Twisted Marine Rope Custom Premium Quality 3 Strands Polypropylene Polyester PP PET Mixed Rope Marine Use Dock Line

This high-end, customized mooring rope is specifically developed for the harsh marine environment. Made from a blend of polypropylene (PP) and polyester (PET) using a three-strand twisting process, it combines strong load-bearing properties with weather and corrosion resistance and buoyancy. It meets the high safety and long-life requirements for ship docking, dock anchoring, and offshore operations.

1. Core Materials and Structure: Balancing Performance and Application Compatibility

The PP/PET Golden Ratio Blend: The inner layer is constructed with a polypropylene (PP) core, leveraging its low density (approximately 0.91g/cm³) to impart excellent buoyancy to the rope, preventing it from sinking and increasing the difficulty of recovery. The outer layer is coated with polyester (PET) fibers, leveraging PET's high breaking strength (over 30% higher than standard PP) and abrasion resistance to enhance the rope's load-bearing and friction resistance, making it suitable for high-stress applications such as dockside friction and ship towing. Stable three-strand twisted structure: Using a "primary twist + secondary twist" double-pass process, the strand twist direction is opposite to the rope body twist (strand Z twist + rope body S twist), effectively offsetting the twisting torque and avoiding twisting and loosening during use. Each strand is precisely controlled by an electronic tensioner to ensure overall uniform force. The diameter tolerance can be controlled within ±2%, making it suitable for dock mooring piles and ship mooring bollards of different specifications.

I. Raw Material Modification and Fiber Preparation
PP/PET Composite Formula Design
Polypropylene (PP) Modification: Blend PP resin with high-density polyethylene (HDPE, ≤30%) and antioxidant 1010 (0.1-2.5‰) to improve strength and weather resistance.
Polyester (PET) Modification: Using a hollow structure design, PET chips are blended with ethylene-vinyl acetate copolymer (EVA, 1.2-3.5‰), antioxidant 1010 (0.1-2.5‰), a secondary antioxidant DLTP (0.5-1.2‰), and a nano-silver-loaded cuprous oxide antibacterial agent (0.1-2.0‰) to form a modified composite. The hollow structure reduces density (1.01-1.1 g/cm³), increases buoyancy, and enhances wear resistance. Melt Spinning and Fiber Forming
PP Fiber Preparation:
Screw temperature 210-240°C, spinneret temperature 200-225°C, cooling water temperature 22-30°C.
Drawing oven temperature 120-145°C, draw ratio 5.6-9.0, to produce high-strength PP tow.
Hollow PET Fiber Preparation:
Melt spinning in a twin-screw extruder, extrusion through a shaped spinneret (with concave hollow holes), and curing with annular air cooling.
Drawing using four pairs of hot rollers (temperatures 70-95°C, 110-130°C, 190-220°C, and 110-140°C, respectively). Draw-up speed 2800-3300 m/min, total relaxation 7-9%, and total draw ratio 5.0-7.1. 2. Hybrid Yarn Production
Sandwich Structure Design
Using a ring twisting process, PP fiber is used as the core yarn and hollow PET fiber as the sheath yarn. An electronic tensioner controls the tension of the PP yarn to at least five times that of the PET yarn, ensuring that the PET completely covers the PP surface (100% coverage), forming a "PP core - PET sheath" composite yarn.
Primary Twist and Final Twist
The hybrid yarn is first twisted (approximately 80-90 twists/meter) and then final twisted into strands. The twist direction is typically Z or S twist. The final twist direction of the three-strand rope is opposite to that of the strands (e.g., Z twist for the strands, S twist for the rope body) to balance torque.
3. Rope Forming and Heat Setting
Three-Strand Twisting
The three composite strands are twisted together using a twisting machine. The twist tension is controlled to be uniform, avoiding any loose or overtight areas. A lubricant (such as paraffin wax or silicone oil) may be added during the twisting process to reduce friction. Heat Setting Treatment
The rope is heat-set using a cylindrical electromagnetic heater at a temperature of 160-180°C (close to the compromise between the PP melting point of 160°C and the PET softening point of 240°C), at a pressure of 1-3 MPa, for 5-40 minutes to eliminate internal stress and stabilize the structure.

IV. Surface Treatment and Performance Optimization
UV Protection
Internal Addition Method: UV absorbers (such as benzotriazoles, 0.1-1.0%) and light stabilizers (such as hindered amines) are added to the PP/PET composite to inhibit photooxidation.
External Coating Method: A UV-P-containing polyurethane or acrylate coating (0.2-0.8mm thick) is applied to the rope surface to form a physical barrier.

Antibacterial and Anticorrosion
The nano-silver-loaded cuprous oxide antimicrobial agent added to the hollow PET fiber inhibits the attachment of marine microorganisms, while the chemical inertness of PP imparts acid and alkali resistance. V. Quality Inspection and Performance Verification
Mechanical Performance Testing
Breaking Strength: Tested using an electronic tensile testing machine according to ISO 10547 to ensure compliance with industry standards (e.g., ≥185kN for a 36mm diameter rope).
Elongation: Tested according to ISO 10545 to verify elastic modulus and permanent set.
Abrasion Resistance: Tested according to ISO 1346 to simulate friction between ropes and docks to assess surface wear.
Environmental Adaptability Testing
Weathering: QUV accelerated aging test (over 1000 hours) to test the effects of UV, high temperature, and humidity on strength and color.
Floating Performance: Ropes are immersed in seawater to verify that their density (approximately 0.95-1.05g/cm³ for a PP/PET blend) meets buoyancy requirements.
Appearance and Dimensional Inspection: Visually inspect surface flatness, lay uniformity, and diameter tolerance (±2%) to ensure compliance with ISO 2307. VI. Packaging and Labeling
Ropes should be packaged in moisture-proof packaging (e.g., polyethylene film and woven bags) and wrapped around paper tubes or wooden reels to prevent deformation. Labels should indicate material composition (PP/PET blend ratio), diameter, breaking strength, compliance standard (e.g., EN ISO 10556), and production batch.

Key Performance: Addressing Key Pain Points in the Marine Environment

Comprehensive Weather and Corrosion Resistance: Benzotriazole UV absorbers and hindered amine light stabilizers are pre-added to the material, and the outer layer is coated with a polyurethane coating containing UV-P (0.2-0.8mm thick). After 1000 hours of QUV accelerated aging testing, the strength retention rate still exceeded 85%, providing long-term resistance to strong UV rays, high temperature, and high humidity at sea. The chemical inertness of PP and the acid and alkali resistance of PET withstand corrosion from seawater salt spray and ship oil, preventing embrittlement and cracking of the rope.

Antibacterial, Antifouling, and Easy Maintenance: Nano-silver-loaded cuprous oxide antimicrobial agent (added at a dosage of 0.1-2.0‰) is blended into the PET fiber to inhibit the attachment of marine microorganisms such as algae and shellfish, reducing rope weight and friction loss caused by bioaccumulation. The smooth surface resists staining and can be cleaned with simple water rinsing, reducing daily maintenance costs. Customizable: The cable supports customizable diameters (typically 8mm-60mm), lengths (10m-500m), and colors (masterbatch can be added to create warning colors such as red, blue, and yellow, or custom colors). The PP/PET ratio can be adjusted based on the application scenario (typically 5:5 to 7:3). For example, nearshore terminals may prioritize a PET ratio for improved abrasion resistance, while offshore operations may prioritize a PP ratio for enhanced buoyancy.

Highly Safety and Compliance Certification: The entire process complies with ISO 10547 (breaking strength testing), ISO 1346 (abrasion resistance testing), and EN ISO 10556 (general standard for marine ropes). The 36mm diameter cable boasts a breaking strength exceeding 185kN, far exceeding the standards of ordinary civilian ropes, making it suitable for high-risk applications such as mooring 1,000-ton vessels and securing large docks.

Applicable Scenarios: Covers all marine mooring needs.
Primarily used for dock mooring: Suitable for docking container ships, bulk carriers, yachts, and other vessels, it connects the ship's mooring bollards to the dock's mooring bollards, cushioning the impact of the ship's swaying waves.
Assisting offshore operations: It can be used as a temporary towing rope, a buoy mooring rope, or for securing offshore platforms and aquaculture perimeter fences. Its buoyancy and corrosion resistance make it particularly suitable for short- or long-term offshore deployments.

Product Value: Dual Assurance of Safety and Efficiency
Compared to single-material ropes, this product, through material blending and structural optimization, addresses both the poor wear resistance and easy stretching of pure PP ropes and the high density and susceptibility to submergence of pure PET ropes. With a service life of 5-10 years (compared to 2-3 years for standard marine ropes), it reduces operational disruptions and costs associated with frequent replacements, making it a cost-effective mooring solution for terminal operations, ship management, and offshore engineering.