Portland cement mass ratios above 1.2 and polycarboxylate superplasticizer demand adjusted to keep static flow-table spread between 180 mm and 220 mm after fiber addition. Compliance for the fiber itself is checked against EN 14889-2:2006, while the cured composite is evaluated under ASTM C1609/C1609M-19a third-point beam loading; residual flexural strength at deflection limits of L/150 and L/600 is used to confirm deflection hardening rather than load softening. On production lines using a 500 L twin-shaft compulsory mixer, fibers are added after the cementitious slurry has reached a homogeneous state, then mixed for an additional 120 s to 180 s; adding fibers before the superplasticizer has dispersed has been observed to form dense bundles that survive mixing and produce surface defects in cast panels. The terminal products in this scenario are precast façade cladding panels, bridge link slabs, and seismic coupling beams. A secondary production route replaces casting with continuous extrusion of thin ECC sheets for internal partition panels; published data for this extruded configuration is more limited than for cast panels, and die wall friction parameters require pilot-scale calibration rather than direct transfer from cast-mix data.
| Application scene | Primary specification | Test method | Addition reference range |
|---|---|---|---|
| SHCC/ECC precast panels | EN 14889-2:2006 | ASTM C1609/C1609M-19a | 2.0 vol% (26 kg/m³) |
| Hatschek fiber-cement sheet | ISO 8336:2018 | ASTM C1185-12(2018) | 0.5–1.5 wt% dry solids |
| Latex-modified repair mortar | EN 1504-3:2005 | ASTM C1579-21 | 0.5–1.0 vol% |
| Extruded cement backer board | ISO 8336:2018 | ASTM C1185-12(2018) | 0.8–1.5 wt% |
| Wet-mix shotcrete | ASTM C1436/C1436M | ASTM C1550-20 | 0.25–0.50 vol% |
Fiber-cement flat sheet production on a Hatschek machine is a dilute-slurry filtration process in which weak wet web layers are transferred onto a forming roll before pressing and curing. STW Type 2 filler is charged into the stock chest at 0.5 wt% to 1.5 wt% of dry solids, with the upper limit set by visible sheet mottling and drainage inhibition rather than by mechanical loss; a representative centerline is 1.2 wt% for exterior-grade boards. The governing product specification is ISO 8336:2018, with sampling and mechanical property verification by ASTM C1185-12(2018) and regional compliance under EN 12467:2012. On the wet line, slurry solids are held between 7% and 12% by mass; rotating sieve cylinders deposit a series of thin films that are vacuum-dewatered and consolidated under 10 MPa to 20 MPa pressure before autoclave curing at 170 °C to 180 °C. PVA fiber filler is not refined with cellulose pulp in a disc refiner; when it is accidentally passed through a refiner gap below 0.5 mm, fiber wrapping and screen blinding have been reported on production refiner plates. Terminal products include flat facade boards, soffit sheets, and fiber-cement roofing tiles. The filler increases wet-web tensile strength enough to reduce end-to-end sheet breaks during the first transfer stage, but exterior-grade moisture movement must be controlled by pairing the PVA fiber with cellulose and silica filler.
Dry-mix repair mortar formulations change their mixing sequence when STW Type 2 filler is pre-blended with redispersible polymer powder because low-shear blending is required to prevent electrostatic fiber balling. The addition ratio is held between 0.5 vol% and 1.0 vol%, approximately 6.5 kg/m³ to 13 kg/m³, depending on whether the repair class calls for structural or non-structural repair. Compliance is assessed under EN 1504-3:2005 repair class R3 or R4, and plastic shrinkage crack resistance is quantified by ASTM C1579-21; packaged material performance for rapid repair grades falls under ASTM C928/C928M. The production process is dry blending in a ribbon mixer at 60 rpm to 90 rpm, followed by site paddle mixing at 300 rpm to 500 rpm, with trowel or spray application to 10 mm to 50 mm thickness. Terminal products are bridge-deck repair mortars and industrial floor toppings. The process boundary is fiber clustering around undispersed polymer powder: pre-wetting the dry mortar for 60 s before mechanical mixing and limiting continuous mixing after fiber addition to 180 s reduce fiber balls and surface tears.
On a twin-auger extruder line producing thin-section cementitious backer board, STW Type 2 filler is metered into the dry premix at 0.8 wt% to 1.5 wt% of the cement-silica-filler mass, with the lower value applied to 6 mm boards and the upper value to 12 mm boards requiring higher flexural toughness. Governing standards are ISO 8336:2018 for fiber-cement flat sheets and ASTM C1185-12(2018) for sampling and testing; if the board is intended as tile backer underlayment, water resistance and reduced thickness swelling are additionally checked under the purchaser’s specification. The extruder typically uses an 18:1 L/D screw with vacuum deairing at approximately -0.08 MPa and die-head moisture content between 22% and 26%. The filler is introduced through a side-feeder after the cementitious paste has been lightly wetted to avoid transient dry pockets on the screw root. Terminal products are tile backer board, ventilated facade panels, and internal partition boards. Process audits show that excessive screw speed beyond 100 rpm at the specified L/D can generate local shear heating above 60 °C; this is the boundary condition beyond which PVA fibers lose dimensional stability and surface fibrillation increases. Batch-to-batch variance in fiber length distribution above ±0.5 mm shifts extruder torque by more than 5% and is therefore controlled at incoming inspection.
Tunnel lining and rock slope stabilization using sprayed cementitious mixtures require fiber addition at the batch plant or hopper because post-nozzle injection produces uneven distribution. STW Type 2 filler is pre-blended with cement and aggregate in a dry-mix or wet-mix shotcrete process at 0.25 vol% to 0.50 vol%, equivalent to 3.3 kg/m³ to 6.5 kg/m³, which is intended for plastic shrinkage crack control and spalling mitigation rather than full replacement of steel wire mesh. The relevant material specification is ASTM C1436/C1436M, with round panel toughness evaluated by ASTM C1550-20 and sprayed concrete conformity under EN 14487-1:2005. On the nozzle side, compressed air is maintained at 280 kPa to 350 kPa and the nozzle is held between 0.5 m and 1.5 m from the receiving surface. When the spray angle deviates beyond 25° from perpendicular, PVA fiber rebound increases disproportionately because the fibers have a larger projected area than cement particles; field rebound losses can bring the retained fiber dosage below target by 20% to 30%. Terminal products are NATM tunnel linings, slope protection shells, and rehabilitation liners over deteriorated concrete. The production boundary is moisture sensitivity: pre-dampened PVA fibers aggregate in the feed auger of mobile shotcrete rigs; dry fibers must be protected at relative humidity above 60%.
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STW Type 2-PVA Fiber Filler is a dry, monofilament polyvinyl alcohol fiber supplied as a free-flowing filler for cementitious matrices and polymer-modified dry blends. The designation identifies a Type 2 polyvinyl alcohol fiber filler, with geometry and surface finish selected for high fiber-count distribution at low addition rates rather than primary structural load transfer. The fiber is commonly specified at cut lengths of 6 mm, 8 mm, or 12 mm, with a nominal filament diameter of 0.026 mm to 0.040 mm. Representative published values for this fiber class include tensile strength near 1,560 MPa, elastic modulus near 41 GPa, elongation at break between 6% and 7%, and density approximately 1.30 g/cm³. These values apply to PVA fiber fillers engineered for cement-based matrices; the product-specific batch certificate should be consulted for actual lot-level data. The filler is used in dry-mix mortar, cement board, wet-process fiber cement, engineered cementitious composite formulations, and shotcrete where control of plastic shrinkage cracking and improvement of matrix toughness are required. STW Type 2-PVA Fiber Filler differs from Type 1 PVA grades primarily in cut-length distribution and surface finishing, which are optimized for dispersibility in low-paste-content filler applications.
The product is supplied in chopped form with a moisture content not exceeding 0.5% by mass when dried at 105°C to constant mass. Cut-length tolerance is typically specified as ±10% of nominal length. Fiber count per kilogram depends on filament diameter and cut length, ranging from approximately 200 million to 600 million filaments per kilogram. The material is suitable for addition to ordinary Portland cement, blended cements, and calcium sulfoaluminate binders. Compatibility with alkali-activated slag or high-aluminosilicate binders should be verified by trial batch because the pore solution chemistry and early-age pH differ from Portland cement systems.
Polyvinyl alcohol fiber is manufactured by solution spinning followed by high-temperature drawing and thermal setting. The resulting monofilament retains hydroxyl groups along the polymer backbone, producing a hydrophilic surface that wets readily in cement paste. This surface behavior contrasts with polypropylene and other polyolefin fillers, which exhibit low surface free energy and often require compounded wetting agents or surface treatment. The Type 2 filler is engineered for high dispersibility in low-water-content dry mixes, with a free-flowing chopped geometry that permits silo storage and auger metering without bridging. The fiber does not require pre-wetting before addition to concrete, but opened bags exposed to relative humidity above 70% should be predried at 60°C for 2 h to restore flowability.
Typical addition rates for plastic shrinkage control in concrete are 0.5 kg/m³ to 1.8 kg/m³. Higher dosages from 12 kg/m³ to 26 kg/m³ are reserved for engineered cementitious composite formulations where pseudo-strain-hardening response and multiple microcracking are required. At these higher dosages, the fresh-state consistency shifts significantly, and high-range water-reducing admixtures are necessary to maintain placement characteristics. Product-specific particle size distribution and fiber length distribution data should be requested for dry-mix filler applications because batch-to-batch variation in cut length can alter rheology and fiber distribution.
The principal difference is the hydrophilic fiber-matrix transition zone. Polypropylene monofilaments have tensile strength of 300 MPa to 700 MPa, elastic modulus of 3.5 GPa to 7 GPa, and elongation at break of 15% to 25%. Under flexural loading, polypropylene fibers pull out at relatively low crack-opening displacements, and their contribution to post-cracking residual strength is limited unless high dosages and fibrillated geometry are used. AR-glass fibers provide elastic modulus near 72 GPa and tensile strength above 1,700 MPa, but they lose toughness during mixing due to filament breakage and can form stiff bundles that impair finishability. Steel fibers have tensile strength of 1,100 MPa to 2,600 MPa, elastic modulus near 200 GPa, and density near 7.85 g/cm³; they provide structural load transfer but introduce corrosion susceptibility, electrical conductivity, and higher mixing energy.
| Property | STW Type 2-PVA Filler | Monofilament Polypropylene | AR-Glass | Hooked-End Steel |
|---|---|---|---|---|
| Tensile strength | 1,560 MPa representative | 300–700 MPa | 1,700 MPa and above | 1,100–2,600 MPa |
| Elastic modulus | 41 GPa | 3.5–7 GPa | 72 GPa | 200 GPa |
| Elongation at break | 6–7% | 15–25% | 2–3% | 3.5–4% |
| Density | 1.30 g/cm³ | 0.91 g/cm³ | 2.68 g/cm³ | 7.85 g/cm³ |
| Surface wetting | Hydrophilic | Hydrophobic | Hydrophilic | Hydrophilic |
| Corrosion risk | None | None | None | Susceptible if cracked and exposed |
| Primary function in cement matrix | Plastic shrinkage control, microcrack distribution, toughness enhancement | Plastic shrinkage control | Early-age crack control in thin sections | Post-crack residual load transfer |
At equal volume fraction, the Type 2 filler generates a substantially higher filament count than steel or AR-glass because of its low diameter and low density. A dosage of 0.9 kg/m³ corresponds to approximately 180 million fibers per cubic meter for 0.026 mm diameter and 8 mm length. The high fiber count reduces plastic settlement cracking and provides distributed microcrack control, but it does not replace structural reinforcing steel in load-bearing sections. Residual flexural strength measured under ASTM C1399/C1399M-10 is lower than that produced by hooked-end steel fibers at the same dosage by mass. The Type 2 filler is therefore positioned as a shrinkage-control and toughness-enhancing admixture rather than a primary structural reinforcement. Published data for the specific STW Type 2 configuration are limited for direct residual-strength comparison; trial batches should be performed to establish project-specific performance.
In production-scale twin-shaft compulsory mixers with batch capacities of 0.5 m³ to 2.0 m³, the Type 2-PVA filler should be introduced after aggregates, cement, and water have formed a homogeneous paste, but before the final high-range water-reducing admixture is added. Addition into the dry aggregate stream can cause electrostatic clumping and fiber balling, particularly at relative humidity below 30%. A vibrating screen or rotary sifter positioned over the mixer mouth improves fiber separation. Mixing time after fiber addition should be 90 s to 180 s at 18 rpm to 28 rpm pan speed. Prolonged mixing beyond 300 s may abrade the fiber surface and generate microfibrils, increasing water demand and reducing slump. The batch temperature should be maintained between 10°C and 30°C. At addition rates above 2.0 kg/m³, a polycarboxylate ether superplasticizer is typically required to offset workability loss caused by the high specific surface area of the fiber filler.
When pumping mixes containing 6 mm or 8 mm fibers, hose diameters below 50 mm and bends with radius less than 250 mm should be avoided because fiber bridging can form at reducers. Slump retention should be monitored with ASTM C143/C143M-20 at the point of placement. Site addition of high-range water reducer should follow ASTM C494/C494M-19 or EN 934-2:2009+A1:2012 limits to avoid segregation. In dry-mix mortar and self-leveling underlayment, the Type 2-PVA filler is preblended with cement, silica sand, and powder additives. The low moisture content and free-flowing chopped geometry make it suitable for silo storage and auger metering. At addition rates of 0.5 kg/m³ to 1.5 kg/m³, plastic shrinkage crack area measured under ASTM C1579-13 is typically reduced by 60% to 90% compared with unreinforced control. This is a representative performance range for PVA fiber fillers; specific STW Type 2 results should be obtained from the supplier’s technical data sheet.
In Hatschek wet-process fiber cement lines, the Type 2-PVA filler is added as a partial or full replacement for cellulose fiber in stock preparation. The fiber disperses in dilute slurry without additional surfactants, but stock chest agitation should be limited to avoid fiber entanglement. Vacuum dewatering retains the fiber fraction; the high aspect ratio and low density allow distribution through the sheet thickness. Pilot Hatschek trials with 150 mesh sieve cylinders and line speeds of 40 m/min to 80 m/min indicate that substitution levels above 10% by mass of total fiber can reduce drainage unless vacuum settings are adjusted. Published data for this specific STW Type 2 filler on full-scale Hatschek machines are limited, so mill-specific trials are required.
The cement pore solution during early hydration reaches pH 12.5 to 13.5, with saturated calcium hydroxide and alkali sulfates. PVA fiber fillers in this class are reported to retain more than 90% of their tensile strength after immersion in saturated Ca(OH)₂ solution at 20°C for 28 days. The hydrophilic surface does not promote alkali hydrolysis under normal Portland cement conditions. However, autoclave curing above 150°C or saturated steam curing above 90°C can soften the fiber surface and reduce crack-bridging efficiency. The product should not be used in formulations containing strong oxidizing agents or concentrated mineral acids. It is also incompatible with cationic flocculants and some amine-based additives because the hydroxyl-rich surface can adsorb admixture molecules, altering rheology and delaying cement hydration.
Dispersion quality should be checked by washing a fresh mortar sample through a 2 mm sieve and inspecting the retained fiber for agglomerates. Acceptable dispersion is typically defined as less than 5% of total fiber mass retained as agglomerated balls after standardized mixing. For production-scale batch release, fiber count per unit volume and distribution can be verified using ASTM C457/C457M-16 petrographic examination or equivalent image analysis on hardened specimens. The material is supplied with batch identification that permits traceability to raw polymer lot, spinning line, and cutting campaign.
| Requirement | Standard or Regulation | Application in Type 2-PVA Verification |
|---|---|---|
| Synthetic fiber-reinforced concrete classification | ASTM C1116/C1116M-10a | Defines Type III synthetic fiber conformance for cementitious mixtures |
| Flexural performance and toughness | ASTM C1609/C1609M-19a | Measures first-peak strength and residual loads at specified deflections |
| Average residual strength | ASTM C1399/C1399M-10 | Evaluates post-crack performance of fiber-reinforced concrete at low fiber contents |
| Plastic shrinkage cracking | ASTM C1579-13 | Assesses restrained plastic shrinkage crack reduction in fiber-reinforced concrete |
| Slump and workability | ASTM C143/C143M-20 | Monitors fresh-state workability loss after fiber addition |
| Polymer fiber conformity in Europe | EN 14889-2:2006 | Specifies definitions, requirements, and conformity evaluation for polymer fibers for concrete |
| Chemical admixture interaction | ASTM C494/C494M-19; EN 934-2:2009+A1:2012 | Guides compatibility when combining fiber addition with water reducers or superplasticizers |
| EU chemical regulation | REACH Regulation (EC) No 1907/2006 | Addresses polymer registration status and safety documentation for European market |
| Restricted substances | RoHS Directive 2011/65/EU as amended by (EU) 2015/863 | Confirms absence of regulated heavy metals and restricted substances in the fiber filler |
For acceptance on a given project, the Type 2-PVA filler should be evaluated in a trial batch using the actual mixing equipment, water chemistry, and admixture system specified for the project. Particular attention is required when the binder is a low-paste-content dry mix or a high-alkali alkali-activated slag, because dispersion and alkali resistance cannot be assumed from Portland cement data. The material should not be overdosed as a substitute for structural reinforcement, and its post-crack contribution is limited by fiber geometry and matrix bond. In applications where high post-crack residual strength is required, a hybrid system with hooked-end steel fibers or supplementary reinforcing bars may be necessary. Published data for the specific STW Type 2 configuration are limited under some extreme processing conditions, and full-scale validation should precede specification.
