Cost control strategy of high-filled magnesium hydroxide in low-smoke halogen-free cable materials

With the tightening of global environmental regulations and the improvement of terminal market requirements for cable safety performance, low-smoke halogen-free cable materials have become the mainstream choice in the industry. As a core flame retardant, the high-filling technology of magnesium hydroxide can not only meet the flame retardant performance requirements, but also significantly reduce material costs. This article analyzes the systematic strategy of high-filled magnesium hydroxide to achieve cost control from three dimensions: material optimization, process innovation, and formula design.

1. Material optimization: from basic powder to functional modification

1. Large-scale application of mineral-based magnesium hydroxide

Mineral-based magnesium hydroxide using natural brucite as raw material has a cost reduction of more than 40% compared with the chemical synthesis method. Through the airflow mill pulverization technology, the raw material particle size is controlled at 3.5-4.5μm, and the specific surface area is optimized to 18㎡/g, achieving uniform dispersion under high filling. The measured data of a certain enterprise showed that when the filling amount of the mineral-based product reached 60%, the oxygen index of the cable material remained above 38%, the tensile strength was ≥14MPa, and the comprehensive performance was better than the traditional system.

2. Double coating modification technology

Through the synergistic modification of silane coupling agent (KH550, KH570) and stearic acid, the interfacial compatibility problem caused by high filling is solved:

Primary modification: Spray silane coupling agent during high-speed stirring at 90-110℃ to increase the activation index to 98%;

Secondary coating: Stearic acid melts at 80℃ to form a hydrophobic layer, the oil absorption value drops from 53mL/100g to 38mL/100g, and the processing fluidity is increased by 40%.

This technology allows the elongation at break to reach 250% when the filling amount exceeds 55%, meeting the mechanical performance requirements of EN 45545-2 for dynamic cables.

2. Process innovation: key path to reduce costs and increase efficiency

1. Synergy of wet ball milling and dynamic shearing

Ultrasonic wave-assisted dispersion is introduced in the wet ball milling process, so that the solid content of the slurry is increased to 70% and still remains stably suspended, and the particle agglomeration rate is reduced by 60%. With the dynamic shear section of the twin-screw extruder (shear rate > 5000s⁻¹), nano-level dispersion is achieved, the melt index of the cable material with a filling amount of 60% is increased to 15.2g/10min, the extrusion speed is increased from 30m/min to 45m/min, and the unit energy consumption is reduced by 22%.

2. Low-temperature processing and waste recycling

Develop a special screw combination with L/D=48 to reduce the processing temperature from 220℃ to 180℃ to avoid particle agglomeration caused by high temperature. At the same time, a supercritical CO₂ cleaning system for scraps is established, and new materials are added at a ratio of 20%, with a tensile strength retention rate of ≥95%, and annual raw material costs are saved by more than 10 million yuan.

III. Formula collaborative design: the art of balancing flame retardancy and cost

1. Particle size gradient compounding strategy

Compound 3-10μm large particles with submicron powders at a ratio of 1:3, use particle size gradient to reduce stacking gaps, and tap density ≥1.1g/mL. The actual measurement of a photovoltaic cable project shows that when the filling volume is 55%, the smoke density (Dm) of the system is ≤80, the combustion toxic gas emission is reduced by 98%, and the resin consumption is reduced by 30%.

2. Construction of synergistic flame retardant system

Red phosphorus-zinc borate synergy: adding 2% microcapsule red phosphorus and 3% zinc borate, the oxygen index is increased from 32 to 38, and the total amount of flame retardant is reduced by 15%;

Carbon nanotube network enhancement: 0.5% carbon tubes form a conductive path, eliminate the risk of static ignition, and save the cost of antistatic agent (saving 800-1200 yuan per ton).

4. Reconstruction of the cost of the whole industry chain

1. Raw material procurement strategy

Select flaky magnesium chloride raw materials with a magnesium content of ≥46%, and reduce unit costs through large-scale procurement. A certain enterprise has locked in mining resources to make the price of magnesium hydroxide ton 15% lower than the market average price.

2. Green manufacturing empowerment

The green electricity calcination process reduces carbon emissions by 60% compared with traditional methods, meeting the EU carbon tariff (CBAM) requirements. At the same time, the decomposition product magnesium oxide can neutralize acidic waste gas, and the cost of waste gas treatment is reduced by 50%.

3. Certification premium conversion

The premium rate of products that have passed international certifications such as EN 45545-2 and TUV is 20-35%. The financial report of a rail transit cable company shows that the gross profit margin of high-filled magnesium hydroxide system products has jumped from 18.7% to 29.3%.

V. Future technology outlook

1. 4D printed cable sheath

Development of shape memory polymer-coated magnesium hydroxide particles to enable the sheath to have self-healing function. Experiments show that the healing rate of 2mm cracks at 80°C is greater than 85%, and the material life is extended by 30%.

2. AI-driven formula optimization

Based on the machine learning model to predict the correlation between particle dispersion state and mechanical properties, the sixth-generation flame retardant system with a filling amount of 65% and an oxygen index ≥ 40% is developed, and it is expected to be industrialized in 2025.

When high-filled magnesium hydroxide is embedded in the cable matrix with nano-level precision, every technological breakthrough is reconstructing the balance formula between cost and performance. From the optimization of mineral raw materials to the process innovation of smart factories, this cost control revolution is driving the evolution of low-smoke halogen-free cable materials towards higher cost-effectiveness and lower carbon emissions. In the wave of new energy and digital infrastructure, companies that master the core technology of high filling have stood at the commanding heights of the industry value chain.