Frequently asked questions about magnesium hydroxide flame-retardant aluminum-plastic panels: balance between addition ratio and performance
In recent years, with the increasing requirements for fire safety in the construction industry, the market demand for flame-retardant aluminum-plastic panels has continued to grow. Magnesium hydroxide, as an efficient and environmentally friendly flame retardant, is widely used in the production of aluminum-plastic panels. However, manufacturers often face a core problem in practical applications: how to balance the relationship between the addition ratio of magnesium hydroxide and the overall performance of aluminum-plastic panels? This article will analyze from three dimensions: flame retardant mechanism, performance impact and optimization scheme, and provide practical solutions for the industry.
1. Magnesium hydroxide flame retardant mechanism and core advantages
Magnesium hydroxide (Mg(OH)₂) decomposes into magnesium oxide and water vapor at high temperatures of 380℃ - 450℃. This process can effectively absorb the heat generated by combustion, and the released water vapor can dilute the oxygen concentration. The dual effect significantly inhibits the spread of fire. Compared with traditional halogen flame retardants, magnesium hydroxide has the following advantages:
- Environmentally friendly and non-toxic: the decomposition products are harmless substances, which comply with RoHS and REACH standards
- Good smoke suppression effect: reduce the generation of harmful smoke during fire
- Strong high temperature resistance: suitable for high temperature environment in aluminum-plastic panel processing
II. The influence of addition ratio on flame retardant performance
Experimental data show that when the addition amount of magnesium hydroxide reaches 50% - 60% of the total amount of substrate, the oxygen index of aluminum-plastic panel can reach more than 32%, reaching the A2 fire protection requirements in GB/T 17748 - 2016 standard. However, excessive addition will cause the following problems:
1. Critical point effect of flame retardant efficiency
When the addition ratio exceeds 65%, the improvement of flame retardant performance slows down significantly. For example, a company tested and found that the oxygen index was 35% when the addition amount was 60%, and it only increased to 36.2% when it was 70%, and the marginal benefit was significantly reduced.
2. Loss of physical properties
- Tensile strength: For every 10% increase in magnesium hydroxide, the longitudinal tensile strength of the sheet decreases by about 15%
- Flexural modulus: When the addition exceeds 55%, the modulus value decreases by more than 30%
- Surface flatness: High additions can easily cause the coating to appear orange peel
III. Technical challenges in processing technology
In actual production, it was found that when the addition of magnesium hydroxide exceeds 55%, the torque value of the extruder will increase by 40% - 50%, resulting in the following problems:
1. The fluidity of the material decreases, and the extrusion speed decreases by 20% - 30%
2. The die pressure increases, and burrs are prone to appear on the edge of the sheet
3. The energy consumption cost increases, and the unit energy consumption increases by 15% - 18%
A case of a Guangdong production enterprise shows that after adjusting the addition amount from 60% to 58%, the yield rate increases from 82% to 89%, saving about 1.2 million yuan in annual production costs
IV. Optimization strategy for performance balance
1. Surface modification technology
Coating magnesium hydroxide with a silane coupling agent (such as KH-550) can improve three key indicators:
- Filler dispersion increased by 40%
- Tensile strength loss reduced to 8% - 10%
- Flame retardant efficiency increased by 15%
2. Compound synergistic system
When using the magnesium hydroxide/aluminum hydroxide (3:1) compounding scheme:
- The total addition amount can be reduced to 50% to achieve the same flame retardant effect
- The peak heat release rate decreases by 28%
- Smoke density decreases by 35%
3. Processing parameter optimization
- The screw temperature is controlled in the range of 195℃±5℃
- The main engine speed is adjusted to 80% - 85% of the rated value
- A two-stage exhaust screw design is used
V. FAQ
Q1: Does the addition of flame retardants affect the weather resistance of aluminum-plastic panels?
After 2000 hours of QUV aging test, the color difference of the board with optimized formula is ΔE＜2.0, which is much lower than the industry standard ΔE＜5.0. The surface-modified magnesium hydroxide can effectively resist ultraviolet degradation.
Q2: How to determine the optimal addition ratio?
It is recommended to select flame retardancy, mechanical properties and cost for multi-objective optimization through orthogonal experimental method. A company determined 58% as the optimal balance point through this method, and the product passed FM certification.
Q3: Does the addition of flame retardants affect recycling?
Experiments show that after the waste containing magnesium hydroxide is crushed, the recycled board made by secondary processing still maintains 85% of the original performance indicators, which meets the requirements of circular economy.
The application of magnesium hydroxide in aluminum-plastic panels requires refined technical control. Through surface modification, compounding technology and process optimization, enterprises can control the loss of physical properties within 8% and reduce the comprehensive cost by 12% - 15% while ensuring the flame retardant grade. With the popularization of nano-coating technology and intelligent control systems, the proportion of magnesium hydroxide addition is expected to be further optimized to 50% - 55% in the future, promoting the development of flame-retardant aluminum-plastic panels towards higher performance.