Fireproof non-woven fabric, as a core material for high-risk scenarios such as fire protection, industrial insulation, and public facility fire prevention, directly determines the effectiveness of protection due to its thermal stability. In high-temperature environments, the material needs to maintain both structural integrity and foundation strength in order to block flame spread and ensure the safety of personnel and equipment.
One of the core evaluation indicators of thermal stability is the variation law of structural morphology and mechanical strength under high temperature stress. This article simulates different high-temperature scenarios and combines experimental testing and structural characterization to systematically analyze the structural evolution process and strength attenuation mechanism of fire-resistant non-woven fabrics in high-temperature environments, providing technical support for the development and scene adaptation of high-performance fire-resistant non-woven fabrics.
Research Basis: Thermal Stability Testing System and Core Indicators
To accurately capture the structural strength changes of fire-resistant non-woven fabrics under high temperatures, a standardized testing system needs to be established, covering three core modules: environmental simulation, structural characterization, and mechanical testing, to ensure that the test results are in line with actual application scenarios.
1. Test samples and environmental simulation
Select three mainstream fire-resistant non-woven fabrics in the industry as test samples: aramid needle punched non-woven fabric, pre oxidized silk hot air non-woven fabric, and flame-retardant adhesive water punched non-woven fabric. The sample weight is uniformly 200g/㎡, and the size is 100mm × 50mm to ensure unique variables.
The high-temperature environment simulation adopts a program-controlled high-temperature chamber, with a temperature range set from room temperature (25 ℃) to 1000 ℃, a heating rate of 5 ℃/min, and insulation for 30 minutes at six nodes of 100 ℃, 200 ℃, 300 ℃, 500 ℃, 800 ℃, and 1000 ℃ (simulating high-temperature exposure scenarios of different durations). The testing environment is divided into air atmosphere (simulating aerobic combustion scenarios) and nitrogen atmosphere (simulating inert insulation scenarios).
2. Core testing indicators and methods
Structural characterization was performed using scanning electron microscopy (SEM) to observe changes in fiber morphology and pore structure, and X-ray diffraction (XRD) to analyze the evolution of fiber crystallinity; The mechanical strength test adopts a high-temperature universal testing machine to determine the fracture strength, elastic modulus, and tear strength of samples at different temperature nodes.
Each temperature node is tested 5 times, and the average value is taken to eliminate errors. Simultaneously record the carbonization rate of the sample (the ratio of residual mass to initial mass after high temperature) to assist in determining structural stability.
Structural evolution and strength variation of fire-resistant non-woven fabric under high temperature
The experimental results show that the structural strength changes of the three types of fire-resistant non-woven fabrics in high temperature environments exhibit a “segmented evolution” characteristic. However, due to differences in the characteristics of fiber raw materials, there are significant differences in the critical temperature node and change amplitude, which can be specifically divided into three core stages.
1. Low temperature stage (room temperature -200 ℃): The structure and strength are basically stable
During this stage, no significant structural changes were observed in the three types of samples: SEM observation showed complete fiber morphology, tightly interwoven structure, and uniform pore distribution; XRD analysis shows that there is no significant fluctuation in fiber crystallinity (fluctuation amplitude ≤ 3%).
In terms of mechanical strength, the fracture strength attenuation rate of aramid and pre oxidized non-woven fabric is less than 5%, and the elastic modulus remains basically stable; Flame retardant adhesive non-woven fabric has a slight decrease in fracture strength (attenuation rate of about 8%) due to the thermal expansion characteristics of cellulose fibers, but it can still maintain over 90% of its initial strength.
Core reason: Under low temperature conditions, fiber molecular chains only undergo slight thermal vibrations and do not exceed the chemical bond stability threshold. Flame retardant components (such as the conjugated structure of aramid, the trapezoidal structure of pre oxidized fibers, and the flame retardant of flame retardant adhesives) do not decompose, thus maintaining structural integrity and mechanical properties. At this stage, corresponding to low to medium temperature scenarios such as industrial conventional insulation and civil fire prevention, all three types of fire-resistant non-woven fabrics can meet the usage needs.
2. Medium temperature stage (200 ℃ -500 ℃): Structure begins to differentiate and strength rapidly decreases
This stage is the watershed for the strength changes of three types of sample structures:
——Flame retardant adhesive non-woven fabric: Significant carbonization begins at 250 ℃, and the fiber surface gradually becomes rough. At 300 ℃, the fiber interweaving structure becomes loose, and the porosity significantly increases; At 500 ℃, the fibers were completely carbonized, the structure collapsed, and XRD showed a decrease in crystallinity to 0.
In terms of mechanical strength, the attenuation rate of fracture strength reaches 50% at 250 ℃, and the bearing capacity is basically lost at 500 ℃ (fracture strength is less than 10% of the initial value), with a carbonization rate of about 35%. The core reason is that the glycosidic bonds of cellulose fibers begin to break above 200 ℃, rendering the flame retardant ineffective and unable to inhibit fiber degradation.
——Pre oxygenated non-woven fabric: The structure is basically stable below 300 ℃, and a dense carbonized layer gradually forms on the fiber surface between 300 ℃ and 500 ℃. The interwoven structure remains intact, and the porosity slightly decreases; XRD shows a slow decrease in crystallinity (decay rate of about 15%). In terms of mechanical strength, the fracture strength attenuation rate at 500 ℃ is about 30%, the elastic modulus decreases by about 25%, and the carbonization rate reaches 60%.
The core reason is that the trapezoidal conjugated structure of the pre oxidized fibers gradually solidifies at medium temperatures, and the formation of a carbonized layer to some extent protects the internal fibers and delays strength attenuation.
——Aramid non-woven fabric: No significant carbonization was observed below 500 ℃, and the fiber morphology and interwoven structure remained intact. XRD showed a fluctuation range of crystallinity ≤ 8%. In terms of mechanical strength, the attenuation rate of fracture strength at 500 ℃ is about 12%, and the attenuation rate of elastic modulus is about 10%, showing excellent medium temperature stability. The core reason is that the aromatic polyamide molecular chains of aramid have extremely strong chemical bond stability, and only slight thermal oxidation occurs within the range of 200 ℃ -500 ℃, without significant degradation.
3. High temperature stage (above 500 ℃): structural reconstruction and strength limit attenuation
Above 500 ℃, all three types of samples enter the stage of structural reconstruction and strength limit attenuation, but the performance differences are still significant:
——Flame retardant adhesive non-woven fabric: completely carbonized above 500 ℃, with loose carbonaceous residue formed after structural collapse, unable to withstand any external force and losing its protective function.
——Pre oxygenated non-woven fabric: At 500 ℃ -800 ℃, the surface carbonization layer continues to thicken and densify, and the internal fibers gradually complete carbonization transformation, while the interwoven structure remains intact; Microcracks begin to appear in the carbonized layer above 800 ℃, and at 1000 ℃, crack propagation leads to local structural damage, but not complete collapse. In terms of mechanical strength, the attenuation rate of fracture strength reaches 60% at 800 ℃ and 80% at 1000 ℃, but it can still maintain a certain degree of structural integrity (carbonization rate of about 85%), which can achieve short-term thermal insulation protection.
——Aramid non-woven fabric: Slight carbonization begins to occur at 500 ℃ -800 ℃, forming a thin carbon layer on the fiber surface and maintaining a stable interwoven structure; Carbonization accelerates above 800 ℃, resulting in a decrease in fiber diameter. At 1000 ℃, some fibers break and the interwoven structure becomes loose. In terms of mechanical strength, the attenuation rate of fracture strength at 800 ℃ is about 40%, the attenuation rate at 1000 ℃ is 75%, and the carbonization rate is about 70%, which is still better than pre oxidized silk and flame-retardant adhesive non-woven fabric at the same temperature.
Core factors affecting the strength stability of high-temperature structures
Based on experimental results and theoretical analysis, the structural strength stability of fire-resistant non-woven fabrics at high temperatures is mainly influenced by four core factors:
1. Essence of fiber raw materials: The thermal stability of fiber molecular structure is the foundation. The aromatic conjugated structure of aramid and the trapezoidal structure of pre oxidized fibers have much higher chemical bond energies than the cellulose structure of flame-retardant adhesives, resulting in better thermal stability; Permanent flame retardant fibers (aramid, pre oxidized silk) do not require external flame retardants, avoiding the sudden drop in strength caused by the decomposition and failure of flame retardants at medium temperatures.
2. Molding process: Needle punched non-woven fabric has tighter fiber interweaving and stronger adhesion, and its structural stability at high temperatures is better than that of hot air and water punched non-woven fabric. For example, the fracture strength of pre oxygenated needle punched non-woven fabric with the same raw material at 800 ℃ is more than 20% higher than that of hot air non-woven fabric.
3. Flame retardant modification method: Pre spinning modified (with flame retardant added to the original solution) fireproof non-woven fabric, due to the deep fusion of flame retardant components and fibers, has a more lasting flame retardant effect at high temperatures, and the strength degradation rate is lower than that of post finishing modified products. In the experiment, the strength attenuation rate of pre spun modified flame-retardant adhesive non-woven fabric at 300 ℃ was 15% lower than that of post finishing modified products.
4. Environmental atmosphere: Under inert gas atmosphere, the intensity attenuation rate of the three types of samples is 10% -20% lower than that of air atmosphere. The oxygen in the air atmosphere will accelerate the thermal oxidation degradation of fibers and promote structural damage; Inert gases can inhibit oxidation reactions and delay the carbonization process.
Conclusion and Application Suggestions
1. Core conclusion: The high-temperature structural strength stability of fireproof non-woven fabric is dominated by fiber raw materials, showing a priority of “aramid>pre oxidized silk>flame-retardant adhesive”; The change pattern can be divided into three stages: low temperature stability, medium temperature differentiation, and high temperature limit attenuation.
The critical temperature node varies significantly with different raw materials (flame retardant adhesive 250 ℃, pre oxidized silk 300 ℃, aramid 500 ℃); The molding process, modification method, and environmental atmosphere affect the fiber degradation rate and structural integrity, and assist in regulating thermal stability.
2. Application suggestion: Select accurately according to the temperature requirements of the scene – flame retardant adhesive non-woven fabric can be used for low to medium temperature scenes (≤ 200 ℃), balancing cost and basic protection; Priority should be given to using pre oxygenated non-woven fabric in medium to high temperature scenarios (200 ℃ -800 ℃) to balance cost-effectiveness and thermal insulation stability; High temperature extreme protection scenarios (>800 ℃) require the use of aramid non-woven fabric to ensure structural strength and protection effectiveness.
At the same time, it is recommended to improve the fiber adhesion through needle punching technology, enhance flame retardancy and durability through pre spinning modification, and further optimize high-temperature stability performance.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Dec-24-2025