Marine aquaculture cage netting and trawl twine. PetroChina Jilin HDPE JHF7750M is an extrusion monofilament grade with melt flow rate in the 0.70–0.90 g/10 min range under ISO 1133-1:2022 condition 190 °C/5.0 kg and density 0.950–0.954 g/cm³ under ISO 1183-1:2019. The resin is processed on a monofilament line with a single-screw extruder of L/D 30:1, barrier-screw geometry, and a melt pump that holds die pressure within ±0.2 MPa. Melt temperature at die exit is controlled in the 230–245 °C band. Hopper drying is not normally required for this grade, but when pellet surface moisture is present after storage above 80% relative humidity, a hopper dryer at 70–80 °C for 2–4 h is used to prevent melt fracture and surface pinholes. The formulation addition ratio is 100 parts by mass JHF7750M, hindered amine light stabilizer at 0.30–0.60 phr, benzotriazole UV absorber at 0.20–0.35 phr, processing aid at 0.02–0.05 phr, and blue-green or orange masterbatch at 2–5 wt%. Compliance for commercial aquaculture netting is anchored to ISO 1806:2002 for mesh breaking force and ISO 4892-2:2013 method A for xenon-arc weathering, with REACH Regulation (EC) No 1907/2006 Annex XVII restricting certain additives and pigments.

The quench bath is held at 30–40 °C, and the gap between die face and water surface is kept below 20 mm to prevent uncontrolled pre-draw and batch-to-batch denier drift. First-stage hot-air stretching is conducted at 95–110 °C at a draw ratio of 1:5.0–1:8.0, followed by second-stage drawing at 105–115 °C to a total draw ratio of 1:8.5–1:10.0. A two-stage draw is preferred because single-stage drawing above 1:7.0 increases broken-filament events on the winder and produces surface cavitation at the draw point. Exceeding the 1:10.0 total draw ratio typically induces surface fibrillation and a nonlinear loss of knot strength; published data for this specific configuration above 1:10.5 is limited. Annealing at 100–110 °C with 3–6% relaxation reduces boiling-water shrinkage to below 1.5% for monofilament diameters of 0.20–0.80 mm. Terminal product forms are aquaculture cage netting, knotless gill netting, trawl twine, and monofilament fishing line with linear density from 200 denier to 2000 denier.

What Limits UV Stabilizer Loading in Agricultural Shade Mesh Extrusion?

Shade cloth and anti-hail netting based on JHF7750M use the same oriented monofilament platform but a different UV additive regime because weathering resistance dominates the specification. The addition ratio is 100 parts by mass JHF7750M, hindered amine light stabilizer at 0.40–0.80 phr, benzotriazole or benzophenone UV absorber at 0.25–0.50 phr, processing stabilizer at 0.03–0.08 phr, and green or black masterbatch at 3–6 wt%. The upper UV stabilizer limit in this application is governed less by dispersion and more by surface bloom; when HALS exceeds 0.80 phr, accumulator rolls on the draw stand show deposit formation after 72 h continuous operation, and the surface haze of the finished monofilament increases. Compliance data for agricultural shade mesh are generated under ISO 4892-2:2013 method A, ASTM G154-23 Cycle 1, and ISO 13934-1:2013 for fabric strip tensile strength, with the finished mesh classified according to shade factor 30–90%.

Downstream conversion begins with monofilament extrusion through a die plate of 1.0–2.0 mm hole diameter, water-quench crystallisation at 35–45 °C, and drawing at 100–115 °C to a draw ratio of 1:6.5–1:8.5. Melt filtration through a 100–250 µm screen pack is used before the die because color masterbatch above 6 wt% can introduce carrier-resin viscosity mismatch and reduce die swell consistency. The oriented monofilament is then warp-knitted on Raschel machines, followed by heat-setting at 100–110 °C to stabilise mesh geometry and reduce web curl. For anti-hail netting, the mesh opening is typically 3 mm × 3 mm to 8 mm × 8 mm, and transverse yarn tension is controlled within ±3% to avoid asymmetric shade distribution. Terminal product forms are greenhouse shade cloth, anti-hail netting, insect-exclusion screens, and windbreak panels; black formulations containing carbon black masterbatch at 3–5 wt% are preferred for long-duration UV exposure.

Rope Stranding: Twist Balance and Monofilament Stretch Ratio

In rope stranding lines running JHF7750M, the monofilament is first drawn to a diameter of 0.20–0.60 mm and then twisted into yarns on ring twisters or braided directly into cordage on 16-carrier or 24-carrier braiders. The addition ratio consists of 100 parts by mass JHF7750M, processing lubricant at 0.02–0.05 wt%, antioxidant at 0.04–0.10 phr, and for outdoor rope, HALS at 0.25–0.50 phr with pigment masterbatch at 1–3 wt%. The processing lubricant reduces yarn-to-guide friction in stranding, but loadings above 0.05 wt% lower the coefficient of friction between filaments and can cause strand slippage under repeated tension; this is detected as longitudinal filament migration during cyclical loading on production test beds.

Compliance for marine and industrial rope is verified under ISO 2307:2019 for breaking force, elongation, and work absorption, with ultraviolet resistance tested under ISO 4892-2:2013 method A. Production includes a post-drawing annealing step at 100–110 °C with 2–5% relaxation, followed by twisting and cabling with opposing S and Z lay directions to achieve torque-balanced rope. The terminal products are mooring ropes, aquaculture longlines, net machine twine, and utility cordage; rope diameters from 4 mm to 40 mm are produced by changing strand count and twist factor while holding single filament tenacity above 0.35 N/tex, measured under ISO 5079:2020.

Industrial filter mesh and dewatering screens. Direct conversion of JHF7750M into filtration monofilament uses a higher draw ratio than rope to suppress creep and stabilise mesh openings under load. The formulation addition ratio is 100 parts by mass JHF7750M, long-term antioxidant at 0.05–0.15 phr, processing aid at 0.02–0.04 phr, and for outdoor UV exposure, carbon black masterbatch at 2–4 wt%. No wax or external lubricant is added because surface lubricants contaminate filter media and reduce seam adhesion. Compliance relies on ISO 13934-1:2013 for fabric strip tensile properties, ISO 11058:2019 for water permeability of geotextile-grade screens where applicable, and ISO 5079:2020 for single-filament tensile verification.

Extrusion is through a 0.8–1.8 mm die hole, quenched at 30–40 °C, drawn to 1:7.0–1:9.5, and annealed at 105–115 °C with 3–5% relaxation. The monofilament is woven on rapier looms fitted with positive yarn feeders; after weaving, the fabric is heat-set at 100–115 °C and calendered to fix mesh apertures within ±5% of nominal. A final slitting and ultrasonic or hot-wedge welding operation converts the roll stock into seamed belts and panels. Terminal product forms are filter mesh for water and wastewater dewatering, sieve screens, conveyor belt fabrics, and insect-exclusion mesh for buildings; mesh opening ranges from 50 µm to 2000 µm.