Fujian Fuwei-Vinylon Staple Fiber

Fujian Fuwei vinylon staple fibre is metered into the Hatschek furnish of non-asbestos fibre-cement sheets at 1.5–4.0 wt% of dry solids, with cut length restricted to 4–6 mm and linear density commonly between 0.8 dtex and 2.2 dtex. In plant operation on a 3.2 m wide Hatschek line running at 35–55 m/min, dry fibre added directly to the hydro-pulper without a pre-wetting stage produces buoyant clusters that float on white water and transfer to the accumulated film as non-bonded agglomerates. Stock consistency is maintained near 1.5–2.5 wt%, and a polyacrylamide flocculant is dosed after fibre dispersion to prevent wash-out of the low-density fibre. The laminate is pressed at 20–30 MPa and autoclaved at 170–190 °C saturated steam; under these conditions the vinylon fibre retains sufficient tensile strength to bridge microcracks, while cellulose pulp requires the calcium silicate matrix to avoid progressive thermal degradation. Flat sheets are assessed under ISO 8336:2017, corrugated sheets under EN 494:2012+A1:2015, and dimensional stability plus freeze-thaw performance under EN 12467:2012+A2:2018. A specific operational boundary is the reduced dewatering rate caused by the hydrophilic fibre surface; at addition above 4.0 wt%, the Hatschek film becomes excessively dense and wet, causing sheet delamination at the trimmer and uneven stacking in the autoclave trolley. Published data for Fujian Fuwei fibre in a full-width Hatschek trial at this dosage extreme is limited, and every furnish change must be validated on the production line rather than a laboratory handsheet former.

What Limits Wet-End Addition Rates in Alkali-Resistant Paper Furnishes?

Under alkaline paper furnish conditions, vinylon staple fibre is metered into separator papers, battery pasting papers and high-wet-strength filter media at 5–15 wt% of total furnish solids. The fibre is cut to 3–5 mm for Fourdrinier forming; fibre longer than 6 mm is known to wrap around couch rolls and cause sheet breaks on paper machines operating above 200 m/min. Because the fibre is non-fibrillating, it is dispersed in a separate chest at 0.1–0.3 wt% consistency with a medium-shear agitator before being metered into the mixing chest at the fan pump intake. The hydroxyl-rich surface of vinylon participates in hydrogen bonding with cellulose and provides wet tensile strength in 30% KOH electrolyte at 70 °C, but retention of cut fibre on the wire requires a charge-demand measurement before selecting a cationic retention aid, because the spin finish may be nonionic or weakly anionic and will alter flocculation. Sheet formation is monitored by grammage uniformity; excessive stock agitation after fibre addition raises the fraction of entangled bundles that create local basis weight variation exceeding ±3% in battery separator grades. Final sheets are calendered to 0.20–0.45 mm thickness, and porosity is controlled by ISO 5636-5:2013. No direct food-contact use is inferred unless migration testing is performed under FDA 21 CFR 177.1670 or an equivalent national regulation. A production-scale failure mode is the sequential dosing of two cationic additives without a 20–30 s mixing interval; this creates hard stock deposits on the forming wire and surface picking at the couch.

Metered at 0.5–1.2 kg/m³, Fujian Fuwei vinylon staple fibre is used in dry-mix shotcrete and repair mortar with cut length 6–12 mm and linear density 1.4–2.0 dtex. The fibre is fed to the aggregate screw conveyor before the mixing auger; pan mixers with rotation above 60 rpm and mixing times longer than 120 s produce fibre balls that increase rebound in dry-process shotcrete. Slump retention is measured by EN 12350-2:2019, and the fibre is not expected to raise compressive strength; its function is control of plastic shrinkage cracking, evaluated by ASTM C1579-21. Wet-mix applications require pre-wetting of the fibre when ambient relative humidity is below 60% because dry vinylon staple absorbs mix water rapidly and can reduce workability within 60 s of addition. Conformity for polymer fibres in concrete is evaluated according to EN 14889-2:2006; when used in sprayed concrete, the fibre must be covered by a European technical assessment for the specific shotcrete mixture. Published data for Fujian Fuwei fibre in a full-scale wet-mix shotcrete robot are limited; dosage should be validated by rebound and sprayed panel tests. A continuous-mixer issue occurs when fibre is injected too close to the water inlet, producing plastic lumps that block a 50 mm pumping line and trigger nozzle pressure-sensor alarms.

When Brake-Pad Preforms Replace Aramid Pulp with Vinylon Staple

Dry blending of vinylon staple fibre into friction-material formulations at 1.5–5.0 vol% replaces aramid pulp partially, primarily to improve green preform tensile strength before hot pressing. Mixing is performed in a ploughshare mixer or Lodige-type mixer with a dry cycle of 120–180 s; fibre is added after phenolic resin and before friction dust particles to yield the most homogeneous distribution. The fibre cut length is 3–6 mm, and pre-drying at 80–100 °C for 2–4 h is required when moisture content exceeds 2 wt%. During hot pressing at 150–170 °C and 25–40 MPa, residual water in fibre generates steam pockets that appear as surface blisters after pad grinding. Vinylon begins thermal degradation near 220–240 °C, while a disc-pad friction surface may exceed 300 °C during a fade test; therefore the fibre is restricted to low-load or low-metallic formulations for passenger brake pads and drum linings, not heavy commercial vehicle pads. Friction performance is screened by SAE J661:2021, and replacement brake linings sold in Europe require ECE R90 approval with vehicle-specific dynamometer testing. Green preform strength is checked with a transverse rupture fixture before pre-curing. A batch-to-batch variance in fibre linear density above ±0.2 dtex produces measurable differences in mixing torque and preform density, so incoming fibre should be conditioned at 50 ±10% RH for 24 h before weighing.

For nickel-iron battery separators, dry-laid carded webs containing Fujian Fuwei vinylon staple fibre are consolidated because the fibre tolerates 6 mol/L KOH at 70 °C without the hydrolysis observed in polyester. The fibre is cut to 38–51 mm for carding, with linear density 0.8–1.7 dtex. The card web is crosslapped and needle-punched at 250–400 punches/cm² to a finished basis weight of 80–120 g/m² and thickness 0.25–0.45 mm. Calendering at 90–120 °C densifies the surface and reduces gas permeability; this step must be controlled because over-calendering closes the pore structure and raises electrolyte retention beyond separator requirements. Thickness after 24 h immersion in 6 mol/L KOH at 70 °C is a mandatory incoming inspection because vinylon swells in hot alkali and changes plate-group compression. Fibre hydrophilicity provides capillary wicking, but nonwoven wet tensile strength is lower than dry; wet tensile strength is measured by ISO 9073-3:2023. Air permeability is determined by ASTM D737-18, and pore size distribution is evaluated by capillary flow porometry. Because separator specifications are cell-chemistry specific, material suppliers often pre-qualify against cell manufacturer internal specifications rather than a single public ISO method; published data for the specific Fujian Fuwei grade in commercial nickel-iron cells is limited. A production failure mode is fibre wrap on the carding cylinder due to excessive spin finish; incoming fibre finish level should be checked against the card clothing supplier’s recommendation to prevent cylinder loading and web defects.

Rubber Friction Layer Compounds and Two-Roll Mill Addition Sequence

Short-cut vinylon staple fibre is introduced into rubber sheeting, V-belts and hose compounds at 2.5–6.0 phr, with cut length 3–6 mm. In an internal mixer, the fibre is added after filler and process oil incorporation, and mixing is extended for 60–90 s at 100–120 °C to disperse without melting or thermal degradation. The polar hydroxyl surface of vinylon provides adhesion to natural rubber, SBR or chloroprene when a resorcinol-formaldehyde-latex pre-dip or in-situ adhesion system is used; direct addition without an adhesion promoter produces lower modulus and interfacial failure at fibre ends. Sheet orientation on a two-roll mill at a friction ratio of 1:1.25–1:1.4 aligns the fibre in the machine direction, and tensile properties become anisotropic; machine-direction and cross-machine-direction tensile stress-strain must both be measured according to ISO 37:2024 because orientation effects are significant. Vulcanization is performed at 140–160 °C, below the thermal degradation onset of the fibre. Tear strength is measured by ISO 34-1:2022, and hardness by ISO 48-4:2018. When fibre loading exceeds 8 phr, Mooney viscosity rises sharply and scorch time shortens; this creates extrusion surface roughness on hose jackets with wall thickness below 2 mm. Fibre moisture content above 1.5 wt% before mixing causes steam porosity in vulcanized sheets and must be controlled by predrying at 70–80 °C for 2 h. With fast accelerator systems based on TMTD, the fibre should be introduced in the second mixing pass to avoid premature crosslinking in the internal mixer.